If you are planning on building a new home then now would be a great time to plan your plumbing layout for an energy and water efficient plumbing system that will end up saving you a whole lot of money and add convenience to your life.
If you already have a home, then there are still economical steps you can take to improve your plumbing efficiency and have a greener system environmentally and save money water and time when using your hot water system.
Cold Water Plumbing
When it comes to an efficient residential plumbing system it’s all about the hot water. The cold water system probably can’t be improved on. When you want cold water you turn on a tap. There is no waste built into the system, unless you have leaky pipes or something. Your cold water system doesn’t consume any energy either.
Water Heaters
Hot water is another story. The hot water system consists of the water heater and the hot water plumbing. Obviously the water heater has a lot to do with the efficiency of your system. Some water heaters are better than others. You may have the old standard storage type gas or electric water heater, or a tankless water heater, or even a heat pump or hybrid water heaters. And let’s not forget about solar water heating.
For the sake of simplicity I’ll just assume you have a storage gas water heater. Most people do. Although the water heater is an important source of efficiency, I won’t get into water heater specifics here. I want to address the piping system and plumbing layout, as these are often not considered when building a new home, or the installation cost is minimized.
Hot Water Plumbing Layout
The main source of inefficiency in a residential plumbing layout is the length and location of the hot water piping. With the hot water plumbing, when you finish using the hot water you generally leave hot water sitting in the pipes where it simply cools off.
That stranded hot water costs a lot to heat. Letting the hot water cool off in the pipes is a major source of energy inefficiency. Then, the next time you desire hot water you have to run the cooled off hot water out of the pipes before you can get your hot water. So not only did you lose the heating energy, now you are running water down the drain too. Not very green.
If you are in the planning stage you can make sure your pipes are as short as possible. The shorter the hot water runs the less energy and water you will waste. Try to locate the water heater as close as possible to the most frequently used fixtures.
Make sure you insulate your hot water pipes. Insulating the pipes will reduce the amount of time you need to run water down the drain while you wait for the hot water to arrive. Shorter waits are also a convenience for the user.
Don’t oversize your pipes. Larger pipes hold more water and so will waste more water along with more heating energy. Most fixtures these days are low flow fixtures and thus you won’t be able to get a higher flow rate with larger diameter pipes. You do however, need to follow your local building codes. As far as hot water pipes go, generally smaller diameter pipes are green.
If you already own a home, there are things you can do to mitigate the energy and water losses associated with the hot water plumbing.
Install a demand hot water system. A hot water demand system will eliminate running water down the drain while you wait for the hot water to arrive. These systems use a small pump to pump the water from the water heater to the fixture without running water down the drain. They utilize the cold water piping to return the cooled-off hot water to the water heaters. When the hot water reaches the fixture the pump shuts off to prevent putting hot water into the cold water line.
There isn’t much you can do to eliminate the loss of heating energy due to the cooling off of the hot water left stranded in the hot water pipes after each use, but at least you won’t be wasting all that water.
If your hot water pipes are not insulated, and you can get to them, it’s a good idea. Also your water heater should have heat traps installed to reduce the leakage of heat into the pipes when they are not in use.
For a greener hot water plumbing system the rules are keep the pipes as short as possible, insulate the hot water piping, and install a hot water demand system. You will be glad you did.
Green Home Improvements
Which brand makes the best tankless water heater?
Monday, August 30, 2010
Friday, August 27, 2010
A.O. Smith Voltex® Hybrid Electric Water Heaters (Heat Pump)
The Voltex hybrid water heater mates a heat pump water heater with an electric storage water heater. Heat pump water heaters are very efficient. The operate much like your refrigerator or air conditioner. They pull heat out of the air and instead of transferring it to back to the air as your air conditioner does, it uses it to heat water.
Pulling latent heat out of the ambient air is much more energy efficient than just generating the heat with electricity. By limiting the electric heating elements to back up heating when the heat pump can't meet demand, and letting the heat pump do most of the work, you get a very energy efficient water heater. Any tank standby losses are small compared to the energy savings from latent heat recovery.
Heat pumps are not perfect. A heat pump has a harder time pulling heat out of the air as the temperature decreases. By the time the ambient air temperature reaches 40 to 45 degrees heat pumps are no longer efficient. The lower the ambient temperature the longer it takes the pump to heat the water too.
The voltex units wrap the storage tank with a long copper pipe under the insulation to transfer the heat from the heat pump to the water instead of using an internal heat exchanger. Since heat pumps need a lot of air to obtain the needed heat, you should not use them in small rooms like closets or utility rooms unless the room is well vented.
