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HVAC Forums => HVAC Help => Topic started by: mattmctree on July 29, 2019, 09:42:17 AM

Title: installing a low pressure cut off switch on propane furnace
Post by: mattmctree on July 29, 2019, 09:42:17 AM
i need to install a low pressure cut off switch in a propane furnace as there was never one installed originally and the heat exchanger fouled up from running on low propane pressure. is this an easy job to do. what does it entail?
Title: Re: installing a low pressure cut off switch on propane furnace
Post by: Admin on July 29, 2019, 09:55:54 AM
Very easy.  Just buy the low pressure kit from the manufacturer.  It will come with instructions.
Title: Re: installing a low pressure cut off switch on propane furnace
Post by: mattmctree on July 29, 2019, 10:21:21 AM
perfect thanks
Title: Re: installing a low pressure cut off switch on propane furnace
Post by: Porcupinepuffer on July 29, 2019, 03:56:00 PM
There's a couple manufacturers out there that don't include this as an essential part of their propane conversion kits. They sell it as a separate part altogether and don't consider it that important. This is usually the reason why you sometimes don't seem then installed. I think it's ridiculous that would it even be considered an optional accessory when running on propane.
Title: Re: installing a low pressure cut off switch on propane furnace
Post by: Sergroum on July 29, 2019, 08:04:30 PM
 In my lifetime, I was dumb enough to have three installations without that kit. Each time the amount of trouble this caused me was insurmountable. Now I gnash my teeth each time I ask if it comes with the unit and I get an innocent clueless stare and a response,"Nah. You don't really need it."
Title: Re: installing a low pressure cut off switch on propane furnace
Post by: Hgye on July 30, 2019, 06:06:59 AM
If it is a Napoleon or Continental and the hx is carboned up because there was no switch, they will replace the furnace for free. They come with a switch now.
Title: Re: installing a low pressure cut off switch on propane furnace
Post by: mattmctree on July 30, 2019, 10:58:20 AM
its on my furnace and i changed out the heat exchanger last season as it was carboned up and co was very high. got the heat exchanger for free but they didnt even recomend a low pressure switch i decided to put one in this year as i was doing some research and saw that most furnaces have one. i dont work on propane that much so wasnt familiar with them. hopefully i havent fouled up my heat exchanger running it for one season
Title: Re: installing a low pressure cut off switch on propane furnace
Post by: street8487 on December 19, 2019, 07:05:32 PM
Low pressure cut out switches should be code on all propane units. Every time i replace a carboned exchanger or install a propane unit it gets a cutout switch.
Title: Re: installing a low pressure cut off switch on propane furnace
Post by: Admin on December 19, 2019, 09:32:15 PM
Yes, I'm surprised they're not.  Installing one is good practice.

By Code we do have to follow the installation instructions.  If you look at the Lennox EL296 manual it does say "a conversion kit (ordered separately) is required for use in propane/LP gas applications", but it doesn't list the LP kit part number.  Their Product Specification document is where you find that part #11K51.  It includes a low inlet pressure switch and instructions requiring it be installed.

Goodman is likely one of the manufacturers Porcupinepuffer mentioned.  The GMVC manual says "The appropriate manufacturer's propane gas conversion kit, must be applied for propane gas installations".  That manual lists part #LPM-03 which only consists of orifices and spring, no pressure switch, even though they sell the low inlet pressure switch as a separate part number.  The LPM-03 manual doesn't even make reference to the low inlet pressure switch.

You would think all manufacturers would want to protect their heat exchanger warranty.  I order a LPS with any Goodman propane install.