Wood/oil combination furnace question

I'm looking to purchase a new wood/oil combo furnace. Either a Caddy or Napoleon HMF150. Both are saying flue size 6" wood only or 7" for wood/oil combo. Well I just had a new 6" stainless liner installed in August. The oil will only be used on occasion if we go away for the weekend or for short amount of time if we are gone all day. Is it really necessary for a 7" flue? What is the reason for the larger flue?

 

ask your insurance company...

 

It's not the insurance company telling me this. It's the furnace manufacturer.

 

yup. and most insurance companies will require units such as these to be installed per the manufacturers recomendations. if it is not, they can deny your claim in the unfortunate event of a loss. which btw, will likely be when you are away and the oil kicks on and burns hotter in the flu than the wood and ignites creosote in your liner. dont want to see that happen to you. if you dont hook up the oil you should be alright.

 

So the reason for the larger flue is because the oil burns hotter? I guess that's what I was trying to understand.

 

no, not necessarily. but likely so if you are burning unseasoned wood. i do not have a definitive reason why the flu needs to be larger. perhaps because there is possibility that both may be in operation at the same time? if the oil was automatic when the boiler temp hits a low, then you start a fire, the oil will still be firing while you are trying to bring the boiler above set point with the wood.
if you plan to be on wood for the most part, i believe there is an electric element that is made to fit where the oil head goes. sorry, dont know specifics of it. may want to look into this that way you can use your new liner and be free of the oil completely.

 

Thanks for the input. I can't completely rid the oil. I have to have backup for when I'm not home. And I'm not paying for electric heat. The insurance company doesn't cover wood only for heat. I have both wood and oil furnaces but the oil isn't hooked up. They also won't cover if both furnaces are in the same chimney unless it's a combination furnace. I'm not spending $2k on a second chimney when both furnaces are getting old.

 

Understood. Sorry i couldnt be much help.

 

RParrotte, Make sure you talk to someone who has the same unit that you are planning to purchase. I haven't heard many good things about the combo units. My BIL was looking at a propane/ wood one (Napoleon was mentioned) and he couldn't find anyone that was happy with theirs. I knew a guy that had a Newmac wood/ oil and he sure wasn't happy with it.

 

Most say the combinations are not very efficient. I can not say. Never had one. I added my wood gasification on and then power vented my oil boiler out the wall. Works great. You may want to look into going this route.

 

Agreed.

 

The two I have looked at are claiming to be very efficient. I guess a manufacturer will tell you anything you want to hear to get you to buy their product. Both dealers I've spoke with haven't had any negative feedback on the units they've sold. I have two good friends of mine that have the Yankee Logwood oil/wood combos and they love them. The only problem with those is that the oil buner is mounted in the firebox with the wood. The Caddy and Napoleon oil burners have their own oil combustion chamber. The Caddy is also "EPA approved".

I have a meeting with the furnace/chimney guy on Wednesday. So I'll know more then as to what I can/will do.

Thanks for all the input guys.

 

I guess I forgot to ask this question. Which part of the unit was inefficient? Oil or wood? If oil, I'm not overly concerned. the oil will rarely be used. The wood on the other hand will be used everyday during the hearing season.

 

I was told about the power vent through the wall by a guy I know. He says it's acceptable for an oil furnace but wasn't sure if it was ok for a combined unit. I don't see how it would be any different. And I'm sure it would be much cheaper than another liner in my chimney.

 

The guy I know that had one installed now only burns oil so I assume the oil works ok and the wood doesn't. Said it never put out enough heat but used up the wood. Seems to me they had to do some rework on the oil to get enough heat too.
I just know there is no way I would ever install one without talking to someone I knew that had the exact model. It's too much money to fool around with. Yup, I'm one of those guys. I will buy anything as long as it's cheap and I think I can make it do what I want, if not then I need to know someone who has one and says it will do what it needs to do.

 

No. Power vent for oil boiler only. Not wood/oil combo. Seperate the two.

 

I meant for the oil side. There's two vents.

 

I'd want separate units just for the fact that if something failed electrically or the fire box failed on a combined unit ,,, you would have backup.
I've honestly never heard anything good about combo units and in 27 years of delivering firewood I've heard a lot. Newer units may be better but I woodn't chance it

 

Just curious what you ended up doing then RParrotte ?

 

I ended up putting a propane monitor type heater. It fixed my insurance issue with the coverage. And I will say, I'm very pleased with the unit. I've tried it out a few times and boy it heats my house just fine. I rarely use it tho. I set it on 60 in the morning when I leave for work and turn it off when I get home. I only get about a 5 hour burn out of my wood furnace, but my thermostat is also set on 78*!! I like walking around in my underwear! So with the propane at least my house is still warm when I get home from work.