Opersting costs - oil vs propane

Radiant Wizard

I'm confused...If your willing to spend the money on a modulating gas boiler then why wouldn't you spend the extra $$ on an outdoor reset control for the Crown CT or ODV boiler that you are using since the Munchkin is costing you much more out of the gate then the Crown. If you did you would basically have a modulating Oil boiler for less money than the muchkin..

Unknown

On the more conventional side of things I'm torn between a Crown Scotch Marine oil fired boiler and a Munchkin fired with propane for a particular job I'm looking at. It'll be hydro air so I'm thinking the Munchkin on propane with it's modulating feature would be the better choice as I'm afraid the oil fired Crown will tend to short cycle. Which set up do you think will result in lower operating costs for the owner? The customer is leaning toward oil.

Brad White_9

Depends on the cost of the fuel per gallon...

If you take propane at 92,500 BTU's per gallon burned at say 90% average efficiency, that will net you 83,250 BTU's to the system.

#2 fuel oil at 140,000 BTU's per gallon burned at say 80% average efficiency (optimistic given probably no modulation), that will net you 112,000 BTU's net to the system.

All things being equal, oil has about 35% more heat per gallon. In other words, your per gallon cost of oil would have to be less than 35% more than a gallon of propane.

If oil costs you $2.50 per gallon, propane becomes viable at $1.85-$1.86 a gallon or lower, if I did my math correctly.

Robert O'Brien

Most

Hydro-air require high temp water negating some of the reset and condensing savings

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Brad White_9

True

The operative phrase being "most". One can select coils to operatet at 130 degree average water temperature; many overlook this and, as you note, Robert, lose the condensing benefit.

Excellent point. I missed that.

Thanks!

Brad

Unknown

Thanks, I most definitely would put outdoor reset on the Crown. I'd probably put it on the Munchkin too unless that turns out to be a dumb idea. I'm not totally familiar with the Munchkin operation yet. My take is the Munchkin modulates it's input according to load while the oil fired boiler has only one input rate. The question was put to me that, given it takes say 5 minutes for an oil fired boiler to reach peak efficiency and a low mass boiler would tend to not run as long to keep up, would the perceived increase in cycle rate offset overall performance? If it DOES then would the Munchkin on propane now become a more viable option. I believe it's a bit more than the $1.85 used in Brad's example. He asked me and I have no certain info on this so I'm trying to research the matter by picking all the good brains around here. I'm thinking it's practically a wash at this point. Like, ok, we could put in a buffer tank so the boiler has more work to do per cycle but NOW we're defeating the purpose of the low mass boiler? I guess if I set my differential pretty wide on the oil fired and make sure the heat load on it is big enough I could achieve longer cycles.

Oh, yes the munchkin may cost more but doesn't require an oil tank and associated piping.

Joe Brix

I would add the DV factor

If you got a chimney to use, then oil. But if the plan is to DV, I'd go LP.

chapchap70_2

Given these two things you wrote:

"The customer is leaning toward oil."
"I'm not totally familiar with the Munchkin operation yet."


I know what I would do if I were in your shoes.

Unknown

Good replies all, thanks!