Maker Pro
Maker Pro

Simple power struggle...

roughshawd

Jul 13, 2020
465
Joined
Jul 13, 2020
Messages
465
My furnace is on the fritz. Blower will not quit. I put one of those digital programmable thermostats on and it worked great for about 6 months. I found a fuse that was extremely corroded inside, replaced it and the breaker started blowing. Put in a new larger breaker, ( the furnace is rated at 60 amps but everything I read said....80 amps or higher. So I got a 100 amp breaker just in case) so because the sequencers drive the elements.. that is to say when one thermostat sequencer gets hot, it shuts the element off so it doesn't burn up, I replaced the blower relay...it turns on one speed when the furnace is cold, then turns on the high speed when it gets warm...that is to say when the furnace is hot, the blower is on full. Because the motor is an upgrade, a 220v single phase with starting capacitor, I suspected the capacitor was stuck. I took it all to a shop and tested them. They both tested good? So I then suspected the thermostat, and put the old manual one back on... Fan still blows all the time. Am I wrong for suspecting my hook-ups? Not really! Anyway the new sequencer is on the way. If you think I did something wrong, please let me know by the pic...of the relay... Where power connects where the sequencer connects and where the motor connects! May the short circuits never find places you don't know you have...
 

Attachments

  • IMG_20230329_141644301.jpg
    IMG_20230329_141644301.jpg
    112.9 KB · Views: 6

Delta Prime

Jul 29, 2020
1,968
Joined
Jul 29, 2020
Messages
1,968
Put in a new larger breaker, ( the furnace is rated at 60 amps but everything I read said....80 amps or higher. So I got a 100 amp breaker just in case)
Hello there! :)
Your post reads as if this is not your first rodeo you're confident in your explanation & I'm not trying to pick a fight but... Fundamentally.
Breakers must be sized to protect the wire (to the load), it is critical that the ampacity of the wire used in the circuit is appropriate for the amperage of the circuit breaker.
4 AWG wire to carry 60 amps.
(This is US National Electric Code, NEC.).
If you use a larger breaker with smaller wire , the breaker won’t trip even when the wire is overloaded, a fire can easily result.
 

roughshawd

Jul 13, 2020
465
Joined
Jul 13, 2020
Messages
465
You guys are so much help!!!

Ok, just like the transformer.... more power bigger wire, more current more wraps...

The idea being a power problem of having too much On and not any Off...
I have to say that the ability to read the wiring diagram instead of the schematic is also at odds here.
It doesn't seem seemly that any given trip switch might fail and leave something on...
even if its just a fan motor. Its not proper for the engineers to miss something like this.

So I am assuming its' a wrong connection some where.

High speed and low speed are activated through the relay, relay trips oneway only remember.
High or Low take your pick, but don't try to employ a power circuit to the relay, the relay fires when its hot, its off its not.
Off being what ever speed - in this case,
Where the employment of low speed is on when immediate heating and when cooling off- AND
Where the employment of high speed is when its hot...
The immediate heating does not require high speed on start up, so I would have to say that the relay is in probably powered when it first starts up, that means the terminal which supplies power to the low side of the motor is the switched one. Then after the heater reaches the heating limit, it trips the sequencer to turn the power off at the relay. This causes the high speed motor coils engaged at the relay off position, to speed up the motor and turn on the third element for more heat. When the three elements reach the limits again, the second sequencer trips the relay, and the power to the first sequencer again turns on the first elements, and slows the motor to compensate for the loss of heat. The cycle begins again when the elements cool and trip the sequncers to their start up positions, and when the thermostat reaches its maximum, it turns off the sequencer power from the transformer, the motor falls into low speed mode until the elements cool and switch the sequencer again, turning off the fan(until you turn up the thermostat again asking for more an increase in warmth).
This motor is a multi-coil 220v shaded pole motor that was wired at the factory for a 2 wire relay hookup. It seemed to work in only one speed when I installed it. There are Blk - Blu - Wht - Red and 2 Or and 2 Yel, the Orange and Yellow are looped and connected together. Or to Or, and Yel to Yel the Blue is just cut off. The Red and Blk are terminals for the relay and the Wht is common.
They have 2 tan wires, one has a white stripe, that connect to a capacitor.

Knowing that it worked all summer is not exactly a good idea to add to this strange situation...
Turn the f-Blower Off.
 

kellys_eye

Jun 25, 2010
6,514
Joined
Jun 25, 2010
Messages
6,514
Unless you want to turn your heating system into a useless pile of junk I suggest you get a professional to look at it.
 

John Canon

Jun 1, 2022
91
Joined
Jun 1, 2022
Messages
91
During the 1990s I repaired hundreds of furnaces. You need an experienced professional to correct your wiring troubles. Have the furnace model number ready when you call the local furnace shops. The most critical point is this: the motor speed taps must only be connected one at a time. There should never be a moment when 2 or more speed taps are connected, even through a resistance. Also do not defeat any of the safety devices or switches. Call the furnaceman!
Not My Fault.jpg
 
Top