Side-exiting natural draft hanging furnace, thermal switch keeps tripping

[Noltz]

Background; Personal 30x40 workshop w/6" insulation, sliding 12x12 barn door thats not well sealed, 13' ceilings, shallow pitch roof. Metal siding inside and out. I grabbed a functional take-out hanging furnace from a garage sale thats 80k BTU, 80% eff, pilot and slung it up 2' from my ceiling. Furnace has a 7" discharge and is natural draft. I slipped on a 7-6 reducer, one twist elbow @ 45°, and 3' of pipe out my wall. About 1/2" rise. Problem is the thermal (or "spill"?) switch keeps tripping so I think I'm not getting enough draft. Pretty sure I have some exhaust getting into the shop too (CO detector is on order)

I'm thinking try lowering the unit another inch or two and see if that helps the draft but has anyone else encountered this and could share their solutions?

 

[danski0224]

A venting table will give you the information you are looking for.

 

[TurnipTruck]

In my non-professional experience, standing pilot(natural draft) heaters need sufficient draft from a tall stack, whereas intermittent pilot(forced draft) can be vented horizontally.

 

[Bert_]

If it's actually natural draft then it needs a vertical chimney ending above the roof. Not horizontal vent

 

[Noltz]

Lowering the furnace worked. Thanks.

 

[PoorUB]

The correct way is a vertical chimney. I would recommend not running it like you have installed it.

In my experience natural draft appliances need to vent through a vertical chimney. Thank God it had a safety as you were most likely dumping carbon monoxide into your shop, and you still might be.

If you are not going to install it correctly, at the very least get a carbon monoxide detector/alarm for the shop before you just get sleepy and take a long nap in your shop.

 

[isb cornbinder]

Our company has installed many horizontal furnaces in workshops. I have one in my home shop. A vertical vent stack is necessary.
We never installed a used furnace. The required inspection made used as costly as a new furnace.

 

[danski0224]

If you are not going to install it correctly, at the very least get a carbon monoxide detector/alarm for the shop before you just get sleepy and take a long nap in your shop

Suggesting that a CO detector can substitute for a proper installation is not good advice.

A UL listed CO detector may not actually sound an alarm under otherwise dangerous conditions.

 

[PoorUB]

Suggesting that a CO detector can substitute for a proper installation is not good advice.

A UL listed CO detector may not actually sound an alarm under otherwise dangerous conditions.

I am not recommending he just leave it installed incorrectly, the OP will do what ever he wants! I just suggest he get a CO alarm to save his ****! Best advice is to install it correctly!

What are the chances the OP will install it correctly, now that it appears to work? My bet is some where between slim to none.

 

[Noltz]

I am not recommending he just leave it installed incorrectly, the OP will do what ever he wants! I just suggest he get a CO alarm to save his ****! Best advise is to install it correctly!

What are the chances the OP will install it correctly, now that it appears to work? My bet is some where between slim to none.

You're right. I am going to do whatever I want. In the original post I said I have a CO detector on order. It'll be here Tuesday. I'm gonna test it. I can afford a new power-vent furnace but with a coming recession I'm not going to spend unnecessarily. I also love trying things and learning what actually works. I fail sometimes and that's okay. I've learned something. Challenged it. I wonder if anyone here would change their mind if I find zero PPM with a side vent. My bet is also slim to none! But that's okay too.

GJ is full of very very smart people that do excellent work and know "the right way" to do things. I'm not gonna vent too much here (pardon the pun) because I appreciate that experts are offering free advice.

 

[TurnipTruck]

I have calibrated tens of thousands of different kinds and types of gas detectors in my career, some of which were exposed to many multiples of lethal doses.
For several years, I was solely responsible for calibrating up to 400 personal Hydrogen Sulphide detectors. Why am I telling you this?
I was shocked when I found this chart for how slowly residential Carbon Monoxide detectors finally alarm:


Here are typical symptoms at various alarm levels:

Anyway, no judging, just raising awareness.

P.S.: the hydrogen emitted from a charging lead-acid battery will be cross sensitive to a Carbon Monoxide sensor at least twenty feet away.

