Installing an Industrial Water Heater

[Machiavelli999]

I am installing a 180KW industrial water heater at my facility.

This is a 480V device and the vendor claims that the FLA is 216.51 amps. I am wondering if I can feed it from an existing 480V, 250A panel that's completely unloaded right now. The feed coming in to this panel is protected by a 250A breaker. The feed out to the water heater will also be protected by a 250A breaker.

I am pretty sure that this complies with code requirements, but do I run the risks of nuisance trips?

The load is non-continuous and I will almost never run this heater at full load. However, it is possible that we may have to run it at or near full load for an 8-minute cycle. Can a regular 250A breaker carry 216.51 amps for more than just a few seconds?

 

[Dennis Alwon]

A 250 amp breaker can carry 250 amps of non continuous load. They also make some breakers that are rated 100% even for continuous load. I assume you don't have that.

So yes it should work ...:thumbsup:

 

[augie47]

Does the water heater have controls with overcurrent devices. I would think it does, but, if not be sure to check 422.11

 

[Dennis Alwon]

Does the water heater have controls with overcurrent devices. I would think it does, but, if not be sure to check 422.11

I think it has to

 

[don_resqcapt19]

I thought the maximum circuit for a water heater was 120 amps. 422.11(F)(3)

 

[hurk27]

A continuous load is any load that will run for more then 3 hours, many water heaters are considered continuous as it can take that long to reach set temp, if it could be considered continuous then 210.20(A) would require a circuit of 270.64 amps, but if not you should be fine, if this is a fast cycle water heater such as a tank-less or limited tank size heater then it may not be considered continuous.

as far as nuisance tripping, resistive heating elements don't have the large inductive inrush like motors and transformers do, while they do have a small inrush cause by the cold element resistance its no where near the current of a transformer or motor or does it last as long as the elements heat up very fast.

But connections are very important and making sure they are tight and clean, a resistance type load can put to test any connection and any heating in the connection can not only damage the connection but also cause the breaker to trip because of heat developed at the connection to it, this also includes the breaker connection to the buss.

 

[Ponchik]

I thought the maximum circuit for a water heater was 120 amps. 422.11(F)(3)

I belive (not sure 100%) that is each circuit supplying to the water heater. So, if there are 3 circuits supplying the unit each circuit can not be more than 120 amps.

In the OP case, maybe it has (2) elements at 108 amps each.

 

[hurk27]

I thought the maximum circuit for a water heater was 120 amps. 422.11(F)(3)

Don they shall be permitted to be subdivided into circuits of not more then 120 amps, there is nothing saying it can't be larger or fed via a single circuit.

The same goes for Commercial Kitchen and Cooking Appliances in (2)

other wise without this allowance we would have to use a single circuit to one appliance but this allows us to use more then one.

I think this was because many load centers didn't allow for large enough breakers to supply the whole load, but the load center would, think of the many tankless water heaters in a house, maybe the service can handle the whole load but at 180 amps the panel manufacture might only allow a max of 125 amp breaker in that panel, so we split it up into 3 60 amp circuits.

 

[don_resqcapt19]

Wayne,
I fell into the trap of the words "shall be permitted". In my opinion, these words should always be read to act as an exception, but for some reason I did not read them that way this time.

 

[GoldDigger]

Wayne,
I fell into the trap of the words "shall be permitted". In my opinion, these words should always be read to act as an exception, but for some reason I did not read them that way this time.

Your eye may have presented your subconscious with the wording from F(1) where it says "shall" instead? A different case, and one in which the separate OCPDs are required to be part of or factory installed on the heater itself or provided by the heater manufacturer as a separate assembly. (That manufacturer-supplied part seems to have crept into another member's earlier comments too.)