pre-ignition

Dave_41

My experience with these boilers on LP indicates that the shutters will be needed, they are rarely used with NG. I have also found that the burners should actualy slope DOWN from the orfices with LP. This seems to help with the heavier gas. One more thing, and I may be wrong on this but I think the manifold pressure on that thing should be 10". Check that rating or conversion plate. I am thinking that it probably was converted as the dedicated LP versions usually had the shutters installed.

BW

pre-ignition

Went on a maintenance call last week.Sometimes the burners would have gas lit inside the burner near the orifice.Not every time and not the same burner.Checked gas pressure and flue pipe.-OK This is a Lars running on LP. Any ideas would be appreciated. Thanks

Jim Pompetti

Need more info. Is the unit off when flame is at orfice or is the system running,What pressure is the unit running at. How old is the saystem is it sooting.

Unknown

Was this unit converted

to LP or did it come as dedicated LP? If it was converted many times the port loading on burners for natural gas cannot be used for LP so new burners dedicated for LP have to be ordered. What you are experiencing is called "Flashback" on ignition. It is caused by the gas-air flow velocity being less than the burning speed of the gas at some point near a burner port.

Having said that I am assuming this is happening with a call for heat and the unit firing and not on shut down?

Do the burners have an air shutter? Have you clocked the burner to make sure it is firng at correct input. What is the gas pressure before and after the gas valve?

If the pressure and input are correct and you have air shutters then because you have a faster burning gas (LP) decreasing the primary air should solve the problem just be careful to not cause the flame to turn yellow.

Once you have adjusted the pressure, input and air do a combustion test to determine safe operation and proper efficiency.

jim lockard

Could be

Low on gas that will cause burning in the tubes or if the LP tank is above ground and its cold. Then the LP will not evaporate quick enough to feed the furnace. Best Wishes J. Lockard

Glen

on the level???

check the unit for level and plumb. Gas after all is a fluid (especially LPG)and follows laws of gravity. Burners must be level.

Empire_2

Also

Just pull the orifices and make sure there is no crap on the inside of the hole. If you have a guage set, make sure you are not going any larger than manuf. sugg. sizes. But I agree...What is the incomming pressure and the manifold pressures?

BW

flashback

1. yes the unit did soot up once earlier-taken down to the water jacket and thorougly cleaned.
2. No air shutters on the burners at this time-I do have them to put on if needed
3.Manifold set to 9" w.c. inlet about 11" w.c.
4.Brand new orifices installed-however waiting for pilot orifice to arrive-possible soot issue again from pilot?
5. burners and unit level
6. according to manuf. orifices-gas spring and pilot only items needing to be changed
7. new pilot coming in tomorrow

thanks for the help

Paul B._2

lp conversions

I'll jump in on this as well, BW contact me directly at Laars, 603-335-6300-x562 with the model and serial number off this boiler.

If this is a JVT or a JVS that is bieng converted to LP, it may need shutters. I can look up the parts the correct LP kit should have.

If it's a larger Mighty Therm boiler we don't offer conversion kits for those, we have too many gas train options to make up kits. Those we review case by case, and make up a parts list.

I can also put you in touch with a Territory Service manager if you need additional help.

Sincerely,
Paul B.