Missing one leg of 240v to outlets

[Monte Milanuk]

So... it's that time of year... time to turn the heaters on

Moved earlier this year to a new (to us) place. Both the (attached) garage and (detached) shop have large 240v heater/fan units mounted near the ceiling. Each unit is on its own 30A breaker, two in the garage on the house 200A panel, and two in the shop on a separate 200A panel there.

That's the good news.

The bad news is, only one out of four heaters is currently working - and its in the garage, not my shop!

Checking at the outlets for the non-working heaters, I get 122v from one leg to the ground, and... about 10-13 vac from the other leg to ground. Leg to leg, I get ~108-110 vac. On the sole working unit, I get 122 on both legs, and 244 across the outlet.

Where it gets a little weird is that back at the breaker panel, I get 122 to ground off *both* legs, and 243 across them. So somewhere between the panel and the outlet, I'm losing one leg - on three out of the four circuits. One circuit, I could perhaps buy into 'bad wiring'. Three? Not so much.

The house isn't exactly new (1999), but it isn't that old either, and it's been pretty well maintained. Plus, what I can see of the outlets and wiring for the heaters looks professionally done.

A little bit of what I've read almost leads me to wonder if there is a switch somewhere on that one leg of each circuit, especially since the heaters *are* high up on the wall, pretty much at the ceiling level and you need a ladder to get to the controls. But if so, they're cunningly well hidden

Any ideas or suggestions? Something glaringly obvious that I'm missing here?

[glenn bradley]

This will be interesting. The home inspection certainly should have shown this on the report. As an example, my clothes dryer electrical outlet was dead but, this was a non-issue as we use gas. Heaters not working would have been on my "fix or offer credit" list during a home purchase.

[ray grundhoefer]

is there a thermostat somewhere you havent found yet

[roger wiegand]

Are you testing with a digital multimeter? If so you may be sensing phantom voltage and actually have no real connection on either leg (which might be better for diagnostic purposes). A switch installed by an electrician would almost certainly be a double pole switch that would open both legs. A double lead tester that buzzes and lights up is actually a better choice for this application, as it won't be fooled by phantom voltage.

A hidden switch would be the most likely bet. I doubt a thermostat would be switching the full line voltage rather than acting through a relay.

[John K Jordan]

Is one good breaker feeding bad multiple outlets? If so, trace from the panel and you will find the problem. If you are lucky it will be a simple bad connection in the first box in the bad string. (Take the cover off each box and check all wires on both sides of the circuit.) Don't forget there may be a junction box somewhere downstream from the panel. People have been known to put junction boxes in odd and illegal places, even covering them with sheetrock and such. If unlucky, the problem may be a wire somewhere in wall or ceiling. A contractor here once killed a lighting circuit with a single poorly-placed nail. An amateur remodeler can do a lot of damage. A power overload can burn through wire or turn a good connection into a bad one. You can buy tools which will help trace wires.

Often the bad connection is in a twist connector which wasn't twisted correctly or loosened up with heating/cooling cycles. You can sometimes smell the problem if there was arcing at the connection.

If not experienced and adept with debugging and reparing power wiring don't die. Call your brother-in-law or someone, or, gasp, an electrician!

My own house was wired in several odd and confusing ways, some involving multiple 3-way and 4-way light switches wired incorrectly by so-called professionals. I have a lot of experience but it was still a challenge to make everything right.

BTW, the low voltage readings are common in a disconnected line - wires running in parallel or in close proximity can pick up voltage induced by other wires.

JKJ

[David L Morse]

I think Ray has the right idea. There could be a 240V thermostat somewhere that, instead of being used as intended to switch both legs of a 240 volt circuit, was used to switch one leg of each of two different circuits.

[Monte Milanuk]

Okay, thanks for the input folks. I was thinking 'switch' as in 'toggle', not 'thermostat' for some reason. Started sighting down the planes of the walls, etc. where I could see behind things. Still nothing in the garage, but in the shop... found the thermostats, squirreled away behind something Probably didn't pay them any mind earlier in the year, as the shop has a separate A/C (window-mount).

I'm very aware of the whole induced voltage phenomenon; it's been a few years (20) but I still have my Fluke and my Wiggy. I can think of about one time that the Wiggy picked up on something the Fluke was giving me bad readings on, and that was a whole separate matter (PLC I/O cards). I'm less concerned about the 'phantom' voltage on the one leg, than I am about the *lack* of 120 v on that same leg. That said, I did a whole lot more 'industrial/utility' type stuff i.e. DC, 3-phase, high voltage and pretty much zero residential/commercial, which is why I'm not shy about asking for help

Now that I'm down to *one* non-functioning outlet, the 'bad wiring' theory is starting to sound better and better. I'll do some more poking and prodding as other projects allow, and see what I can find.

[Brice Rogers]

If you end up exhausting all other possibilities, you may want to consider buying/using a circuit tracer. What you would do is to either trip the breaker or pop it out and then connect the circuit tracer signal generator to the (disconnected) wire and then you use the probe along the walls to trace where the wiring goes. Mine makes a warbly sound that gets louder the closer I am to the wire. You can detect the signal through drywall. But I doubt that it would work through metal conduit except where the wires ended in a J box somewhere. They cost around $25.

[Julie Moriarty]

My first thought is a bad connection in a junction box. If both legs at the panel are good, both legs at one heater are both good, but one leg in the next three heaters are bad, I would start at the good heater and trace it back to the junction box that feeds that heater. That's probably where the faulty connection is.

Of course it is possible that the next JB downstream has the problem but it should be one or the other. If you have access to these JBs (and it sounds like that's part of the problem) use your Wiggy or Fluke to test the voltages of each wire and splice, just as you described in your first post. If the connections look good but the voltage is lost between JBs, it's possible somewhere in between the wire of one leg was severed.

Is this conduit or NM or what?

[Arthur Fleming]

If I’m following this correctly, both outlets in the shop are controlled by thermostats, and are now functioning properly? There is now one outlet with a voltage/circuit problem in the garage, which is fed from the main house panel? If these are correct facts, what is used to control the garage heater that does work? Thermostat not on the unit? Or a thermostat on the unit? If there is a thermostat on a wall for the functioning unit, that would make me think there is one, not yet found, for the non functioning unit. Or as already suggested by another reply, some one used a 2 pole line voltage thermostat, and is only switching 1 half of each outlet with each pole. Which could indicate only 1 pole of the thermostat is working. This is just a thought I had while reading this thread.

[Monte Milanuk]

Arthur,

Yes, both outlets in the shop are controlled by thermostats, and both are working at this point.

One outlet in the garage is not working - 120 vac on one leg, nothing on the other. The other outlet in the garage works just fine.

All four outlets are each on their own 30A breakers.

All of the heaters are identical models as far as I can tell, and look like this:

20191026_065143.jpg

The ceiling in the shop is a bit higher than in the garage - not a lot, but I'm guessing that since that space was intended to be more 'occupied' they decided to put more easily accessible thermostats on the wall just inside the door, right next to the switches for the lights and the overhead door.

So far as I can find, there is no separate thermostat(s) in the garage, beyond what is shown on the ceiling-mounted units.

I do need to pull the panel off and check the voltage at the breaker on the one circuit in the garage to double check that there is good voltage present on both legs of the breaker. That is the one circuit I can't specifically remember checking - so of course I have to *re-check* it to be sure