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SVreX
SVreX MegaDork
4/2/18 4:33 p.m.
SkinnyG said:
SVreX said:

You only need as many circuits as the number of machines you may run at the same time. 

Unless there is the joy of code/inspection/outlet-limits sort of thing.

If not, giv'er!

That is a popular misconception. 

There is absolutely nothing in the National Electrical Code that precludes multiple 220V outlets on a single 220V circuit. 

SVreX
SVreX MegaDork
4/2/18 4:42 p.m.

I've built about 30 radiant slab buildings, and lived in one. 

STM317 has hit a lot of the high points.  

Except the typical system is not generally insulated 100% underneath. The perimeter is insulated, usually the outer 3' or so, PLUS the exterior exposed edge of the slab. 

BTW, its special insulation.  Needs to be insect resistant.  Standard foam board is wonderful termite food, and completely inappropriate for ground contact.

They are wonderful systems, and there is a LOT that can be done poorly in building them, especially by well-meaning folks who think they know what they are doing. 

frenchyd
frenchyd Dork
4/2/18 5:08 p.m.

In reply to SVreX :

I’ve Visited an average of 20 construction sites a day for 22 years. Only rarely do I see an area not completely covered in foam if it’s going to have in floor radiant heat.  

It might be the difference where you live. As you are aware Wisconsin is in the Northern tier of states and that must account for the difference.  

 

SVreX
SVreX MegaDork
4/2/18 6:22 p.m.

In reply to frenchyd :

I don't doubt people do that, and I'll agree that things vary by region.

However, I've never seen a design spec that showed that. 

The soil under the center of a heated building is not a thermal loss. It's part of the thermal mass. 

 

RossD
RossD MegaDork
4/2/18 7:33 p.m.

Foam below the slab keeps from a big loss. I can check the Ashrae book tomorrow for reasons.

frenchyd
frenchyd Dork
4/3/18 1:08 a.m.
fasted58 said:

http://www.mrheater.com/product.aspx?catid=50&id=180

I was planning one of these: 75K BTU propane or NG (propane will convert to NG as well) till I dig the gas line. Hangs from ceiling joists w/ minimal clearance. Shop is over 900 sq. ft.

I can get a free used forced air furnace from my HVAC contractor buddy but it'd hafta sit in the 'well' of the addition next to the gas powered equipment, and ducting into the shop floor would be a pita.

Anybody have one? Comments/ recommendations?

DIY duct work is a Royal pain in the posterior. Careful measurement and planning is required  along with just the right combination of pieces. Make a slight mistake anyplace and warm air won’t reach because of too much turbulence or too much length/ bends.  Now a pro will be able to have everything needed or fabricate the required pieces.  On the other hand it took countless trips to the big box store as I put my back up system together.* I still have  about 20 pieces left over that were altered or used and replaced. That I can’t return.  

* In a 5500 sq.ft. House with 105 windows / whole wall areas overlooking the lake and other views heat loss on sub 20 below zero days. I ducted forced air as back up  underneath windows. Turns out the infloor radiant heat is it’s own back up when the power is out because of all the thermal mass in the Timbers. But it is still nice not to have the chill of walking in front of windows on cold blustery days.  

PEX on the other hand comes in a nice roll and “staples” to the foam so easy  ( there are plastic “ staples” that hold the PEX in place on the foam until the concrete is poured)  PEX Only takes a small hole rather than a complete re-engineering of floor joists to fit  in the allotted space..  

Then once you see how easy the PEX goes in for floor heat  you’ll use it for all your plumbing needs. Saving yourself countless hours of cutting and fitting.  PEX is just the easy button not to mention not having to sweat sweating fittings together again. ( yes, pun intended, sorry about that)  Plumbing  inspectors  must love seeing PEX in earthquake zones. But please don’t cheap out. Use the brass fittings not the plastic ones. According to my plumbing buddies plastic will find a way to crack or break in 5-7 years. 

SVreX
SVreX MegaDork
4/3/18 5:53 a.m.

I'm not sure how I feel about that...

We usually tie the PEX to wire reinforcing mat. This leaves the PEX fully imbedded in the concrete, near the center of the pour. Stapled to insulation would mean the PEX would not be imbedded on the bottom, and that the concrete would have weak points poured into it at each waterline. 

I'd have to study that idea a bit more before I was willing to do it  

...and I would NEVER put a joint in the PEX in the concrete, regardless of whether the fitting was plastic or brass.  PEX should be continuous in the concrete, with all joints above the slab.   

 

frenchyd
frenchyd Dork
4/3/18 6:52 a.m.

In reply to SVreX :

Absolutely agree no fittings in the slab.  ( I was talking about plumbing needing brass fittings.)

