New heat in the shop ..electric furnace help

Well got a old electric furnace out of a mobile home put it in my shop wired it up ran fine for about 20 minutes then kicks the breaker ..anybody know anything about this units..this thing is quite 40000btu and I just knew I could get in there out the cold weather. .

Some/most electric Heat units have 1,2 and three heat elements, how long is the supply to you furnace ? If your wire is to small it will heat the breakers up and throw them.
Have a tech disconnect one element and see if it will run/heat for you.

Kicks "what" breaker?

The main in the fuse panel? How big is it

"Here's how" the majority of electric furnaces are setup for many years

Most electric furnaces are fed off MULTIPLE breakers in the fuse panel, as well as having some breakers right on / in the furnace

Generally, "they work" like so:

1....First a 20/30A (220-240V) circuit powers the controls, the blower, and usually, just one element

2....Next, depending on how big the furnace is, additional 40 or 50A breakers power the next sets of heating elements in sets of two

What I mean is, each element is "nominally" 5KW or about 20A or so draw.

40,000 BTU is not very big. A 5KW element is nominally 17,000 BTU

That would seem to be only two elements. In that case "it might be" that there is only one circuit, so one 40A breaker would be "marginal"

Other:


Breakers can develop loose connections both where they clip into the buss in the rear of the panel, and the wire set screw / connection. This creates HEAT which causes the breaker to trip

Also, breakers DO simply "get weak" or go bad for other reasons. So even if it's wired properly, with large enough wire, and enough breaker capacity, "it might be" you have a breaker going bad

A "standard tool" for every HVAC guy especially working on something like this is a clamp - on ammeter commonly called an "amprobe"



BE DARN CAREFUL messin' round in those. They operate off 220-240 which means that BOTH legs of the power are hot, and the control devices (relays or sequencers) ONLY SWITCH one leg. This means that EVERYTHING inside there is HOT at all times 120V to "ground."

67Dart273 said:

Kicks "what" breaker?

The main in the fuse panel? How big is it

"Here's how" the majority of electric furnaces are setup for many years

Most electric furnaces are fed off MULTIPLE breakers in the fuse panel, as well as having some breakers right on / in the furnace

Click to expand...

Thank you for jumping in :glasses7:

This is a member that can gide you threw this earthmover :cheers:

It has a breaker on it that's a 60a duel breaker the it has about 8 ft of solid Cooper from it to my Welder plug which is 240 plug with 4 wire solid Cooper. .it runs my might and stick Welder no problem ...now come to think of it ..it just kicks my breaker in the panel box not on the furnace..I'm not to sure of the size in my panel box but I think it's around 40 duel breaker but not sure .

Yup. Look for a nameplate on the furnace. You might need a 50-60A circuit to feed it. IF IF the wire is large enough on the welder circuit, "you might" get by swapping in a 50A breaker.

Thank you very much..I didn't think about the breaker in the panel box being to small til I read your first comment then I said to myself the Welder is not a steady pull of power so it can continue to run the heater is a constant pull with needs a bigger breaker ..I hope this solve the problem. .I need heat and heat those loud blower heaters ..this was free and plan to put 2 vents on the bottom blowing heat from front to back of shop and hope it warm things up pretty good. ..

Mine was doing that and the wires to the breaker were loose.

General rule of thumb, the breaker in the panel shouldn't be smaller than the breaker on the unit!! I say 50a in the panel, that would run most any steady load, it's what they use for hot tubs and other large power draws!! Heck, the breaker to my sub in the garage is 60a, and it runs the entire garage!!

Here's one chart

usawire-cable.com/pdfs/nec%20ampacities.pdf

If you have no8, and it's UF cable (romex) it's not large enough for a 50A breaker. That is, right on the borderline

As you can see, "it's complicated"

https://forums.mikeholt.com/showthread.php?t=88185

I would be very tempted to toss a 50A breaker in there and KEEP the 40A handy.

Sounds like a recipe for a house fire! Find out what size wire you have and DO NOT exceed the amp rating for the wire size! You can easily unplug the low voltage "control" wire from a sequencer to lower the total amp draw of the heater. What is the KW rating on the heat kit in the heater?

Thanks guys...I got it all working like it should. ..I use to be a Forman with the power company and have done some small wiring like my house and shop..but it's been so many years ago so it was better to get some insight but once I started it seem to come back to me...I'm a truck driver now so all that stuff I don't use anymore lol..but I appreciate all the help...I use to put in subdivision and set 3phase transformers cable phone and gas ..made up a bunch of cans ..set light poles street lights ..but it was about 10 yrs ago run dips all that crazy stuff lol..

The breaker in my main box was way to small for the furnace so I put in a 50 and the wire is aluminum that runs the furnace I forgot the size but it came out the house with the furnace. ..

I'll post a pic of it later today...man you can't really hear the thing running. .got the shop up to 75 last night while I was initially. .but 68 70 will do while working on something. .going to replace the old thermostat with a little up to date 1 has the old style from the 70s but it works ...

Aluminum wiring????????

That could be bad news - especially in a high current installation like this. You may already know - the other critical thing about Al wiring and the Electric Code, is that you MUST use AL/Cu rated connectors.
WE have Al wiring in my house and I've had 1 near miss where the receptacle for the dryer overheated.
If it were me - replace the Al wiring with Cu now - before you have a fire. It is not worth the risk.
Not sure about your area- but up here, the insurance companies no longer insure houses with Al wiring unless Cu pigtails are installed at all connections.

Aluminum wire is used all the time for larger gauge circuits like ranges and electric furnaces. I'd bet most if not all available large gauge devices are rated for Cu and Al. All you really need to do is to use proper anti-ox "grease" and tighten them properly.

It does not hurt to check tightness after a few years. I've found a few Cu connections loose, as well as POS (Pacific whatever they are called) panels which are CRAP quality and which have POOR connections between breakers and the buss connection

The worst of these was one of our sheet metal guys when I was "in that" in the eighties. He had bought a 'then new' nice manufactured home.........hardly a trailer

This was "all electric" with electric heat, dryer, range, and water heater. So it "should have" been designed with adequate electrical in mind.

One of the large circuits (forget, dryer, range, furnace) was giving him fits. Turned out to be CRAP breakers (OEM) which DID NOT MAKE good contact at the buss.

Bear in mind this was "as built" and "nearly new." Bear in mind this was AFTER the aluminum trailer wiring debacle. Some of these panels should have resulted in federal criminal action.

If the breaker in your main box was "way too small", what size wire is hooked up to it? I hope it's #6! If you're pulling 40 amps on a #10, the wire will become a fuse!!! The breaker MUST be the weak link in the circuit!

Be ready for an increase in your electric bill. Electric furnaces are 100% efficient but electricity isn't cheap. This winter LPG is lower than it's been in a long time. Just be sitting down when you read the bill...

Just depends, LOL, on how high "juice" is in the area. Regardless, you are right, they "suck" wattage, or more correctly, "kilowatt hourage"