Automated Recirculating Hot Water System

[drozwood90]

Wow...old thread!

I was looking through, the last time I wrote, I was i a different house!

I agree with Rick, there is not a one size fits all solution. It sounds like Rick has a same level of tankless units that I had (where they could talk to each other).

Nice aren't they?

Well, I liked the one I had in my last house...too bad the builder wouldn't let me put one in this house (track...so he didn't want to confuse the installers...?? WHAT?).

Oh well...it's fine, eventually we'll put another tankless unit in...and I'll turn the existing tank into a pre-heat tank for the solar that I plan to put in.

--Dan

 

[felixrosbergen]

I am an engineer (civil / structural, but still) and i still can't visualize how a hot water circulator works when not using a dedicated return and using the cold water line instead?

I've also heard of little electric units that mount under the sink that suck a lot of power but pretty much instantly heat the cold or lukewarm water in the hot water pipe and they then switch off when the hot water from the main tank/tankless reaches them. This seems rather elegant to me but apparently needs a good sized electrical circuit.

My main gripe is my kitchen where we need 20 seconds of hot water every once in a while and it take a long time to get warm. For the shower i don't care too much since you can turn it on and then undress or whatever and there is also significant use them so the relative losses are less. For the kitchen i end up waiting longer for the hot water to arrive then i actually use the hot.

Like i said i heard about these electric units, but haven't seen one. Anybody know what i'm talking about and have a link of some kind? Since the sink is above my unfished basement and close to the electrical distribution panel it wouldnt be a terrible ordeal to get a circuit put in. I have a spare circuit for a disposal but not sure if that sufficeint size.

 

[amirm]

I am an engineer (civil / structural, but still) and i still can't visualize how a hot water circulator works when not using a dedicated return and using the cold water line instead?

I am also and engineer and have the same issue . But work they do. We have one top of our hot water heater and it makes a huge difference on how long it takes for the water to get hot at the top. So much so that I was getting beat up hourly when ours broke and had to get it fixed. They do inject some hot water into cold pipes though so your cold water is not really cold unless you let it run for quite a while. We think this is a bonus as you don't freeze your hand in cold water in winter.

FYI, these things can damage your pipes if they get air in them. Ours did, and proceeded to create a pin hole in our copper pipe which took some time to figure out.

In our second house, we are putting two hot water tanks instead of a single larger one. We had this before and it eliminates the need for the above pumps which can waste a lot of energy as they recirculate the hot water in the uninsulated pipes in your house.

Like i said i heard about these electric units, but haven't seen one. Anybody know what i'm talking about and have a link of some kind? Since the sink is above my unfished basement and close to the electrical distribution panel it wouldnt be a terrible ordeal to get a circuit put in. I have a spare circuit for a disposal but not sure if that sufficeint size.

We had a house before where they had installed a tiny electric water heater under the sink. It worked pretty well but I don't recall the brand.

 

[JimS]

The circulators that use the cold water line for the return pull hot water from the heater tank and force it back the cold water line and into the tank. That is the total loop. They shut off when the water at the faucet gets to a given temperature or after a given time so the cold water line gets somewhat warm. The pump doesn't need to be very big. Although the whole system is at pressure the only DIFFERENCE in pressure across the pump is due to the flow it generates and the flow rate (and thus the pressure) doesn't have to be that high. I would guess they use a spring check valve to prevent the hot and cold from mixing when the pump isn't running. I see no reason why they would need a large electric circuit. The Chili Pepper is one example and several others have been named I believe. Google is your friend...

Here is an explanation of how it works:
http://www.chilipepperapp.com/howit.htm

They also claim a typical current of 2.5A - pretty low. I am not plugging this model - just using it as an example. I just bought a small circulation pump, a check valve, and made my own timer control. Different manufactures have slightly different control methods.

 

[dougmeredith]

FYI, these things can damage your pipes if they get air in them. Ours did, and proceeded to create a pin hole in our copper pipe which took some time to figure out.

I've never seen this said before. How would this system introduce air into your pipes? Why would the air cause a hole in a copper pipe?

