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Adding Voltage Monitoring to 400 amp 3 Ph.entrance #199921 03/14/11 02:53 PM
Joined: Mar 2011
Posts: 5
E
eric14779 Offline OP
New Member
I am adding a SSAC voltage monitoring relay to an existing 3 Ph. main entrance.

I am concerned with how to tap into the 3 legs and connect to the monitor.

this will be a permanent metering hookup.

I am thinking of using small 1 amp inline fuses on each with 14 Ga. wire. With the fuse as close to each of the taps as possible.

this box is a big fused disconnect.

I am sure that the NEC has something to say about how to do this.

any input is appreciated.

2017 / 2014 NEC & Related Books and Study Guides
Re: Adding Voltage Monitoring to 400 amp 3 Ph.entrance [Re: eric14779] #199935 03/14/11 09:32 PM
Joined: Apr 2002
Posts: 7,105
HotLine1 Offline
Member
Eric:
First...Welcome to ECN forums!

You should get responses in this section....

I'll be back later


John
Re: Adding Voltage Monitoring to 400 amp 3 Ph.entrance [Re: eric14779] #199939 03/14/11 10:33 PM
Joined: Jan 2005
Posts: 5,316
renosteinke Offline
Cat Servant
Member
As they say in New York: Fagaddaboutit! At least, as you plan on doing it.

First off, lots of luck finding a terminal strip that will take both your feeder wires AND something as small as #14. Marathon might be a possibility.

Of greater concern is the AIC, or interrupting capacity, of the little fuses. It's simply amazing how running the power through the main breaker and adding a few feet of wire reduces your AIC requirements.

You don't do this sort of thing in the meter box, or even the switchgear. Rather, you go downstream and do it in a control panel. After all, you need some place to mount that little relay. Come to think of it, that's where you mount the terminal block as well.

With all the malarky about "70E" and such, you might consider using a 'finger-safe' fuse/fuseholder design. Personally, I like the Bussmann "CubeFuse Class J" variety - no chance of someone putting a type CC fuse in there!

Re: Adding Voltage Monitoring to 400 amp 3 Ph.entrance [Re: eric14779] #199943 03/14/11 11:01 PM
Joined: Sep 2002
Posts: 131
T
tsolanto Offline
Member
Actually it's Fugetaboutit! Just a little spelling error.lol

Re: Adding Voltage Monitoring to 400 amp 3 Ph.entrance [Re: eric14779] #199952 03/15/11 10:30 AM
Joined: Mar 2011
Posts: 5
E
eric14779 Offline OP
New Member
I have found that I have space in a sub panel to put in a 15 amp 3 pole breaker that I can use to feed the monitor. Kind of overkill on the amps but 15 is as low as I can find in 3 pole.

I will use 14AWG wire and that should be OK no?


Last edited by eric14779; 03/15/11 10:31 AM.
Re: Adding Voltage Monitoring to 400 amp 3 Ph.entrance [Re: eric14779] #199954 03/15/11 10:53 AM
Joined: Apr 2002
Posts: 7,105
HotLine1 Offline
Member
Eric:
What you have to check is the mfg specs (of the monitor) and determine the MAX OCP they specify.

You may find that the MAX OCP is somewhere in the 1 to 5 amp range. If that is the case, a midget fuse block (finger safe preferred) should be installed in the subpanel (space available) or in your monitor enclosure.

A circuit breaker 'lock-on' will be a great addition!

!4 should not be an issue.


John
Re: Adding Voltage Monitoring to 400 amp 3 Ph.entrance [Re: eric14779] #199955 03/15/11 11:11 AM
Joined: Mar 2011
Posts: 5
E
eric14779 Offline OP
New Member
HotLine1,

the monitor specs call for a 2amp fast acting to protect the equipment.

says fuses are not required to protect the monitor.

Re: Adding Voltage Monitoring to 400 amp 3 Ph.entrance [Re: eric14779] #199960 03/15/11 07:42 PM
Joined: Apr 2002
Posts: 7,105
HotLine1 Offline
Member
OK, what is the 'equipment'?? that is 2 amps??

And, NO OCP for the monitor?? SSAC has no requirement/spec to protect the relay device?



John
Re: Adding Voltage Monitoring to 400 amp 3 Ph.entrance [Re: eric14779] #199972 03/16/11 09:52 AM
Joined: Mar 2011
Posts: 5
E
eric14779 Offline OP
New Member
John,

see the specs for the SSAC PLMU Series 3 Phase Voltage Monitor at:

www.ssac.com/pp1.htm select the PLMU link

spec sheet says that the 2 amp fuses are "recommended" not required ???

I think that if I run 14Ga. wire from a 15 amp breaker to the Monitor, that in the event of a short, the breaker would trip before the 14ga. wire is damaged...

the monitor may not survive but this setup should prevent the monitoring lines from turning into flaming ropes. Again if there is a mishap...


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