LP ovens and performance

[NicksPizza]

I have converted my Blodgett 981 deck oven from natural gas to LP using the blodgett-provided conversion pieces. They are two aperatures that go in the burner and pilot. The question I have is whether I actually did it right. Can anyone tell me?

I have the oven connected to 20 tank like you have you home gas grill hooked to. I am using a standard grill hose to run from the back of my oven to the tank, as it has that honking big plastic knob connector I need. The knob is connected through a small regulator to the hose that runs up to the oven. I am curious if I have starved the oven in how I have it set up. The burner does not run as hot as I remember it running on natural gas, but that was a year+ ago. Is there an internal regulator that functions just fine and I need to remove the exterior one? Should I use the natural gas aperatures when running 20 tank versus the big stationary monsters some people have for their gas supply?

I used to drive this oven through Friday nights (though with some real slowing) . . . and now it seems to be struggling to bake up two 12-inch pies at the same time in less than 18 minutes. Just checking things out.

Anyone out there guide me where I need to look? I can certainyl take the pilot/valve assembly apart and replace the fittings to see how it works, but that seems silly if someone has a good pointer for me.

 

[Bubba]

You need to change out the orifice.
LP gas and natural have different densities.
I have done this on a smaller lincoln 1132.
It is a kit you buy.
Bubba

 

[Rick_G]

It sounds like he changed the two orifices (orafi?) out. I went the other way with my Lincoln and in addition to the orifice change I had to change out the spring on the regulator in the oven and adjust the gas supply pressure while the oven was under load. Propane runs at a higher pressure and also requires less gas volume per BTU if I recall correctly. That is why the orifice in so much smaller. Looking at my Lincoln manual it requires 7" water column when configured for Nat Gas. The LP model requires 11" water.

George???

 

[NicksPizza]

Rick G:

It sounds like he changed the two orifices (orafi?) out. /quote]

Good call both of you. I did indeed already change both of them . . . one in the pilot and one in-line where the air mixer adjuster is. I could not remember orafice . . . so I called it aperature. I did get the kit from Blodget. REALLY tiny little pieces. The regulator, however, was not part of that kit.
Rick G:

George???

you may be right. :lol:

 

[George_Mills]

Hi Nick:
You ask Is there an internal regulator that functions just fine and I need to remove the exterior one? There is no internal regulator. You should have the exterior one checked. Pressure in to the regulator should be should be 11 WC inch minimum 13 WC inch maximum. Pressure into the oven should be 10 WC inch You also need a regulator on the tank itself so that the pressure to the regulator is not to high
Should I use the natural gas apertures when running 20 tank versus the big stationary monsters some people have for their gas supply? NO use the propane ones

The gas line from the tank to the oven should be 3/4 inch

1 gallon of Propane ~= 4.23 lbs ~= 91500 BTU

1 lbs of Propane ~=22000 BTU

20 lb tank of propane holds prox 4 gallons of propane (prox 366,000 BTU’s)

Your ovens are 50,000 BTU/hr each or 100,000 BTU for two. Running full tilt you could use up a tank of gas in just under 4 hours. You will burn less when there is no or little product passing through.

George Mills