Melted Wire

[Aaron]

Oooh, I don't have an amp clamp and it's getting closer to Christmastime.

[rchesterton]

I’m considering an upgrade to this Heater. Will my eight gauge wire still work or do I need to remove it and install six gauge?

[emtnut]

That a 480 Volt unit !

If you need more heat, you may need to look at 2 - 5Kv units (240V)

[Aaron]

Or consider a natural gas powered heater.

[rchesterton]

I have considered gas, but we live in an area where electricity is owned by our local municipality - very cheap. Is the heater above (480 volt) just not a reasonable application for residential use? The house has 400 amp service - garage is pretty big - very tall ceilings and 3 full size bays. I have two heaters in my smaller garage 5000 watts each. That works well for me. I am sure it would work well here too.

It was quite a challenge getting the line pulled from the garage to the box for the 7500 watt heater. We would like to avoid rerunning the line or putting in an additional one, if possible.

Plus, gas is something that I have never worked with and don't want to mess with. I have heard it is easier than water or electricity - but I'll leave that to the pros.

[Aaron]

Gas is not hard to run if you use flexible corrugated stainless steel tubing (CSST). You could run the CSST yourself, and if you're uncomfortable with making joints and connections, you could hire a pro to do that part for you. You would have done the "heavy lifting" by running the line.

You don't have 480V service to your house, which is why you can't use that heater. 480V is three-phase service that typically only serves commercial buildings.

If you stick with electric and want the BTUs, then you'll need to go with emtnut's suggestion of using two heaters. Obviously I assume your garage is well insulated; if it's not then this is all for naught.

[rchesterton]

Yes, it is a very well insulated garage. I am not into heating the neighborhood (as my father would say).

Thanks for all of the information and advice. I'd love to find a 10000watt heater so I can take advantage of our low electricity cost but may have to consider gas.

[Aaron]

Gas would probably be a lot cheaper if you are aiming to heat a garage, honestly.

I would love to have a heated garage. Not in the cards for me.

[rchesterton]

I am kind of dwelling on the electric heater option still...This one is 7500 - 10000 watts - seems good. The 7500 one we had in there worked great until it melted the wire. Had to be an issue with the actual heater...no other cause found.

Would you think this would be OK? We have #8 gauge wire run already...we just want it up asap. Gas is a whole other project and we have done the leg work, spent time and money already to get it run, etc.

I am just not sure what the 1 or 3 phase means, and the 208 vs 240?

[Aaron]

Yeah that one looks like it could work since you'd be using single-phase 240. I wonder if these heaters are the ones that get mounted off a bracket, high near the ceiling?

The 10,000 watt load would require beefier cabling though, I think. I think it would draw 7500 watts with the 208V setup, but that is three-phase which you don't have.

[rchesterton]

I just spoke with a technical rep from the place I am getting it (bought it -pick up tomorrow). I am planning to run 6/2 and take out the #8 (ugh). It's about 75 feet between the breaker box and the heater.

I'm also replacing the 40amp breaker with a 50 amp. The amperage indicates that it draws 42 amps at 10Kw. So, 50 amp should be good to go, right? 1.25x42 = 52.5 - which is just a rule of thumb calculation, correct?

[rchesterton]

Oh, and yes...they are mounted high with a bracket. The rep told me they are "unit heaters" and are meant to run for the season (with a thermostat) rather than my "utility" heaters that I turn on and off when needed. Sound right? They will last running constantly?

[Aaron]

Yeah if that's what it's designed for, then that's what I'd expect it to do. Thermostats are a good thing. Set it to something reasable for a garage in winter, say 65F/18C then turn it off completely when you’re not in there.

Bummer about needing to upgrade your wire.

[rchesterton]

Amp wise....50 amp breaker safe to use? 55 is hard to find and 60 is too big I am sure.

[emtnut]

I just spoke with a technical rep from the place I am getting it (bought it -pick up tomorrow). I am planning to run 6/2 and take out the #8 (ugh). It's about 75 feet between the breaker box and the heater.

I'm also replacing the 40amp breaker with a 50 amp. The amperage indicates that it draws 42 amps at 10Kw. So, 50 amp should be good to go, right? 1.25x42 = 52.5 - which is just a rule of thumb calculation, correct?

Not a rule of thumb, it's a code requirement for a continuous load.
You are over a 50A breaker, so you have to go to the next available breaker.

I can't see the model number on that pic, but if you post it I can look at the specs. Or you can check it out yourself. The manufacturer often specifies what is needed, and that trumps whatever code says.

[rchesterton]

Ah, ok. Thanks for that correction. The model is 2yu69, the manual is lengthy and I was not sure what to look for. Any help is appreciated!!

[emtnut]

Manual just says to follow NEC .

I can't say for sure with NEC (and I think your in the US). CEC would allow 60A breaker with #6AWG. But I know there are differences on how NEC and CEC handle heating loads .

I think you're stuck going with the 55A breaker. Maybe Aaron can confirm.

[Aaron]

Article 424 ● Fixed Electric Space-Heating Equipment

424.21 Switch and Circuit Breaker to Be Indicating

Switches and circuit breakers used as disconnecting means shall be of the indicating type.

424.22 Overcurrent Protection

(A) Branch-Circuit Devices. Electric space-heating equipment, other than such motor-operated equipment as required by Articles 430 and 440 to have additional overcurrent protection, shall be permitted to be protected against overcurrent where supplied by one of the branch circuits in Article 210.