In our second house, we are putting two hot water tanks instead of a single larger one. We had this before and it eliminates the need for the above pumps which can waste a lot of energy as they recirculate the hot water in the uninsulated pipes in your house.

How do the two tanks eliminate the need for the hot water recirculation system? Is it because you put the tanks in different locations so that they are closer to where the hot water is needed?

Doug

 

[Steve]

Like i said i heard about these electric units, but haven't seen one. Anybody know what i'm talking about and have a link of some kind? Since the sink is above my unfished basement and close to the electrical distribution panel it wouldnt be a terrible ordeal to get a circuit put in. I have a spare circuit for a disposal but not sure if that sufficeint size.

We had a house before where they had installed a tiny electric water heater under the sink. It worked pretty well but I don't recall the brand.

That actually sounds more like you are talking about a small tankless unit. Yes, the tankless units do draw quite a bit of power. I had looked at them and pretty much given up on an electric tankless. A small 2 gallon point of use water heater was another option. But with that I saw a question posed that had no answer. Even with a small POU water heater, you would have that 'instant' hot water, but what happens when that 2 gallons is depleted? Even though the tank is fed from hot water you still have x gallons of cold water from the pipes coming through so it sounds like there will be some mixing and hence temperature variation going on there. I pretty much surmised that the recirc would work best.

The circulators that use the cold water line for the return pull hot water from the heater tank and force it back the cold water line and into the tank. That is the total loop. They shut off when the water at the faucet gets to a given temperature or after a given time so the cold water line gets somewhat warm. The pump doesn't need to be very big. Although the whole system is at pressure the only DIFFERENCE in pressure across the pump is due to the flow it generates and the flow rate (and thus the pressure) doesn't have to be that high. I would guess they use a spring check valve to prevent the hot and cold from mixing when the pump isn't running. I see no reason why they would need a large electric circuit. The Chili Pepper is one example and several others have been named I believe. Google is your friend...

Here is an explanation of how it works:
http://www.chilipepperapp.com/howit.htm

They also claim a typical current of 2.5A - pretty low. I am not plugging this model - just using it as an example. I just bought a small circulation pump, a check valve, and made my own timer control. Different manufactures have slightly different control methods.

Yes, they all have a bypass valve under the sink that that pulls hot water from the tank, thus drawing away the non-hot water and it pushes it into the cold pipe where it gets forced back into the water heater. The advantages from what I have learned, is besides the benefit of the instant hot water (after the flushing) is that you don't waste any of the water down the drain. With a typical fixture of 2.5GPM you are wasting 2.5 gallons of water for every minute it takes to get hot. Multiply that by how long it takes and how many times per day its done and it could add up to alot of wasted water. Besides the 'green' effect I also heard it effectively turns a standard tank into a self-cleaning tank. This is because the cold water is forced in and stirs up sediment at the bottom much like a self cleaning tank would do.

But for me, its mostly about the convenience in the shower. Sure, you develop habits like mentioned above to work around how long it takes, but I prefer to have it hot within a few seconds. So, it seems there are 2 types of circulators (besides the dedicated line ones). You have ones like the Grundfos and Laing which sit on the heater tank and push hot water through the system while you put bypass valves at the sink(s) you want. You can have multiple bypass valves in case your plumbing is not daisy chained. The other type uses a smaller pump and valve that you put in at the location you want the instant hot (best at the end of a daisy chained line). These pull the water through. Chilipepper, Metlund and Redy Temp are examples of this type. The Chilipepper has a bunch of negative reviews so I am personally focused on the Metlund or Redy Temp systems. I would hook them up to a relay on the Elk in addition to a push button. That way I can run them via rules (like for a minute or so at certain standard times of the day when use is likely) as well as have the button if use out of band is needed. The Metlund unit has a fixed temp sensor and goes until the water temp is 6-8 degress above the baseline (sitting temp). They claim that keeps hot water out of the cold line and that the real hot stuff is only a second or so away. The Redy Temp uses a user adjustable temp sensor so you set the temp you want it to shut off at. I guess a disadvantage of that is if the thing is set to high you can get alot of hot in the cold line.

