Looking for recommendations on hot water source for infloor radiant heating

kwilson

This is my situation …
Northern Wisconsin new home build. Will have hydronic radiant floor heating in basement and 1st floor. Basement tubing is in by me and pressurized good. 2,200 sq ft home. My flooring contractor who was initially interested in helping me with this project, has blown me off. My building plumber has zero knowledge and has no interest in assisting. I am a mechanical engineer and have 30 years of remodeling experience but have never tackled this type of project but have been doing plenty of research. 

LP serves the home (not natural gas). 

I am trying to determine best hot water heat source for flooring. I will use a 2nd 50 gallon tank for domestic. 

I’ve read and heard that an electric on-demand is not reliable and to go with gas. Several questions:
1. Why is electric such a headache?  (Did these people buy poor quality units and their opinion is based on that experience?) Side note: I also work for the largest utility in Wisconsin and know the country’s long-range push for electric and reduction in gas. May not impact things now but 5-10 yrs it might. 

2. Anyone have the pros/cons of tank vs on-demand vs boiler? I still need to size it but rough guess, 60k BTUs
3. There’s tons of information available but can anyone recommend a single source document/book on best practice radiant floor plumbing?
4. Lastly, I am confident in my problem solving and technical abilities and while you don’t know me … are there just too many moving pieces to this project for me to take on myself? I believe I can do this, if given the right direction. 

Thank you, in advance for any feedback. 

jesmed1

Since you mentioned that you work for a utility and are aware of the trend towards electric, you might want to look into cold-climate air-to-water heat pumps for your application. Heat pumps are ideal for the low-temp water of radiant systems, and with high COP's during the shoulder seasons you can get significant savings on operating cost vs. LP.

https://forum.heatinghelp.com/discussion/189108/air-to-water-heat-pump-for-radiant-floor?utm_source=community-search&utm_medium=organic-search&utm_term=heat+pump+radiant+floor

hot_rod

Was a heat load calculation done for the job, and a radiant design?

This would help you determine what size boiler you need, required supply temperatures, pump sizes, etc. Without that data you are just guessing.

This calculator will help determine fuel costs. Use the actual delivered fuel cost, LP or electric, not the price per gallon or Kwh. Use the number with all the taxes and fees included when comparing costs.

Air to water heat pumps are an option if you want to use electricity. But they need to be matched with a compatible system. Basically the lowest possible operating temperature. Generally below 120F supply temperature.

Don't even consider a tankless water heater. Completely the wrong device for a radiant heat source.

More on heat pumps in this Idronics issue.

https://www.caleffi.com/sites/default/files/media/external-file/Idronics_27_NA_Air-to-water heat pump systems.pdf


https://coalpail.com/fuel-comparison-calculator-home-heating

WMno57

Two types of AtWHPs. Monobloc and Split. Monobloc requires Glycol, Split requires working with refrigerants. You don't want glycol. I'm not going to tell you it's Illegal (like one person here) to work with refrigerants, just that if you are "undocumented" you may have to be creative in obtaining refrigerant. In your location in the North Woods you will find very little to zero expertise in installing and maintaining an AtWHP. AtWHPs are rare in the US.
LP is cheaper than electric resistance BTU for BTU.
Domestic water heaters are for high temp rise - low volume. Boilers, Mod-Cons, and ATwHPs are for low temp rise - high volume. So don't try to heat your home with a big box store water heater.
You can save yourself a lot of time and grief by limiting your search to Boilers and Mod-Cons (Modulating Condensing Boiler). My opinion: rule-out the mod-con due to their high drama maintenance, shorter life, and hard to get proprietary parts and get a simple cast iron boiler. I think DIY install and maintenance will be easier with this. Almost zero maintenance with CI and LP.

the country’s long-range push for electric and reduction in gas. May not impact things now but 5-10 yrs it might.

Outside of the CI boiler, all the other options will fail (become e-waste) before traditional fuels become hard to get.

hot_rod

The load number is critical.
2200 sq feet at 7 btu/ sq ft= 15,400 BTU/hr at design
2200 sq feet at 25 btu/sq ft = 55,000 BTU/hr at design

Hopefully your home is built to the lower number.

If so and you want simple, I'd use a second LP water heater, dedicated to radiant

looks like .13 is average for Wisconsin power
Hovering around 2 bucks for LP

So here is how that pencils out in the fuel cost calc.