Voltex hybrid heat pump water heaters have several modes of operation that are selectable from the control panel.
Efficiency Mode
The most energy-efficient setting using only the heat pump for heating the water. The electric heating elements will not operate in this mode.
Hybrid Mode
This mode uses the heat pump for efficiency, but will use the element for quick recovery following increased hot water usage. It's more efficient that electric only but not as efficient as heat pump only operation.
Conventional Electric Mode
In conventional mode, the heater works like a conventional electric water heater. In this mode you won't save any energy over a conventional storage water heater.
Vacation Mode
Vacation mode keeps the tank temperature at 60°F (15.6°C) during vacation or extended absence to reduce energy costs and to provide freeze protection for the water heater.
A.O. Smith has two models, a 60 gallon model and an 80 gallon model. The 60 gallon model when in Efficiency mode has an energy factor of 2.4 and a first hour recovery rating of 51 gallons.
In Hybrid mode it has an EF of 2.33 and a first hour recovery of 68 gallons.
In Electric mode the EF is .88 and the recovery is 66 gallons.
As with the other models discussed the Voltex is Eligible for the 30% Federal tax credit.
Instant Hot Water Systems Explained and 5 Brands Compared
Pulling latent heat out of the ambient air is much more energy efficient than just generating the heat with electricity. By limiting the electric heating elements to back up heating when the heat pump can't meet demand, and letting the heat pump do most of the work, you get a very energy efficient water heater. Any tank standby losses are small compared to the energy savings from latent heat recovery.
Heat pumps are not perfect. A heat pump has a harder time pulling heat out of the air as the temperature decreases. By the time the ambient air temperature reaches 40 to 45 degrees heat pumps are no longer efficient. The lower the ambient temperature the longer it takes the pump to heat the water too.
The voltex units wrap the storage tank with a long copper pipe under the insulation to transfer the heat from the heat pump to the water instead of using an internal heat exchanger. Since heat pumps need a lot of air to obtain the needed heat, you should not use them in small rooms like closets or utility rooms unless the room is well vented.
Voltex hybrid heat pump water heaters have several modes of operation that are selectable from the control panel.
Efficiency Mode
The most energy-efficient setting using only the heat pump for heating the water. The electric heating elements will not operate in this mode.
Hybrid Mode
This mode uses the heat pump for efficiency, but will use the element for quick recovery following increased hot water usage. It's more efficient that electric only but not as efficient as heat pump only operation.
Conventional Electric Mode
In conventional mode, the heater works like a conventional electric water heater. In this mode you won't save any energy over a conventional storage water heater.
Vacation Mode
Vacation mode keeps the tank temperature at 60°F (15.6°C) during vacation or extended absence to reduce energy costs and to provide freeze protection for the water heater.
A.O. Smith has two models, a 60 gallon model and an 80 gallon model. The 60 gallon model when in Efficiency mode has an energy factor of 2.4 and a first hour recovery rating of 51 gallons.
In Hybrid mode it has an EF of 2.33 and a first hour recovery of 68 gallons.
In Electric mode the EF is .88 and the recovery is 66 gallons.
As with the other models discussed the Voltex is Eligible for the 30% Federal tax credit.
Instant Hot Water Systems Explained and 5 Brands Compared
Thursday, August 26, 2010
GEOSPRING GE Hybrid Water Heaters (Heat Pump)
The GeoSpring hybrid water heater manufactured by General Electric is an electric storage type water heater with a heat pump mounted on top.
Heat pump water heaters work just like heat pumps in refrigerators and window air conditioners. Its much less expensive to move heat around than it is to generate heat with electricity. The heat pump water heater uses a heat exchanger to cool the air and the recovered heat from the air is put into the water with a second heat exchanger.
Like all of the other storage heat pump water heater brands, it works great in warm climates and not so well in cold climates. It saves energy since it’s less expensive to move heat from the air to the water than it is to just generate the heat with electricity.
Heat pumps need a lot of air to recover heat from, so they have fans to move the air through a heat exchanger. Typically a heat pump water heater should not be located in an unvented closet or storage room. Normally you would want at least 800 to 1000 cubic feet of volume in the room where you locate the unit.
Heat pump technology has been around forever and is very reliable. If you look around in the forums online you won't find many unhappy owners of heat pump water heaters like you will with tankless water heaters.
GE claims their hybrid unit can save up to 62% and up to $320 per year on your water heating bill, and that it's the most energy efficient 50-gallon electric water heater you can buy. It is ENERGY STAR® qualified with an energy factor of 2.35 (in the default Hybrid mode).