At this point I think I am leaning toward the Metlund D'Mand system over the RedyTemp but I would still love to hear from people that have either of these units installed.

 

[ano]

The circulators that use the cold water line for the return pull hot water from the heater tank and force it back the cold water line and into the tank. That is the total loop. They shut off when the water at the faucet gets to a given temperature or after a given time so the cold water line gets somewhat warm. The pump doesn't need to be very big. Although the whole system is at pressure the only DIFFERENCE in pressure across the pump is due to the flow it generates and the flow rate (and thus the pressure) doesn't have to be that high. I would guess they use a spring check valve to prevent the hot and cold from mixing when the pump isn't running. I see no reason why they would need a large electric circuit. The Chili Pepper is one example and several others have been named I believe. Google is your friend...

Here is an explanation of how it works:
http://www.chilipepperapp.com/howit.htm

So, it seems there are 2 types of circulators (besides the dedicated line ones). You have ones like the Grundfos and Laing which sit on the heater tank and push hot water through the system while you put bypass valves at the sink(s) you want. You can have multiple bypass valves in case your plumbing is not daisy chained. The other type uses a smaller pump and valve that you put in at the location you want the instant hot (best at the end of a daisy chained line). These pull the water through. Chilipepper, Metlund and Redy Temp are examples of this type.

Yup, there are three types. The ones with a pump at the HW tank, the ones with a pump at the faucet, and the ones with return piping to the water heater.

I have had two of the three.

1) A Chilipepper has a pump under the sink or around the location you want hot water at. you push a button and it pumps water from the hot side into the cold side until the water get hot, then it stops. Its very energy efficient because it just runs a short time, BUT you need power under the sink to run it, and you basically need one at every sink you want hot water at. I hear they are more popular in Europe. To me, they are very limited, unless there is really just one sink or location you really want hot water at.

2) The second solution I'm presently using. A pump (Watts in my case) is installed at the hot water heater on the hot side and it pressures that side compared with the cold. You them must install these valves between the hot and cold at strategic locations. The valves open when the water is cold, and close when the water is warm (not hot). The pump, when running forces the hot water down the pipe into the cold water line. When the water gets warm, the valves close so more hot water doesn't go into the cold line.

These are O.K., but 1) the water starts warm and still takes some time to get hot, 2) some warm water goes into the cold line, 3) and when the pump is running, there is some energy waste because your warming water to a faucet you might not use, and 4) it may take many valves to cover all the faucets in the house. I use an automation system to turn on and off the pump. Its on when I'm likely to need hot water, off otherwise.

3) There is a third method which works best of any type, but also uses the most energy. Run a return pipe from the furthest hot water faucet back to the water heater and connect it to a drain at the bottom. Then install a pump anywhere in the return line.

So the pump, forms a loop that pumps the water from the hot water line, back to the base of the HW heater. (This is how hotels do it, by the way.) The water is always hot, and the cold water is still cold. BUT it wastes the most energy because you are keeping that loop hot. Insulating the pipes helps. There is also extra pipe wear from the constantly flowing water, but you can automate it to reduce this wear and reduce energy use.

So, there you go, no ideal system. #1 doesn't waste much energy, but but only works in a limited way. #2 is a compromise between energy use and functionality. You only get warm water to start, and your cold water is warm as well. #3 is best, but can use lots of energy.

Some people use multiple water heaters, but that causes added energy use as well. It uses more energy to maintain two tanks of water than one larger tank.

 

[broconne]

We are close to going under contract on a new home and have had the extra piping, insulation and pump priced out. It isn't a particularly cheap option. Coming in around $2000 for a 3800 sq ft home in North Carolina.

 

[JimS]

Seems high to me but some people would say I'm cheap. There seem to be big mark ups on special items like this. It also may not be something they are that familiar with. Everyone along the way probably gets a premium markup on this sort of thing - person that modifies the plans, electrician, plumber, general contractor, etc. The actual cost of materials is quite a bit less. That's one reason I was my own general contractor and did things like this myself. I had the plumber put in the return line but put in the pump, pushbutton, timer, and wiring myself.

