Radiant Heat Pump questions - technical sizing

[Crazy Legs]

Ok, I've got a 24 x 30' garage and i'm using the CPI RHP-1 in my garage for my PEX, i've got 800' of line in my floor with a 50 gallon Electric Hot water heater and it works great. i have 4 input & 4 output lines and my valves are almost off, maybe open 1/8 or 1/4 turn and my pump is on low.

My dad's building a 36 x 64' garage and its got about 2000' feet of PEX beneith and he's still deciding on a boiler, water heater, or possibly using 2 water heaters.... anyway, we were wondering can we use the RHP-1 instead of the RHP-2, it has the same pump just bigger 1" lines going to and from it, plus you can run zones which we don't need. aka we can save $500 if we can use the smaller panel..... since my valves are almost off and pump on low, we thought it might be big enough to run his floor???

Thanks!

 

[Crazy Legs]

no replies on this?

 

[Crazy Legs]

how about this instead? - using CPI's heat requirement formula form it says my dads in floor heating will require a hot water heater or boiler etc with output of 101,676 btu's per hour needed.
The biggest hot water heater i've found at Menards is 75,000 btu's and i found the Bosch tankless water heaters are 117,000 for $600 or 175,000 btu's for $1000 - would a tankless be ok?

Any help is appreciated.

 

[kvom]

I was advised not to use a tankless heater for hydronic by my supplier, Radiantec.

 

[billpa68]

i been using a bosch 125 for years works great but is only 44,000 btus

 

[BBQ&Love]

I was advised not to use a tankless heater for hydronic by my supplier, Radiantec.

With all due respect, they are a hack outfit and I wouldn't pay any attention to them.

 

[Jackfre]

Daikin Altherma is a hot water heat pump. It has been in the market for two years. I've not spoken with any contractors who have worked with them, and cannot offer first hand knowledge of their performance, but it is worth a look. Hot water heat pumps for dhw are cost effective and efficient. They do not have great recovery but overall performance is good.

 

[tmars]

With all due respect, they are a hack outfit and I wouldn't pay any attention to them.

Really, I am about to order a kit from them. What problems did you have and who would you recomend? I am planning a 30x40 garage. Thanks

 

[keweenawbee]

As I mentioned in another thread, I bought a RI kit from them, which consisted of the tubing and custom manifolds, what's not to like? I won't on my next project, but I was a little green at the time. The zoning & boiler piping kits seemed high priced, given the sum of parts, but all the vendors of that sort of thing seem high.

 

[BBQ&Love]

Really, I am about to order a kit from them. What problems did you have and who would you recomend? I am planning a 30x40 garage. Thanks

I have just followed behind them a lot, trying to fix the mess their systems are.

I shouldn't knock them. They made me a lot of money over the years.

You are much better off to get your system designed right and buy your stuff from pexsupply.com, etc.

PM me some details about your setup and I'll see if I can point you in the right direction.

PS. Until 2 years ago, I did this professionally. I despise that outfit with every pore of my being. It's one thing to tell people they can do this stuff themselves. It's another to say that and then promote some of the most jacked up designs, ideas, etc. you can find in the field. A lot of their stuff I would look at and ask "Why? What in the world are these idiots trying to prove?" More than once I provided free designs and sold my parts at cost to friends just to keep them from being jacked over by these people. Other times I charged for my design and made a profit on my materials and still saved the customer money, frustration, and delivered a better system.

I am out of the business now so I should probably just chill about it.

One more thing. There are any number of ways to do radiant. I am not one of those guys who was locked in on one certain way so that isn't why I despised them.

 

[rburke65]

22rifle...what determines the size of the pex? Slab thickness, sq. footage, insulation, heat source. Looking to do possible a 32'x56'.

 

[koditten]

I really like my conventional boiler. Yes there is a bit more plumbing involved, but that is a non issue. My boiler is a standing pilot boiler. No electronics to worry about. Pilot assembly, gas valve, roll out switch and a relay. Thants about it. Believe me no one is going to be able tell me that I am further ahead buying a high efficint boiler. It would take me 20 years to recoupe the extra cost of hi-efficiant unit.

I like the fact that you don't run out of hot water on super cold days. This is what boilers are designed for...to make hot water to heat your structure.

Find out your energy losses and have a pro design it. It's not that expensive.

 

[BBQ&Love]

22rifle...what determines the size of the pex? Slab thickness, sq. footage, insulation, heat source. Looking to do possible a 32'x56'.

The heat loss combined with how you will use the building are what my programs use to determine the size of the PEX.

One thing I did to cut cost without sacrificing performance on shop slabs was to build my own manifolds. (Or buy pre-built copper ones) No flow adjustments cuts the cost way down. The catch is that you have to have all your loops the same size. (Within 10%)

 

[Addrock]

I'm NE of you, 24 X 36, 2 X 6 walls, good not great ceiling insulation, 2" hd foam under the slab, 3 windows, 2 OH doors, 1 man door. That said my heat calculation figured to be 70,000 btu. I then sized a tankless HW heater, put together my system and sized a pump. The pump I bought was a variable speed the speed that I figured the slowest speed would work. As I added more antifreeze to the system the heat transfer was less efficient so I ended up using the high speed. I only have 3 months gas bill but the peak was $160 for home and garage.

 

[hyvolt]

Check out radiantcompany.com. I have used them a couple of times, very help-full. I have done several floors, all with tank-less heaters. All of them work very well.

 

[jvitez]

I know nothing about radiant heat installation, so I can't help you there. But one "gotcha" is input vs output heat ratings. If your heat loss calcs say you need 101,676 btu/hr, that's the output requirement. The 75,000 btu/hr Menards water heater is 75K input. Operating efficiency is about 75% for a standard water heater, so you're only going to get ~56,250 btu/hr output. Two of these piped in parallel would do the trick from the pure heat generating aspect, but I've read a lot of pro/con threads about water heaters vs boilers for radiant, so you'll have to decide which is best for you.

Just don't get caught confusing input for output rating.

BTW: electric heating is rated at 100% efficient, so if you need 4500 W heat input, a 4500W electric water heater will be perfect. The conversion factor is 3.414 btu/W, so 4500W= 15,360 btu. A regular NG/propane water heater would need to be at least 20,478 but/h input rating to give the same heat as the electric water heater.

 

[theoldwizard1]

@huvolt - Nice work ! What brand tank-less heater do you use ?

 

[hyvolt]

Takagi. Got it for radiantcompany.com They are very helpful. Give them the size of the shop, window sizes, door opening insluation ect. They will draw a plan, size pumps and ship it to you. (this pic. is the heater for my shop)