Radiant floor in concrete slab for shop.... Contractor bailed out

nitrojoe

Any help or info is much appreciated. I searched for a discussion already, and didn't find anything really close to my situation. I had a single door, 3 bay shop built 2 years ago. I had a contractor design the radiant system for the concrete floor. I met him through a mutual friend. The general contractor was waiting to pour the slab because my radiant guy kept putting me off. After a month of no shows, and a pissed off General, I decided to lay it out myself. The materials were there with his tubing layout, so I put down the insulation, and laid the pipe. Slab got poured and the shop built. Radiant guy is now totally mia.....and I want to get this done. I live in Oregon.....radiant isn't a big thing out here, so finding help has been difficult. Seems there is a ton of ways to skin a cat.....and the cat doesn't like any of them. I'm thinking I can finish this myself. but maybe not. Maybe I should stick to restoring cars.

Here's what I got:
726 sq'(33x22) with a 6" (counting the insulation) concrete slab. 10' foot ceiling, stick built, well insulated, with sheet rock walls and ceiling.
I did the heat loss calculator as best I could understand it and it came up 16,224 btu/hr
4 runs of 1/2" aquapex fairly close to 100' per run. 18" center in the middle, 12" centers outside.
Heat will be by electric water heater. I have not purchased yet. (I live on the side of a mountain in a town of 300 people, natural gas is not an option).

I just want a simple system that will maintain a constant temp. I work with bare metal a lot on these cars, and its not uncommon for the outside temp to go from 80 to 40.....humidity nightmare. I have no pump, no manifold, no heater....just tubing and the pex tools. Shop is wired for the heater. Do I do a closed or open system? Is there someone that can make me a list of parts to buy that knows what they are talking about? I don't know enough to just order a bunch of stuff online and build it. I am admitting I am over my head. I'm tired of looking at those tubes coming out of floor and being cold. Thank you for taking the time to read this. I'm attaching pics of the tubing.......no laughing. Thanks again

tbrooks

I'm just learning about this stuff myself. I can tell you, you should definitely get something with outdoor reset. This will help the heater/boiler to keep up with those outdoor temp swings. Personally I think closed systems are better/safer, but being in a shop this may not be as much of an issue, or it could be more since the water probably won't get used as much. These guys can help you get it figured out, but to make it right may require more than you think. These systems are complex, and to make them work right takes the right components.

SWEI

How much time do you want to spend learning?

What are your energy costs for electric, NG, LPG?

nitrojoe

I don't want to learn about it really......I'm not opening a radiant heat store for sure. All I have is electric, I'm not going to babysit this thing with wood. Costs of utilities aren't a deal breaker.

nitrojoe

They are complex.....i don't want to know more than I do already. i was talked into this, I think its a great idea. The reality of it hasn't been that way. I'm working on a 1906 Cadillac tonight.......I could care less about pumps and flow valves and head pressures.

Gordy

Gotta,post a pic of that Caddie.

Paul Pollets

too bad you didn't use barrier type pex. Now you will be limited to an "open" system and either bronze or stainless pumps.

nitrojoe

I will post a pic of it tonight....I've got Rolls Royce convertible I am doing too. Open system it is then.....Thank You!!!

Ironman

Unless you have an unusually low electric rate in your locale, the electric water heater is by far gonna be the most expensive to operate. How about using propane?

Though you may not care about learning particulars, if you're doing everything yourself, you're inescapably faced with particulars. That's why that was mentioned. And not dealing with them now will only lead to undesirable consequences later.

One in particular: your slab is a high mass heat emitter. That means that it takes a long time to heat it up and it will give off heat for a long time. If the water temp is not modulated by a smart control, the slab will overheat the building because it will continue to give off heat for many hours after the thermostat is shut off. It's called the flywheel effect. Being a car guy, I'm sure you can relate to that. At the very least, a Tekmar 519 radiant floor thermostat with a slab sensor should be used.

Bob Bona_4

I'm thinking lp with possibly an IBC 5-55 mod con. Like Bob said, be sure to embed a 3/8 copper tube, less than 8 foot long with minimum bends for a stat slab sensor.

nitrojoe

Thanks for the replies.....I will check to see if a propane truck can get up here to service a tank.

4Johnpipe

There are some decent electric boilers available. I would invest in more tubing and space the tubes closer together (utilize lower water temps) and potentially look into solar panels to offset the electric cost.

Zman

What you need is a closed system that contains no ferrous parts.
You don't want a system that is open to your domestic hot water system.
The simplest way is to use an electric on demand water heater.
There are companies out there that sell the water heater and all the parts preconfigured. You just hang it on the wall, purge the air out, plug it in and let er rip.
If you divide your BTU calc by 3,412, that will tell you how many kilowatts you need. If you want to be able to ramp it up more quickly, you may want a bigger unit.
I agree with the folks that are suggesting outdoor reset and other bells and whistles.
In reality, you came here wanting the simplest possible solution.

If you want to compare the costs of other energy options down load heatcalc.xls

Gordy

It was done with Aqua pex Zman. That's making it open. I don't think the intent is mixing with domestic. I think the concrete is already poured also so committed on the tube spacing.

Gordy

One thing comes to mind humidity was mentioned. OP Restores cars. The radiant Will do little to control humidity if it's a huge concern. Actually that is one of the benefits of radiant in the home air is not as dry. Op is in Oregon state in the mountains.

nitrojoe

Yes.....slab is poured. Maybe humidity is the wrong term. I just know that when there is a big temp swing, I get rust on bare metal. Warm car will pull the moisture out of the air like a cold beer can on a summer day. If the temp stays pretty consistent, I don't have a problem. I'm not near the ocean. System in the shop is stand alone....no domestic water involved. Intrigued by the electric boiler. I haven't called the propane people yet. Thanks again for the comments

SWEI

http://www.thermolec.com/en/productview.aspx?type=product&id=62 is the smallest electric boiler with built-in ODR control I know of. Not expensive.

nitrojoe

Pic of Caddy as promised. Also convertible Rolls and California Special Mustang. Thanks everyone.

nitrojoe

Quick question: Can I loop the 2 middle runs and the 2 outer runs together? Effectively making 2 200' runs instead of 4 100' runs. Thank You!!

Jamie Hall

I'm no expert on radiant design, believe me! But two thoughts come to mind with your idea of making 2 200' runs. The first is... why? You'll lose less energy pumping with the shorter runs. Also, there will be more difference of temperature with the long loops -- unless you push more flow through them. I can see it from the control standpoint, though -- but if it were mine I'd run them in parallel rather than in series.

Zman

4-100' runs would be a better plan especially given that you are a little light on the amount of tubing in the slab. You will have much higher flow rates and experience less heat drop with the loop.

nitrojoe

Got it.....Thanks. I was thinking less fittings and plumbing...not flow and efficiency.