I used a standard pump something like the 5P429 here ( Regular $183, looks like it is on closeout for $140):
http://www.grainger.com/Grainger/items/5P429

with a standard check valve (estimate of $5)

A fan control relay (actually used for many things, not just fans) that mounts to a standard electric box, 2E852 here $32:
http://www.grainger.com/Grainger/items/2E852

And a custom PIC microprocessor based controller for time delay that switches the 24VAC to the relay. I planned to do more with it but for just the time delay there are fairly low cost solutions out there.
Here is a 24VAC unit for $48 (includes $6 for socket). Use one shot mode.
http://web3.automationdirect.com/adc/Shopp...s)/MS4SM-CE-ADC

This stuff can be found lots of places, not just Grainger.

So the total so far is about $230. It might be worth it to just buy a packaged pump/control that has all the control stuff. I would guess materials for return line would be about $50 - $100. Total is $330. The main part of the cost is the labor and markups.

 

[sic0048]

Keep in mind that copper prices are also very high right now. I haven't looked that the prices that recently, but I believe it's running somewhere around $1 for material. Add in labor and the costs can get pretty high, pretty quickly.

 

[dpilati]

Just another data point here. 4000 sq foot home in NC - recirc system quoted at $1000. Sure copper is expensive but it is rarely used around here - PEX rules this locale.

This was with a timer and thermostat based system. ie - you can set the time for 5-8 am and it will run until the temp is up and then shut off until it cools down.

Personally - $1000 is a bit much but also remember that insulation needs to be added to all the hot water lines by code (around here) and I think normally, only lines in outside walls need to be insulated. I also don't know if they were talking just one circuit to the furthest point since they are not exactly daisy chained....

 

[broconne]

Just another data point here. 4000 sq foot home in NC - recirc system quoted at $1000. Sure copper is expensive but it is rarely used around here - PEX rules this locale.

This was with a timer and thermostat based system. ie - you can set the time for 5-8 am and it will run until the temp is up and then shut off until it cools down.

Personally - $1000 is a bit much but also remember that insulation needs to be added to all the hot water lines by code (around here) and I think normally, only lines in outside walls need to be insulated. I also don't know if they were talking just one circuit to the furthest point since they are not exactly daisy chained....

Yeah this was PEX here. The plumber gets his extra cash. The builder gets his markup.. And more importantly from his cost perspective has to fully warranty it for a year.. Double the hot water piping, double the chances of leaks.. yada yada. Or at least that is how it seems to work.

 

[ano]

Yup. My previous house had polybutylene pipe. Claimed at the time to be the latest and greatest. Cheaper and better than copper. It was used for more than 10 years before the leaks started. After the largest class action suit in history, with billions paid, and most companies involved now bankrupted, the nightmare continues for those that had the pipe installed in their houses. But I'm sure the home builders made some extra profit by using the stuff.

If you are currently working with a builder to spec out a hot water loop, don't let the builder tell you regular copper pipe is enough. You need higher gauge copper pipe to prevent leaks if you plan to run the thing for more than a few minutes a day. Constantly moving 120 degree water stresses the pipe.

If you don't want that expense, consider other solutions, like non-loop systems.

 

[MrRedytemp]

