Oil / Wood Combo Furnace

Good Morning and Happy Hallowe’en !

I am prepping for an inspection this coming week and the property has a wood / oil combination furnace. This will be my first inspection which has this particular combination unit installed.

Are there any major point outs that I should look for or a not to miss item ?

I will attach a photo , but there appears to be soot or discoloration on the walls above the floor vents.

Any information would be greatly appreciated so I can arm myself with more knowledge ahead of the inspection.

Much appreciated in advance.

In general, oil burns hotter than gas… there should be a NACHI course on inspecting an oil-fired equipment, things to check: oil tank, its location (inground/above), the oil supply line, tiger loop, filters, firematic valves, fusible links, OSVs, the vent/smoke pipe, their clearances, if and how a WH is connected to the chimney, barometric damper, etc… there is a lot involved, nobody is going to retype pages of info you need to know. Good luck :slight_smile: If you have something more “specific”, do ask.

Hi Simon ,

Yes I agree , although its not just a standard Oil Furnace or one that couples to WH etc. It is a wood / oil combination furnace.

I haven’t yet seen the furnace itself , just trying to garnish some insight from anyone who has inspected a combination furnace wood / oil.

The wall “staining / discoloration” other than , possible creosote build up or poor damper control , could there be other causing, that may be not so commonly known ?


Ops… completely overlooked that…

I’ve never seen one in person… if I did, I would want to make sure it’s allowed in my locale. From there… things depend on whether it’s a single unit combo or side-by-side unit. If a single unit, the vent has to be of proper gauge, if the client is going to burn wood… the cleanings have to be more often… as far as the stains above the floor registers, the heat exchanger may have been compromised and now allows combustion fumes (such as CO)/soot to enter the house. Again… many unknowns, but this is very atypical and I would advise the client accordingly. Definitely have a good heating oil/heating contractor look over the setup and ensure there is nothing wrong before the heating season. You can only do/inspect so much visually… there needs to be CO test, combustion test, draft test, etc… The stains above registers is definitely a big red sign.

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Thanks Simon,

My thoughts exactly. At this point I am unaware of the furnace set up and if its a single combustion chamber or double. There are many unknown factors to list and dwell upon but having extra presumptive thoughts never hurts, as I allows the eyes to look upon other items if more people referring there options.


So thanks for the insight

Definitely take pics and post them here… this is going to be a unique experience :slight_smile:

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I will most certainly. As this may be a newer item for many on here.


Thanks Jeffrey - best get some more coffee now :coffee:

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Recommend a WETT inspection for the wood furnace and also check the manufacturer’s installation manual. Ducts for supply and returns have special requirements. For example, if there is a power outage while the wood furnace is on the air flow could reverse where the return air becomes supply air. Also, if the oil furnace turns on, the wood furnace should turn off to prevent overheating. There is usually 2 thermostats so that is easy to verify.


Thank you Marcel , for that insight - I will make sure to double check for the dual thermostats and also an emergency power supply to support the blower fans to reduce the backdrafting.
:ok_hand: :ok_hand:

Hi Evan…How’s things going for you in Moncton? Did you get your insurances figured out? I will be doing some inspections in Moncton, in the near future.

Hi Junior ,

Yes managed to get this insurance side all addressed and sorted, had to run through a broker in Toronto for the quickest service and less run around.

How are things on the Island ? As your are around the Montague area, correct ?

If you make it to Moncton, I would enjoy a coffee and to pick your brain on a few things if possible.

cheers mate

Great thanks! For sure, I’ll look you up when I’m over that way.

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looking forward to it … also , have you ever come across the combination furnaces , Wood and Oil ?

Haven’t yet.

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