Furnace that takes fuel oil and NG

[JHZR2]

Hello,

I have a hot water radiator system in my home. Our home used to have an oil burner, and still has a tank in the basement. About 25 years ago, it was converted to natural gas with the installation of a new boiler.

So our home has both.

Is there a furnace that either constantly uses both, or can be selected to run either at my selection? This way I can select based upon what is cheapest, and potentially stock up on heating oil in the summer, and if I run out in the winter, no worries...

My parents have a coal/fuel oil stoker in their weekend home. This is the kind of thing that I'd like but fuel oil and gas.


Any thoughts?

Thanks,

JMH

 

[GROUCHO MARX]

Some states make home owners remove old, unused oil tanks.

 

[bmwtechguy]

"Dual-fuel" heating systems are not so common, probably because the upfront cost is high, but the benefit is worth it in some cases. I have a heat pump/ac unit with an oil furnace as the "emergency" system, rather that the high current (and cost) coil resistance heater that most have. I can choose to use only the oil furnace when it gets really cold and I usually do this. Otherwise the condenser unit keeps going into a defrost cycle and works rather ineffeciently.

On your boiler system it's probably not real easy to set up a dual fuel system, but I'm sure there is a way if you really want to. But it will cost you to buy another fuel oil furnace and then tie it into the current system again. I would look into a unit that's designed to burn drain oils if I had to do it all over again. I do add some used ATF and stuff to the #2 fuel oil tank now and again to save money. Burns really clean, too.

 

[Gary Allan]

The flue on your gas burner is (probably) inadequate to handle the CFM of an oil burner. I believe that they have induced draft for the exhaust.

 

[oilyriser]

diesel cogen. Too bad small scale cogen systems aren't well developed in North America.

 

[brianl703]

Originally Posted By: Gary Allan
The flue on your gas burner is (probably) inadequate to handle the CFM of an oil burner. I believe that they have induced draft for the exhaust.


Modern gas burners have induced draft flues.

 

[Gary Allan]

Then we're in agreement? I'm unsure if you're asserting that the induced draft of the contemporary gas burner would enable an oil burner to be used in place of a gas fired setup or not.

..btw..on larger gas (for a larger building) I've seen standard sized flues with electric post boiler doors that prevent (I assume) cold air migration back through the boiler when not operating. These didn't appear to use induced draft.

 

[Matt_S]

Originally Posted By: Gary Allan
..btw..on larger gas (for a larger building) I've seen standard sized flues with electric post boiler doors that prevent (I assume) cold air migration back through the boiler when not operating. These didn't appear to use induced draft.


I had one of those on my former house (NG/forced air system). It made the inspector very nervous-in-the-service. The danger is, of course, that if that door gets stuck, you get CO poisoning. He recommended to manually open the door and cut power to the motor.

 

[Gary Allan]

That was my first thought at looking at this. Upon further inspection, the mechanism had a "proving switch".

Oddly, and you would think that some underwriter would have caught this, we had the door of a Johnston 1500hp boiler blow open (the big and massive fan spinning around and the baffle doors blown wide open) because the FireEye® scanner read the venetian shutter doors as open from the position of the drive motor. The linkage arm was broken. The boiler never purged and filled up with NG. The pilot lit, scanner read a good flame, the big gas valve opened, and KABANG!. Luckily we were blowing down another boiler at the time. WE installed another proving switch (micro-switch) to assure that the linkage cycled (high purge/low purge/pilot) before letting the main gas valve open.

 

[brianl703]

Originally Posted By: Gary Allan
Then we're in agreement? I'm unsure if you're asserting that the induced draft of the contemporary gas burner would enable an oil burner to be used in place of a gas fired setup or not.


I'm just saying that modern (since 1980-something) gas burners use induced draft flues. It was unclear as to whether you were saying that gas burners use induced draft flues, that oil burners do, or that both do. Do/did oil burners use induced draft flues as well?

Incidentally, the actual flue pipe diameter seems to be unchanged. I believe the diameter is determined based on the BTU rating of the attached furnace without regard for whether it is induced or not.