Since I work for Redytemp I'll see what I can do to stick to the facts. Heater mounted systems which use a crossover valve underneath the sink can be inviting since they do not require any electric under the sink. This is due to the fact that they use a thermostatic valve that opens and closes based on temperature of water contacting the valve. Inside the valve materials expand and contract to allow flow to occur. When the water contacting the valve 95F or higher, the valve closes to prevent crossover from occuring. The issue with this situation is that anytime water contacting the valve is less than 95F the valve is open. Using cold water in the home causes the water pressure in the cold water line to drop, when this happens water from the hot water line crosses over into the cold water line because the valve was open. Though, you may only wanted to use cold water, flush a toilet, water your lawn...water still crosses from the hot water line into the cold water line through the open valve...until water from the water heater causes the valve to close when 95F water contacts the valve. This can be annoying to someone trying to get as cold water as possible because they may have to wait for 80F through 94F water to finishing emptying out of the hot water pipes before they get water exclusively from the cold water pipes. A second thing to consider is that the pumps on top of the water heater cycle on and off bases on time of day and not based on water temperature as other undersink systems do. We discovered this only after a closer examination of thermostatic valve after reading how some systems on the market have caused some owners to complain that they now have to wait for cold water from their cold water lines. We also wonder why since we had not been receiving complaints from Redytemp owners. What was the difference between ours and theirs? That's how we discovered the problem or flaw with the thermostatic valves. Why doesn't the Redytemp make a person wait a long time for cold water comfort like others on the market? This is due to Redytemps adjustable temperature control which allows the homeowner to regulate how hot is too hot or how much is too much pumping into the cold water line. Water not hot enough, turn the temp dial clockwise, water from the cold tap causing too long a wait, turn the temp dial counter clockwise. Since homes are different, having different pipe types, etc. heat is absorbed at a different rate in the cold water line. Having a pump running constantly as with heater mounted pumps with a thermostatic valve allows for a near constant bleed over of warm water entering into the cold line with no breaks for the cold line to recover from the slow but constant feed of warm water entering it. Redytemp cycles on and off bases on temperature chosen by the owner. The brief period between Redytemps cycles allow for the water in the cold water line to recover and regain it's cold water comfort state. Adjustable temperature capability lets the homeowner tune into the temperature that works best for their home / their desired comfort is ultimately higher when they can choose what temperature feels best. Adjustable temperature control lets them do just that.

On demand systems cycle on only after being activated by the user or a sensor. The Metlund system does just that. When considering this system the user should be aware that pumping stops when the water temperature is 7 degree's above ambient room temperature. I believe that most would hardly consider water that is 7 deg higher them room temperature to be hot...unless your in 29 palms in the summer with no air conditioner. The Redytemp can also be activated in single cycle operation by using the RJ11 jack on the front of the Redytemp. The two middle wires a phone cord plugged into the Redytemp and wired into say a doorbell button to act as a momentary contact switch would cause the Redytemp to activate and pump until the water in the hot water line reaches the temperature chosen by the home owner and stop. Many homeowners wanted the convenience of sheduled hot water readiness along with the ability to get hot water during scheduled-off time periods. That's why the Redytemp was engineered with both timer and single cycle overide capabilities. I apologize for the long sentences and hope to not appear too biased. Why are there not more comments about the Redytemp on the internet? We wish there were more positive comments out there for people to read but have come to the conclusion that there's so little because people are not having problems with their Redytemp systems.

As required by the regulations of this site I am required to state that I do work for Redytemp.

 

[dpilati]

Yup. My previous house had polybutylene pipe. Claimed at the time to be the latest and greatest. Cheaper and better than copper. It was used for more than 10 years before the leaks started. After the largest class action suit in history, with billions paid, and most companies involved now bankrupted, the nightmare continues for those that had the pipe installed in their houses. But I'm sure the home builders made some extra profit by using the stuff.

If you are currently working with a builder to spec out a hot water loop, don't let the builder tell you regular copper pipe is enough. You need higher gauge copper pipe to prevent leaks if you plan to run the thing for more than a few minutes a day. Constantly moving 120 degree water stresses the pipe.

If you don't want that expense, consider other solutions, like non-loop systems.

Well - getting a bit off topic here but..... Pex is not polybutylene. Pex has been around for a lot longer than polybutylene - I've worked with both and they are quite different. It is a bit like saying Masonite was the point of failure and led to a very large class action suit etc etc so don't use Hardie Plank - Brick is the only option. Copper itself has problems (not even as indestructible as brick). I've done my research and am building with Pex. I sold 2 houses this past year - both built in 1993 with polybutylene pipes - neither one had a leak in 15 years. And BTW - neither buyer even brought it up. FYI - both houses had Masonite and 1 required a few thousand $$ in replacement - the class action suit paid for most of that.

Pex is far superior to polybutylene and copper is not indestructible (repeated for emphasis).