 

[Noltz]

I have calibrated tens of thousands of different kinds and types of gas detectors in my career, some of which were exposed to many multiples of lethal doses.
For several years, I was solely responsible for calibrating up to 400 personal Hydrogen Sulphide detectors. Why am I telling you this?
I was shocked when I found this chart for how slowly residential Carbon Monoxide detectors finally alarm:
...
Anyway, no judging, just raising awareness.

P.S.: the hydrogen emitted from a charging lead-acid battery will be cross sensitive to a Carbon Monoxide sensor at least twenty feet away.

Now THIS is great information. Thank you very much for posting this chart. You confirmed the numbers I was told by an OHSA rep I know. I'll make sure to have the furnace run for several hours and then come check what the meter says (my alarm has a read-out on it).

 

[PoorUB]

I wonder if anyone here would change their mind if I find zero PPM with a side vent. My bet is also slim to none! But that's okay too.

Make sure to test it in all conditions and temperatures. Wind direction alone might be enough to screw you over.

Seriously, it should be installed with a proper vertical chimney. I can be as simple as single wall heavy gauge pipe and using B-vent where clearances are an issue.

Also, you should not have reduced the vent size. If they put a 7" on it, they want a 7".

 

[Galaxywide]

Make sure to test it in all conditions and temperatures. Wind direction alone might be enough to screw you over.

Seriously, it should be installed with a proper vertical chimney. I can be as simple as single wall heavy gauge pipe and using B-vent where clearances are an issue.

Also, you should not have reduced the vent size. If they put a 7" on it, they want a 7".

Yeah, having just installed an older 80% furnace pretty much everything about OPs install is somewhere between incorrect and hazardous. The furnace installation manual should have venting requirements, including size, type and minimum height. Mine required a vertical outlet, with height equal to or greater than horizontal run - and it's induced draft with a blower!

 

[danski0224]

I wonder if anyone here would change their mind if I find zero PPM with a side vent. My bet is also slim to none!

The issue is that it isn't installed to manufacturer specifications.

There is a great deal of liability in taking this approach.

A typical residential CO detector is NOT suitable as a safety device as you intend to use it. Additionally, if it did alarm, the equipment will not shut off.

And even if it was tested with something like a combustion analyzer, that test really only proves that it was working at that time. It is not a guarantee that the equipment, installed outside of manufacturer specifications, will be operating safety tomorrow.

All of this is a problem with forums.

Just because one ******* does it, and it works, and proclaims it online, doesn't mean that the next ******* reading it will be so lucky.

 

[Noltz]

Make sure to test it in all conditions and temperatures. Wind direction alone might be enough to screw you over.

Seriously, it should be installed with a proper vertical chimney. I can be as simple as single wall heavy gauge pipe and using B-vent where clearances are an issue.

Also, you should not have reduced the vent size. If they put a 7" on it, they want a 7".

Well I'm gonna do something you'll never see again on the internet;

I was wrong. Ya'all were right. It's not working reliably. Under windy conditions it still trips. I've tried a number of different configurations of rise and whatnot but with and without the cap in the gusty winds right now it'll trip. The barn door (12x12') was wide open.

So I just came back to say thank you to all that replied and I'm satisfied now after experimenting and challenging the norm that this style furnace cannot be side vented.

 

[danski0224]

Once again, venting tables will tell you how to vent it properly.

Or, the instructions (if it's new enough). Furnaces from the last 15 years or so contain a VERY detailed section about venting.

Side venting, if allowed, will be covered in the instructions.

It is NOT permissible to side-vent Type B vent pipe, unless there is a power exhauster outside. Just because others have done it does not make it right.

I looked at a boiler flue that was *mostly* vented properly, but it was about 18" short on rise. Owner installed. Used the manufacturer supplied draft hood. Guess what. The heat exchanger was plugged with soot and it probably never vented properly, and I was called only because it wasn't working. Honestly, he was lucky to not have died from CO poisoning. I fixed it, but have the tools and knowledge to do so.

There can be issues, even when following the manufacturer recommendations. The standard and typical tech is not going to find them.

 

[Bert_]

Put a t outside the wall and run b vent above the roof. An outside chimney isn't great for draft but it could use the existing hole and wouldn't cost much.

 

[Noltz]

Put a t outside the wall and run b vent above the roof. An outside chimney isn't great for draft but it could use the existing hole and wouldn't cost much.

Might try that before I throw in the towel on this. I'd like to use it but it's too much hassle