An A2WHP would get you cooling, if that is needed and dhw, all from one box.
Nothing wrong with glycol in a properly installed and maintained system.

All our cars and trucks run glycol

Jamie Hall

As has been said, don't even think about tankless for a radiant floor application. They are designed -- and granted, work well -- for relatively low flow, high temperature gain, very intermittent use. A radiant floor is none of the above. A good, simple, correctly sized boiler will do the job very nicely. A few air to water heat pumps will also do the job -- a very few. Check the COP at low temperatures --some are no better than electric resistance. Most just simply don't work at all.

Hot_water_fan

First, you need your heat loss. Second, you need to use an appliance designed for space heating, not for domestic water heating. Third, why do your contractors keep blowing you off? I’m worried about number 3! 

Mustangman

There are 3,412 BTUs per KW. One gallon of LP has 91,500 BUTs.. So it takes 26.81 KW to equal the 2.00 a Gallon LP. 26.81 x .13= 3.48. Unless LP goes up to 3.48 a gallon, LP is a better source... cost wise.

WMno57

If so and you want simple, I'd use a second LP water heater, dedicated to radiant

Simple is good. @hotrod what are the advantages and disadvantages of a simple tank domestic water heater vs a CI boiler. Tank WH is cheaper. CI boiler may last longer. 80 percent boiler more efficient than tank water heater? Anything else?

All our cars and trucks run glycol

They live outside or in a garage. If they leak, not a problem. Glycol soaked carpet, PROBLEM!
Automotive is not an anaerobic system, so corrosion inhibitors (CIs) that come with glycol are required. Auto manufactures spend millions and have chemists on staff to insure CIs are compatible with all the components in their brand's system. And they still screw up (DexCool and some GM V6 intake manifold gaskets). DexCool is awesome in the LS engines, lasts 2 and 1/2 times as long, and doesn't erode water pump seals, but not for everything. About half a dozen different specification automotive glycols on the market today. They work great in their own brand's cars. There is no longer a universal coolant that works in everything automotive.
Less testing in Hydronics. You are rolling the dice. There may be a compatibility issue between a CI chemical and a metal or gasket.
A home's hydronic system is anaerobic. Less need for corrosion inhibitors, particularity if you have good water which is a buck a gallon at walmart and never needs to be changed.
Glycol needs to be maintained and reduces heat transfer.
Maybe I shouldn't obsess about this, since I doubt an AtWHP will last longer than 10 years anyway. Maybe they come with "Lifetime" glycol. I.E. the expected lifetime of the throw away heat pump.

Hot_water_fan

Additionally, when we talk about “tankless” we mean a tankless domestic water heater being used inappropriately as a central heating source. They also make tankless boilers which are totally fine. 

kwilson

Thank you everyone for taking the time to share your knowledge and expertise!
@hot_rod: I have not done a heat load calculation and only recently have been researching to understand all the components.  This must be done next - thank you for the information! I do have the the floor design … 10 loops in the basement (2 zones), 12 on the 1st floor (2 zones). Question: where does the .13 represent? I’m guessing it’s some type of constant based on my location?? If it helps, the home is being built in Armstrong Creek, WI. The walls and basement rim joists will be insulated with closed-cell spray foam. Panel of glass to face the lake, W-NW direction. The 1/2” tubing was laid 6” apart from the windows for 3 rows, then every 12”. This is where being an engineer helps with the problem solving but I also understand that this is uncharted territory for this girl. Thank you again for all your help!
@WMno57: I was not planning on using glycol as I’ve read that provided the water is good, it only acts as an insulator and not efficient. 

@Hot_water_fan: Not contractor”S” blowing me off, just one. He installed a friend’s system who lives a couple hours away. My friend reached out and asked him if he was interested, he said yes. I started contacting him last Fall but I’m guessing he had a change of heart. Instead of telling me, he just ignores my calls n texts. 

hot_rod

Here is a free trial for a simple, accurate heat load calc. A bargin at 99 bucks if you want to have a copy. www.hydronicpros.com.

Or download this Uponor CDAM for a manual sheet and example of how to input your numbers.
https://www.ashcroft.com/wp-content/uploads/2020/08/manual-pressuregauges-installation.pdf


Is the 2200 sq ft for total basement and upper? Or 2200 on each level?

