generator transfer switch

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stew

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federal way,washington
customer has a community well pump system 120/240 delta 3 phase. wants a generator transfer switch installed. If the generator(about 25 or 30 kw) has its own breaker is a fused disconnect necessary and if so why? The switch would be installed just beside the meter outdoors. The 200 amp service panel is just inside back to back on the interior wall.
 
If the transfer switch is installed electrically on the secondary side of the service panel, it does not require fusing.

If the transfer switch is installed electrically on the supply side of the service panel, it is required to be suitable as service equipment and have a disconnecting means that has overcurrent protection as well.
 
what i am having trouble with is that this is just a switch. The gen set has overcurrent protection for when it supplies the load and the panel has protection for when it supplies the load so why the seemingly rendundant protection. When the gen suppleis the conductors to the panel they are protected by its device and when the utuilty supplys the power the main is at the panel. It would seem that if the switch was service rated then fusing is redundant.
 
the swithch to be used will be suitable for service equip. My question is does the location also require fusing? seems redundant if the gen set already has protection and protects the wiring between the gen set and the panel.
 
stew said:
the swithch to be used will be suitable for service equip. My question is does the location also require fusing? seems redundant if the gen set already has protection and protects the wiring between the gen set and the panel.
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What do you want to operate on standby power? Just the pump or every thing in the building? If you are going to power the building then you would come from the meter into a service rated trans. switch which has a breaker in it to act as OC protection and disconnecting means. You then come into the trans. switch from the gen. side which has a breaker that acts as OC and disconnect. The breaker at the gen set is to protect the gen.
 
stew said:
the swithch to be used will be suitable for service equip. My question is does the location also require fusing? seems redundant if the gen set already has protection and protects the wiring between the gen set and the panel.
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If the transfer switch is to be used as the service disconnect, the NEC requires the service disconnect to have overcurrent protection.
230.70 & 230.90 - .91
 
I dissagree that the gen breaker is "only" to protect the gen set. It of course does protect the gen set but it also acts as the protection for the conductors from the generator to the service panel. It would seem to me that when the gen is connected to the panel its breaker is then protecting the gen and the wiring from the gen to the panel and the existing panel breaker is still the service disconnect with the transfer switch just being a switching device and nothing more. If you use the transfer switch as the service disconnect then you would also have to unbond the neutral in the panel in the building and bond the neutral at the transfer switch only correct? If thats what has to be done then the transfer swithch would yes have to be fused .
 
stew said:
I dissagree that the gen breaker is "only" to protect the gen set. It of course does protect the gen set but it also acts as the protection for the conductors from the generator to the service panel. It would seem to me that when the gen is connected to the panel its breaker is then protecting the gen and the wiring from the gen to the panel and the existing panel breaker is still the service disconnect with the transfer switch just being a switching device and nothing more. If you use the transfer switch as the service disconnect then you would also have to unbond the neutral in the panel in the building and bond the neutral at the transfer switch only correct? If thats what has to be done then the transfer swithch would yes have to be fused .
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OK, answer these questions and we can go from there. What are you going to supply, the building and its equipment or just the pump? The transfer switch dose it switch the neutral?
 
We are supplying the existing building panel which supplies the pump and 2 outlet circuits plus lites. 95% of any load will be the pump. No the neutral will not be switched.
 
So then Peter conversley if you do not use the transfer switch as the disconnect but simply as a means to switch from gen to utility then the panel breaker is still the service disconnect in the utility position and the generator breaker protects the wiring from the gen to the panel with the panel breaker still the service disconnect correct? Thus in my mind all protection is still in place so fusing is no longer necessary am I right?
 
stew said:
So then Peter conversley if you do not use the transfer switch as the disconnect but simply as a means to switch from gen to utility then the panel breaker is still the service disconnect in the utility position and the generator breaker protects the wiring from the gen to the panel with the panel breaker still the service disconnect correct? Thus in my mind all protection is still in place so fusing is no longer necessary am I right?
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I am not sure if you are speaking to me, although you may be surprised how often I am called Pete or Peter..

