Manual transfer switch ahead of OCPD

Status
Not open for further replies.
M

Mddocstanley

Member
I am installing a 400 amp residential service. I do not seem to be able to find a 400 amp manual transfer switch with an integral OCPD. I am limited severely with space and would like to keep pieces of equipment at a minimum. I am installing first the Meter can, next the Manual transfer switch and then next to it the 400 amp load center, all 3 pieces of equipment are side by side. Since I cannot find the manual transfer switch as described I am thinking that installing one without integral OCPD, and then the loadcenter with a 400 amp main breaker, may be all I need for this install. The manual transfer switch is rated for use a service equipment and has an "off" position. Question:#1- are the conductors from the service lateral to and through the manual transfer switch to the Main breaker on the loadcenter considered the service entrance conductors? #2 Would the transfer switch be considered the service disconnect and the Main breaker in the loadcenter the OCPD satisfying article 230.91?
Thanks for the input in advance.
 
Mddocstanley said:
Question:#1- are the conductors from the service lateral to and through the manual transfer switch to the Main breaker on the loadcenter considered the service entrance conductors?
Click to expand...
Yes


Mddocstanley said:
#2 Would the transfer switch be considered the service disconnect and the Main breaker in the loadcenter the OCPD satisfying article 230.91?
Thanks for the input in advance.
Click to expand...
Yes

Now I have a couple of questions.
Question:#1- Are you under the 2008 cycle

Question:2 - If the answer to question 1 is yes how do you plan to comply with 702.5(B)?
 
Mike ,..I'm wondering what your concern was in regard to your question #2?? Would you like to see two panels? one fed by the optional stand by system for the selected loads ??
IF so,...

Why could he not decide just by shutting off breakers in a single panel prior to switching to stand by system??

From EC&M Mike Holt

702.5 ? CAPACITY AND RATING
The sizing for Optional Standby Power Systems is now based on the type of transfer switch used; manual versus automatic.
(A) Available Short-Circuit Current. Optional standby system equipment shall be rated for the maximum available short-circuit current at its terminals.
(B) System Capacity. The calculated load on the standby source shall be in accordance with Art. 220 or by a method approved by the authority having jurisdiction.
(1) Manual Transfer Equipment. The optional standby power source shall have adequate capacity for all equipment intended to operate at one time. The user of the optional standby system selects the loads to be connected to the system.

Author's comment: When a manual transfer switch is used, the user of the optional standby system selects the loads to be connected to the system, which determines the system size.
Click to expand...
 
Mddocstanley said:
Florida has not adopted the 2008 version as of yet to the best of my knowledge.
Click to expand...
Mike, I am not picking on you specifically:wink:, because I see and hear this comment often.

I know in some areas there are many different jurisdictions, but in general, why shouldn't a contractor know what codes are currently being enforced in their normal work locality?
 
Mddocstanley said:
I am installing a 400 amp residential service. I do not seem to be able to find a 400 amp manual transfer switch with an integral OCPD. I am limited severely with space and would like to keep pieces of equipment at a minimum. I am installing first the Meter can, next the Manual transfer switch and then next to it the 400 amp load center, all 3 pieces of equipment are side by side. Since I cannot find the manual transfer switch as described I am thinking that installing one without integral OCPD, and then the loadcenter with a 400 amp main breaker, may be all I need for this install. The manual transfer switch is rated for use a service equipment and has an "off" position. Question:#1- are the conductors from the service lateral to and through the manual transfer switch to the Main breaker on the loadcenter considered the service entrance conductors? #2 Would the transfer switch be considered the service disconnect and the Main breaker in the loadcenter the OCPD satisfying article 230.91?
Thanks for the input in advance.
Click to expand...






If the manual transfer switch is rated as suitable for service equipment, it should have a breaker in it which becomes the service disconnect.


The grounding for the service should be in the transfer switch enclosure, and the panel you are installing is as "SubPanel" and the grounded conductor and the EGC need to be isolated from each other.


What is the brand/model number of your unit?
 
M. D. said:
Mike ,..I'm wondering what your concern was in regard to your question #2?? Would you like to see two panels? one fed by the optional stand by system for the selected loads ??
Click to expand...
It wouldn?t nessaraly require two disconnects as long as one of the things that Mike Holt pointed out is followed.
Look closely to what is being said in Section 702(B) of the 2008 cycle of the NEC.
(B) System Capacity. The calculations of load on the standby source shall be made in accordance with Article 220 or by another approved method.
In come cases across America the code officials are letting the installers do a utility average in order to size a residential generator.

M. D. said:
Why could he not decide just by shutting off breakers in a single panel prior to switching to stand by system??
Click to expand...
I wouldn?t have a problem with letting the home owner decide what he wanted on the generator as is allowed by 702.5(B)(1) last sentence as long as what he decided to connect to the generator was included in the calculation.
What I can?t see happening is a calculation being made to size the generator and then the home owner deciding that they was wanting to turn one circuit off and another one on. How would this affect the requirement for the calculation?

Now let?s look closely at what Mr. Holt said in his comment:
Author's comment: When a manual transfer switch is used, the user of the optional standby system selects the loads to be connected to the system, which determines the system size.
Click to expand...

I think what he is saying is that the homeowner has to decide what he wants on this generator before the generator can be sized by these words, ?which determines the system size?

A quick read of the comments on the proposal for this change in the code one can clearly see that it is not the intend of this section to install a manual transfer switch and then let someone start switching off one circuit so another one can be switched on.
It is clear that the circuits being installed for the manual transfer switch must be calculated before the generator can be sized.

If someone is wanting to disconnect one circuit to connect another circuit then simply use a portable generator and cords to accomplish this feat.
 
Hey,
In our county I have been told that they will adopt the 2008 when the state adopts it. I can guarantee you that they will not notify anyone that they have made the change, neither will the state. I dont know about your locality, but the several cities and the counties in my area allow different interpretations of the code and enforce them as they see fit. In other words if you work in some areas they want a disconnect at the water heater and some areas don't. Also I have been caught installing installing smoke alarms on ceilings within 36 inches of the end of a ceiling fan blade, which was never enforced untill about 2 yrs ago and had about 20 houses already roughed in and several were in violation of this. No notice ahead of time that they were going to start enforcing this, I actually never knew it was required. one county says that the distance (the 36 inch clearance from a smoke alarm) does not have to be maintained at the return air and another county says yes it does. I can guarantee that when either changes their mind no one will be informed ahead of time. I understand my responsibility for always complying to proper code for all work performed, but my only point here is that when local rules change usually there is no notification.
Mike
 
Status
Not open for further replies.
Top