Basement loads are much lower typically. So a WAG. upstairs at 20 btu/sq. ft. 1100X20= 22,000
Basement at maybe 10 btu/ ft 11,000.

So it is possible to have a load around 30,000- 35,000 btu/hr.

I would not count on much more than 25-27 btu/sq ft from a comfortable radiant floor.

Getting back to the ccA2WHPO, cold climate heat pump option. This chart shows performance down to -10. Designs that require 120 SWT maximum could still run a 2 COP at -10

So if you are in that 30K load range a 4 ton HP could handle the load down to -10 with a good COP.

I don't see a lot of sub zero temperatures in that area?

Glycol is only needed in the piping if you use a Monobloc heat pump and the glycol is only in the HP up to the plate HX. Pics below.

If an LP boiler is you choice, I like the Lochinvar WHB 055 for loads below 45,000BTU/hr.
Plenty of power for an indirect DHW tank also.

kwilson

Oh my - a million thank you’s Bob! @hot_rod

I’ll print and read everything off over this next week. 

The new home design is 30x30 plus a 12x20 addition. So the basement is 1,140 sq ft and the 12x20 is the mechanical room. I should note that because of the water table level, my basement is only 3’ underground with 5’ above. However, only 2 large egress windows in both bedrooms, no others. All loops will start/end there, and with no windows - it should stay plenty warm. 1st floor is also 1,140 sq ft. There is a 450 sq ft open air loft … convection air should keep it warm. 

You are correct, not a lot of sub zero temps unless wind chill plays a factor. 

If I may ask one more question: what are your thoughts on a fresh air HRV or ERV? A “must have”??

hot_rod

A blower door test will determine how much the home “leaks”. You want a tight structure but not unhealthy as far as air changes 

GroundUp

I will agree with the others that a "tankless/on-demand" should be avoided at all costs- regardless of fuel type. A boiler or heat pump are the only appliances to be considered for this application. With that said, I'd like to touch on the electric side of things- if your utility provider offers a dual fuel rate, electric may very well be a viable option for you. An electric boiler has no moving parts and only a few components to operate, making them far more reliable than any high efficiency gas boiler will ever be. The heat pumps get to be a bit more complex and don't really have much of a track record in our climate just yet, but they're moving right along. The multiplier is approximately 25 so if you can get your dual-fuel power for $.07/kwh, that calculates out to $1.75/gal propane equivalent using an electric resistance boiler. No maintenance, no headaches, just heat. Price comparison of course will vary based on your actual rates and heat loss, but here in Central MN the electric boiler almost always wins with heat loads under 50,000 BTU as we can get our power for as low as 4 cents in some areas- my house is 6.5 cents on dual fuel. Just throwing this out there, but if you'd be interested in a prefabricated boiler system that you could simply hang and connect on site (LP or electric), I have been custom building and shipping them all over the country for several years now. You're about 6 hours away from me the way it looks, but I'd be happy to discuss options with you if you'd be interested in exploring that avenue. My direct email is sales@mnfloorheat.com if you want to reach out.

hot_rod

Wisconsin has some off peak rates, and traditionally great solar rebates that maybe you could tie into

www.dsireusa.org will have programs listed for Wisconsin

kwilson

@GroundUp, thank you for the information! Wisconsin Public Service does not offer a dual fuel rate, but what an interesting concept. I actually work closely with our Regulatory dept that develops our regulated revenue rates … I’m going to inquire if that is something they have considered. We are actually working on the rate case for 2025
Thank you for the boiler system offer as well! I have much reading to catch up on, as everyone has been great with sharing their knowledge. I’m one of those that need a decent foundation before making any decisions. Do you have a website or any literature to share? 

@hot_rod unfortunately WPS only has TOU. Ugh, I thought I was fairly confident that I going LP but now I’m back to considering electric. Thankfully I have a little time before I commit. (Basement complete with subfloor. Until road snow loads lift, building will resume … late April/early May.)

GroundUp

@kwilson my site is mnfloorheat.com but be warned, it's pretty archaic. I'm not the type who does well with technology and the person I hired to build the site kind of dipped out halfway through so it ended up half-asked. If you'd like some more information/background, please feel free to shoot me an email and we can talk it over!

ukie

There are new products on market . Air to water heat pump . European brand for cold climate. You can heat and cool the floors in summer . You will need a back up heat source . Can be LP , wood , or electrical if you have a generator