Radiant Tubes in the Floor...Now What?

[mopar440_6]

Ok guys, the shop is almost finished and the temps are falling quickly here in SC PA. After the issues I had with the HVAC sub-contractor who tried to screw me over on the insulation, I'm a bit wary of the local guys so I figured I'd start here.

Building specs are as follows:
50'x60'x14.2' Pole building
Steel exterior and interior
6" slab
2" Owens Corning Foamular under slab
one zone, 9 loops (~310' each) of 1/2" pex on 12" centers stapled to foam
Blown in cellulose filling wall cavities ~8" (R22?)
~12"-14" blown in cellulose in ceiling (R40?)

The load calc that I did myself came out around 75K BTU. My end goal is to have a full mod-con propane boiler setup to power the radiant. However, after all of the extra little costs of building the shop, I'm going to be significantly over budget. So, paying to have a $4,000 boiler installed is probably out of the question this year. But I already have an 80 gallon electric A.O. Smith water heater that was free (IE - I don't care if I kill it in a season or two).

So, my question is, would it be possible to temporarily set up the rest of the radiant system (manifolds, pumps, expansion tank, etc) in tandem with the water heater and change it out for a boiler next season?

 

[UpstateNY]

Yes, d/l this:

http://www.google.com/url?sa=t&rct=...d/414/&usg=AFQjCNHVwAg7bPSBqO8lEtRgBhMKDnK7aw

 

[37ford4dr]

you mean spend your money on setting up the manifolds correctly and using a "make shift system with only a recirculation pump, expansion tank and use the current heater your have now?

so this is what you are thinking??


that the recirculation pump is designed for your length of tubing and the number of manifolds, so that would be usable in both applications, there fore the manifold would be the same and no wasted money.......... and I am not sure on the expansion tank but I think that is sized for the BTUs and I don't think a bigger one is going to hurt you.....now the big question..... would the monitoring and control system would be applicable to both systems? You may be able to find the sweet spot and just leave the system on all the time and put the recirculation pump on a timer set up

I think the real problem with your idea is that the current electric heater you have may be too under powered to bring the temperature up to where you want it.
and I have no idea what the cost of electric would be for that running all the time, I bet its a chunk of change though

 

[Rookie2]

That's one hell of a slab of concrete , you may get away with three 80gal water heaters . IMO

And don't even start without antifreeze in the system.

 

[kabinenroller]

In my first building 24x30, I installed an electric 40 gal. hot water heater. I used it one season because it could not recover fast enough to keep that small building warm. (60degrees) I swapped it out for a 40 gal. Propane unit and it worked fine. Electric just cannot recover fast enough for radiant floor heat.
My existing building has an on demand propane unit that has no problem keeping the 1600 sq. ft. warm.

 

[Majordisorder]

Your water heater might work if you replace the 4500 watt elements with 9000 watt elements and run a separate 220 to each element.

 

[myredracer]

On estimating a size for a hot water tank, not sure where the location is, but approx. 6 watts of electric per square foot would be a ballpark figure for a house, but you won't be heating the space up to 70+F degrees. Maybe around 4 watts/ft.? So for 3000 sq. ft. at, that would be 12kw. Or at 5 watts/ft, would be 15kw. 75K BTU would be the equiv. of 22kw which suggests 12-15kw is about right (doesn't allow for recovery tho.).

Don't know the heater element rating, but it's not going to be near 12kw. Maybe it's two 4500 watt elements operating in flip-flop? 4.5kw is nowhere near what you need. Without doing a detailed heat loss calculation for the specific geographic location, it's hard to know if that will keep it much above freezing in the coldest temps.

What about just using a few electric unit heaters or some other type of electric heaters? Maybe even rent some portable ones? Then you can finish the rest of the hydronic system at your leisure and do it once instead of hooking up something and having to undo it later on.

You could try and find one or two more heaters on CL perhaps for cheap or free. But then you'll need the power to run them. For 3 x 4.5kw, that's 70 amp wire and breaker.

Just got our in-floor hydronic heating in our attached garage/workshop operating after a number of years while finishing the rest of the house. I totally love the radiant heating! Took until the next day for the slabs (3 total) to come up to operating. temp. Have the temp. set at 60F which feels a little cool at first but once physically working away, it's fine. Can't wait to see the next gas bill (not)...

 

[Yourfired]

Yes you can definitely do so. You might put too much strain on the electric water heater in the meantime, that is a lot to handle for an electric. If you say it doesn't matter to you then go ahead and do so. Sound like one hell of a concrete floor.

