Tankless water heaters are all the rage now. Green is in and tankless heaters are considered greener than storage water heaters. They don't have standby losses and so are typically more energy efficient than tank type units.
Tankless Water Heater Savings
The dollar amount of tankless water heater savings is realatively small, and makes the payback iffy over the lifetime of the heater. Tax rebates are substantial though, and with the rebates many more home owners can expect to save enough money to more than pay for the unit. That is if there are no breakdowns.
Tankless units are more complex than storage heaters, and thus are more likely to breakdown and more expensive to repair. A service call or two can wipe out any savings realized by reduced standby losses.
Water Conservation and Saving Water
Tankless water heaters are not water conservation friendly. It takes them up to 20 seconds longer to deliver hot water since they must first heat the water and then deliver it to the fixture. A study done by the Australian government found that tankless water heaters typically take 10 to 20 seconds longer to deliver hot water than a storage type heater.
While you purge the cooled off hot water from the hot water pipes, you are running water down the drain. The longer the wait, the more water gets run down the drain.
Since tankless units require a minimum flow rate the keep the heater turned on of typically 1/2 gallon per minute to 3/4 gallons per minute, you will have to run the hot water at a higher flow than you might normally run it, and mix it with additonal cold water to get the temperature where you want it. A trickle of warm water will no longer be an option.
So for those people who for one reason or another run a small stream of warm water will have to make do with a much larger stream of warm water, again, wasting water.
Tankless water heaters are marketed with slogans like "endless hot water". Does this sound like a water conservation product? You don't buy a tankless water heater for saving water.
Tankless Water Heaters Need More Love... or At Least More Attention
Because tankless heaters are limited in the gallons per minute that they can heat to a specified temperature, one must consider the inlet temperature when deciding on a size. Too small, and the heater will not be able to meat your peak load demands and the temperature at the fixture will decrease as the flow rate is turned up at the faucet.
Too large of a model, and it will be difficult to adjust the temperature without the heater shutting off. And if you live where the water temperature varies widely from summer to winter, then you may have to change the outlet temperature setting on the heater as the seasons change.
Most gas tankless water heaters need to be plugged into a 110v outlet to power the electronics need to control the unit. Some units use the flowing water to spin a tiny generator powering the controls. Bosch water heaters have such a feature. So most units won't be able to supply hot water during a power outage.
I have seen a lot of chatter in forums about the need to clean the Bosch units frequently due to that tiny generator...
If you live where temperatures go below freezing you will have a new worry... damaging the heat exchanger. With a storage water heater freezing isn't going to happen. With a tankless unit you have to protect it from freezing as freezing will destroy the heat exchanger.
Some units come with a little built in heater for freeze protection... so much for eliminating standby losses...
Recirc Pumps and Hot Water Demand Systems
Most tankless water heaters will not work with a traditional hot water recirc pump. Read the warranty. Even so, most circulating pumps won't pump enough water through the heater to turn it on anyway.
Hot water demand systems are on the other hand ideal for tankless applications. They don't circulate the hot water, they get your hot water to the fixture without running water down the drain, and they can often get your hot water to the fixture more quickly.
However, most hot water demand systems still suffer from the "tiny motor" syndrome. Hot water circulating pumps typically range in horsepower from about 1/120 to 1/8 horsepower with around 1/40 kind of typical. Our competitors such as Act Metlund which makes several models, the S-50T, the S-70T, and the S-02T. The S-50T is not recommended for tankless systems, and the S-70T for systems with less than 100 feet of pipe. Compare the CP6000 with the Metlund D'mand System. Metlund VS Chilipepper
Our pump, the Chilipepper CP6000 with it's big 1/3 horsepower motor will run any tankless water heater on the market.
All brands including Rinnai, Takagi, Noritz, and Bosch work better when you combine them with a hot water demand system. See a comparison of the various models from the above brands. Compare Tankless Water Heaters
Point of Use Water Heaters
The most water and energy efficient plumbing layout is to have the heater a close as possible to the end use fixture. This can virually eliminate the wasted water, and eleminates the need for a pump. Often it is an ideal application for a small electric tankless water heater.
Tankless water heaters can provide you with "endless hot water" and can save you money, but there are other considerations, so choose carefully...
Bill the Hot Water Guy
Monday, August 31, 2009
Saturday, August 29, 2009
Slow Hot Water
Today I would like to explore the topic of "Slow Hot Water".
First lets get something straight... there is no such thing as "Instant hot water" if you are referring to heating it! Even though you occasionally hear the terms "Instant water heater", when referring to tankless water heaters, technically there is no such thing. It takes time to heat water. More on that later.(maybe even my next blog actually)
Lets define what we mean by "Slow Hot Water". For our purposes slow hot water will refer to the speed at which hot water is delivered to the fixture where you are trying to obtain it, from the time you turn on the faucet.