Here are some of the specifications:
Electrical Circuit Required Dedicated 30 Amp Min.
Electrical Consumption - Lower Element 4,500 Watts - Maximum Heating
550 Watts - Minimum Heating
Electrical Consumption - Upper Element 4,500 Watts - Maximum Heating
550 Watts - Minimum Heating
Electrical Power Required 240 Volts/ 208 Volts (L1, L2, Ground) 60 Hz
Energy Factor (hybrid mode) 2.35
First Hour Rate (FHR) 63 Gallons
Operating Air Temperature Range: 45° to 120° F
Standard Electric Mode - Standard Recommended Range 32° to 150° F
Operating Water Pressure 20-125 PSI (30-80 PSI recommended)
The GeoSpring Hybrid Water heater has several modes of operation which you can select on via the control panel.
Modes Of Operation
In eHeat™ mode the water heater operates only the heat pump for heating the water. This is the most efficient mode, and will produce greatest amount of savings.
Hybrid mode. In hybrid mode it uses the heat pump as its primary means to heat the water, the standard electric elements only come on when needed, automatically reverting back to using the heat pump only once the demand has been met. This is the default mode the electric water heater is shipped in.
High Demand mode: Operates much like Hybrid mode, but lets the system know in advance that it will be experiencing a larger water demand than normal. The water heater will be react faster by cycling on the heating elements sooner and for a longer duration of time.
Standard mode. This mode shuts the heat pump off and uses the electric elements only to heat the water, just like a regular electric water heater. Standard mode is used for operation when it gets extremely cold (less than 45°F).
Vacation setting: Vacation setting drops the temperature set point to 50°F saving energy, but also preventing the water from freezing. You set how many days you will be away on vacation, between of 3 and 90 days. The day before you get home the heater restores the previous settings. When you get home the hot water will be waiting.
The Emergency Economic Stabilization Act provides consumers with a 30% tax credit on the purchase and installation price of an ENERGY STAR heat pump water heater.
Information about hot water circulating pumps: Recirc Pumps
Green plumbing layouts for hot water conservation: Plumbing Layouts
Heat pump water heaters work just like heat pumps in refrigerators and window air conditioners. Its much less expensive to move heat around than it is to generate heat with electricity. The heat pump water heater uses a heat exchanger to cool the air and the recovered heat from the air is put into the water with a second heat exchanger.
Like all of the other storage heat pump water heater brands, it works great in warm climates and not so well in cold climates. It saves energy since it’s less expensive to move heat from the air to the water than it is to just generate the heat with electricity.
Heat pumps need a lot of air to recover heat from, so they have fans to move the air through a heat exchanger. Typically a heat pump water heater should not be located in an unvented closet or storage room. Normally you would want at least 800 to 1000 cubic feet of volume in the room where you locate the unit.
Heat pump technology has been around forever and is very reliable. If you look around in the forums online you won't find many unhappy owners of heat pump water heaters like you will with tankless water heaters.
GE claims their hybrid unit can save up to 62% and up to $320 per year on your water heating bill, and that it's the most energy efficient 50-gallon electric water heater you can buy. It is ENERGY STAR® qualified with an energy factor of 2.35 (in the default Hybrid mode).
Here are some of the specifications:
Electrical Circuit Required Dedicated 30 Amp Min.
Electrical Consumption - Lower Element 4,500 Watts - Maximum Heating
550 Watts - Minimum Heating
Electrical Consumption - Upper Element 4,500 Watts - Maximum Heating
550 Watts - Minimum Heating
Electrical Power Required 240 Volts/ 208 Volts (L1, L2, Ground) 60 Hz
Energy Factor (hybrid mode) 2.35
First Hour Rate (FHR) 63 Gallons
Operating Air Temperature Range: 45° to 120° F
Standard Electric Mode - Standard Recommended Range 32° to 150° F
Operating Water Pressure 20-125 PSI (30-80 PSI recommended)
The GeoSpring Hybrid Water heater has several modes of operation which you can select on via the control panel.
Modes Of Operation
In eHeat™ mode the water heater operates only the heat pump for heating the water. This is the most efficient mode, and will produce greatest amount of savings.
Hybrid mode. In hybrid mode it uses the heat pump as its primary means to heat the water, the standard electric elements only come on when needed, automatically reverting back to using the heat pump only once the demand has been met. This is the default mode the electric water heater is shipped in.