The draft inducer is there to make the furnace more efficient, not to make a smaller flue act as a larger one.

 

[JHZR2]

fortunately I dont have forced air, just hot water radiators. The whole setup was done for an oil burner back in the day. The chimney, etc. is sized for that. Anything necessary could be reverted.

Since my tank was in the basement, there wasnt any requirement to remove it. It is in good shape, not apparently rusty, and seems fine.

Problem is finding brands of diesel cogen or whatever the unit would be called, at least here in NJ.

Thanks,

JMH

 

[Gary Allan]

Quote:
I'm just saying that modern (since 1980-something) gas burners use induced draft flues.


I see. I figured this must be the (probable) case based on older vs. newer.

Quote:
Do/did oil burners use induced draft flues as well?


None that I'm aware of. I think the required atomization demands a pre-fuel blower.

Quote:
Incidentally, the actual flue pipe diameter seems to be unchanged. I believe the diameter is determined based on the BTU rating of the attached furnace without regard for whether it is induced or not.


This I'm unsure of .. Let's see where we're probably in agreement ..but with different observations. I've never seen a "power burner" in residential gas. That is, I don't think I've ever seen a residential steam setup using natural gas. Most that I've seen are all recirculate hot water types. These don't require as high a specific btu output ..and merely have to heat water. Hence the gas output could resemble your oven and the induced draft merely evacuates the nasties. On these setups ..btu/hr vs. btu/hr ..the stack size is vastly different. Mine is 7" flue ..while my neighbors gas furnace is about 2" and looks and sounds like a dryer vent. Now the church that I saw the gas fired (recirc water) boiler ..sure 8" pipe.

Interesting side observation: One of the churches, that I got to see their boiler room, used oil fired. Three of them. They didn't have the flue damper and had really small air inlet pipes that were piped to outside air. Incredible length ..and a mini-damper on the inlet air (on the inside). The outlet side was 8" and dumped into a huge (assumed for coal) stack. I don't know how they balanced the air

The stuff is going to expand in volume.

 

[Gary Allan]

Originally Posted By: JHZR2
fortunately I dont have forced air, just hot water radiators. The whole setup was done for an oil burner back in the day. The chimney, etc. is sized for that. Anything necessary could be reverted.

Since my tank was in the basement, there wasnt any requirement to remove it. It is in good shape, not apparently rusty, and seems fine.

Problem is finding brands of diesel cogen or whatever the unit would be called, at least here in NJ.

Thanks,

JMH


Buy a 2 cylinder Perkins disel setup for an 18 wheeler for extended shut down. Route exhaust to boiler/furnace. Route coolant to boiler furnace. Enjoy avoided costs and 5kw (which I, for some reason, think will serve your needs).

There's more to it than that ..but..

 

[JHZR2]

Originally Posted By: Gary Allan
I've never seen a "power burner" in residential gas. That is, I don't think I've ever seen a residential steam setup using natural gas.


My parents' home, built in the early 1920s, has steam heat (originally coal, converted to oil via an insert, then replaced with a gas system).

Many of the other homes around them are set up the same way... Lots of normal or slightly large (I suppose they have a pretty big home, but its no 5000 sq. ft mcmansion) homes have NG-fired steam.

JMH

 

[brianl703]

Originally Posted By: Gary Allan
Mine is 7" flue ..while my neighbors gas furnace is about 2" and looks and sounds like a dryer vent.


It's probably a 90% efficient furnace. The flues for those are different. Smaller pipe, plastic pipe. I don't think you want to hook one to a standard flue like you'd have used with a less efficient furnace. Reason being that the flue gas is lower in temperature and will condense inside a normal flue.

What I'm thinking of are the 80% efficient furnaces (electric pilot, inshot burners, induced flue). The flues for those are, I believe, sized similarly to those you'd have used with a 60% efficient furnace (standing pilot, ribbon burners, draft flue).

(I think most of the efficiency gains from the 80% furnace come from the loss of the standing pilot as well as the induced flue which means that warm air isn't escaping when the furnace isn't running..so the flue gasses from the 80% should be the same temperature as from the 60%)