For some of you the there is no wait... if you have a hot water recirculating pump or system for instance. A recirc pump that keeps the hot water pipe full of hot water eliminating slow hot water from your vocabulary. It's nice but expensive.
Some people will have a short wait... say less than 30 seconds, although if you are waiting for hot water 30 seconds can seem like 30 minutes, all the while running precious drinking water down the drain. Some people will have a moderate wait... say more than 30 seconds and less than 1 minute. An many have a long wait...over 1 minute. Running water down the drain for one minute will result in a waste of between 1 and 3 gallons or more, depending on the fixture flow rate.
Many of our customers have described waits of over 5 minutes! Wow. That is slow hot water!
What are the causes of slow hot water?
The first thing one thinks of is the distance from the water heater to the fixture. That can give you a rough idea, but can be very inaccurate. There are a number of reasons that the straight-line distance from your water heater to your hot water fixture is inaccurate.
Plumbing Layouts
Your actual plumbing layout plays a major role of course in the speed at which you get your hot water. The actual pipe length will depend on whether your plumbing is located in an Attic, under a crawl space, in the walls, or under a slab.
Another factor is what type of piping material is used, soft copper, hard copper, galvanized pipe, or plastic pipe? Since some of the hot water cools off from contact with the pipe as it travels to the fixture, the pipe material and weight are important variables as well in how long it takes.
Your plumbing layout quite possibly does not follow a straight line route. Most copper and galvanized pipe residential plumbing systems follow the joists and beams and make sharp right angles to get from point A to point B.
With these things in mind lets take a look at the plumbing layout for a house with the piping primarily in the crawl space. The water heater is a gas model on a stand 24" off the floor of the garage. The pipe will begin as 3/4 inch diameter hard copper pipe, and transition to smaller branch lines of 1/2 inch dia.
The pipe would exit the top of the water heater, using right angle elbows it would extend up a foot or so, and run down the side of the heater and into the crawl space below the floor. By this time you have already used 6 to 8 feet of pipe and you haven't yet started the journey to the fixture. That journey can consist of a variety of changes in direction through the use of elbows and T fittings, and the pipe diameter can be reduced to the 1/2 inch dia. for branch runs from the major hot water feed to the individual fixtures.
The diameter of the pipe is chosen to provide the minimum flow rates for the various fixtures. The flow rate is different for different types of uses. For instance, a kitchen sink fixture requires a higher flow rate than a bathroom faucet, but not as much as a bathtub fixture.
By not using a plumbing layout with a straight run from the heater to the fixture, 15 or twenty extra feet can be added to the run if it traverses several rooms. So the pipe length may very well be substantially longer than is at first apparent. Every fitting also adds to the virtual length of the pipe. (Elbows and direction changes cause a larger pressure drop than straight pipe.)
Pipe Material and Pipe Insulation and Hot Water Tunneling
As the heated water flows through the pipe, it gives up some of its heat to the pipe material. As much as 50% of the wait time is caused by the hot water being cooled off by the cold pipe as it travels through the plumbing. To make things even more interesting, the actual speed of the water through the pipe affects how much heat gets transferred. When the water is traveling at higher velocities it gives up less than the expected amount of heat because most of the HOT water is traveling through a small channel through the not-flowing cooled off hot water in the pipe.
The hot water "tunnels" through the center. With slower flows the water moves more like a bullet nosed column of hot water pushing the cooled off hot water out ahead of it. Therefore, speeding up the hot water flow rate results in a even faster than expected arrival of hot water due to the tunneling effect.
Other interesting observations are that some plastic piping such as PEX can lose more heat than copper or galvanized pipe to the ambient air space around it; another unexpected result. Insulating the pipe reduces the heat loss from the pipe and as expected this time, can reduce the wait time for that slow hot water.
Pumping the same number of gallons per minute through a smaller diameter pipe causes an increase in the velocity of the water and a shorter wait time. However, since smaller pipes have larger pressure drops, an undersized pump motor could cause an actual increase in wait time if a pumping system is being used.
Saving Water with Low Flow Fixtures or Not!
Saving water is always a priority these days, but low flow fixtures can cause a huge waste of water. Many people have fixtures with flows of down to 1 gallon per minute. With flow rates that low, the water travels in the "bullet" mode and takes longer to reach the fixture, causing more water to be run down the drain.