High Demand mode: Operates much like Hybrid mode, but lets the system know in advance that it will be experiencing a larger water demand than normal. The water heater will be react faster by cycling on the heating elements sooner and for a longer duration of time.
Standard mode. This mode shuts the heat pump off and uses the electric elements only to heat the water, just like a regular electric water heater. Standard mode is used for operation when it gets extremely cold (less than 45°F).
Vacation setting: Vacation setting drops the temperature set point to 50°F saving energy, but also preventing the water from freezing. You set how many days you will be away on vacation, between of 3 and 90 days. The day before you get home the heater restores the previous settings. When you get home the hot water will be waiting.
The Emergency Economic Stabilization Act provides consumers with a 30% tax credit on the purchase and installation price of an ENERGY STAR heat pump water heater.
Information about hot water circulating pumps: Recirc Pumps
Green plumbing layouts for hot water conservation: Plumbing Layouts
Tuesday, August 24, 2010
A.O. Smith NEXT Hybrid Water Heaters (Tankless)
The A.O. Smith hybrid water heater has a small "buffer tank". A.O. Smith isn’t saying what size the tank is, but rumors are that it is around 15 to 20 gallons. With a buffer tank the unit can deliver hot water faster since it doesn’t have to heat the water first, there is sufficient hot water in the tank to begin sending water to the fixtures right away just as a storage water heater would do. Before the buffer tank runs out of hot water the tankless heater gets up to temperature and begins supplying the hot water.
This also allows the burner to not have to fire with relatively small hot water uses, such as washing hands in a bathroom sink. The NEXT is a condensing type water heater with a 90% “thermal efficiency.” It has a secondary heat exchanger used to capture heat from the flue gas and put it into the buffer tank.
It should also work with hot water circulating systems unlike most tankless water heaters. The buffer tank should also eliminate the "cold water sandwich" that tankless water heaters are famous for.
The NEXT Hybrid achieves a very high efficiency--it is rated at 90% "thermal efficiency." The high efficiency is achieved through a process in which a secondary heat exchanger is used to capture the heated flue gas from the tankless unit and route it back through the buffer tank to extract additional heat. So, not only does the buffer tank have benefits in terms of hot water delivery, but it also helps the NEXT Hybrid achieve its high-efficiency, condensing performance.
Since the heater has a storage tank it will have standby losses like a standard storage water heater, but they will be substantially smaller due to the smaller size of the buffer tank. It will probably have less than half the losses of a standard gas tank type water heater which puts it at around $2-$4 dollars per month in energy usage.
Through the end of 2010, the product is eligible for a $1,500 tax credit (assuming that other energy improvements have not used up this credit).
More information about tankless water heaters.
Learn more about electric storage water heaters
All about gas storage water heaters.
This also allows the burner to not have to fire with relatively small hot water uses, such as washing hands in a bathroom sink. The NEXT is a condensing type water heater with a 90% “thermal efficiency.” It has a secondary heat exchanger used to capture heat from the flue gas and put it into the buffer tank.
It should also work with hot water circulating systems unlike most tankless water heaters. The buffer tank should also eliminate the "cold water sandwich" that tankless water heaters are famous for.
The NEXT Hybrid achieves a very high efficiency--it is rated at 90% "thermal efficiency." The high efficiency is achieved through a process in which a secondary heat exchanger is used to capture the heated flue gas from the tankless unit and route it back through the buffer tank to extract additional heat. So, not only does the buffer tank have benefits in terms of hot water delivery, but it also helps the NEXT Hybrid achieve its high-efficiency, condensing performance.
Since the heater has a storage tank it will have standby losses like a standard storage water heater, but they will be substantially smaller due to the smaller size of the buffer tank. It will probably have less than half the losses of a standard gas tank type water heater which puts it at around $2-$4 dollars per month in energy usage.
Through the end of 2010, the product is eligible for a $1,500 tax credit (assuming that other energy improvements have not used up this credit).
More information about tankless water heaters.
Learn more about electric storage water heaters
All about gas storage water heaters.
Monday, August 23, 2010
Hybrid Water Heaters - Combination Gas Tankless & Storage Tank
There are several manufacturers of hybrid water heaters that use a combination storage tank and tankless water heater. The idea is to eliminate some of the problems associated with tankless water heaters while still taking advantage of the positive side of tankless heaters like high energy efficiency and endless hot water. By using a much smaller tank the standby losses are much smaller than those associated with a full sized gas storage tank type water heater.
Hybrid tankless water heaters have a set of pros and cons just like any other appliance.
Tankless water heaters have some annoying characteristics that a small storage tank can solve. For instance, there is the cold water sandwich. A small holding tank can solve that problem.
