water heater for radiant floor

Tyler Kingery

I have a customer who has asked me about a standard water heater with side taps to use in his radiant floor system as opposed to a boiler. Does anyone have any thoughts god or bad??

Jamie Hall

Other than the obvious one that a water is built to heat water for domestic use, and a boiler is built to heat water for heating... not really. But tell me: would you recommend using a Chevy Silverado (or Ford 150) to haul your lumber and your Honda Civic to haul the kids, or the other 'way round?

Gordy

First thing was a heat loss done?

If so what is the load?

Water heater is not recommended. It will bring baggage you don't want.

Gordy

I will add a water heater will not be as efficient as a ci boiler, but it will be more efficient than its intended use as a water heater.

The control of it becomes sloppy at best.

Tinman

For me, it has to have an H stamp to use it for space heating.

Rich_49

Come on guys , all good points but there are choices that work real good . Warmboard bought light duty's by the truckload and they are heat only units . Is the Pioneer a phoenix or is the Phoenix a Pioneer , which came first ?

These are all completely programmable to make them act just how you want . If he was hoping to do it with a cheap water heater tell him to forget it .

http://www.htproducts.com/pioneer.html
http://www.htproducts.com/phoenixwaterheater.html
http://www.htproducts.com/phoenixldwaterheater.html

Ironman

The other issue: legionella.

If the side taps go to an internal coil, then this is not an issue. If they access the potable water in the tank, then you'll create a legionella breeding machine.

Water heaters that have those taps that access the tank are NOT designed for radiant floors: they are designed to connect an AHU with a hydronic coil and stringent guidelines must be followed.

Bottom line: use the right tool for the job - a boiler. Or at the very least, a dedicated water heater for each. But that would cost as much as a cheap boiler.

Gordy

Rich said:

Come on guys , all good points but there are choices that work real good . Warmboard bought light duty's by the truckload and they are heat only units . Is the Pioneer a phoenix or is the Phoenix a Pioneer , which came first ?

These are all completely programmable to make them act just how you want . If he was hoping to do it with a cheap water heater tell him to forget it .

http://www.htproducts.com/pioneer.html
http://www.htproducts.com/phoenixwaterheater.html
http://www.htproducts.com/phoenixldwaterheater.html

Come on Rich those cost more than a water heater, and you know why people are inclined to want to use a water heater.

hot_rod

Electric water heaters can work. Bradford White has some hydronic specific gas fired combi tanks.
One caution with gas fired is running them hot enough to prevented continuous condensing. Run it at 130 and mix Dow if needed.

Gordy

"Standard" water heater was the original question.

Rich_49

Please advise . How many standard water heaters have side taps . It is also my understanding that this would not be used as a dual purpose unit .

Bob also mentions the condensing issue which is quite valid . Does not change the fact that H20 heaters are available that are more than capable of being used as the OPs customer wants . The fact that it costs more concerns me not . Just wanted to allow poster the opportunity to research what he CAN use and advise his customer .

In short , a water heater that any manufacturer states is space heating capable , that has condensing capability can be used as a space heating source for low temp applications . One that has modulating capability is even better . If a water heater is to be used as a dual purpose appliance it must have a form of separation between the DHW and space heating medium .

Gordy

Still does not change why someone wants to use a water heater.

Cost whether it matters to you, or not. Those htp products most certainly are options with higher costs. I would assume the OP is an installer, and has run into budget constraints.

taylorjames

Rich said:

Please advise . How many standard water heaters have side taps . It is also my understanding that this would not be used as a dual purpose unit .

Bob also mentions the condensing issue which is quite valid . Does not change the fact that H20 heaters are available that are more than capable of being used as the OPs customer wants . The fact that it costs more concerns me not . Just wanted to allow poster the opportunity to research what he CAN use and advise his customer .

In short , a water heater that any manufacturer states is space heating capable , that has condensing capability can be used as a space heating source for low temp applications . One that has modulating capability is even better . If a water heater is to be used as a dual purpose appliance it must have a form of separation between the DHW and space heating medium .

I agree with you that it would not be used as a dual purpose unit.

ChrisJ

Standard water heaters with side taps.

The 19 gallon electric unit I just installed last night only has side taps. There are many lowboy units like this.

My 50 gal Bradford White power vent has a drain on the bottom side and the T&P on the side, top. I also recall seeing them mention using this heater for space heating which I was surprised by, but I guess it works if you only need 30,000-40,000 btu/h.


From the current Bradford White 50 gal power vent manual :






I have no clue what the pros and cons of this are but I can't see a power vent water heater being all that terrible regarding efficiency. Would it beat a 82% AFUE boiler?

Mark Eatherton

Both the UMC and the IMC do allow for the use of water heaters for doing space heating. I don't suggest it be a contiguous fluid in the system due to Legionella. It must be "Listed and approved" for space heating applications. If used as both a DHW heater and a space heater, it MUST have the thermal capacity to handle both loads simultaneously. Good luck with that.

