Overload on Electric Heater

[wirestu]

All,

I have a 6 kW 240 Volt submersible electric heater that goes in a underground storage tank. I am protecting the unit by a 30 Amp 3 Pole GFCIE only circuit breaker. My question is I have a combination motor starter to be used for the unit. Can I leave the overload section in place or should I just leave the contactor.

Thanks in advance.:roll:

 

[iwire]

I don't know of any code rule prohibiting it but I would remove it.

It can only be a source of problems.

 

[cadpoint]

Will I can totally understand Mr. Iwire's statement!

I just have to ask if there's other smarts that will have now have any control on the elements? The contacts are for that interface and the overloads are for safety.

You have exactly what you need to use to address the electrical requirements
in this type system. I'll assume there's a few way to get it done, just be safe!

 

[templdl]

All,

I have a 6 kW 240 Volt submersible electric heater that goes in a underground storage tank. I am protecting the unit by a 30 Amp 3 Pole GFCIE only circuit breaker. My question is I have a combination motor starter to be used for the unit. Can I leave the overload section in place or should I just leave the contactor.

Thanks in advance.:roll:

Is it some reason that you elected a 30a breaker and if so how did you determine that 30a breaker and its associated TC would do what?

The starter seems like is a good idea but it is a NEMA device intended to control and protect motors. The contacter should work just fine if the FLA rating is less than that of the contactor. One good thing is that the contactor is expecting to feed an inductive load and your load is a piece of cake being resistive.
The OLR w/heater should not affect the operation unless the heater size conflicts with the FLA of the heater.
If you select to use this route you my consider removing the heaters and jumpering them if the OLR is adaptable to that. Or replacing the heaters with ones with a higher vslue, high enough to keep you out of trouble.
Just some thoughts....

 

[iceworm]

All,

I have a 6 kW 240 Volt submersible electric heater that goes in a underground storage tank. I am protecting the unit by a 30 Amp 3 Pole GFCIE only circuit breaker. My question is I have a combination motor starter to be used for the unit. Can I leave the overload section in place or should I just leave the contactor. ...

The few times it has come up, I have pulled/disabled the overload. Reference NEC 240.9 - it is pretty clear.

ice

 

[iceworm]

... 6 kW 240 Volt submersible electric heater .... protecting the unit by a 30 Amp 3 Pole GFCIE only circuit breaker. ... I have a combination motor starter to be used for the unit. ...

Couple of questions you didn't ask - and already have a plan. So, just curiousity on my part:

1. Does the 30A, 3pole GFCIE (GFE? As in 30ma?) feed the combination motor starter?

2. The circuit breaker in the combination controller -

Is it a mag-only (Instantaneous)?
Is it a Thermal-magnetic?
Fuses?​

As I said, just curious

ice

 

[petersonra]

All,

I have a 6 kW 240 Volt submersible electric heater that goes in a underground storage tank. I am protecting the unit by a 30 Amp 3 Pole GFCIE only circuit breaker. My question is I have a combination motor starter to be used for the unit. Can I leave the overload section in place or should I just leave the contactor.

Thanks in advance.:roll:

I would get rid of the overload. It serves no purpose on a heater load like this. It don't think it will harm anything to leave it in place nor is it a code violation, but it just does not serve any useful purpose.

Presumably the heater bundle has some kind of high limit trip, and some kind of control to turn it on and off. Those are probably needed.

 

[Jraef]

All,

I have a 6 kW 240 Volt submersible electric heater that goes in a underground storage tank. I am protecting the unit by a 30 Amp 3 Pole GFCIE only circuit breaker. My question is I have a combination motor starter to be used for the unit. Can I leave the overload section in place or should I just leave the contactor.

Thanks in advance.:roll:

If your combination starter is using a mag-only circuit breaker, you cannot use that breaker without the OL relay, and technically, it can only be used as a motor controller (used as intended issue).

 

[ptonsparky]

If your combination starter is using a mag-only circuit breaker, you cannot use that breaker without the OL relay, and technically, it can only be used as a motor controller (used as intended issue).

I had a factory rep try to tell me once that Pump Panels were only meant for pumps and using them for anything else was incorrect. I asked him why did his come with class 20 overloads when most pumps required 10s.

 

[Jraef]

I had a factory rep try to tell me once that Pump Panels were only meant for pumps and using them for anything else was incorrect. I asked him why did his come with class 20 overloads when most pumps required 10s.

Well, as you know, that's just plain wrong. A pump panel is not inherently a special class of anything, it's just a combo starter with a few accessories that is SOLD cheaper for the agg pump market because that's what the market will bear.