With regard PEX and rebar or Matt.  I’ve been told that PEX does flex even within concrete.  Given that wire or rebar will abrade PEX.  I’ve also seen where someone wiring PEX  to mesh or rebar over tightens  the wire and risks puncture from the broken end of wire. It may not show up during the pressure test but over time may puncture. 

The plastic staples into foam solves all those issues plus the “stapler” they use means you’re not down on your knees doing one at a time. You stand up kick the PEX about into place, use the “stapler” to put it exactly where you want it and push down. Set!

SVreX
SVreX MegaDork
4/3/18 7:00 a.m.

In reply to frenchyd :

I understand it would be easy. 

If it compromises the structural integrity of the concrete or the thermal efficiency, it's NOT worth it. 

Overtightening is not a problem if you use zip ties or plastic straps  

30 projects, over 20 years.  I've never had a problem or callback, including the projects that are now 20 years old.

 

frenchyd
frenchyd Dork
4/3/18 7:44 a.m.

In reply to SVreX :

 I learned about PEX  in slabs watching guys who did it all the time. That was their niche.   In 22 years visiting over 100,000 job sites I saw only two scars indicating a leak had been detected, opened up,and repaired. In one the contractor told me it was a piece of a blade from the mixer that had broken off. The second turned out to be a razor sharp rock. 

Now admittedly not all of those sites had in floor radiant heat but a serious percentage did. 

It’s a competitive market and if you save an hour over a guy on his hands and knees tying I can see where  you’d pretty much have to do it that way.  

SVreX
SVreX MegaDork
4/3/18 8:16 a.m.

In reply to frenchyd :

I have no interest in trying to win this. 

turtl631
turtl631 HalfDork
4/3/18 9:51 a.m.

Radiant sounds pretty awesome if you're building from scratch.  I'm definitely going to research this more.  I try to keep the garage around 45°F in winter then kick up the thermostat to 55 or so if I'm going to be working out there.  Still, car parts and the slab are cold.  I have poor circulation and my extremities get cold really easily.  Standing on a warm slab would do wonders.

Ransom
Ransom GRM+ Memberand PowerDork
4/3/18 10:00 a.m.

As much as I think in-floor heat sounds fantastic, I think the repeated need to add anchors in as-yet unknown spots for future stands and fixtures suggests that I'm probably better served with a slab that doesn't require a treasure map to drill. But maybe that's still a misconception on my part, depending on the thickness of the slab, or just how complete the PEX coverage needs to be.

The current arrangement has basically worked; sure I wouldn't mind more heat faster, but it's a garage, not a living room, so I'm usually moving, and wearing coveralls. The little 220V heater I hung up does a decent job of heating the current half-fiberglass-insulated-2x6-wall/half-cinder-block arrangement. Or, I guess I could say it takes the chill off fairly effectively, especially if I turn it on and then go have coffee and come back. The new shop will be significantly larger, but won't be part cinder block.

I'll also look into heat pump setups; in the name of happy neighbors, I'll probably be doing a lot of work with the doors closed. Here in Portland, winter tends to sit in the 30s and 40s with a few dips into the 20s and a few teens; but then the last couple of years have seen multiple weeks of 90s and 100s summer heat, so being able to take the edge off that would be good, too.

Whatever active thermal control happens, I'm certainly going to be insulating thoroughly for both comfort and noise attenuation.

SVreX
SVreX MegaDork
4/3/18 11:48 a.m.

Portland Oregon?

Heat pump is not gonna help you at all. 

Ransom
Ransom GRM+ Memberand PowerDork
4/3/18 12:05 p.m.

In reply to SVreX :

Yes, Portland, OR. I suppose research would uncover the reason as I moved along. I do appreciate the warning, but would love the gist of why that's the case. I'm going to guess "wrong climate", but without a "why" I'm left scratching my head...

"Okay, Google. Why won't a heat pump work well in Portland, Oregon?"

(As an aside, I actually ran that search more or less, and it came up with people mostly arguing in favor of a heat pump in Portland...)

SVreX
SVreX MegaDork
4/3/18 12:13 p.m.

Climate. No heat to pump. 

Jcamper
Jcamper Reader
4/3/18 12:20 p.m.

In reply to SVreX :

Uh, my house uses heat pumps. Work awesome, very low energy cost. They are the most efficient solution in this climate as far as I know. Jcamper

dculberson
dculberson UltimaDork
4/3/18 12:32 p.m.
SVreX said:

Climate. No heat to pump. 

"The heat pump is effective by itself down to temperatures around 25 to 30 degrees Fahrenheit. At that point, either a gas furnace or an air handler with supplemental electric heat will kick in and help heat your home." according to trane.com. So while it will work most days it sounds like there's a number of days in the winter where it won't work.

Ransom
Ransom GRM+ Memberand PowerDork
4/3/18 12:43 p.m.