Having had lived with a water heater as an energy source, I can tell you that it is terribly inefficient and not something I would even consider selling to a good customer.

There is an effort afoot to try and change both codes to eliminate the use of single fluid tank style space heaters unless there is a heat exchanger to isolate the space heat from the potable water. With all the attention that Legionella has generated over the last year, I don't see a lot of opposition to the proposals. The additional cost of the heat exchanger and associated equipment is minor compared to the loss of life...

I did a green house job many years ago for a DIYer, and we installed a 6 gallon electric water heater. Due to the continuous operation during extremely cold weather, all the internal wiring overheated and it caught on fire. I wouldn't recommend that use unless it is specifically approved for that application.

Travel safely out there...

ME

ChrisJ

Mark Eatherton said:

Both the UMC and the IMC do allow for the use of water heaters for doing space heating. I don't suggest it be a contiguous fluid in the system due to Legionella. It must be "Listed and approved" for space heating applications. If used as both a DHW heater and a space heater, it MUST have the thermal capacity to handle both loads simultaneously. Good luck with that.

Having had lived with a water heater as an energy source, I can tell you that it is terribly inefficient and not something I would even consider selling to a good customer.

There is an effort afoot to try and change both codes to eliminate the use of single fluid tank style space heaters unless there is a heat exchanger to isolate the space heat from the potable water. With all the attention that Legionella has generated over the last year, I don't see a lot of opposition to the proposals. The additional cost of the heat exchanger and associated equipment is minor compared to the loss of life...

I did a green house job many years ago for a DIYer, and we installed a 6 gallon electric water heater. Due to the continuous operation during extremely cold weather, all the internal wiring overheated and it caught on fire. I wouldn't recommend that use unless it is specifically approved for that application.

Travel safely out there...

ME

Mark,
Power vented and direct vented tank heaters are that inefficient?

hot_rod

ChrisJ said:

Standard water heaters with side taps.

The 19 gallon electric unit I just installed last night only has side taps. There are many lowboy units like this.

My 50 gal Bradford White power vent has a drain on the bottom side and the T&P on the side, top. I also recall seeing them mention using this heater for space heating which I was surprised by, but I guess it works if you only need 30,000-40,000 btu/h.


From the current Bradford White 50 gal power vent manual :






I have no clue what the pros and cons of this are but I can't see a power vent water heater being all that terrible regarding efficiency. Would it beat a 82% AFUE boiler?

Most of the water heaters designed for mobile home use, in all sizes, are side tapped. it may not be a commonly stocked item, however.

This has always been a controversial issue using a conventional, tank style heater for dedicated radiant. As I recall a former RPA person pushed this option to provide more "'affordable" everyman radiant systems.

I am not a fan of combined Hydronic/ DHW systems, but I did see several on display at CMX in Canada last week, mainly with air handlers. For that use they need to be listed and labeled is how I understand it.

For dedicated hydronic applications I'm not sure. Is it any different than installers using tankless for radiant, as far as listings are concerned? Most do not have a H stamp, but some of the hydronic specific products do not either.

Mark Eatherton

ME


Mark,
Power vented and direct vented tank heaters are that inefficient?

Chris, any time you have a tall vessel filled with hot water that has a hole (flue) running directly through the core of the stored water, you are going to have a continuous draft which pulls cool room air into the combustion chamber, and allows it to rise up through the vessel, heating the air, and losing energy. The higher the overall profile, the greater the stack action.

It might be less for PV and or a DV, but it is still there nonetheless. Mine was a 40 gallon atmospheric, 40K btuH, and it used to really get on my nerves as I would hear it running when I knew there was little to no demand. Tis the nature of the beast.

If it were such a great idea, the Europeans would have discovered it long ago and be touting it today, no?

ME

ChrisJ

Mark Eatherton said:

ME

Mark,
Power vented and direct vented tank heaters are that inefficient?

Chris, any time you have a tall vessel filled with hot water that has a hole (flue) running directly through the core of the stored water, you are going to have a continuous draft which pulls cool room air into the combustion chamber, and allows it to rise up through the vessel, heating the air, and losing energy. The higher the overall profile, the greater the stack action.

It might be less for PV and or a DV, but it is still there nonetheless. Mine was a 40 gallon atmospheric, 40K btuH, and it used to really get on my nerves as I would hear it running when I knew there was little to no demand. Tis the nature of the beast.

If it were such a great idea, the Europeans would have discovered it long ago and be touting it today, no?

ME

With all due respect to the Europeans, I don't think they're god's gift to efficiency or the best designs.

I can see how an atmospheric heater has terrible efficiency, but I fail to see how you can compare a direct vent or power vent heater to it? When we lost power from Sandy my PV 50 gal heater was still burning hot 3 days later. I run it at 140 and I'd bet the water was still 110-120F.

