240 Volt portable heater will not come on.

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  #1  
Old 12-04-18, 07:26 PM
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240 Volt portable heater will not come on.

The heater is a 240 volt, 4800 watt, 20 amp, DynaGlo portable heater, that I want to use to heat a small shop. The shop is detached and has a 100 amp sub panel (there is a 100 amp breaker in the main service at the house that feeds the sub panel in the shop). The sub panel has a 40 amp breaker to a dedicated 240 volt NEMA 6-30R single outlet. There is nothing else on that 40 amp circuit. The outlet is wired so that the white common wire goes to the "ground" prong receptacle and the hot (red and black) wires go the the two other prong receptacles. The bare ground wire is attached to the outlet box via a green screw.

I measured 240 volts between the hot leads at the outlet, and about 120 volts between either of the hot leads and the common.

When the heater is plugged in to the outlet, the yellow power light on the heater goes on, but it goes off as soon as I turn the power control clockwise. The fan doesn't come on. As far as I can tell, the heater coils don't heat up, although I haven't left the heater on for more than about 10 seconds. This is a brand new heater. We also have an older 240 volt heater that does the same thing when plugged into that outlet. The old heater used to work at our old house (we moved over the summer).

The voltages at the outlet measure as expected, so why would neither heater work?

Does the breaker (40 amps) have to be matched the heater, which is 20 amps?

One other thing; the sub panel has the grounds and common wires connected to a single bar. Everything I've read indicates that now a sub panel has to have common wires floating and connected to their own bar, and the grounds go to a separate bar. I can see the safety issue, but could that be why the heater doesn't comes on?

Any ideas how I can trouble shoot this further?

Thanks.
 
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  #2  
Old 12-05-18, 12:09 AM
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The sub panel has a 40 amp breaker to a dedicated 240 volt NEMA 6-30R single outlet.
A 6-30 should be on a 30 amp breaker. That needs to be changed.

The outlet is wired so that the white common wire goes to the "ground" prong receptacle and the hot (red and black) wires go the the two other prong receptacles. The bare ground wire is attached to the outlet box via a green screw.]
That is also wrong. There is no common. If you mean neutral it is not used on a 240v circuit*. White capped off. Bare to ground. Red and black to the hots.

Sounds like you don't have the hots to the right slots.

*Neutral is only used on a 120//240v citcuit such as a cook stove.
 
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Last edited by ray2047; 12-05-18 at 02:56 AM.
  #3  
Old 12-05-18, 07:10 AM
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What is the voltage across the hot conductors of the branch circuit at or behind the receptacle when the heater is turned up? (Should be about 240.)

You could have a loose connection perhaps in a junction box in the middle of that branch circuit or behind the receptacle.
 
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Old 12-05-18, 08:20 AM
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Thanks.
A 6-30 should be on a 30 amp breaker. That needs to be changed.
I'll pick up a 30 amp breaker today.
That is also wrong. There is no common. If you mean neutral it is not used on a 240v circuit*. White capped off. Bare to ground. Red and black to the hots.

Sounds like you don't have the hots to the right slots.

*Neutral is only used on a 120//240v citcuit such as a cook stove.Attached Images
The hots (red and black) are connected as per your diagram. But I have the white wire connected to the ground in your diagram. I'll connect the bare ground wire to that location and cap the white wire. Question: The bare ground is currently connected to the outlet box via a screw. Should I disconnect the wire from the screw and connect it to the outlet, or run a pigtail from the screw to the outlet, leaving the bare wire grounded to the outlet box?

The reason I had the white wire connected to the ground is because the previous owner had a NEMA 10-50R receptacle in the box, and it had the white wire connected to the ground. If I remember correctly he told us it was supposed to be for a welder.

I'll get some pics of the outlet wiring and the sub panel wiring today and try to post them.
 
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Old 12-05-18, 08:35 AM
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Thanks.
What is the voltage across the hot conductors of the branch circuit at or behind the receptacle when the heater is turned up? (Should be about 240.)
With the heater plugged in, where would I measure that? Without the heater plugged in I read 240 volts between the hots on the receptacle.
You could have a loose connection perhaps in a junction box in the middle of that branch circuit or behind the receptacle.
The only thing on that circuit is the outlet.
 
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Old 12-05-18, 09:28 AM
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The bare ground is currently connected to the outlet box via a screw. Should I disconnect the wire from the screw and connect it to the outlet, or run a pigtail from the screw to the outlet
Yes pigtail to box and receptacle. Note my corrections were to be helpful in getting it right but it should have worked despite the errors.

