ELECTRIC WATER HEATER

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Dennis Alwon said:
I just did a load calc using 32 amps x4 for the water heater or 30,720 watts. I used 4,000 sq.ft added the typical range, dryer, microwave, dw, etc. I used 10000 watts for the a/c unit. I came up with 183 amps using the optional cal and 238 using the standard
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I get 208.5A using 220.82 when I add a 32A EV charger. And now they have 40A and 48A and 80A chargers.
I used 36kW for the water heater because that's a spec I found for one of these online.

I mean, I guess you're right, by itself it's not technically the back-breaker it seems like. It only becomes that when the homeowner wants to add another big load. But it still just seems wrong to add 120A additional amps to a home with a 200A service. If everyone takes a shower at the same time the EV is charging...

I also believe that you can turn off one or two of the heating elements (i.e. or or two of the 40A breakers) to these things and they still work, as long as your GPM isn't too high. Not sure if it's in the manual but I had a homeowner tell me they were doing that, iirc.
 
Dennis Alwon said:
@ING23 Did the city say you must use that calculation method? If so, then why did they pass the job
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That is the method the City Use on their web site , I am not doing any job yet . This hole new community (all electric) has the same , more o less appliances. No idea how the builder get away with this. I just want to be sure I am not missing something here.
 
ING23 said:
That is the method the City Use on their web site , I am not doing any job yet . This hole new community (all electric) has the same , more o less appliances. No idea how the builder get away with this. I just want to be sure I am not missing something here.
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Well, it's quite possible as Dennis pointed out that with the optional load calc the installations comply with the NEC. (Stupid, in my opinion, but compliant.)

Now, if nobody told the utility, they might be pretty mad.
 
jaggedben said:
My point was simply that a competent person doesn't install a 150A water heater on a 200A service for a single family home. You get a different water heater or a different size service.

Another way to put it is that most people don't bother to actually do load calcs for new single family homes, and just spec a 200A service. And most of the time that works out fine. But not with an electric on demand water heater.

I agree that the other details suggest that this wasn't the only aspect of the electrical that was rushed and sloppy.
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This is because loads over i think either 40 or 50 amperes for dwellings have to be divided and a 150 ampere water heater on a 200 ampere service is hard or impossible to balance?

If unbalanced loads such as this how does this affect things, voltages?
 
Jpflex said:
This is because loads over i think either 40 or 50 amperes for dwellings have to be divided and a 150 ampere water heater on a 200 ampere service is hard or impossible to balance?

If unbalanced loads such as this how does this affect things, voltages?
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Huh ?? a 240v load on a 240v service is pretty balanced !
 
Jpflex said:
This is because loads over i think either 40 or 50 amperes for dwellings have to be divided and a 150 ampere water heater on a 200 ampere service is hard or impossible to balance?
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There is no such rule in the NEC I'm aware of. I've seen a steam shower on a 90A breaker, and car chargers on a 100A. It seems like for water heaters there may be something in the product standards because they all seem to be made this way after about 60A.

Jpflex said:
If unbalanced loads such as this how does this affect things, voltages?
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As augie said, this is not an unbalanced load on a single phase residential service. It might create some imbalance on the utility higher-voltage-level distribution network if there were a lot of these in one neighborhood and they weren't balanced, but that's above my pay grade. My guess is the utility might just need to replace/upgrade distribution transformers sooner than they wanted if they didn't get the heads up as the subdivision was going in.
 
jaggedben said:
There is no such rule in the NEC I'm aware of. I've seen a steam shower on a 90A breaker, and car chargers on a 100A. It seems like for water heaters there may be something in the product standards because they all seem to be made this way after about 60A.
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there is such a code requiring (if i remember correctly) a specific appliance load over a certain amount to be divided within the power distribution panel but I do not have my code book as it’s at work
 
jaggedben said:
There is no such rule in the NEC I'm aware of. I've seen a steam shower on a 90A breaker, and car chargers on a 100A. It seems like for water heaters there may be something in the product standards because they all seem to be made this way after about 60A.
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Jpflex said:
there is such a code requiring (if i remember correctly) a specific appliance load over a certain amount to be divided within the power distribution panel but I do not have my code book as it’s at work
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It would appear that this required by 422.11(B) in the 2020. It says in essence that a household appliance with surface heating elements with a demand greater than 60 amperes shall have the power supply subdivided into two or more circuits each with an OPCD not greater than 50 amperes.
 
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