There may be some draft up through it, but I suspect the blower and piping stifle it quite a bit. It's nothing compared to an atmopsheric one, especially one that doesn't even have a damper.


Such a shame there's no easy numbers you can compare between them eh?

Larry Weingarten

"Such a shame there's no easy numbers you can compare between them eh?"

Seems to me that this is one place where the EF test actually could be useful. I looked up Bradford EFs and found .60-.64 for atmospheric and .65-.70 for power vent, (for 50 gallon tanks). It suggests that standby losses from the flue are actually a lot less with the power vent configuration.

ChrisJ

Larry Weingarten said:

"Such a shame there's no easy numbers you can compare between them eh?"

Seems to me that this is one place where the EF test actually could be useful. I looked up Bradford EFs and found .60-.64 for atmospheric and .65-.70 for power vent, (for 50 gallon tanks). It suggests that standby losses from the flue are actually a lot less with the power vent configuration.

What do those numbers mean though?
I recall seeing them, but had no way to compare it to AFUE ratings.

BobC

Why on earth would a company give a consumer access to number that might let them compare units - that's un-American!

Bob

ChrisJ

BobC said:

Why on earth would a company give a consumer access to number that might let them compare units - that's un-American!

Bob

But a 6HP shop vac is.

Mark Eatherton

Chris,

http://energy.gov/energysaver/estimating-costs-and-efficiency-storage-demand-and-heat-pump-water-heaters

It's an AFUE for water heaters... I know how much you like AFUE. According to Dan H., that's what the bums standing on the island say to you when you drive by them without giving them spare change. "Yo, AFUE!!!"

ChrisJ

Mark Eatherton said:

Chris,

http://energy.gov/energysaver/estimating-costs-and-efficiency-storage-demand-and-heat-pump-water-heaters

It's an AFUE for water heaters... I know how much you like AFUE. According to Dan H., that's what the bums standing on the island say to you when you drive by them without giving them spare change. "Yo, AFUE!!!"

I certainly hope that was sarcasm.
I hate AFUE, but it's at least something.

SWEI

This is worth reading. It points out the problems with the EF pretty clearly.

Larry Weingarten

Hello and thanks for the link. The Energy Factor test has changed. It has been redesigned to represent a little more closely how we really use hot water, and this has a big impact on how efficient different heaters test out. For example, tankless did nicely with the old test of six equal draws, but won't do so well with many smaller draws as specified in the new test, Uniform Energy Factor. Here is a link that get you started down this twisting path! http://aceee.org/sites/default/files/pdf/conferences/hwf/2015/Plenary-Darlington.pdf

Yours, Larry

ps. I don't know of any correlation between UEF and AFUE.

J Van Lund

We designed an hydronic infloor heating system using John Siegenthaller's , 1st Edition, with powerful hand calculations fourteen years ago. We installed a Bradford White 40 gal dedicated electric water heater wired simultaneously with two 5500 watt elements for a 1500 SF 24,000 Btu/hr heating load. Delta T was 10 degF. Max.operating Temp 110 to 120F and flows anywhere from 5/8 to 3/4 gpm depending on which of six zones was running. It has worked flawlessly here in the Pacific NW. No maintenance for 13 years. Now we need to drain the water heater and check the mineral deposits on the elements and shop vac out any stuff in the bottom. Also need to check the P/T valve to see if it is responsible for a pressure drop from 13-15 psig to atmospheric upon shutdown last month. What was interesting was the presence of popping in the water heater upon start up after long sunny days or startup in the late fall for the past two heating seasons. We suspect steam was being driven off the elements from trapped water under the mineral deposits which caused a temporary measured pressure drop as the steam mixed with cooler water and condensed. These systems are indeed fascinating for a DIYer trying to diagnose issues. By the way, the "professional" who installed the system placed the pump so it pumped toward the expansion tank, installed a pump larger than the one specified, and did not install a P/T gauge on the return per plan. So sometimes if you want it done right, seek understanding, and do it yourself.

hot_rod

There really should not be much mineral build up in a closed loop system. Unless you have had a small leak there should not be much water added to the original fill

How hard or what TDS is your local water?

J Van Lund

Hi Hot Rod: Yes, it's a closed system. Well water has a pH = 8.4-8.5 with TDS = 640-680 with Mn & Fe present - also Trihalomethanes and some chloride. On a POU undersink water heater, the heating element was all gummed up after only 7-8 years, but that is an open system. Need to do the inspections and see what's going on. Thanks, John

hot_rod

That is a very high TDS number. I'm on Long Island this week measuring 27- 50 ppm TDS. I would de-mineralize water with that high number. We measured some 700 ppm in Utah

Boiler manufacturers are putting the acceptable levels in the manuals, most are well under 100 ppm


Imagine telling a customer their boiler failed due to water quality in 3-5 years, no warranty and a 10 K replacement cost

Time to bone up the industry on fluid quality, and how to address it

J Van Lund

Hi Hot Rod: Yes, we need to demineralize the water and need to pay attention to water quality. I'll download Caleffi's "idronics 18 design journal and learn something new.

