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Re: 240V feeder and HV cabinet ground question

Original poster: "Gerry  Reynolds" <gerryreynolds@xxxxxxxxxxxxx>

Hi Jim,

If I got this right, your pool cabinet is no longer part of your pool system and will be dedicated to your coiling??? There is a pool near by where all metal things are grounded to house ground??? The dedicated 60 amp breaker will service only your coil??? The power routing from the 60 amp breaker has 2 wires for 240, a safety ground wire, and a neutral wire??? If the load is balanced across the 240 Vac, it is possible you may only have a three pin connector (two hots and ground). You may want to check to see how the ground and neutrals are handled in the breaker box. On my breaker box, neutral and safety grounds become one at the box and the ground is connected to earthground via the main water pipe into the house.

Looking at this from an engineering point_of_view only (since I dont know all the details of code). I would ground the cabinet to your dedicated mains ground to minimize any potential difference with any other pool hardware. Since the power branch is dedicated to your coil, I can see no problem in also grounding the cabinet and your pig to one of your earth RF ground rods durring operation. I would, however, disconnect the RF ground from the cabinet when non operating to prevent galvanic corrosion, but then again the cabinet is bolted to a concrete slab so it is already grounded to earth in a way. The mains safety ground can not carry any return current from the 240 mains so if the load is unbalanced, you will need a 4 pin connector (2 hot, a neutral to carry the unbalanced line return current and a safety ground.

Gerry R.


Original poster: "Jim Mora" <jmora@xxxxxxxxxxx>

Hello all,

I am planning to put my 14400/5KVA along with my HV DC components in a
gutted Swimming Pool cabinet. The cabinet will be bolted to a preexisting
concrete slab. It is about 50 feet from my dedicated 60 amp Pump safety
switch. Witch is well grounded to the mains (#4)20 feet away and a copper
water pipe. That is probably a neutral no-no but it is close. This is where
my control rack will be rolled.

The ongoing saga of ground questions:

1. The HV cabinet is at nearest 8 feet from one of three RF ground rods
(maybe not connect this one to the coil?).

2. I have 70 feet of AWG# 8 direct burial w/ground, 18" ground cover, a
minimum 16 feet parallel to the TC planed location.

3.IMPORTANT: shall the HV cabinet thoroughly grounded with the mains along
with the case lug of the Pig (no neutral connection). HV out will be floated
on both sides via 50KVDC cable 10 to 12 feet long.

Note: current limiting will be entirely attempted by break rate and a large
variac for voltage ramp up. And yes I have a breaker box adjoining the
safety switch with 30, 40, and 50 amp main breakers at hand. The control
cabinet has a large contactor in it and will be energized by a remote fiber
momentary dead man switch.

Any help on question #3 will be greatly appreciated as I view it as a safety
issue.

Thanks
Jim Mora
Ojai Ca.