Newbie questions for in floor heating.

[mxrx81]

Hi,

I live in Minnesota so it can get quite cold here but my questions are easy for most of you. I have a 30x40x14 garage which is 1200 sq ft. and have one zone with 4 loops and not sure what water heater/boiler is big enough for this. Would electric work on something like this? I am leaning towards propane though. I have seen people with 40 gallon water heaters but I just think it overkill for this setup especially if I fill it with cryotech glycol I just want something simple and effective. Thanks in advance.

 

[papp101]

It's all about how much heat your building looses.

Do you have insulation under and around the sides? Windows? Insulated garage doors? Insulated walls and ceilings? And what target temp? Will you run the floor at 44 to keep the ice out, or 55 to work, or 70 to wash cars naked?

Run this calc, then come back with the number.

https://www.loadcalc.net/

I'm in Minneapolis, and love my heated floor. I run it at 44 with a wall thermostat, and only have to plan about 4 hours in advance to get the temp up to 55 which is usually all the more that's needed.

Where are you located?

My heat load came to 27kbtu per hour at above average design temp, so I looked at Nat gas boilers as I was close to the house. The small ones are actually more expensive, but I found and 80k ncb-80e Navien with a 5:1 turn down ratio which means if it doesn't need all 5 jets, it can dial down the output to match the need. I got a smoking deal off Craigslist. Msg me if you're interested in more info.

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[75gmck25]

My BIL has a 1500 sq ft farm garage/man cave in North Dakota and has it set up so he can heat the man cave end (about 1/3 of the floor space) for living space and set a different temp in the garage end for working on projects.

He decided to use electric because the building is in a rural area and he wasn't sure the propane dealer would be able to calculate his infrequent usage and keep him on the right fill schedule. Its not a simple trip for the dealer to just stop by and check the tank. He leaves the man cave portion at about 70 all the time, but I'm not sure what temp he uses for the garage portion. The building was built with the right insulation under the slab and in the walls and ceiling, so its quite comfortable.

I don't think I would consider using a simple water heater for this application because when you need heat you really do need it. Water heaters are designed to run infrequently to heat, and then store water until it cools. This is different than a heating system that may run very frequently in sub-zero weather.

Bruce

 

[yeldogt]

A run of the mill tank water heater has a burner in the high 20's BTU wise -- at 80% -- you only get low 20's. So ... if your building needs 50k BTU's? not going to work. The reverse is true with the tankless ... they put out 160 -190K. Unless it's a model that can modulate -- what do you do with all the extra BTU's?

Tank type water heaters are not designed to be running all the time ... in a small space they can work. Tankless require proper piping to make them hold up and run with some efficiency.

You need to figure out the heat loss and then see what you can get from your tubing ... with only 4 loops and that size building .... what's the spacing and length?

 

[mxrx81]

If I remember correctly the spacing is about a6 inches and al loops are about 280 Feet. I am going to install r60 in the ceiling and r 19 in the walls since there 2x6 framing. There is two inch foam under the slab and around the perimeter as well. The garage doors are two in foam which I believe is r20.

 

[papp101]

Thats good info. How many garage doors and what size and are they insulated?
Any windows and what size?
Lastly, what's the roof pitch?
What major town are you closest to?

This all helps for the heat loss calc, then you can see what's needed. My guess at 50 degrees design temp, you need something like 40 or 50k.

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[papp101]

And btw, yeldogt is the bomb. He helped me with mine!

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[mxrx81]

Im in Rochester, MN I have two 12x12 garage doors that are well insulated and I think there r20. I have 4 windows which are 4feet by 5 feet. The roof pitch is 4/12. Did you build your own panel, I am thinking about building it myself vs the one at Menards.

https://www.menards.com/main/plumbi...n-concrete-system/6959772/p-1471978652456.htm

 

[yeldogt]

Sound like you have a good set up -- especially if you have that close spacing. I find the close spacing really helps -- faster response and lower temp water.

I would still plug your numbers into a heat loss calculator -- see what it needs. The ceiling height is really not a factor ... radiant should be on all the time .. to some degree.

I would make your own setup -- simple is best. But, you need a few items to make it all work correctly. Spend once.

I'm in the mid atlantic so while we get cold weather -- we don't typically have a month of single digit temps. I also have back up systems -- so I have never used any glycol in my systems. Same with a water heater. I will say that my very well insulated 1500+ studio can be heated with a 4000kw electric heater ... so you see how proper insulation can reduce BTU need.

I always tell people to get a copy of "pumping away" -- google around the authors site after reading. Like many things there are more than one way to achieve the goal .. follow one of them to success.

Understand the efficiency of a water heater -- especially with propane . What's your electric rate? In some areas when you punch in lower electric rates getting an electric boiler (not a water heater) is the way to go. Do you have reliable power ?

 

[fitter30]

How long are the loops and pipe size?

 

[mxrx81]

How long are the loops and pipe size?

It’s half inch tubing and about 280 feet. There all about the same length.

 

[fitter30]

Figgering water temp difference of 20* 33,600 btu's, 8.4 feet of head + 2' for piping 10.4'
3.6 gpm taco 007 pump

 

[mxrx81]

One question that I have is should I go with a boiler system or tankless water heater. Tankeless water heater is simpler and cheaper to setup from what I know so far.

 

[mxrx81]

The pumps say 0 to 17 gpm, how would you ajust it to 3.6gpm?

 

[mxrx81]

This is the setup that I think I will eventually have incorporate, the picture shows the hot and cold T'ed together under the water heater? What's going on there?

It's all about how much heat your building looses.

Do you have insulation under and around the sides? Windows? Insulated garage doors? Insulated walls and ceilings? And what target temp? Will you run the floor at 44 to keep the ice out, or 55 to work, or 70 to wash cars naked?

Run this calc, then come back with the number.

https://www.loadcalc.net/

I'm in Minneapolis, and love my heated floor. I run it at 44 with a wall thermostat, and only have to plan about 4 hours in advance to get the temp up to 55 which is usually all the more that's needed.

Where are you located?

My heat load came to 27kbtu per hour at above average design temp, so I looked at Nat gas boilers as I was close to the house. The small ones are actually more expensive, but I found and 80k ncb-80e Navien with a 5:1 turn down ratio which means if it doesn't need all 5 jets, it can dial down the output to match the need. I got a smoking deal off Craigslist. Msg me if you're interested in more info.

Sent from my Pixel 2 using Tapatalk

 

[TurnipTruck]

This is the setup that I think I will eventually have incorporate, the picture shows the hot and cold T'ed together under the water heater? What's going on there?

That is primary/secondary loops with closely-spaced tees. The boiler has to have an internal pump for that to work.

 

[brewchief]

That makes since.... Im still not sure if I want to go the boiler route or tankless water heater.

A boiler is a far better choice, most tankless water heaters will specifically say not for space heating, some have made it work but often it doesn't really work as well as it should.

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