Fusing of the transfer switch is not required.
Don't forget about 702.8(A)&(B).
 
Pierre C Belarge said:
The location of the transfer switch in relation to the service disconnect is the reason whether or not the transfer switch would be required to be suitable as service equipment.
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Stew, by your other post.
The trans. switch is service rated and you are placing it between the meter and MDP.
If you come into the trans. switch from the meter it would land on the breaker which acts as OC and disconnect. No other fusing requried.
The feed from the gen. would land on a breaker which acts as OC and disconnect. You would bond the neutrals and EGC in the trans switch. Then take four wires to the MDP and Gen. set.Then separate the neutrals and grounds in MDP and make sure the neutrals are isolated in the gen. set. and bond EGC to the frame.

Originally Posted by stew
So then Peter conversley if you do not use the transfer switch as the disconnect but simply as a means to switch from gen to utility then the panel breaker is still the service disconnect in the utility position and the generator breaker protects the wiring from the gen to the panel with the panel breaker still the service disconnect correct? Thus in my mind all protection is still in place so fusing is no longer necessary am I right?
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Yes, you are correct but the trans. switch would have to feed another dist. panel. And you would probably need disconnecting means for the gen. at the trans. switch.

As for the breaker protecting the gen. you are correct you could allow the breaker on the gen.set to be the only OC protection. However the installs I do I cannot and will not depend on that one breaker to protect the gen. set. The ones I install are classified in the legally requried category. They supply power for emergency. communications. So we are talking about something that has high potential of damage from lightning. All the disconnects I set also have OC protection and I purposely step down one size from the rating of the OC protection on the gen. set.
 
Stew

I agree with your thinking, but, as PeeWee says everyone has a BIG BUT and this one is not in agreement with article 230.82 it?s been mention before that if you put a transfer switch on the load side of the meter base the transfer switch must be service rated because the transfer switch thus becomes the service switch. The reason, reading 230.82 a transfer switch is not allow to be placed ahead of the service switch. There are eight subsections in 230.82 and none of which refer to transfer switches. The next problem crops up in 230.91 that state the service overcurrent device shall be an integral part of the service disconnecting means or shall be located immediately adjacent thereto. Having the disconnect outside and the overcurrent device inside is not immediately adjacent thereto.

If you look at the ROP, 2008 section 230.82, a proposal was introduced to allow a transfer switch ahead of the service disconnect BUT this proposal was rejected. It was also stated in the panel?s response that this were allowed it could be done without compromising safety. This proposal was in reference to the meter insert type transfer switches (Generac) that are UL listed only to be under the control of the serving utility thus exempt from the NEC.
 
So then what does 230.82(5) refer to when it says "circuits for standby power systems"? Seems like sloppy writing if transfer switches aren't included here -- how else are you going to get a standby power system circuit here if there is no transfer switch?
 
230.82(5) Is for ?Taps used only to supply load management devices, circuits for standby power systems???.? Section (5) is not referring to transfer switches but for example, taps to monitor the loss of normal power to signal an automatic transfer switch and standby systems.

A transfer switch can be installed there (if you are referring to just after the utility meter) by having an OCD(s) as an integral part of the switch or placing the transfer switch immediately adjacent to the OCD.
 
I have a question to try and make the installing a little bit clearer, Is the ATS a manual switch or an automatic switch with or without overcurrent protection.
Rick
 
stew said:
now i am confused. pierre(not peter)says I can but apparently Mvillines says I cant. Use and unfused transfer swithch that is. who is correct?
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Stew, Pierre and Mvillines both said if you use an unfused transfer switch, you are require to use an OCPD imediately next to the transfer switch. Having the OCPD on the other side of the wall does not qualify.
Mvillines said:
A transfer switch can be installed there (if you are referring to just after the utility meter) by having an OCD(s) as an integral part of the switch or placing the transfer switch immediately adjacent to the OCD.
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Pierre said:
If the transfer switch is to be used as the service disconnect, the NEC requires the service disconnect to have overcurrent protection.
230.70 & 230.90 - .91
Click to expand...
Rick
 
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