Furnace repair question

[spirithorse]

Greetings!
I know this is a strange question for the Scroll Saw Village forum but, I hope there is someone here
familiar with Heating.
I have an old Peerless propane heater/furnace in my garage which is my work shop for scrolling.
It has been a real work-horse but, this year the first time I lit the furnace it made a slightly louder
'pop' or 'whoosh' when the burners ignited and I saw flashback at the opening to light the pilot light.

I never looked it over very closely before now because it always worked well and I had it inspected
by an HVAC company when it was first put into use.

You will see in the photo (best one I could get in the confined area with a flashlight and camera phone)
there is an orifice or open hole right before the pilot light.
It seems to me that propane could be escaping there during the staging of the furnace before the burners
actually ignite which can take about 2 minutes from the time the thermostat is turned on.
I always turn the furnace on at the lowest temperature setting when I first turn the furnace on but, if I am
correct that propane may be escaping before the actual ignition, that would be enough gas build up to make
the unusual 'pop' and flashback that has never occurred before.

That hole does not look to be threaded or anything but, I do not know if that allows air to be mixed with the propane
in front of the pilot light or maybe there was actually another orifice that looks like the pilot light orifice that has
come loose. There wasn't any such orifice looking like a pilot light in the pan at the bottom of the furnace when I
was inspecting everything and cleaning it.

I had my gas supplier run tests today to check the gas regulator (which read about 12.5 on the manometer) and
they checked for leaks with a pressure test of the lines and a soapy water test on all the fittings.
I heard one of the two service men say the pressure may have dropped almost imperceptibly but, when the other
repairman asked if there were any leaks he replied "No, it's not leaking anywhere".

I wish I could have found a picture of that assembly area of the Peerless heater/furnace on the web which would
let me know for sure if that 'hole' or orifice actually had a fitting in it before. As I mentioned, if there had been something there,
I should have found it in the bottom pan of the furnace.

Sorry so long winded but, I wanted to give as much important information as possible to get definite answers instead of
any suppositions. The blue arrow indicates the pilot light and the red area shows the hole right in front of the pilot light.

Even any images showing the pilot light area of an old Peerless furnace would probably be informative.

God Bless! Spirithorse

[Wichman]

Spiders love propane and will spin their webs in the smallest areas, and it doesn't take much to foul the system.

If I were you I would shut off the gas and turn off the pilot light. Then using and air compressor blow the dickens out of everything you can get to.

Once that's done I would turn everything back on and try it again. Once. And only once. If the problem persists call a pro, there may be parts that have just worn out. I hate sudden loud noises so, call the pros.

 

[teachnlearn]

The by product of burning propane is water. Depending on venting, type metal of the heater they could have rusted. Burner could have larger burn holes. Adjustment of the air/ gas mixture or depending on the manufactures decision to use circuitry to program the running of the unit it could be circuitry. I worked on appliances/ heating in the 80s and the industry has changed with high efficiency, venting with pvc pipe and getting air from the outside with pvc. I use to work on everything for my parents 1960 Desoto car. I now own a 2016 SUV with 35 computers in it.

I love to tear things apart and fix it my self. Though I'm fully familiar with the brake system of my car, I don't have the computer system to connect to it or the continued training and up dating of new systems. I wouldn't put my family in possible danger of my brakes not working. Nor would I buy a 600 dollar computer to work on the car a few times a year.

Qualified HVAC techs and company's use specialized equipment to double check the burn mixture/ off gasing and pressures of a furnace. I enjoy talking and visiting with furnace techs and appliance repair people and trading service call stories. Gawking at their newest equipment. This is more of a safety issue which a good reputable HVAC tech would find. You could have a gas leak in the system. Part failure creating a higher gas to air mix and possible carbon monoxide issue which they have meters and alarms for. If it were mine I would either decide if its worth replacing because it a small replacement unit or call a service tech. Not worth having your shop full of propane or carbon monoxide. I bring up the carbon monoxide cause yearly inspections look for burn through/ rust and propane has moisture as a off burn which helps with rust.

New designs of furnaces have sensors and electric controls that are tough to just look at with out diagnostic equipment. Could be the control board/ again found with equipment most home owners don't have. A sensor failure could happen also which a tech would find and fix. 'That's dependent on the age of your furnace.'  RJF

[teachnlearn]

By the way, if the furnace is in your shop, you SHOULD have a carbon monoxide detector in your shop AND home if connected to the shop. RJF

[spirithorse]

Thanks @Wichman and @teachnlearn

I appreciate the replies. I did have the gas company check everything out and had an HVAC tech
look at the system but, that was before I saw the hole pictured above and I doubt if he saw it because he
was pretty sure there must have been a gas leak and he gave me a can of sealant to apply to the fittings
myself and didn't charge me anything. We were friends long before he became HVAC certified.
If I cannot find a schematic, I'll call him back and tell him to make sure I am charged accordingly and to
check out any other areas that I may have overlooked since the pressure test and gas leak test were good.

God Bless! Spirithorse