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Welcome, my name is XXXXX XXXXX I will do my best to help you with your issue.Does the fan come on?
Yes, it almost seems like it's blowing to fast and not allowing heat transfer from the heat exchanger.
I don't see any provision for adjusting the fan speed which leaves me to think the main burners aren't firing high enough which could be due to low gas pressure
The gas pressure could be low at the burner manifold or possibly the supply pressure could be low
Is the 100lb tank adequate for a 45000 btu furnace? For the amount I'll be using the garage (weekends) I didn't want to invest in a huge tank.
It's not a question of the tank's volume it's a matter of the regulator pressure setting. This really should be checked with a low pressure gauge that reads in inches WC (water column). Your tank is probably big enough for your purposes
Is there anything I can do to check this? Are you referring to the regulator in the furnace? There isn't a regulator at the tank, so I'm assuming it's in the furnace.
There should be a regulator between the tank and the unit otherwise you can have pressures that are way too high and could damage the gas control valve. The gas supply pressure should be ~11" wc and the manifold pressure 9.5" WC. You could buy a gauge and check it yourself but you also need to install a regulator at the tank
These gauges can be a bit pricey with costs around $50 not uncommon
Could that be what's causing the no heat problem, to much pressure? Can this regulator be bought at an RV center? They heat those with propane, right?
The high pressure might have damaged the gas control valve and that might be the cause. You need to go to a plumbing supply house and get a regulator that can be adjusted and a gauge if you want to do this. I don't go to RV centers so I don't know if they carry adjustable regulators, they might. If after you install the regulator and set/check your pressures if you still have a problem it could be due to damage to the gas valve.Here is a link to the manual for your unit. You might find it usefulhttp://www.lennox.com/pdfs/installation_maintenance/Lennox_LF24_IOM.pdf
I just ran across this while I was waiting and it flows 11 wc. What do you think, might possibly work?
Yes that's a decent option. I don't like that it's not adjustable but it doesn't really need to be
Thanks for your help, I think I'm in the right direction now.
I went out and bought a dual stage regulator that was pre set to 11wc. Problem solved, furnace is performing as it should.
I glad I could help.
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