I have not seen any Code article that stated otherwise.
As to it's being grounded by an equipment ground or a grounded service conductor, that would depend on the type installation.
If the fire pump transfer switch is considerd service equipment and is required to have the grounded conductor brought to it, why would you want to switch it. Most likely the neutral is not even needed for the fire pump. Unless its one big single phase pump.I assume the fire pump ats is 4-pole type with switched neutral in order we can ground it?
The fire ATS has two coming feeder, normal feeder tap to secondary of building utility xfmr, emergency feeder was fed out of emergency generator (considering separate devrived system) So, ATS should has switched neutral?
If we treate fire pump ats as a separate service, should we gound the ATS?
Then, do we need neutral wire to bind to ground at ATS?
I wouldn't agree with the inspector on this one if i understand what you described. You have two utility power sources for the fire pump transfer switch. You installed the main bonding jumper on the load side of the switched neutral. So if they are both utility sources, then they are both energized all the time and the OCPD for each service is the A.T.S. If a fault happens in source two while the switch is in the preferred source one position, how is the fault path going to return to source two transformer.In Kentucky, the inspector made us insulate the neutral from the transformer (totally seperate service from transformer), which was also the ground because it was not needed as a neutral. We had to use the neutral/ground from the main building service to ground the fire pump. He was concerned that there would be a parallel of the neutrals with the fire pump and the building which I can kinda see his point. But he also made us bond on the load side of a four pole ground fault transfer switch, which makes the ground fault function of the switch virtually useless.
anbm, article 250.24(C) states that the grounded conductor (neutral) shall be brought to the service disconnect, but it only needs to be sized per 250.24(C)1 using table 250.66.
A grounding conductor does not need to brought in with the grounded conductor.
At the ATS, the main bonding jumper will need to be installed on the service grounded conductor.
Rick
RUwired, if we treat fire pump ATS as a separate service entrance disconnect/board, we need to ground it or bonded to building grounding system (water metal pipe, building steel, rod, etc).
Then, when fire pump ATS is switched to emergency power source (serving from emergency generator), will this create ground loop violation? Because we bonded the generator to building grounding system as it is separate devried system (assume both generator and fire stays inside)
Same thing happens when fire pump ATS on normal utility power.
If the fire pump locates inside building (concrete structure not building steel), how do you bond the fire pump/ats to grounding sytem? Drive a ground rod?