Carefully with the breaker off pull out the receptacle and plug in the heater. Turn on the breaker and carefully measure the voltage on the receptacle
 
  #7  
Old 12-05-18, 12:20 PM
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Sub-panel:
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Outlet:
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The outlet now has the bare ground connected to the "ground" plug receptacle of the outlet. I haven't replaced the 40 amp breaker with a 30 amp breaker yet.
I re-measured the voltages at various places with and without the heater plugged into the receptacle.

Without heater:
Across the hot leads at the lugs at the tops of the bus bars: 190 - 225 volts
Across the breaker at the red and black wire connectors: 200 - 225 volts
At the outlet where the red and black wires connect to the outlet: 190 - 225
The readings are different depending on which tester lead goes to which wire.

With the heater plugged in and the temperature dial turned all the way on, I measure 0 volts at all three of the above locations. With the temperature dial turned all the way off I read about 200 - 225 volts at the above locations.

Some additional info:

The sub panel is about 150 feet away from the main service entrance at the house. The cable from the house to the shop is buried in conduit. There are three wires. There is no ground cable in the conduit. I see a painted cable coming out of the ground next to the shop where the conduit comes up. It's hard to see in the picture but that ground cable comes up thru the sub panel base, then it looks like it's clamped to the conduit, then connects to the neutral bar. There is no separate ground bar.

A couple months back we had an electrician check for a break in the lines from the house to the shop, because we were getting no power to the 240 outlet. He found a break underground near the house service entrance and fixed it. He tested the power at the shop sub panel and said it tested good. I don't know specifically what the "break" was or how he fixed it.

There are three 120 volt circuits in the shop, and there are no issues with any of them that I can tell.

Questions:
At this point should I still replace the 40 amp breaker or first try to figure out what's causing the voltage to be 0 with the heater plugged in?
Are the measured voltages when the heater is not plugged in too low? Should they be reading closer to 240?
Why am I reading 0 volts when the heater is on? Even back at the sub panel bus bars?
 
  #8  
Old 12-05-18, 12:45 PM
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Just to rule out the breaker since it needs replacing anyway put in the new 30 and test.

Best guess though you need to replace the wires to the house.. if as it sounds EMT was used it is probably rusted away.

A bit off topic but...
The shop is detached and has a 100 amp sub panel
Not an expert but looks like a 60 amp panel to me.
 

Last edited by ray2047; 12-05-18 at 01:06 PM.
  #9  
Old 12-05-18, 01:17 PM
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Originally Posted by ray2047 View Post
Just to rule out the breaker since it needs replacing anyway put in the new 30 and test.

Best guess though you need to replace the wires to the house.. if as it sounds EMT was used it is probably rusted away.

A bit off topic but...Not an expert but looks like a 60 amp panel to me.
I'll replace the 40 amp breaker.

I was wrong about the conduit. The conduit is only used from the house main service entrance to the trench where the cable is buried, and from the trench up to the sub panel in the shop. I don't know what kind of cable it is; my wife saw the cable when the electrician fixed the break, and it wasn't in conduit.

What voltage should I be reading across the hot leads at the shop outlet when the heater is plugged in and turned on?

The cable from the house to the shop is connected at the main house service entrance to a 100 amp breaker. If I plug in the heater in the shop, turn it on, and read 0 volts across the hot leads at the 100 amp breaker at the house, does that indicated that the cable is defective?
 
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Old 12-05-18, 02:05 PM
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You should get not less than 220v-230v or more..

If I plug in the heater in the shop, turn it on, and read 0 volts across the hot leads at the 100 amp breaker at the house, does that indicated that the cable is defective?
I'd suspect the breaker first. Note a new breaker may need to be smaller if that is a 60 amp sub panel. I"d replace the 100a breaker with a 60 amp breaker.Or just as a test if you have a 240v 50a or larger breaker just as a test move the wires ti it.
 

Last edited by ray2047; 12-05-18 at 04:55 PM.
  #11  
Old 12-05-18, 04:59 PM
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Thanks for the responses.

I replaced the 40 amp breaker with a 30 amp, but the heater still doesn't come on.

Not sure what the sub panel is rated for. I just said 100 amps because that's what the breaker at the main panel at the house says. I haven't been able to see any writing on the cables that would tell me what size the wires are.