For those of you who are not familiar with the “cold water sandwich”, it’s what happens when the flow of hot water is shut off briefly and then turned back on. The heater requires a few seconds to come up to speed after its been shut down, during which a slug of cold water can pass through to the faucet or shower fixture. It’s not a big deal, but it’s something to be annoyed by.
Another annoyance is the difficulty in getting a very small flow of hot water since tankless water heaters require at least a ½ gallon per minute or more to initiate and sustain heater operation. Tankless water heaters also take longer to get the hot water to your fixture, causing you to waste water running it down the drain while you wait for the hot water to arrive. The small tank would solve that problem as well.
Normally you can’t use hot water circulating systems with tankless water heaters, but with a small tank that problem goes away as well. You can use a hot water circulating system with the hybrid units.
The only real downside I see to the storage tank side of the equation is that you will now have standby losses. The standby losses won’t be as great as with a full size tank, but they will exist. I don’t consider it a big problem since for a small buffer tank used with a tankless water heater probably only uses about $1-$3 dollars per month to compensate for standby losses.
Since a tankless unit is involved you will still probably need a larger than standard diameter gas line to feed the hungry little beast, and larger venting than with a standard gas water heater. The heater will most likely require a drain line for exhaust condensate. The installation will be more expensive as a result of these requirements. Installation is very important with tankless units, more so than with storage heaters. Be sure to have the installation done by factory trained individuals if possible.
If it works, I really like the idea of the tankless – storage combination. The strange problems that tankless units typically create like the low flow and cold water sandwich problems and especially the water conservation issues are solved by the hybrid tankless storage water heater concept and you get endless hot water if you need it, not to mention a small amount of energy savings due to the higher efficiency of the tankless burners.
And hot water circulating systems can be used with tankless hybrid water heaters for homes with long hot water lines.
Hybrid Water Heaters - Heat Pump Type
Hybrid Water Heaters -Tankless / Storage Type
Tankless Water Heaters - Selecting A Tankless Water Heater
General Water Heater Information - All About Water Heaters
Hybrid tankless water heaters have a set of pros and cons just like any other appliance.
Tankless water heaters have some annoying characteristics that a small storage tank can solve. For instance, there is the cold water sandwich. A small holding tank can solve that problem.
For those of you who are not familiar with the “cold water sandwich”, it’s what happens when the flow of hot water is shut off briefly and then turned back on. The heater requires a few seconds to come up to speed after its been shut down, during which a slug of cold water can pass through to the faucet or shower fixture. It’s not a big deal, but it’s something to be annoyed by.
Another annoyance is the difficulty in getting a very small flow of hot water since tankless water heaters require at least a ½ gallon per minute or more to initiate and sustain heater operation. Tankless water heaters also take longer to get the hot water to your fixture, causing you to waste water running it down the drain while you wait for the hot water to arrive. The small tank would solve that problem as well.
Normally you can’t use hot water circulating systems with tankless water heaters, but with a small tank that problem goes away as well. You can use a hot water circulating system with the hybrid units.
The only real downside I see to the storage tank side of the equation is that you will now have standby losses. The standby losses won’t be as great as with a full size tank, but they will exist. I don’t consider it a big problem since for a small buffer tank used with a tankless water heater probably only uses about $1-$3 dollars per month to compensate for standby losses.
Since a tankless unit is involved you will still probably need a larger than standard diameter gas line to feed the hungry little beast, and larger venting than with a standard gas water heater. The heater will most likely require a drain line for exhaust condensate. The installation will be more expensive as a result of these requirements. Installation is very important with tankless units, more so than with storage heaters. Be sure to have the installation done by factory trained individuals if possible.
If it works, I really like the idea of the tankless – storage combination. The strange problems that tankless units typically create like the low flow and cold water sandwich problems and especially the water conservation issues are solved by the hybrid tankless storage water heater concept and you get endless hot water if you need it, not to mention a small amount of energy savings due to the higher efficiency of the tankless burners.
And hot water circulating systems can be used with tankless hybrid water heaters for homes with long hot water lines.
Hybrid Water Heaters - Heat Pump Type
Hybrid Water Heaters -Tankless / Storage Type
Tankless Water Heaters - Selecting A Tankless Water Heater
General Water Heater Information - All About Water Heaters
Heat Pump Hybrid Water Heaters
Heat Pump Hybrid Water Heaters are basically an electric water heater with a heat pump mounted on top. There isn’t much new about a heat pump water heater with a 40 or 50 gallon tank. They have been around for over 40 years.
