Anybody had experience with lennox elite 90 gas furnace? 2 stage upflow.
It was installed 2 years ago and I have had the guys out here 4 times.
1) -first time was incorrect install on the exhaust pipes.
2) -2nd time was a part failure in the furnace.
3) 3rd time was supposedly the thermostat failure — heater would turn on but the blower would not function. change batteries in stat.
4) same as above
Now the heater fires up but the blower won’t come on. They say it’s the thermostat (expensive robert shaw 2 stage) and maybe the batteries . They have been charging to come out the last time and I am getting frustrated with them. I am to the point of calling the owner and complaining , but I would like to know if anyone out there may know of a fix for this first , being as how their guys don’t seem to be figuring it out.
Thanks Don
Replies
Don
I know nothing about that thermostat or that furnace. In fact my only knowledge of furnaces in for the simple "old style" that I have.
But I am an electrical engineer.
This just does not ring true.
The thermostat does the call for heat which inturn causes the burning to fire (and in one like yours there are probably other things that happen like vent fans).
Then either after a time period or after the heat exchanger warms up the blower is started. None of that has to do with the thermostat.
The only feature of the thermostat that has to do with the fan is the on/off/auto funtion. In all of the thermostats that I have seen, including the electronic ones, that is just a mechinical switch.
So that switch might be bad or a loose connection in the wiring, but changing batteries should not have anything to do with it other than jaring the switch and wiring as you change them.
When you have this problem what happens if move the switch from auto to on?
Look into a sticking or non functioning hi/lo limit switch. Limit switch might be incorrectly set. Tempermental or dead fan contactor. Poor electrical / mechanical conections. The probe / sensor [limit switch] may have a pin hole or a crack in it. Cold and it meters just fine. Hot and it goes haywire. You can have a poor electrical connection even with speed / quick connectors. Cold - hole closed. Hot - hole open. A hole wil screw up the bi-metel function of the limit switch.
Find a new HVAC mechanic.
Can you post the serial number of the unit? Electrical schmatic? Sounds like I would lean toward an electrical fault without seeing or knowing more.
Take a pensil eraser and clean the battery contacts and battery ends in your thermostat. A little much humidity can cause oxidation to form on the contacts and batteries. [Electrolisis]
howdy guys;
Thanks for responding:
I had a hvac tech here for 1.5 hrs. scratching his head and I told him your opinions!
He ended up replacing the main circuit board (looks like a computer mother board) so we shall see if that does the trick...it is under a 5 year warranty (parts only of course) but I am getting a credit back on the mis diagnosis of previous trip , so they are ok guys.
I'll keep ya updated.
Don