 

[BadgerBoilerMN]

No.

Even if you estimated load is correct, likely half of that, you will not be able to keep up.

A 40 gallon propane water heater should keep the place above 50°F if the worst weather if you set and forget the thermostat. Naturally you will want a direct vent water heater so you don't have to cut a vent through the roof. Now you are getting into money.

You might consider an electric boiler in the short term, the install the PVC or PP vent through the wall later with the new LP ModCon.

You should really have an ACCA Manual 'J' done before you invest in a good ModCon.

 

[VHF]

I concur. A standard electric water heater with interlocked 4500W elements will provide about 15K BTU/hr. So it won't even come close to meeting a 75K BTU/hr load.

(Watts * 3.4 = BTU/hr)

An adequately sized electric boiler would do the trick, but could easily cost over $500/month to operate during the winter.

 

[mopar440_6]

Now that the holidays are over, I'm back to working on my heating solution especially since the electrician should be finished by the end of the week.

Based on the responses and research I've done so far it seems that using the electric water heater temporarily is a definite no-go. But, I need to figure something out so that I can get my final inspection and floor coating done.

As previously mentioned, cost is a limiting factor right now. I should have a couple official quotes by next week for having the system professionally installed but I'm guessing all will be well over what I can afford.

I'm comfortable doing DIY plumbing and electrical and I'm a mechanical engineer by trade so I can do design work and calculations. However, without doing HVAC work everyday I don't have access to all the data/calculators/knowledge base to make sure that I'm designing the system correctly. The Grundfos manual is the best information I've gotten so far, so thanks UpstateNY! But that still leaves me lacking more information than I'm comfortable designing a system with.

So, hopefully you guys can point me in the right direction. Where do I go from here?

 

[goneflyin2002]

It is a lot of money (2995) but a Viessmann 100 would be the right ticket for your place and it's an awesome piece of equipment.

 

[finn]

Budget ~$1000-$1500 for pumps, manifolds, expansion tanks, CU tubing, fittings, filters, flanges, valves, vents, auto fill valves, flanges, controllers, gages and more.

Heating w/radiant isn't cheap.

 

[UpstateNY]

It is a lot of money (2995) but a Viessmann 100 would be the right ticket for your place and it's an awesome piece of equipment.

Is that product recommended as a radiant heat solution given the use of glycol etc in the water ? It doesn't seem to say so on their web site ?

 

[sands35]

Budget ~$1000-$1500 for pumps, manifolds, expansion tanks, CU tubing, fittings, filters, flanges, valves, vents, auto fill valves, flanges, controllers, gages and more.

Heating w/radiant isn't cheap.

If that is your budget, then start looking for used stuff on Craig's list. A new basic boiler is ~1500-2000. A tankless water heater is $900 (or so - last I looked was ~2 years ago). The other stuff is about the same for a simple single zone, not that expensive if you can DIY. A primary/secondary design has 2x the parts.

 

[mopar440_6]

It is a lot of money (2995) but a Viessmann 100 would be the right ticket for your place and it's an awesome piece of equipment.

It seems that all of the mod-con boilers around that size (which is what I would need assuming I did the load calc correctly) are in that same $3-4K ballpark.

Budget ~$1000-$1500 for pumps, manifolds, expansion tanks, CU tubing, fittings, filters, flanges, valves, vents, auto fill valves, flanges, controllers, gages and more.

Heating w/radiant isn't cheap.

Heating isn't cheap. But radiant is a whole lot more efficient than some other options. My estimates were around $1500-2000 for everything except the boiler but I was also figuring in a propane tank.

Is that product recommended as a radiant heat solution given the use of glycol etc in the water ? It doesn't seem to say so on their web site ?

Their tech data sheet didn't really give any specifics from what I saw either. However, it is listed as a boiler rather than a water heater, thus I would assume that it is rated for heating.

If that is your budget, then start looking for used stuff on Craig's list. A new basic boiler is ~1500-2000. A tankless water heater is $900 (or so - last I looked was ~2 years ago). The other stuff is about the same for a simple single zone, not that expensive if you can DIY. A primary/secondary design has 2x the parts.

That's not my budget, that was a budget recommendation for everything except the boiler. I'm honestly not sure what my current budget is at the moment and likely won't know until the electrician is done.

 

[BadgerBoilerMN]

You can get a final inspection without a boiler. Tell you ran out of money...

I have used electric space heaters to keep my shop above freezing while working out the kinks.