(B) Resistance Elements. Resistance-type heating elements in electric space-heating equipment shall be protected at not more than 60 amperes. Equipment rated more than 48 amperes and employing such elements shall have the heating elements subdivided, and each subdivided load shall not exceed 48 amperes. Where a subdivided load is less than 48 amperes, the rating of the supplementary overcurrent protective device shall comply with 424.3(B). A boiler employing resistance-type immersion heating elements contained in an ASME-rated and stamped vessel shall be permitted to comply with 424.72(A).

I'm guessing 60 is okay? The heater itself may have a breaker or fuse.

[emtnut]

I seems that NEC limits #6 romex to 55Amps (CEC allows 65A ... go figure !)

So unless you run larger cable (or #6 THHN in conduit), the max breaker is 55A for you.

[rchesterton]

We have a Square D box and Square D only makes 50 and 60 AMP breakers. I cannot get a 55 amp.

Looking back at the manual, however, it states that the AMPs at 10Kw are 42. I am not too clear on why I would need to get up to 55.

[rchesterton]

To clarify, I know that you take 1.25 X the max AMPs to come up with that number...I just don't know why.

[emtnut]

We have a Square D box and Square D only makes 50 and 60 AMP breakers. I cannot get a 55 amp.

Looking back at the manual, however, it states that the AMPs at 10Kw are 42. I am not too clear on why I would need to get up to 55.

A heater is considered a continuous load (for NEC, that means it could be 'on' for more than 3 hours)
Breakers are only rated at 80% for a continuous load (because over time the heat can stop the trip from working). That is why we need to upsize the breaker.

For your situation, you need to protect for 52.5 A. Code says to pick the next higher breaker.
You mentioned that the 55A was 'hard to find' ... that provision isn't in code . If it is available, that's what you have to use. The fact that they don't exist, allows you to go to a 60A breaker.

Hope that helps

[rchesterton]

That helps a lot. Thanks!

One last thing...if I go w a 60 amp breaker and #6 wire, are they compatible together?

In other words what is the max amp load for #6 wire? I imagine it needs to be 60, if I am using a 60 amp breaker, right?

[rchesterton]

So, do you guys think it is safe for me to use the #6 or just go with the THHN in conduit?

I am leaning toward playing it safe and just getting the THHN #6 and conduit. I picked up a 60 amp breaker.

If I go with THHN:

1. What type of conduit do I use?
2. What "flexible" conduit can I use at the end (where it comes out of the wall in the garage and attaches to the heater)
3. Does the ground have to be the same gauge?
4. When buying THHN do I just get a roll of black, roll of white, and a roll of green?

[emtnut]

That helps a lot. Thanks!

One last thing...if I go w a 60 amp breaker and #6 wire, are they compatible together?

In other words what is the max amp load for #6 wire? I imagine it needs to be 60, if I am using a 60 amp breaker, right?

For this application they are. The wire is rated at 55A (@60˚). You are only drawing 42A.
The breaker is required to be upsized (125%), the cable doesn't require that.

In other words, 60A on #6 romex is good to go.


**Note, this is for a dedicated load. If you were installing a 60A subpanel, you would require #6 THHN or #4 Romex **

[Aaron]

Plus I think cables and conductors are rated for at least 75°C if not 90°C these days. That should be marked on the sheath of the cable or the insulation of the conductor.

[emtnut]

Plus I think cables and conductors are rated for at least 75°C if not 90°C these days. That should be marked on the sheath of the cable or the insulation of the conductor.

Yes, most are rated 90˚ , some are 75˚ (like twn75 )

NEC requires you to use the 60˚ column. CEC changed that in 2012 code cycle, and we can use the 75˚ column.

Basically, the higher temp allows for derating and for attics and lighting applications.

[rchesterton]

I got started over the weekend installing the new and taking out the old. I thought I would update you on what I found.

First step was taking the old heater down - again that was 240V / 7500 Watts. According to that manual, the max amps would be 31.3 at 75Kw.

I used #8 with a 40amp circuit.

When I pulled the old line out I found some startling evidence:

1. When I unscrewed the terminal for the black line into the heater it literally flaked apart - burned to a crisp. The first two or three inches of the black leg was also charred. Couldn't even tell it was a copper line- just black and brittle.

2. About 10 feet down the line (toward the box) where the line turned into the wall of the garage and then down into the basement, I had a junction box that served as protection for the line. There was no junction, the line just went from conduit into the box and through the wall into the basement. I didn't know another way to protect the line so I used a box. At that spot, there was blackening around the conduit (where it went into the junction box) and also around the screws that held the clamps together. The line was intact however. No breaks in the insulation or anything like that.

No other evidence from that point back to the box. Everything else seemed ok. But that was close. Could have resulted in a fire. It appears that there was tremendous heat building up in that line. Thank God it didn't result in a fire.

My connections were solid at the heater. There was a slightly loose connection at the breaker - but the lines were still firmly placed. The black one seemed fairly easy to unscrew. Could that have been the reason this happened?

Did I use the right materials? I lost some confidence with this project and want to be sure to do everything I can to avoid that situation again.

[Aaron]

Yeah you may not have torqued the conductor tight enough at the breaker termination. This may have caused some higher resistance that didn't trip the breaker for whatever reason. Or perhaps the breaker is faulty. Yes, very dangerous at any rate.

[rchesterton]

I am now using #6 conductors. The use of the junction box I described...is that appropriate? I didn't know how else to protect the line going into the wall. Should I clip the ends of the lines going into that box and make an actual junction? Right now, the gauge is so heavy that to make the turn (from the top hole to the middle hole) is really tight - the conductors are super stretched at the point they are curved in the box and through the hole. Is it best to actually make a junction or leave it as is? I could take a picture later if that helps explain what I am concerned with.