I think I'll take a closer look at the main service at the house. It's located on the exterior of the house in a not very weather tight enclosure, so I wonder if the 100 amp breaker feeding the line to the shop is bad or the contact with the buses is corroded. I suppose that could explain why the voltage at the sub panel measures low.
 
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Old 12-05-18, 05:39 PM
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You checked at the receptacle for 240v and had it with the heater off/unplugged.
When you turned the heater on you read 0v. At that point..... check from either hot leg to ground. If it's a break..... one wire will show near 120v and the other probably nothing.

Leave the heater plugged in and on and keep checking back towards the main panel. Check at that breaker that supplies the sub panel. The heater plugged in and turned on will supply the load needed to show the fault.
 
  #13  
Old 12-05-18, 06:25 PM
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Nitpicking.

Electrical fault -- Undesirable or unwanted connection or touching of wires or other metal objects so as to permit a current flow in an undesired manner or in an undesired direction or of an abnormally large magnitude.

It is acceptable for the voltage at the receptacle to drop a small percentage, say 5% for the 150 foot distance to the main panel,, when the heater kicks on.
 
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Old 12-06-18, 08:19 AM
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Originally Posted by PJmax View Post
You checked at the receptacle for 240v and had it with the heater off/unplugged.
When you turned the heater on you read 0v. At that point..... check from either hot leg to ground. If it's a break..... one wire will show near 120v and the other probably nothing.

Leave the heater plugged in and on and keep checking back towards the main panel. Check at that breaker that supplies the sub panel. The heater plugged in and turned on will supply the load needed to show the fault.
Thanks. I will do that today. As soon as it warms up a bit, and I have my breakfast.
 
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Old 12-06-18, 08:28 AM
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Originally Posted by AllanJ View Post
Nitpicking.

Electrical fault -- Undesirable or unwanted connection or touching of wires or other metal objects so as to permit a current flow in an undesired manner or in an undesired direction or of an abnormally large magnitude.

It is acceptable for the voltage at the receptacle to drop a small percentage, say 5% for the 150 foot distance to the main panel,, when the heater kicks on.
Thanks for the info.

So, I'm getting more than 5% voltage drop without the heater being plugged in.

The reason I mentioned corrosion at the main service entrance is because we lost power at one of our 120 volt kitchen circuits last summer. I was measuring like 5 volts at one of the outlets. This happened after my wife replaced some switches with dimmers on another circuit. I blamed her . But the electrician said it was a corroded connection between the breaker for the circuit and the bus. He fixed it by removing the breaker and cleaning it up.
 
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Old 12-06-18, 01:15 PM
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Main panel at house:
Name:  main-panel.JPG
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You can see the 100 amp breaker with the two large cables connected near the top left of the picture. Those two cables along with the neutral leave the panel at the left side of the panel into the conduit. I forgot to rotate the image, the left side is actually the bottom.

You checked at the receptacle for 240v and had it with the heater off/unplugged.
When you turned the heater on you read 0v. At that point..... check from either hot leg to ground. If it's a break..... one wire will show near 120v and the other probably nothing.

Leave the heater plugged in and on and keep checking back towards the main panel. Check at that breaker that supplies the sub panel. The heater plugged in and turned on will supply the load needed to show the fault.
With the heater plugged in and turned all the way on I measured voltages at these locations:

Shop outlet:
Between hots: 0 volts
Between each hot to ground: 120 volts (both sides).

Sub panel in shop:
Between hots where the cables enter the panel: 0 volts
Between each hot to the ground lug: 120 volts (both sides.)

Without the heater plugged in this morning I measured 150 - 210 volts at the outlet and at the top of the sub panel, and 120 volts from each of the hots to the ground. Yesterday I read about 190 - 220 as I recall. Maybe because today is a lot colder, I don't know.

At the main panel outside the house (with the heater plugged in and turned on):
At the 100 amp breaker where the two hot cables attach: 240 volts
Between each hot at the breaker and the neutral cable coming from the shop where it attaches to the neutral bar: (both sides) 120 volts. Is that the right location? I assumed it's ok since the neutral bar and ground bar are supposed to be connected in the main panel.

I also tested at the main panel without the heater plugged in and it reads the same as above.

Any ideas why I get these results? I'm getting 120 volts to the shop no problem, even with the heater load.

One thing: the neutrals and grounds are not isolated in either panel. I'm not sure how that affects the test.

Anyway, since I read the full 240 volts at the main panel and 0 volts at the sub panel with the heater on, I guess the problem is in the cable connecting the two. Is that a reasonable conclusion? Could there be another explanation?
 

