PEAK PUTTERS

I'm working on my dad's furance and I'm at a loss why only one of the heating elements apprear to be getting hot even though each elements show 120v when the system is running. It's a long story, so this would be a good time get a beer. First, it's a 197Os furnace with four elements... no heat pump. All sequencers work as there is 120v coming out of all of them. Two sequencers had toasty wires heading over to the heat elements and two of the 120v supplies from the breaker to the sequencers were toasty as well. Element #4 was a broken coil. The other coils show connectivity between legs... passed the ohms test. Each element has 120v going to it; however, a amp test shows element #3 pulling about 8amps and the other two pulling less than one amp. The air passing through the furance around 106F. I replaced all of the toasty wires with 10ga and soldered connections. Does anyone have an idea why the other two elements arent pulling amps despite having 120v to each leg?

what is the ohmic value of each element? what does the wiring diagram show for ohmic values? it may be that they are not all the same wattage it may progressively increase the heating depending on need. and each may have a different value. E=IxR 120v=8xR? so 120/8=15ohms. so each element should be 15 ohms, is that what you had for your ohm test per element?

you would thing they would be operating off 220v ash range.

scumby wrote:what is the ohmic value of each element? what does the wiring diagram show for ohmic values? it may be that they are not all the same wattage it may progressively increase the heating depending on need. and each may have a different value. E=IxR 120v=8xR? so 120/8=15ohms. so each element should be 15 ohms, is that what you had for your ohm test per element?

you would thing they would be operating off 220v ash range.

Ouch, I think something in my head popped. Perhaps he should call an HVAC tech? Anyone know a honest one or a leppercon?

i can probably take a quick look at it to see if it's over my head.

btw... cycling on and off of a circuit with a decent amp draw causes expansion and contraction of connections. loose connections cause heat and that can cause overheated wires such as you pictured.

on board ships it is an annual inspection of all circuit breaker panels and connectors to check for loose connections. we would cheat and use a thermal imager to look for loose/hot connections with live panels, tighten as necessary. usually with an electrically safe screwdriver so we could do it live.

ask me about not using a conducive screwdriver and 440v.

You are the Bomb! Perhaps we can pow wow about this on Thursday?

Lost connection on the Neutral side? Just because you read 110v going to the element doesn't mean the 110v is making it all the way to neutral. No circuit loop=no amp draw.

I think the furnace (240v-500AMP) it wired like an older style appliance: two hot leads and the furnace is tied to the ground (no neutral lead). I have connectivity between the aluminum ground wire and the screws that hold the elements into the furnace.

Wrench wrote:Lost connection on the Neutral side? Just because you read 110v going to the element doesn't mean the 110v is making it all the way to neutral. No circuit loop=no amp draw.

I'll visually inspect the aluminum ground connection to verify that it's not loose or burnt. Thanks for the comment.

scumby wrote:what is the ohmic value of each element? what does the wiring diagram show for ohmic values? it may be that they are not all the same wattage it may progressively increase the heating depending on need. and each may have a different value. E=IxR 120v=8xR? so 120/8=15ohms. so each element should be 15 ohms, is that what you had for your ohm test per element?

you would thing they would be operating off 220v ash range.

The ohmic readings for three of the elements 0.00 each. The busted element reads oL (open). Perhaps I'm testing them wrong. I watched a pile more videos today and know I think I know enough now to be slightly less than dangerous.

0 ohms is a direct short. did you disconnect the elements from the system? you may be reading thru something else.