If you change the switch, and the house burns down, it's YOURS to defend and buy. Not sure I would want that popularity. Maybe a smaller btu burner is the better option or add a duct to relieve some back pressure.
Identical means symmetric in every wayUnderstood, but as I said I have two identical furnaces, one uses an L160, the other an L170. I personally don't see there being any harm in allowing a furnace to run 20 degrees hotter. It's a giant metal chamber with nothing to catch on fire, perhaps the fan motors and sensors won't last as long but it's already an older, low efficiency furnace to begin with.
But then again I'm by no means an HVAC expert, there must be some technical reasons why I should/shouldn't use an L170 switch?
Your Agilent :thumbup:...great meter. By your above post it sounds like you are too close to the heat exchanger. Usual distance from the supply plenum is 3 to 6 ft to avoid radiant heat influence.Well according to my multi-meter that 160F switch doesn't trip until after 185F on my meter. I'm also not going to make any claims that I put that thermocouple in the same spot as the switch, it honestly ended up roughly 1" behind the switch when I wrapped it around one of the legs so it was closer to the heat source. These numbers aren't perfect.
I will say though speaking relative to my thermocouple the switch tripped at 185F and the max operating temperature I measured was 195-200F. It's close and the L170 could very well not even fix it.
:laughing::yes: I am lucky in that regard too...I got all top of the line Testo and Fluke instruments.I'm using an Agilent U1253B meter with a bluetooth dongle to pole the data, hence the graph. My profession affords me some toys.:brows: I trust the meter but I'm not 100% sold on the thermocouple itself, it was whatever I could scrounge up.
When I get back from work I'll post some duct photos!
" Are you the same guy that was asking all the questions about your trailer heat?Wow, thats quite the octopus goin on there LOL
anyways, lowering the output is a definite option, but that also comes at the cost of reducing efficiency. every heat exchanger has a specific BTU and airflow where it is its most efficient. too much fire and your blowing it all out the flue (and burning up the heat exchanger), same goes for airflow across the heat exchanger, too low of airflow and heat exchanger temp gets too high (heat out the flue and burning it up!) and as backwards as it sounds, too much airflow across the heat exchanger reduces efficiency as the exchanger cannot transfer the heat to the air at a fast enough rate
The biggest thing you need to do, is measure your return air temp and compare that to your hot air (getting a flue temp wouldnt hurt). Your furnace is rated for XXX* heat rise, which you are likely exceeding greatly. you need to either adjust the firing rate (BTU) or airflow to get the heat rise within spec.
Where is the air return ducted? is it possible that this unit is sucking in a fairly high temp return air which would cause the excessive heat?
This is probably the most accurate statement concerning your over temp prob, Czardestructo.Post brand and model number of that furnace.
You can't get an accurate temp reading in that plenum, as any probe would see IR heat and read a much higher temp.
Post what size those 2 ducts are, and what size return it has. From what little can be seen in those pics. You don't have nearly enough air flow for even a 45,000 BTU 80% furnace.