I wonder how effective and expensive the supplemental heat is... And I really need to do some very rough research into the scale of these approaches. Anything for this larger shop is going to be more involved and expensive than the $100 electric heater I've got now, but I suspect there are some huge differences in the cost and work involved between some of these systems.

Karacticus
Karacticus GRM+ Memberand Dork
4/3/18 12:57 p.m.
fasted58 said:

http://www.mrheater.com/product.aspx?catid=50&id=180

I was planning one of these: 75K BTU propane or NG (propane will convert to NG as well) till I dig the gas line. Hangs from ceiling joists w/ minimal clearance. Shop is over 900 sq. ft.

I can get a free used forced air furnace from my HVAC contractor buddy but it'd hafta sit in the 'well' of the addition next to the gas powered equipment, and ducting into the shop floor would be a pita.

Anybody have one? Comments/ recommendations?

I've got an overhead radiant tube heater in my garage-- works great in Iowa's arctic climate.  It's the sort of thing that looks like this, though mine is a straight run rather than the "U"

Use it to maintain the (insulated) garage at 40F, and then crank it up when I'm working out there.  Once it's on, doesn't really matter what the ambient temperature is if you're in line of sight to it, you're warm.

Robbie
Robbie GRM+ Memberand PowerDork
4/3/18 12:57 p.m.

Heat pumps can and do work down lower than freezing even. But pay attention to the model and it's designed usage.

A heat pump is the opposite of an ac unit. No one thinks about an ac unit as a "cold pump", but that is what it is. Perhaps if they did, people would worry about stuff like "there's no cold to pump!"

The trane website is probably talking about their own range of heat pumps, and/or common residential units, but it is certianly not ALL heat pumps.

I'm planning to run a heat pump in my garage in Chicago. Spec'd correctly it will heat in negative 5 outdoor weather and cool in 100 degree summer days.

Jcamper
Jcamper Reader
4/3/18 1:47 p.m.
Ransom said:

I wonder how effective and expensive the supplemental heat is... And I really need to do some very rough research into the scale of these approaches. Anything for this larger shop is going to be more involved and expensive than the $100 electric heater I've got now, but I suspect there are some huge differences in the cost and work involved between some of these systems.

Yep, like I said before, in my mind it comes down to how often you are going to be occupying it. Heat pumps and in floor heating both make a lot of sense in houses or places you want to keep a very even temp, but that is not my shop use case. 

A couple electric heaters hung from the ceiling and a ceiling fan can heat a well insulated shop up quickly and are a few hundred bucks, take up zero floor space, require no ducting or ventilation, and are safe.   During the weeks you are not out there you are spending exactly zero in electricity. Both shops I have had in this area have stayed above freezing inside even on multi-day below freezing cold snaps thanks to enough thermal mass in the concrete floor and stuff inside. Spend your money and time elsewhere in my opinion. 

Ian F
Ian F MegaDork
4/3/18 1:58 p.m.

In reply to Jcamper :

It might depend on how cold your shop gets.  I have a nice little 220V electric heater for my garage which will get it as warm or warmer than my house.  However, I still need to turn it on a good hour before I plan to be out there.  It's also berking loud, so having the radio on becomes pointless.

Jcamper
Jcamper Reader
4/3/18 2:42 p.m.
Ian F said:

In reply to Jcamper :

It might depend on how cold your shop gets.  I have a nice little 220V electric heater for my garage which will get it as warm or warmer than my house.  However, I still need to turn it on a good hour before I plan to be out there.  It's also berking loud, so having the radio on becomes pointless.

Good point, mine are loud too. 

Reading back through my posts I sound pretty cut and dried but all these questions are very specific for regions, dwelling types, use cases, and energy prices. Let the math guide you! I don’t think I need to tell Ransom that, but thought I would throw that in here. 

I happen to be an EE for a local electric utility so have seen a large sampling of actual bills/structures. Our electricity prices are very low (mine are 8 cents per kWh) thanks to a huge hydroelectric system. My shop is only 1000 sq. ft. and our winter is generally 43 F and raining. 

Sorry if I came off as a know it all. Not my intension. If I had gas plumbed or spent more time out there I could end up with a different solution. Just happened to have specific experience/knowledge for Ransom. 

Jcamper

STM317
STM317 SuperDork
4/3/18 6:22 p.m.

I'm leaning toward a ductless mini split for my heating/cooling needs, although that's still a ways off. I didn't have the time or budget to run gas to my shop, so being able to heat/cool it to reasonable temps with a single unit, and without bulky ductwork taking up valuable shop space seems like a nice option. I'm more likely to work on stuff if I'm comfortable. I don't need it to be 70 degrees year round, but 50 in the winter and 75ish with lower humidity in the summer sounds a lot better than whatever heat/humidity Mother Nature deems necessary. I'm confident that a properly sized mini split can handle that task.

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