Portable Generator Fixed Connection

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Hello All,
I would like some input from others on the following. I'm used to stand by generator connections, consisting of generator, automatic transfer switch, generator panel so forth. I have installed standby sets for business up to 1000KW and homes as well, with the same set up or with unit sized to carry load of home 12/15/20KW depending on home. I had a residential customer yesterday asking me to install a permanent connection for a 7.5KW portable. I looked at the existing conditions, explained I would need to indentify the protected loads, transfer them to a generator panel and place a manual transfer switch in the circuit. No problem, except when they asked for a price to do the work and I quoted them about $945.00. I suppose the internet cuts both ways and sometimes the stupid rises to the top as the homeowners went into rant about how the sites they had visited, said the cost to do install a manual transfer switch would be about $250.00. Personally, I don't see how, unless they plan on a connection guaranteed to kill the linemen attempting to repair the line. Any thoughts or suggestions? Is there a code complaniant method for making this connection to a home that is in fact as cheap as $250.00?

Thanks in advance for your input and be safe out there!
Steve
 
Re: Portable Generator Fixed Connection

Probable by not selecting loads, just the whole house ahead of the service panel. It is optional stand-by and does not require selecting loads. I assume you are talking labor only?

[ September 09, 2004, 04:35 PM: Message edited by: dereckbc ]
 
Re: Portable Generator Fixed Connection

There is a GenTrans system that may be the one your customer is refering to. The gentrans is a panel that has dpdt breakers, and you pick six circuits that can be on the generator. Its a prewired panel, but the circuits are only 15 amperes. A better way is to install a separate panel fed from a two mechnically interlocked two pole breakers, by using equipment from SQ D or Cutler Hammer, etc. Your solution results in the entire house being able to run from the generator, the ones I've described result in the most critical circuits only. Not the same at all.
 
Re: Portable Generator Fixed Connection

I will be calling gentran in the a.m.,but wanted some input from some of you experts.Customer wants gentran connected to a portable generator.Generator has clearly stamped on frame "neutral connected to frame".If gentran does not switch neutral, won't i be in violation of the nec?I don't want to remove neutral to frame connection because customer may use 120v outlets on generator ,and I don't want to void any warrantees,and I want it to be safe. It seems that i will be forced to make my own set up.Also,gentran model#30216 says in specs max. load per circuit from generator 15a,max load per circuit from load center 20a.Does this mean that I can connect 20a loads to gentran,but be careful not to use circuit fully loaded?Thanks for your help!
 
Re: Portable Generator Fixed Connection

You are correct on the generator neutral bonding and one of the few to understand this :).
Yes the neutral should not be bonded to the frame with portable generator, actually it was explained to me by a member of CMP05 (Art 250), that the CMP is aware of this and does not feel it is a problem as it would be worse to unbond the generator neutral, then a line to case fault from a receptacle would have no return path.

But try and explain this to the customer.
 
Re: Portable Generator Fixed Connection

Isn't the answer more complex than this (or maybe I'm one of the many who get this wrong)? If you're connecting at the Service Equipment, then I would think you can make this work. If you're connecting to a panel where neutral and ground are separated, then you must have a transfer switch that switches the neutral or you must unbond the generator neutral and ground. If this is your case, then I think your fear is correct.

But if you install this at the service, preferably just before the main disconnect, then won't a 2-pole transfer switch do what you want AND allow anything in the house to be run off the generator? You can get manual 200A transfer switches rated as Suitable for use as Service Equipment for about $350. This should be all you need other than wire and a means to connect to the generator. This switch must be mounted immediately next to the main disconnect panel because it has no overcurrent protection.

I detest those Gentran type panels. They have lousy feeling breaker paddles, limited current handling capability (A 30A one is the largest I've seen), and only one breaker pair can be handle tied.

I never considered the potential problem with unbonding a portable generator. Does this bond affect the grounding pin of the receptacles, or only the metal frame? Removing the bond to the grounding pins and then disconnecting the "portable" generator would be quite dangerous.
 
Re: Portable Generator Fixed Connection

I don't believe where the transfer switch is mounted matters,if you are not switching the neutral,generator must not be bonded at the case.IF you did put before panel now we have to seperate neutrals and grounds because it is now a sub panel,is this correct?I called gentran...was told to look at article 250-20d fpn#1 "an alternate power source such as an onsite generator is not a seperately derived system if the neutral is solidly interconnected to a service-supplied system neutral"...still does not address the neutral to frame connection .
 
Re: Portable Generator Fixed Connection

Hmmm, good question. I guess it comes down to what is the main disconnect, the breakerless transfer switch or the main breaker in the adjacent breaker panel. I'm guessing the transfer switch would be the disconnect, because not much is allowed upstream of the disconnect. This means 4 wires to the panel from the transfer switch, which could be an issue in an existing installation. Ideally, both items could be considered a grouped disconnect and you can use just 3 wires between the two.

Also, if the generator has a circuit breaker would it be required to run 4 wires from the generator to the transfer switch, even if the transfer switch is wired like a service (i.e. using a combined grounded/grounding conductor)?
 
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