Radiant Floor Shop Heat Completion - Need help/suggestions

woodwkr

Hi everyone I built a garage/woodworking pole barn construction shop a few years ago. At the time I was able to put 1/2" oxygen barrier pex tubing in the floor. Put 2" foamular under the concrete with a vapor barrier under the foam. From what I have gathered from the information here I did the correct thing here. The part I did not do so well with was the perimeter insulation. The perimeter only has 3/4" foam board between the concrete and the 2x outside framing. The tubing is in the floor and I am now wanting to complete the system. I have been gathering all the knowledge I can to design the system. I have been reading as much as I can here. I would like your opinions/help to be sure that I get this right and don't have to make a lot of changes later.

The building is 40'x48' for a total square footage of 1920 sq. ft. The floor has 2 zones with 4 loops each of a little less than 300' per loop. The walls are 12' high and the roof has a pretty steep pitch. The walls are spray foamed to a minimum R13 and ceiling minimum R20. I actually think the R values are higher. Have 3 10x10 insulated doors. 6 windows and a regular door. Location is Virginia.

I have tried various heat loss calculators from various websites using a low outdoor design temp of 16 F and an indoor temp of 60. Depending on the website I get anywhere from 31,000BTU to 45,000BTU loss. Does this sound reasonable? From this I would like to use a Rinnai E50C boiler, I have a local contractor that is a Rinnai dealer and willing to work with a DIY person. He thinks the boiler is not large enough. What do you think?

Using the Rinnai design manual (https://www.rinnai.us/documentation/downloads/800000050.pdf) as a guide modeling after drawing 6 on pg. 12 I have attached a sketch of what I can visualize the system looking like. I have also attached my calculations for the flow and head loss of the system. I calculate the head loss using 1" pipe throughout and as a second way of doing things reducing to 3/4, but I think the head loss (if my calculations are correct) would suggest going with 1". What do the experts say? I would like to use the Taco veridian VT2218 as the circulators. Between the speed and delta T options with the circulators I am hoping to have an efficient system. Although not in the sketch I plan on a back flow preventer and a couple of valves (one for a bypass as seen in the Rinnai design).

I hope I have listed the majority of the information needed for you guys to tell me if I am on the right track or to give suggestions on how to make things better. My name is Jason. Thanks!

Zman

Jason,
So what's your day job?
I think you are off to good start. I didn't check your math but it sure looks close.
You will need check valves on the circulators so they don't back flow when only one is operating.
You are going to want to give some thought to how you are going to purge this thing. You want to set it up so you can pump water through each loop individually. Usually it is a matter of a couple hose bibs and isolation valves in key places.
Carl

woodwkr

Thanks Carl, the manifolds have valves on each circuit and the manifold itself has a valve on the end. I am hoping that I can purge using these valves.
Jason

Zman

You should be able to isolate he loops that way. You will still a way to put water in a take it (with air) out. It could be as simple as 2 hose connections with a ball valve between them somewhere on the 1" return pipe.

woodwkr

Finally after playing phone tag for a week or two got the contractor on the phone. He asked a few more questions verifying size and insulation values. Then he said he had to make a call and would call me back. On the message he left he said that I needed a 96000 BTU boiler. That seems excessive to me. Will the floor even be able to emit that many BTU's? At this point I am not sure what I need. Any suggestions?

Paul48

Find another contractor. Your calculations are probably accurate. Find a contractor that works from a heat loss, and wants to do his own.

Ironman

Where in VA are you located?

Paul Pollets

Just for fun, I ran the calcs through Uponor ADS v7.7 and came up with 25,422 BTU total load; 5.1gpm required @ 6.3ft. head. I used the Roanoke default which has a 17 degree design temp. I presumed the 6 windows were 3'x3'. This is for a 65 degree indoor temp.

Rich_49

The guy that says you need 96K is a QUACK . Do not call him back , find someone who knows what he is doing .

hot_rod

woodwkr said:

Finally after playing phone tag for a week or two got the contractor on the phone. He asked a few more questions verifying size and insulation values. Then he said he had to make a call and would call me back. On the message he left he said that I needed a 96000 BTU boiler. That seems excessive to me. Will the floor even be able to emit that many BTU's? At this point I am not sure what I need. Any suggestions?

It depends on the type of boiler he was suggesting. Some of the tank style boilers have high outputs like that but with 80 gallons or more capacity and modulation they can be a good match for some radiant systems.

Paul Pollets

Since there are no mod-cons made with a 26K input, a small modulating boiler with an input of 50-90K would be more than adequate, especially if an indirect DHW load was to be added. Most of the time it would fire at the lowest setting.

woodwkr

I think that the contractor is "old school". I was really shocked when he came back with such a high BTU. I haven't been able to ask him yet where that number came from, but am glad that the people here agree that is overkill. As I mentioned in the first post I was originally looking at the Rinnai E50C which is a 50000 BTU boiler. From my calculations and the members calculations above (thanks by the way for doing that) I think this boiler may work. I found out that I have a member local to me and still want to talk with him.

Ironman

woodwkr is about 20 minutes from me. I'm gonna meet with him in the next couple of days and make some recommendations.

Paul48

@woodwkr

You're in good hands.

woodwkr

Well after many months and some help from Ironman I managed to get the system installed. Seems to be doing well, but we haven't had any really cold weather. Just wanted to post this as some closure and thanks for all the help and suggestions.