What do you think of the HYDROFILL treatment filling units by Caleffi? I will ask my local heating pro if he has one and can fill the water heater after a thorough inspection. Otherwise, I'll figure out a way to do it myself, since that is where the satisfaction lies.

Worst case scenario is to buy another water heater at $800 and have it last another 13 years, which in all probability will outlast me. Not too bad considering the cost of replacing a boiler. Thanks and fair winds, John

hot_rod

We have quite a few HydroFills out in use. Contact the local suppliers or rep in your area to see if someone nearby has one. Some of the wholesalers and distributors are renting them out on a job by job basis.

If you have high mineral content water, either de-mineralize it on site or you can sometimes purchase water from a local water treatment company. You would need some plastic barrels to haul it, of course.

J Van Lund

Hi Hot Rod: Here is a photo of the water heater elements after 13 years of no maintenance in a closed hydronic system with well water with TDS 640-680 ppm and pH = 8.4-8.5. We shop vac'd the pile of chipped off pieces with a 3/4" flexible marine water hose duct-taped to the shop vac. Removed the gummed up P&T (top mounted) and will refill with RO treated 99% free of everything water by HIY (Haul It yourself). Thanks, John

Mark Eatherton

Having lived with a water heater for both CH and DHW for the past 12 months, I can tell you that your statement is factually incorrect if a reasonably efficient machine is procured.

I should have qualified my statement. I used a 40 gallon, 40 K atmospheric water heater. If I had an EF of .50, I'd be amazed.

I should have known you'd be climbing on me about that. I guess I need to think, WWBS when I post. (What Will Brian Say). In other words, no comparison..., so YOUR statement is factually incorrect, because I didn't give you all the facts. My bad.

As a master plumber, charged with protecting the health of my customers, I can not recommend the use of a potable water heater with one contiguous fluid for doing both CH and DHW.

It causes the water to become tainted, which is against the codes. The use of a heat exchanger for people who want to cut corners and not purchase a real heating appliance should be (and may be in the future) mandatory. It is too attractive to the DIYer, who doesn't realize the risks associated with the application. I presume this is a temporary fix on your part. I replaced mine with a real boiler.

Even though you say it is more efficient, how efficient can a large storage tank held at a constant of 155 degrees F be over a modcon appliance that is room temperature even when it's off? Seems similar to holding a CI boiler at 180 waiting for a DHW load to show up.

ME

ChrisJ

I am very curious now.

Why are you not allowed to circulate domestic hot water for heating because "it could become tainted" but you are allowed to circulate cold water through sprinkler systems (designed for it of course) before bringing it to fixtures?

I'm sure baseboard and other setups could easily be made to carry potable water and meet current lead standards etc.

Rich_49

ChrisJ said:

I am very curious now.

Why are you not allowed to circulate domestic hot water for heating because "it could become tainted" but you are allowed to circulate cold water through sprinkler systems (designed for it of course) before bringing it to fixtures?

I'm sure baseboard and other setups could easily be made to carry potable water and meet current lead standards etc.

I presume you are referring to a Uponor AquaSafe combination system ChrisJ ? 2 completely different types of creatures there , the Uponor system uses city water that is that does not sit and grow trash within it . Other systems for fire suppression must have backflow prevention , separate water services in NJ and a bunch of engineering and a plethora of other nonsensical code required expense . The problem with not separating DHW from heating water comes right after the off season when nasty stuff has been in the heating portion of the piping w/o being circulated for a few months , I would add , that this is exactly the situation that has happened during conventions and the like and caused out breaks of the disease . That is why NJ requires annual and even 4 xs yearly certification of RPZBFP in restaurants , hospitals , acute care facilities , you get the picture .

jamescock

Water heaters are not very efficient though. If you're planning on heating continuously, you're probably better off with a small high-efficiency boiler. Depending on how much you run it, and how long you're planning on living there for, fuel cost will be WAY more than the initial cost of the heater/boiler. Might be a case of saving money in the short run will actually cost you more money over the long term.

Rich_49

@jamescock

Q . When is a water heater not a water heater ?
A . When it is a modulating condensing tanked vessel that can be used for space heating and programmed specifically for that purpose .
Guess you've never seen anything like this . Keep in mind that leveraging mass holds out the burner for quite long periods and we all know the most efficient appliance is the one that's idle (off) .

http://www.htproducts.com/pioneer.html

But wait , it's not much different than this

http://www.htproducts.com/phoenixwaterheater.html

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