Shop Heating Question

[Tom Spring]

Hi guys... new to the forum here, in fact this is my first post... I wish I had found this site 4 months ago...

First a little background... I'm building a new 24'x32' freestanding woodshop. I spent all last winter planning and had the foundation put in last May... I contracted the foundation and will contract the main electrical connection and the heater/gas line work... the rest I'm doing myself. I'll post a few pictures of the progress...

My question today is about a heater... I live in Alaska, so it gets pretty darn cold in the winter. For insulation I'm putting in R-21 on the walls and R-38 in the ceiling. I plan on putting in a 45,000 BTU Reznor brand gas fired heater. I'd like some feedback and guidance on the pros and cons of a seperated combustion chamber version vs a non-seperated combustion chamber... price is definately a factor here, as a seperated combustion chamber unit will run me about $1,000 more than the non-seperated combustion chamber type. I've read some other threads and the "dust explosion hazard" doesn't really seem all that realistic...

Any thoughts? Please... :-)

[dennis kranz]

Wish I could help you with what you want to know. What I want to know is how are you going to get any work done with that view? I'd be looking out the back window most of the day. Good luck on your shop. My shop/ shed is going up tomorrow.
Dennis

[Tom Godley]

The view is great -- WOW.

By separated - are you speaking of sealed combustion?


The sealed combustion units are just that - no open flame. They use outside air for the combustion process. This is better because they do not draw in air from the heated space - they will not de-pressurize the heated space. They have a fan that draws this air in from outside. The sealed units are more modern and are normally more efficient

Regular combustion units have the flame open to the heated space -- some of the units have covers around them and also have makeup air from the outside. But this is normally just an add on.


The fire risk all depends on what vapors you are making in the shop - also some open flame units can be effected by some chemicals as they draw in the fumes and burn them

[Ken Fitzgerald]

What shop?...Anyone see a shop.....Didja see those mountains?....Oh..:rolleyes:

Welcome to the Creek!

I'm not a HVAC expert so I'll defer the question to someone more knowledgeable. I have a hanging 75,000 btu natural gas heater in my shop. Typically when I first start it up each heating season, I"ll smell a little burned wood smell but after that it's not a problem. I suspect if I run the fan before I allow it to get hot that might eliminate the problem.

[Tom Godley]

de pressurize?? I think I was still in bed.

I wanted to say that the sealed units will not create a negative pressure in the shop. The open units will draw in the heated air from your shop - this will require cold air to be drawn in from all the cracks around the building to "make up" this combustion air.

[David G Baker]

Tom,
I have a natural gas fired Modine 75K BTU "Hot Dawg" ceiling hung forced air furnace in my 30'X40'X10' well insulated pole building. It works great but the only complaint that I have is that I wish that I had spent the money and bought a furnace that used outside air for combustion. The air inside my building stinks real bad if I haven't had the doors open for a while. I have a carbon monoxide detector in the building near the heater and it hasn't gone off so the air is probably safe.
I looked at the Renzor units and found from the research that I did that the units may consume a lot more fuel than the forced air units. On the plus side they also heat everything in the building so when you touch items made of metal your hands don't hurt from the cold metal.
I live in Mid Michigan and have some pretty cold Winters, maybe not as cold as yours but if you work with metal hand tools it really gets painful after a while. I keep my building temp at around 55 degrees during the cold season and heat it to 65 degrees when working in it.

[Ken Garlock]

Hello Tom, and welcome to the Creek. Do stop in frequently, the water is always warm.:)

Tom, your site/countryside is beautiful. Thanks for posting the pictures.

Now a couple thoughts. and opinions.
First off, you don't have sufficient insulation. I would double wall the shop with an inside wall identical the the 2x6s you are using(?). That would allow you to double your insulation and approach an R40. Yes, it will cost more, but it is money spent only once, whereas you will be paying a heating bill every month. Second, go with at least R50 in the attic. Here again, you spend your money once and save spending it on heating.

I am on the flip side of your situation. I live in north Texas where the summer temp can approach 110, but seldom gets below 10 in the winter. When we built, I used 8" thick SIP walls with an R30 rating; in the ceiling we have the equivalent of R50.

Second thought. If you don't want to spring for the sealed combustion furnace you could do what I did when I lived in Ohio back in the 1970s. I ran a piece of 4" PVC pipe to the outside on one end, and brought the other end up to the air intake for the gas burner. That provided fresh air for combustion and thus relieved any negative pressure in the house. IF I were to do it again today, I would place an electrically operated damper in the PVC pipe to allow cold air flow only when the furnace was actually running.

Once again, welcome.:D

[Jim Becker]

Sealed combustion would be my choice. It keeps the heat exchange contained and eliminates most of the issues with fumes or other substances being sucked into the heater when it's in use.

BTW, welcome to SMC! And your place is absolutely beautiful...

[Tom Spring]

Thanks for the info guys... I'd rather go with a sealed combustion heater myself, but it looks like I won't be able to afford the extra $$$... so I'm going with a non-closed combustion heater.

And yeah, the views here are pretty awesome :) They help ease the pain of the country's highest gas prices and the extra shipping I have to pay to get anything delivered here :mad:

And as for an update... I've recently learned that no one here in Anchorage rents Ditch Witch trenchers.... looks like I'll be renting a mini excavator to dig the trenches for my electric and gas lines... On the positive side, I did get the rest of the wall insulation up today and got the windows trimmed out...

[Jim Becker]

Tom, if your site needs any other grading, etc., rent a small TLB (tractor-loader-backhoe) to do both your trenching and that work at the same time. It may cost you less money that way with one rental, etc. Some of the mini-excavators have a blade, too, but there are limits to what can be done with that setup that are not there with the TLB.

[Tom Spring]

Well, thought I'd post another update on my shop-in-progress...

Spent all day today in the cold Alaska rain with my rented mini-trencher digging my 170 feet on trench so I can run my electric and gas line... WAY better then digging by hand, but man my back is killing me... now the heating contractor can come in next week and run my gas line and install my Reznor heater... I also decided to go with the cheaper non-selaed combustion chamber unit... I'll probably regret that decision down the road, but my wife keeps pointing out that I'm already overbudget on this project :o

Also spent this past weekend putting the rest of the siding up (LP SmartPanels... the most cost effective siding option for me)... put up the first row of vapor barrier on the ceiling and got the first row of drywall installed... I must admit, seeing drywall go up is a good feeling... a friend of mine also put in the first couple rows of ceiling insulation while me and another friend were wrestling the drywall up...

Back to work tomorrow... hopefully I'll get more drywall up this weekend and get the electrical roughed in...

[Ken Fitzgerald]

Hang tough and stay with it Tom! The results will make you grin!

[Yuchol Kim]

I have both Hot Dawg (similar to Reznor) 75k BTU in the garage and Sterling sealed combustion 75k BTU in the shop. I see a huge difference between the two. The Sterling puts out a lot more heat. It's built more heavy duty, slightly bigger and the sealed combustion means it burns cleaner (no dust to turn the flames yellow/orange). It's not a safety issue, just performance. If you're considering Reznor, I would strongly suggest you look at Sterling. Nothing wrong with Reznor, it's just that Sterling is better. Also, it had free shipping direct from the factory (AK might not apply).