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#32177 12/17/03 02:34 PM
Joined: Mar 2002
Posts: 179
D
derater Offline OP
Member
Have a cust. who wants a way to tell when his power is on at panel.He wants to turn off main to run house via generator when power is out,but know when it comes back on.So connection would have to be before main.Any suggestions?

#32178 12/17/03 06:47 PM
Joined: Jan 2002
Posts: 1,457
E
Member
Use a listed generator tranfer switch. One big enough to do the entire house will be automatic. Any other type will do a portion of the loads so when the remainder come on he will know. Do not rely on him switching the main as the transfer switch.

#32179 12/27/03 08:39 AM
Joined: Jul 2002
Posts: 8,407
Member
I wouldn't recommend the installation of indicators or such devices on the Line-Side of a Main Switch without asking the PoCo first.
Power companies get rather finnicky about things like this, especially where there is a chance that a Generator could back-feed into the Grid.
BTW, I hope that the guy has got a reasonably large generator, you'd be amazed how many people under-estimate the current draw of a few appliances.

#32180 12/27/03 09:07 AM
Joined: Jan 2003
Posts: 4,391
I
Moderator
Quote
He wants to turn off main to run house via generator when power is out,but know when it comes back on.

This would be a code violation and would be dangerous to utility workers.

Advise the customer strongly to do the right thing as Scott has said.

You should not even consider helping this customer back feed a panel with a generator.

Besides the moral responsibility you have, you will be liable injuries to the utility workers that get blasted by a back feed.


Bob Badger
Construction & Maintenance Electrician
Massachusetts
#32181 12/27/03 02:09 PM
Joined: Nov 2002
Posts: 267
W
Member
As long as there's a transfer switch involved, maybe your customer possibly lives in an off the beaten track neighborhood where he can't just look out his window and see street lights and the neighbors. So he's probably thinking he doesn't want to let the generator keep running unbeknownst to power being back on. I had a situation like this and simply placed a rated cabinet light into the main panel. Always lit when power was on, off when not.

#32182 12/27/03 02:29 PM
Joined: Jan 2003
Posts: 4,391
I
Moderator
Wirenutt, I would be interested to know how you attached "a rated cabinet light into the main panel" on the line side of the service disconnect.

230.82 prohibits almost anything from being connected on the line side of the main service disconnect.


Bob Badger
Construction & Maintenance Electrician
Massachusetts
#32183 12/27/03 07:41 PM
Joined: Jul 2002
Posts: 8,407
Member
One way that a reasonable level of safety could be acheived, is by the use of 2 inter-locked contactors, so that only 1 can be energised at a time. [Linked Image]

#32184 12/27/03 09:56 PM
Joined: Sep 2003
Posts: 123
M
Member
If the guy wants to do it right use a transfer switch that will transfer back when the power is on. Anything else is way too risky.

#32185 12/28/03 06:57 AM
Joined: Jan 2003
Posts: 4,391
I
Moderator
Hi Trumpy

The rules are pretty strict as far as transfer equipment especially ones that handle the whole service.

Quote
702.6 Transfer Equipment.
Transfer equipment shall be suitable for the intended use and designed and installed so as to prevent the inadvertent interconnection of normal and alternate sources of supply in any operation of the transfer equipment.
Transfer equipment and electric power production systems installed to permit operation in parallel with the normal source shall meet the requirements of Article 705.

Transfer equipment, located on the load side of branch circuit protection, shall be permitted to contain supplementary overcurrent protection having an interrupting rating sufficient for the available fault current that the generator can deliver. The supplementary overcurrent protection devices shall be part of a listed transfer equipment.

Transfer equipment shall be required for all standby systems subject to the provisions of this article and for which an electric-utility supply is either the normal or standby source.

Quote
230.82 Equipment Connected to the Supply Side of Service Disconnect.
Only the following equipment shall be permitted to be connected to the supply side of the service disconnecting means:

(1) Cable limiters or other current-limiting devices.

(2) Meters, meter sockets, or meter disconnect switches nominally rated not in excess of 600 volts, provided all metal housings and service enclosures are grounded.

(3) Instrument transformers (current and voltage), high-impedance shunts, load management devices, and surge arresters.

(4) Taps used only to supply load management devices, circuits for standby power systems, fire pump equipment, and fire and sprinkler alarms, if provided with service equipment and installed in accordance with requirements for service-entrance conductors.

(5) Solar photovoltaic systems, fuel cell systems, or interconnected electric power production sources.

(6) Control circuits for power-operable service disconnecting means, if suitable overcurrent protection and disconnecting means are provided.

(7) Ground-fault protection systems where installed as part of listed equipment, if suitable overcurrent protection and disconnecting means are provided.

As you can see transfer equipment is not listed, the only way to install transfer equipment that switches the entire service is to get a transfer switch that is also rated/listed as a service disconnect.

I could not put together a couple of contactors or even one contactor that was double throw to make my own transfer switch.

Many panel makers produce a panel with two mains that are mechanically interlocked so only one can be on at a time and are listed as service equipment.

Trumpy I know you know the dangers here but I think many people do not realize that under the right conditions that their little generator can back feed a POCO transformer and produce some high voltages.

Bob

[This message has been edited by iwire (edited 12-28-2003).]


Bob Badger
Construction & Maintenance Electrician
Massachusetts
#32186 12/28/03 10:41 AM
Joined: Nov 2002
Posts: 267
W
Member
IWire;
Real simple, just attach it to any circut breaker as you would a transformer for a door bell. Get a light that's 120 volts but rated at 250 or more.

~Andy

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