Last edited by heinzg; 12-06-18 at 01:34 PM.
  #17  
Old 12-06-18, 01:29 PM
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One of the hot lines between the house panel and the shop subpanel has rotted out in the middle or has a bad connection.

Enough power gets through the bad spot so your meter can register 120 volts hot to neutral with the heater unplugged although I suspect not enough for a hair dryer or even a 100 watt incandescent light to work on a shop receptacle on that half of your shop feed. When the heater is plugged in and turned on, the heater innards energize the bad half of the shop feed using the good half of the shop feed. Thus you can measure 120 volts hot to neutral on both sides but the heater itself does not work under those conditions.
 

Last edited by AllanJ; 12-06-18 at 01:45 PM.
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Old 12-06-18, 04:16 PM
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You shouldn't do any testing with the heater on. power will feed through the heater element and you will get 120 volts to ground on both legs even though you really do not have both legs there. If possible remove the heater, and any other 240 volt equipment, from the circuit(s) and retest. I suspect you will get different results.
 
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Old 12-07-18, 12:49 PM
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You shouldn't do any testing with the heater on. power will feed through the heater element and you will get 120 volts to ground on both legs even though you really do not have both legs there. If possible remove the heater, and any other 240 volt equipment, from the circuit(s) and retest. I suspect you will get different results.
Thanks for responding.

The only thing on the 240 volt circuit is the heater outlet.
Without the heater plugged into the outlet, here's what I measured this morning:

At the shop sub panel where the cable from the house main service comes in at the top of the bus bars:
200 - 210 volts between the hots
100 - 120 volts between either hot and the neutral cable where it attaches to the ground/neutral bar.

At the heater outlet:
200 - 210 volts across the hots, 100 - 120 volts across either hot and the ground wire.
The readings at the sub panel vary depending on which tester probe I use on which test point.

Then I measured at the house main service:
At the 100 amp breaker feeding the shop:
250 volts across the hots where they come out of the breaker.
120 volts across either hot and the neutral where it connects to the neutral bar.

So there is 16% - 20% voltage drop to the shop with no load.
Yesterday, when the heater was plugged in I got 0 volts across the hots at the plug as soon as I turned the heater on.

What do you think is going on based on these results?
Any other tests you could recommend?

I think the cable is bad somewhere between the house and the shop.
 
  #20  
Old 12-07-18, 07:08 PM
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Wires/cables typically do not go bad unless they are poorly installed (wrong type of wire/insulation in the wrong location) or are damaged somehow.

I would recommend disconnecting the feeder wires from the lugs in the sub panel, and the breaker in the main panel, and check the wire for corrosion. Strip and reconnect the wires making sure that they are good and tight, and that they have anti-oxidation paste on the connections (The wires appear to be aluminum)

Also check voltage coming out of the 100 amp breaker in the main panel to make sure you are getting 120 to ground and 240v between hots.
 
  #21  
Old 12-08-18, 11:35 AM
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Did you measure each hot to ground under load?
The no load readings are a false reading or phantom voltage from a high impedance digital meter. One or both of the hot lines is open somewhere between the breaker and the plug.
 
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Old 12-08-18, 04:38 PM
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There may (should?) be a Safety Switch that removes power from the heater elements if the device is knocked over. The switch could be mounted in the heater body with an extension to the floor.

With the heater unplugged, check the bottom of the heater. If it's an older heater, the switch could be an internal mercury-filled tilt switch.
 
  #23  
Old 12-08-18, 08:47 PM
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I am.going.with a bad section of cable that is touching enough to pass voltage but fails under any heavy load.
 
  #24  
Old 12-10-18, 11:10 AM
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Thanks for all you guys' responses. This is a great forum and you've all been very helpful.

I did look for a reset switch on the old heater, but didn't find one. My wife took the heater apart and cleaned whatever contacts she could. It didn't look like there was a reset switch inside either. Then we bought a new heater (now returned), and it also didn't work.

I don't think there is corrosion at the sub panel. There may be at the main service. I'll do a bit more testing at that end.

I talked to the electrician that spliced the cable break a few months back, and his opinion is that the cable probably needs replacing. Something I didn't know; he said in the area where he made his cable splice, the cable was only buried 6" deep.

If I don't find any corrosion or whatever at the main panel, I'm probably going to replace the cable. I might have some questions later about figuring the total load at the shop and the right size/type of cable.
 
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