Disconnect for water heater

[Jf99]

I'm trying to find the code article that states that a water heater disconnect needs to be 125% of the the disconnect rating. I'm working with 12.3 kw water heater at 240v. I've looked in 422.13

 

[letgomywago]

Just get breaker locks

 

[Jf99]

Prints are requiring a disconnect at the water heater

 

[letgomywago]

I don't think you need to size disconnects with the 125 percent rating. I might be wrong but a 60 amp disconnect should be fine.

 

[Jf99]

So in theory I could have

80A breaker @ 150% of the 51A,
#6thhn @ 125% for the conductors
With a 60A disconnect

 

[letgomywago]

So in theory I could have

80A breaker @ 150% of the 51A,
#6thhn @ 125% for the conductors
With a 60A disconnect

So I'd check the nameplate and make sure that's the correct wattage.

 

[Jf99]

It's a 3 phase unit that's reconfigured to single phase.

STCE31-50-120 is the model #

 

[ramsy]

So in theory I could have

80A breaker @ 150% of the 51A,
#6thhn @ 125% for the conductors
With a 60A disconnect

Doesn't 422.11(F)(1) restrict branch circuit heater appliance loads > 48A to a 60A breaker?

Especially, since branch circuit rating is the same as supplementary OCPD, with interlocked heating elements that prevent operating together.

 

[Jf99]

I miss read 422.11(E). That's where I was getting the 150%.

Yeah I believe you're right

Doesn't 422.11(F)(1) restrict branch circuit heater appliance loads > 48A to a 60A breaker?

Especially, since branch circuit rating is the same as supplementary OCPD, with interlocked heating elements that prevent operating together.

 

[Another C10]

I've presented this similar scenario for plan check and it passed fine. On yours I'd submit ..

12300 / 240 = 51.25 x 125% = 64.06A

70 Amp breaker and 70A slow blow fused disconnect if possible with a #6 THHN or #4 if its over 100ft.

 

[Jf99]

I've presented this similar scenario for plan check and it passed fine. On yours I'd submit ..

12300 / 240 = 51.25 x 125% = 64.06A

70 Amp breaker and 70A slow blow fused disconnect if possible with a #6 THHN or #4 if its over 100ft.

I believe the panel has an existing 70A breaker I could use. I would just need the non fused disconnect. I'm assuming a 100A since the 125% would put me over for a 60A disconnect.

 

[ramsy]

60A disconnect or breaker is slightly too small.

210.20(A) & 230.208(B) requires sizing OCP 125% of continuous loads, except where listed for 100% of its rating.

51 x 1.25 = 63.75A or next highest 70A

UL 489, and DIVQ prohibits loads that exceed 80% of molded case circuit breaker rating, unless otherwise marked

51 / 60 = 85%,
51 / 70 = 73%