Does a water heater need to be fused higher than its FLA

[jasonsim]

I am working on drawings that includes an industrial water heater. It is a three phase 208 volt heater and has a FLA of 99.9.

I was just going to put it on a 100 amp breaker but, I was just asked if the breaker size should be larger. I don't see anything in the spec sheet that requires it to be fused larger and I cant find anything in the code book about it being larger either.

Should I go ahead and fuse it at 125% to be safe? That would increase the cost a lot.

 

[Smart $]

Assuming a storage-type water heater, 422.12 requires it to be considered a continuous load. 210.19/20 requires 125% for conductor and OCPD ratings.

 

[petersonra]

Assuming a storage-type water heater, 422.12 requires it to be considered a continuous load. 210.19/20 requires 125% for conductor and OCPD ratings.

422.13 Storage-Type Water Heaters. A fixed storage-type
water heater that has a capacity of 450 L (120 gal) or less shall
be considered a continuous load for the purposes of sizing
branch circuits.

is the heater smaller than 120 gallons?

 

[HEYDOG]

I would also look at 422.11(E)(3)

 

[Smart $]

is the heater smaller than 120 gallons?

In addition to assuming a storage-type, I figured such being 3? and drawing 100A would likely be large enough... but an assumption all the same.

 

[mbrooke]

Id go 125%. Keep in mind that if the voltage goes up due to normal utility swings the current does to. 99.9 is pushing the limits.


One more thing, if the FLA is based on 240 volts and you have a 208 volt supply FLA will go down enough to use a 100 amp breaker.

 

[Dennis Alwon]

I believe you can protect the water heater at 150%. So a 4500 watt element at 240v could be installed on a 30 amp ocpd