A heat pump water heater works just like those awful air conditioners in motel rooms. Instead of blowing air through a heat exchanger to warm or cool it, the heat pump water heater runs the water through the heat exchanger to heat it.
Heat pump water heaters are probably the most efficient way of heating water in the right circumstances. Heat pumps work better when there is actually heat to pump. When the air is warm there is plenty of heat for the heat pump to pull out of the air and the heat pump is efficient.
As the air temperature decreases there is less heat to capture from the air the heat pump will have to work harder, and will become less efficient.
When you get down to around 40 degrees Fahrenheit there isn’t enough heat in the air for the heat pump to work so you will have to rely on the electric resistance elements to heat the water. At that point you might as well have a standard electric water heater.
Obviously your climate will have a large influence on the desirability of a heat pump water heater. They would be great for Arizona, not so great for Alaska.
Some of the drawbacks to a heat pump water heater are the inability to work well at cold ambient temperatures’ as we have just discussed, they are slower than molasses at heating the water, they can’t heat the water quite as hot as a standard electric, they have more parts and are more expensive to repair than a standard electric water heater.
Heat pump water heaters require plenty of air flow, so you can’t put them in a closet or small storage room. Heat pump water heaters require cleaning of the air filter, some manufactures recommend at least once a year and others suggest monthly.
A clogged or dirty air cleaner will cause the heat pump to work less efficiently and in some cases will shut off the heat pump until the filter is cleaned. During that period it will be in electric heating element only mode and will cost considerably more to run.
Heat pump water heating technology has been around for a long time and is very reliable. You won’t find very many unhappy owners of heat pump water heaters on the internet and in the forums as you do with tankless water heater owners.
With heat pump water heaters the larger the tank the better. Since the heating elements are typically only called on to supply heat when the hot water demand has nearly depleted the hot water in the storage tank, the larger the tank the less often the heating elements will be used and the more heat pump use occurs.
If you live in a warm climate like Florida, and you live in an all electric neighborhood and don’t have access to natural or propane gas, then a heat pump water heater is a viable option for you. A heat pump water heater can cut your water heating bill roughly in half saving you hundreds of dollars a year.
Heat pump hybrid water heaters cost more than standard tank type heaters, but under the right conditions, such as a warm climate, will have a fairly rapid payback.
Here is more information about water heaters:
Hybrid Water Heaters - Heat Pump Type
Hybrid Water Heaters - Tankless / Storage Type
Tankless Water Heaters - Tankless Water Heaters
General Water Heater Information - All About Water Heaters
Rheem - Hybrid Water Heater
GeoSpring - GE Hybrid Water Heater
A.O. Smith - Voltex Hybrid Heat Pump
A.O. Smith - Hybrid NEXT Tankless Heater
A heat pump water heater works just like those awful air conditioners in motel rooms. Instead of blowing air through a heat exchanger to warm or cool it, the heat pump water heater runs the water through the heat exchanger to heat it.
Heat pump water heaters are probably the most efficient way of heating water in the right circumstances. Heat pumps work better when there is actually heat to pump. When the air is warm there is plenty of heat for the heat pump to pull out of the air and the heat pump is efficient.
As the air temperature decreases there is less heat to capture from the air the heat pump will have to work harder, and will become less efficient.
When you get down to around 40 degrees Fahrenheit there isn’t enough heat in the air for the heat pump to work so you will have to rely on the electric resistance elements to heat the water. At that point you might as well have a standard electric water heater.
Obviously your climate will have a large influence on the desirability of a heat pump water heater. They would be great for Arizona, not so great for Alaska.
Some of the drawbacks to a heat pump water heater are the inability to work well at cold ambient temperatures’ as we have just discussed, they are slower than molasses at heating the water, they can’t heat the water quite as hot as a standard electric, they have more parts and are more expensive to repair than a standard electric water heater.
Heat pump water heaters require plenty of air flow, so you can’t put them in a closet or small storage room. Heat pump water heaters require cleaning of the air filter, some manufactures recommend at least once a year and others suggest monthly.
A clogged or dirty air cleaner will cause the heat pump to work less efficiently and in some cases will shut off the heat pump until the filter is cleaned. During that period it will be in electric heating element only mode and will cost considerably more to run.
Heat pump water heating technology has been around for a long time and is very reliable. You won’t find very many unhappy owners of heat pump water heaters on the internet and in the forums as you do with tankless water heater owners.
