Unit Heater Disconnect

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mstrlucky74

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Confused by the attached. First question, if the unit has a built in disconnect why would have to install another disconnect by the unit.


Second, another note says to install 3P/25A circuit breaker and a 3P non fused disconnect next to the unit heater. The unit heater says it is single phase. Can't have 3P ckt breaker and disconnect switch.
 

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mstrlucky74 said:
Confused by the attached. First question, if the unit has a built in disconnect why would have to install another disconnect by the unit.


Second, another note says to install 3P/25A circuit breaker and a 3P non fused disconnect next to the unit heater. The unit heater says it is single phase. Can't have 3P ckt breaker and disconnect switch.
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That is definitely over specification for what is being supplied, but is not violating any code either. A simple single pole toggle switch is plenty of switch to get the job done, yet still isn't needed if the unit already has a disconnect on it.
 
kwired said:
That is definitely over specification for what is being supplied, but is not violating any code either. A simple single pole toggle switch is plenty of switch to get the job done, yet still isn't needed if the unit already has a disconnect on it.
Click to expand...

Also the 3P cb and disco is wrong if it's a single phase unit.
 
mstrlucky74 said:
Really? So from a technical standpoint why would they ask for 3P on a single phase unit? It wouldn't affect the wiring?
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Some designers have "boilerplate" specifications for certain things and the spec is the same across the board regardless if it is single or three phase. They may give their blessing to change it if you ask.

If only supplying a single phase load you can just use one (or two) poles of the switch and it still works, and there is no NEC requirement that you only have a single pole switch for this purpose, you could use a six pole switch if you had one.
 
kwired said:
Some designers have "boilerplate" specifications for certain things and the spec is the same across the board regardless if it is single or three phase. They may give their blessing to change it if you ask.

If only supplying a single phase load you can just use one (or two) poles of the switch and it still works, and there is no NEC requirement that you only have a single pole switch for this purpose, you could use a six pole switch if you had one.
Click to expand...

But it seems senseless that you would only need one phase conductor for the unit heater and only run one phase conductor but install a 3P breaker and switch. Right?
 
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