Electric Tankless Water Heaters (and gas)
Tankless water heaters, especially the electric tankless units, take time to heat water. They are not instant. For the water to reach full temperature it must travel completely through the heat exchanger which takes time. An Australian government study stated that tankless water heaters typically took 10 to 20 seconds longer to get hot water to the fixtures than tank type storage water heaters.
Obviously adding 10 to 20 seconds to the wait time does not help the slow hot water problem.
So there you have it, a fairly comprehensive discussion of why the hot water is slow. You know what to do about it, get a Chilipepper pump of course. A must have accessory for any water heater storage or tankless, electric or gas, or even solar, oil burner, wood burner or other heater as well! Yes, even heat pump water heaters!
Until my next blog... Bill the Hot Water Guy
First lets get something straight... there is no such thing as "Instant hot water" if you are referring to heating it! Even though you occasionally hear the terms "Instant water heater", when referring to tankless water heaters, technically there is no such thing. It takes time to heat water. More on that later.(maybe even my next blog actually)
Lets define what we mean by "Slow Hot Water". For our purposes slow hot water will refer to the speed at which hot water is delivered to the fixture where you are trying to obtain it, from the time you turn on the faucet.
For some of you the there is no wait... if you have a hot water recirculating pump or system for instance. A recirc pump that keeps the hot water pipe full of hot water eliminating slow hot water from your vocabulary. It's nice but expensive.
Some people will have a short wait... say less than 30 seconds, although if you are waiting for hot water 30 seconds can seem like 30 minutes, all the while running precious drinking water down the drain. Some people will have a moderate wait... say more than 30 seconds and less than 1 minute. An many have a long wait...over 1 minute. Running water down the drain for one minute will result in a waste of between 1 and 3 gallons or more, depending on the fixture flow rate.
Many of our customers have described waits of over 5 minutes! Wow. That is slow hot water!
What are the causes of slow hot water?
The first thing one thinks of is the distance from the water heater to the fixture. That can give you a rough idea, but can be very inaccurate. There are a number of reasons that the straight-line distance from your water heater to your hot water fixture is inaccurate.
Plumbing Layouts
Your actual plumbing layout plays a major role of course in the speed at which you get your hot water. The actual pipe length will depend on whether your plumbing is located in an Attic, under a crawl space, in the walls, or under a slab.
Another factor is what type of piping material is used, soft copper, hard copper, galvanized pipe, or plastic pipe? Since some of the hot water cools off from contact with the pipe as it travels to the fixture, the pipe material and weight are important variables as well in how long it takes.
Your plumbing layout quite possibly does not follow a straight line route. Most copper and galvanized pipe residential plumbing systems follow the joists and beams and make sharp right angles to get from point A to point B.
With these things in mind lets take a look at the plumbing layout for a house with the piping primarily in the crawl space. The water heater is a gas model on a stand 24" off the floor of the garage. The pipe will begin as 3/4 inch diameter hard copper pipe, and transition to smaller branch lines of 1/2 inch dia.
The pipe would exit the top of the water heater, using right angle elbows it would extend up a foot or so, and run down the side of the heater and into the crawl space below the floor. By this time you have already used 6 to 8 feet of pipe and you haven't yet started the journey to the fixture. That journey can consist of a variety of changes in direction through the use of elbows and T fittings, and the pipe diameter can be reduced to the 1/2 inch dia. for branch runs from the major hot water feed to the individual fixtures.
The diameter of the pipe is chosen to provide the minimum flow rates for the various fixtures. The flow rate is different for different types of uses. For instance, a kitchen sink fixture requires a higher flow rate than a bathroom faucet, but not as much as a bathtub fixture.
By not using a plumbing layout with a straight run from the heater to the fixture, 15 or twenty extra feet can be added to the run if it traverses several rooms. So the pipe length may very well be substantially longer than is at first apparent. Every fitting also adds to the virtual length of the pipe. (Elbows and direction changes cause a larger pressure drop than straight pipe.)
Pipe Material and Pipe Insulation and Hot Water Tunneling
As the heated water flows through the pipe, it gives up some of its heat to the pipe material. As much as 50% of the wait time is caused by the hot water being cooled off by the cold pipe as it travels through the plumbing. To make things even more interesting, the actual speed of the water through the pipe affects how much heat gets transferred. When the water is traveling at higher velocities it gives up less than the expected amount of heat because most of the HOT water is traveling through a small channel through the not-flowing cooled off hot water in the pipe.
The hot water "tunnels" through the center. With slower flows the water moves more like a bullet nosed column of hot water pushing the cooled off hot water out ahead of it. Therefore, speeding up the hot water flow rate results in a even faster than expected arrival of hot water due to the tunneling effect.