With heat pump water heaters the larger the tank the better. Since the heating elements are typically only called on to supply heat when the hot water demand has nearly depleted the hot water in the storage tank, the larger the tank the less often the heating elements will be used and the more heat pump use occurs.
If you live in a warm climate like Florida, and you live in an all electric neighborhood and don’t have access to natural or propane gas, then a heat pump water heater is a viable option for you. A heat pump water heater can cut your water heating bill roughly in half saving you hundreds of dollars a year.
Heat pump hybrid water heaters cost more than standard tank type heaters, but under the right conditions, such as a warm climate, will have a fairly rapid payback.
Here is more information about water heaters:
Hybrid Water Heaters - Heat Pump Type
Hybrid Water Heaters - Tankless / Storage Type
Tankless Water Heaters - Tankless Water Heaters
General Water Heater Information - All About Water Heaters
Rheem - Hybrid Water Heater
GeoSpring - GE Hybrid Water Heater
A.O. Smith - Voltex Hybrid Heat Pump
A.O. Smith - Hybrid NEXT Tankless Heater
Monday, August 9, 2010
The Best Tankless Water Heater
Which is the best tankless water heater will depend on who is purchasing it and for what application. The best tankless water heater for your cabin in the mountains’ will not be the best one for your 4,500 square foot home in Florida. It may be a different model for the same home in Colorado.
For some people the best tankless hot water heater will be the one that saves the most energy, or the one with the least maintenance, or even the one that is the least expensive. For others, the ability for the tankless heater to work with a hot water circulating system, or the ability to deliver very low flow rates would be the best tankless water heater.
If you are looking for a point-of-use water heater you will have an entirely different set of critera than if you are in need of a whole-house unit.
Some tankless water heaters are designed for mounting indoors, and some are designed for mounting outdoors on an external wall. The outdoor units usually come with an internal heater to protect against freezing… very important in many areas. If your heat exchanger becomes damaged due to freezing temperatures, the warranty will not cover it.
First, be certain you are better off with a tankless unit than a standard storage heater. There is little similarity between tankless and storage type heaters. About the only thing they have in common is they consume similar fuels and produce hot water.
Energy Savings
I suspect that one of the big reasons people convert from tank type heaters to tankless heaters are to be green and reduce their energy bills while reducing their carbon footprint. Further I would think that the primary reason to save energy is to save money. Let’s take a look at the savings from a tankless heater over a conventional tank type heater.
Tankless water heaters are said to be more energy efficient than standard tank type water heaters primarily because they do not have standby losses. You can figure out a ball park figure for standby losses from heat leaking out of the tank full of water with the following formula:
H = A (T1-T2)/R
H = Heat loss in Btu/hr
A = Surface area in square feet
T1 = Hot water temperature in Degrees Fahrenheit
T2 = Air temperature in Degrees Fahrenheit
R = R-value of the insulation in ft2hrF/btu
My assumptions:
Tank dimensions: 60 inches tall by 22 inches in diameter.
Area = 36.5 square feet.
R value = 16
Hot water temperature = 140 degrees
Ambient Air temperature around heater – 55 degrees average over a year
H = 36.5 * (140 – 55)/16 =194 Btu/hour
Btu/month = 194*24*30 = 139,680 Btu = 1.39 Therms per month
Assuming $0.60 per therm your standby heat loss from the tank will cost you about 83 cents a month.
Although the standby losses are a little higher for colder climates, standby losses will never add up to a huge amount of money. You might be better off buying a high efficiency tank type water heater.
Endless Hot Water
It would seem to me that the next most common reason for going tankless would be for the endless hot water. In my opinion this would be the most realistic reason for switching to tankless. Running out of hot water is a real pain in the shower.
As long as you choose a tankless heater that is big enough for your needs you will get your unlimited amount of hot water no matter which brand you choose. There isn’t one tankless brand that stands out above the rest as far as I can see.
To learn more about proper sizing of a tankless hot water heater: Sizing a tankless water heater
Here is an article where I compare Navien, Rinnai, Takagi, and Nortiz brand tankless water heaters. Compare Tankless Water Heaters.
Reliability
For some people the best tankless water heater is the one that is the most reliable. Tankless water heaters are highly complex machines, unlike their tank type cousins. They monitor things like inlet water temperature and flow, outlet temperature, exhaust temperature, and gas pressure and flow. They have one or more onboard computers to makes sense of all the data streaming in from the sensors and control the burners and some models even control the flow of water through the unit.
Needless to say there are a lot more things to go wrong. The most important thing to consider when choosing a tankless heater for your home is the installation. Improper installation is the most common cause for tankless water heater problems.