That said, there are a few suppliers selling "definite purpose" pump panels and since the starters they use in them are only UR, not UL, that could be partially true for THOSE versions. But on those, the OLs usually are Class 10.

 

[Bigjabe]

I have a question about this too... is it ok to use a standard combination starter including MCP breaker (magnetic only) and smart O/L relay to power a resistive load (in this case a heater). I can't imagine a possible issue - as long as you can prove that the O/L would kick out before the damage curve on the cable.

My understanding is that MCPs can't be used on their own, but as long as they have an O/L relay that protects the cable against overloads, it should all be good?

Thanks!

 

[Jraef]

I have a question about this too... is it ok to use a standard combination starter including MCP breaker (magnetic only) and smart O/L relay to power a resistive load (in this case a heater). I can't imagine a possible issue - as long as you can prove that the O/L would kick out before the damage curve on the cable.

My understanding is that MCPs can't be used on their own, but as long as they have an O/L relay that protects the cable against overloads, it should all be good?

Thanks!

No.
The NEC code section that even allows the use of Instantaneous Trip circuit breakers as part of a combination controller is "Part IV. Motor Branch-Circuit Short-Circuit and Ground-Fault Protection". So if it is not a motor branch circuit, the exception allowing them does not apply.

 

[Bigjabe]

Hmm, interesting... does anyone happen to know about the CEC? They talk about instantaneous-only breakers in the motor section as well, but there's no wording that implies (at least to me) that they wouldn't be allowed elsewhere.

Does anyone know the intent of the rule not allowing it? Seems to me that it's the same idea as a digital relay on MV breaker.

Thanks!

 

[iwire]

Hmm, interesting... does anyone happen to know about the CEC? They talk about instantaneous-only breakers in the motor section as well, but there's no wording that implies (at least to me) that they wouldn't be allowed elsewhere.

Does anyone know the intent of the rule not allowing it? Seems to me that it's the same idea as a digital relay on MV breaker.

Thanks!

An instantaneous only breaker would be a fire hazard on circuits that did not also have overloads on them if it was sized not to trip on inrush and it would be a nuisance tripping problem if sized to the conductor sizing.

 

[Haji]

Bigjabe:
Your magnetic starter and smart O/L relay combination is not factory tested. So get the current/time characteristics of the magnetic starter and O/L relay from the manufacturers and see if there is a proper coordination between the two for any prospective short circuit event. Armed with the data showing that there is indeed proper coordination between magnetic starter and smart O/L relay combination so that the O/L relay would not be damaged during any prospective short circuit event, approach the AHJ of your area for this and get their clearance for your usage of such equipment set up.

And do not forget to report the outcome here.

 

[Bigjabe]

Haha, I've actually already done that! I superimposed the Trip curves of the mag-only breaker and the OL relay and the cable damage curve, and sure enough there are no circumstances under which any damage to any equipment could occur. To me, that proves that it should be ok - whether it's connected to a motor or not! Just have to talk to the AHJ now

But seriously, a combo motor starter still only has one job - protect the load and protect the cable. They use OLs and mag-onlys just to avoid the inrush problem but they still must fully protect the cable and load. And they still do with a heater so what's the problem.

 

[Bigjabe]

An instantaneous only breaker would be a fire hazard on circuits that did not also have overloads on them if it was sized not to trip on inrush and it would be a nuisance tripping problem if sized to the conductor sizing.

Yup totally agree! I'm not talking about disabling the OL Relay though, I'm saying keep the OL relay in tact to protect against overloads.

 

[iwire]

Yup totally agree! I'm not talking about disabling the OL Relay though, I'm saying keep the OL relay in tact to protect against overloads.

In my opinion what you propose would be a listing violation.

 

[Bigjabe]

In my opinion what you propose would be a listing violation.

I think you're probably right... makes me angry when something would work totally fine in an application but it just hasn't been "listed" yet. In my opinion it just exposes the industry for the silly cash grabbing jokers they are. Especially as an engineer, who should be given some amount of logical reasoning ability, rather than just following ill-conceived rules.

 

[Jraef]

I think you're probably right... makes me angry when something would work totally fine in an application but it just hasn't been "listed" yet. In my opinion it just exposes the industry for the silly cash grabbing jokers they are. Especially as an engineer, who should be given some amount of logical reasoning ability, rather than just following ill-conceived rules.

I'll conceived? If you had seen how many times I have seen idiots turn up the dials on motor overloads, or just keep putting in bigger and bigger heaters until the "problem" went away. Sure, YOU would never do that, but rules are not there for reasonable people, they are there for idiots.