Other interesting observations are that some plastic piping such as PEX can lose more heat than copper or galvanized pipe to the ambient air space around it; another unexpected result. Insulating the pipe reduces the heat loss from the pipe and as expected this time, can reduce the wait time for that slow hot water.
Pumping the same number of gallons per minute through a smaller diameter pipe causes an increase in the velocity of the water and a shorter wait time. However, since smaller pipes have larger pressure drops, an undersized pump motor could cause an actual increase in wait time if a pumping system is being used.
Saving Water with Low Flow Fixtures or Not!
Saving water is always a priority these days, but low flow fixtures can cause a huge waste of water. Many people have fixtures with flows of down to 1 gallon per minute. With flow rates that low, the water travels in the "bullet" mode and takes longer to reach the fixture, causing more water to be run down the drain.
Electric Tankless Water Heaters (and gas)
Tankless water heaters, especially the electric tankless units, take time to heat water. They are not instant. For the water to reach full temperature it must travel completely through the heat exchanger which takes time. An Australian government study stated that tankless water heaters typically took 10 to 20 seconds longer to get hot water to the fixtures than tank type storage water heaters.
Obviously adding 10 to 20 seconds to the wait time does not help the slow hot water problem.
So there you have it, a fairly comprehensive discussion of why the hot water is slow. You know what to do about it, get a Chilipepper pump of course. A must have accessory for any water heater storage or tankless, electric or gas, or even solar, oil burner, wood burner or other heater as well! Yes, even heat pump water heaters!
Until my next blog... Bill the Hot Water Guy
Friday, August 28, 2009
All About Hot Water
Ok, this is my first official blog. I was hesitant to start a blog since I wasn't sure I could come up with something to blog about often enough to make it worthwhile, but I figured out what I could do if my brain was too slow.
Publish some of the more interesting emails we get from potential customers, and my response to them. We get all kinds of emails from people who don't understand one thing or another, and I have to assume a lot of them don't read either. If they did they would have found the information they were looking for right on the front page in many cases. LOL Go figure.
Hot water... the last frontier.
In a way hot water is like the final frontier. It seems like every other way to conserve energy and water has been covered many times over. Low flow everything from toilets to shower heads and high efficiencty appliances like dishwashers and washing machine are now common place.
Now maybe it's time to address the enourmous amount of wasted water and energy that could be saved from our hot water plumbing distribution systems. Todays large homes tend to have long and large diameter hot water piping which leads to a great deal of water being run down the drain, and heat energy slowly disspating from the pipes full of hot water sitting there cooling off.
Conservatively a demand hot water pump like the Chilipepper can save a typical family of four over 10,000 gallons of water per year. With over 50 million single family homes in the United States, if everyone had one of these systems we would save over 500,000,000,000 gallons of water per year. That doesn't count condos apartments and commercial uses if applicable.
It's very inexpensive and typically will pay for itself in a couple of years. In addition, the home owner gets his hot water faster which is always nice.
The demand pumps are easy to install and use very little electricity, usually less than $2.00 per year to operate. These systems even work with tankless water heaters, which is good since tankless water heaters take 10 to 20 seconds longer to get hot water to the fixture which means running more water down the drain.
Well, I think thats about it for my first blog post...
Bill the Hot Water Guy
Publish some of the more interesting emails we get from potential customers, and my response to them. We get all kinds of emails from people who don't understand one thing or another, and I have to assume a lot of them don't read either. If they did they would have found the information they were looking for right on the front page in many cases. LOL Go figure.
Hot water... the last frontier.
In a way hot water is like the final frontier. It seems like every other way to conserve energy and water has been covered many times over. Low flow everything from toilets to shower heads and high efficiencty appliances like dishwashers and washing machine are now common place.
Now maybe it's time to address the enourmous amount of wasted water and energy that could be saved from our hot water plumbing distribution systems. Todays large homes tend to have long and large diameter hot water piping which leads to a great deal of water being run down the drain, and heat energy slowly disspating from the pipes full of hot water sitting there cooling off.
Conservatively a demand hot water pump like the Chilipepper can save a typical family of four over 10,000 gallons of water per year. With over 50 million single family homes in the United States, if everyone had one of these systems we would save over 500,000,000,000 gallons of water per year. That doesn't count condos apartments and commercial uses if applicable.
It's very inexpensive and typically will pay for itself in a couple of years. In addition, the home owner gets his hot water faster which is always nice.
The demand pumps are easy to install and use very little electricity, usually less than $2.00 per year to operate. These systems even work with tankless water heaters, which is good since tankless water heaters take 10 to 20 seconds longer to get hot water to the fixture which means running more water down the drain.
Well, I think thats about it for my first blog post...
Bill the Hot Water Guy
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