An improperly installed heater can wait years before the problems show up. The heater may work fine with small draws, but when a large draw is required suddenly there is a problem. If the heater requires the condensate from the flue to be drained, and the installation isn’t done right, the condensate can drip on the heat exchanger and after a couple of years suddenly the heat exchanger goes out due to corrosion from the condensate. This will not be covered by your warranty.
More about tankless water heater installation: Tankless Water Heater Installation
My advice is to find a local plumbing company that will stand behind their water heaters, have professional factory trained installers, and can refer you to some happy customers. Get the right size unit from the right local supplier and you will have found the best tankless water heater for your needs.
For some people the best tankless hot water heater will be the one that saves the most energy, or the one with the least maintenance, or even the one that is the least expensive. For others, the ability for the tankless heater to work with a hot water circulating system, or the ability to deliver very low flow rates would be the best tankless water heater.
If you are looking for a point-of-use water heater you will have an entirely different set of critera than if you are in need of a whole-house unit.
Some tankless water heaters are designed for mounting indoors, and some are designed for mounting outdoors on an external wall. The outdoor units usually come with an internal heater to protect against freezing… very important in many areas. If your heat exchanger becomes damaged due to freezing temperatures, the warranty will not cover it.
First, be certain you are better off with a tankless unit than a standard storage heater. There is little similarity between tankless and storage type heaters. About the only thing they have in common is they consume similar fuels and produce hot water.
Energy Savings
I suspect that one of the big reasons people convert from tank type heaters to tankless heaters are to be green and reduce their energy bills while reducing their carbon footprint. Further I would think that the primary reason to save energy is to save money. Let’s take a look at the savings from a tankless heater over a conventional tank type heater.
Tankless water heaters are said to be more energy efficient than standard tank type water heaters primarily because they do not have standby losses. You can figure out a ball park figure for standby losses from heat leaking out of the tank full of water with the following formula:
H = A (T1-T2)/R
H = Heat loss in Btu/hr
A = Surface area in square feet
T1 = Hot water temperature in Degrees Fahrenheit
T2 = Air temperature in Degrees Fahrenheit
R = R-value of the insulation in ft2hrF/btu
My assumptions:
Tank dimensions: 60 inches tall by 22 inches in diameter.
Area = 36.5 square feet.
R value = 16
Hot water temperature = 140 degrees
Ambient Air temperature around heater – 55 degrees average over a year
H = 36.5 * (140 – 55)/16 =194 Btu/hour
Btu/month = 194*24*30 = 139,680 Btu = 1.39 Therms per month
Assuming $0.60 per therm your standby heat loss from the tank will cost you about 83 cents a month.
Although the standby losses are a little higher for colder climates, standby losses will never add up to a huge amount of money. You might be better off buying a high efficiency tank type water heater.
Endless Hot Water
It would seem to me that the next most common reason for going tankless would be for the endless hot water. In my opinion this would be the most realistic reason for switching to tankless. Running out of hot water is a real pain in the shower.
As long as you choose a tankless heater that is big enough for your needs you will get your unlimited amount of hot water no matter which brand you choose. There isn’t one tankless brand that stands out above the rest as far as I can see.
To learn more about proper sizing of a tankless hot water heater: Sizing a tankless water heater
Here is an article where I compare Navien, Rinnai, Takagi, and Nortiz brand tankless water heaters. Compare Tankless Water Heaters.
Reliability
For some people the best tankless water heater is the one that is the most reliable. Tankless water heaters are highly complex machines, unlike their tank type cousins. They monitor things like inlet water temperature and flow, outlet temperature, exhaust temperature, and gas pressure and flow. They have one or more onboard computers to makes sense of all the data streaming in from the sensors and control the burners and some models even control the flow of water through the unit.
Needless to say there are a lot more things to go wrong. The most important thing to consider when choosing a tankless heater for your home is the installation. Improper installation is the most common cause for tankless water heater problems.
An improperly installed heater can wait years before the problems show up. The heater may work fine with small draws, but when a large draw is required suddenly there is a problem. If the heater requires the condensate from the flue to be drained, and the installation isn’t done right, the condensate can drip on the heat exchanger and after a couple of years suddenly the heat exchanger goes out due to corrosion from the condensate. This will not be covered by your warranty.
More about tankless water heater installation: Tankless Water Heater Installation
My advice is to find a local plumbing company that will stand behind their water heaters, have professional factory trained installers, and can refer you to some happy customers. Get the right size unit from the right local supplier and you will have found the best tankless water heater for your needs.
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