Non sep derived genset/ solid neutral ats-480v3ph

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ctaylo360860

ctaylo360860

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I'm hoping to get some understanding on SE rated ATS vs non SE rated ats…. I have a non sep derived genset system with a solid neutral ats… I will do my bonding of grounding and grounded conductors at the ats. and isolate them at the gen set and 400amp load center. Im wondering if im allowed to put a non SE rated ats before the SE( aka existing 400a load center) ? im asking because of 230.82 (6) this is all under 2017 NEC... Any and all help is greatly appreciated!
 
ActionDave said:
Welcome to the forum.

You have a lot of abbreviations going on. I'll assume by SE you mean service entrance.

Where is your service disconnect?

Why would you want a transfer switch ahead of the utility meter?
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sorry about the abbreviations, I'm new to this... you are correctly assuming SE means Service entrance, and ats meaning automatic transfer switch. So currently I have an existing 400a service being fed from the secondary side of utility transformer. my Service disconnect is a main breaker at the 400amp load center. the meter is CT'd at the utility transformer as it meters a lot of different equipment, so the ats would be after the meter but on the supply side of the of the service disconnecting means. basically i need to add my ats before the 400a load center so it can tell if utility power is disrupted and turn on the vehicle mounted genset to power the 400amp load center... I'm wondering if the ats needs to be se rated or not because of cost or safety concerns.... the ats is all outside and there is no building or structure... this install is for a flat storage corn bunk..
 
Well code wise you either make the ats service rated and use it as your service disconnect or you put it in after the service disconnect. In your case that would mean bonding the neutral at the ats and floating it at the 400A panel. I prefer to put the ats after the service disconnect generally.

The exception in 230 you mentioned is to allow for the utility to do cold sequencing on their meter, at least that's the way I understand it.
 
okay so 230.82 (6) as I understand it says emergency lighting, fire alarm systems, fire pumps, standby power, and sprinkler systems are permitted to be connected ahead of the normal service disconnecting means only if such systems are provided with a separate disconnection means and overcurrent protection. my genset has a 300a ocpd which would make it a separate disconnecting means.... i know in 2020 this is going away and it will have to be SE rated , but im still under 2017 code... so as I'm interpreting it I could land my wires coming from secondary side of utility to the line side of the non se rated ats. from the load side of the ats I would feed my 400a main breaker which is my service disconnect. then from my gen set i would run to the gen set side of ats. i would bond my grounding conductor and grounded conductor at my ats solid neutral. i would Isolate my grounded and grounding conductors at my 400a load center, and i would also need to isolate the grounding conductor at the genset from the frame of the genset. 250.54 allows for install of an auxiliary ground from the frame of the genset to ground rod.....
 
so even if the ats is not SE rated that would still be considered a service disconnect? I'm thinking to just get away from confusion or problems with inspection I will order a SE Rated ats... at this point I'm just curious if I'm interpreting the code correctly, or if this is at all possible to have a non se rated ats on the supply side of the service disconnect...... I'm not taking away from you expertise, I really appreciate all the help! Is there away to get more people to chime in on this discussion, I'm new to this forum and don't know if i posted the thread correctly....
 
ctaylo360860 said:
sorry about the abbreviations, I'm new to this... you are correctly assuming SE means Service entrance, and ats meaning automatic transfer switch. So currently I have an existing 400a service being fed from the secondary side of utility transformer. my Service disconnect is a main breaker at the 400amp load center. the meter is CT'd at the utility transformer as it meters a lot of different equipment, so the ats would be after the meter but on the supply side of the of the service disconnecting means. basically i need to add my ats before the 400a load center so it can tell if utility power is disrupted and turn on the vehicle mounted genset to power the 400amp load center... I'm wondering if the ats needs to be se rated or not because of cost or safety concerns.... the ats is all outside and there is no building or structure... this install is for a flat storage corn bunk..
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Based on your description you should be using a service rated, solid neutral ATS installed between the POCO transformer and the existing main breaker panelboard. The ATS will now be your service disconnect. Remove the exisiting main bonding jumper in the 400 amp panel. Remove the neutral bonding jumper in your genset. You will need an EGC from the ATS to the genset. Remove the GES from the existing 400 amp panel and reconnect it at the ATS.
 
In regard to post #10 if you already own the ATS and it is not service rated you could simply add an enclosed breaker ahead of it to be your service disconnect and do the main bond and GES connection there. Note: you can not install a non service rated ATS ahead of the service disconnect.
 
texie said:
Based on your description you should be using a service rated, solid neutral ATS installed between the POCO transformer and the existing main breaker panelboard. The ATS will now be your service disconnect. Remove the exisiting main bonding jumper in the 400 amp panel. Remove the neutral bonding jumper in your genset. You will need an EGC from the ATS to the genset. Remove the GES from the existing 400 amp panel and reconnect it at the ATS.
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so my plan is remove the existing wiring from my 400a panel and land on my ats. (3 ungrounded conductors, and 1 grounding conductor from the secondary side of utility transformer to the line side of my solid neutral ats. I will set a ground rods and bond my grounded conductor and grounding conductor at the ats. I will then feed my ocpd at the 400a panelboard from the load side of the ats with five wires (3 ungroudned conductors, a grounding conductor and a grounded conductor) isolating the grounded and grounding conductors at the 400a panelboard. my vehicle mounted genset will also have five wires to the ats. because this is a non seperatly derived system i will have my grounding conductor isolated from the grounded conductor and frame of the genset. 250.54 I will also set auxiliary grounding electrode at the generator.... i thought that i could get away with a non se rated ats because of how 2017 nec 230.82 (6) read...
 

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texie said:
I'll say it again. Under no circumstances can a non service rated ATS be connected to service conductors.
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okay, I wont ask again lol. I appreciate your input in this discussion! so now if i were to add a enclosed breaker before the non se rated ats. I would just need to make sure that the withstand and closing ratings would match up with my ats manufaturing specs...
 
ctaylo360860 said:
okay, I wont ask again lol. I appreciate your input in this discussion! so now if i were to add a enclosed breaker before the non se rated ats. I would just need to make sure that the withstand and closing ratings would match up with my ats manufaturing specs...
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Now you're cookin'. All ATS manufacturers will have info. as to the type and brand of acceptable OCPD to be used ahead of the ATS per UL listing requirements.
 
okay great, thanks again. now I'm make sure I'm sizing my grounding conductors correctly... in my se rated ats I'll run a grounding electrode conductor from ats ground to earth. I should be able to get away with #6 because its going just to ground rods... I then need to run a supply side bonding jumper from ats neutral to ground. I will size my ssbj according to 250.102 (c). currently there are 2 parallel 250kcmill aluminum service conductors. 250.102 (c) over 900 through 1750 calls for 2/0 copper. I also need to size my main bonding jumper from ats ground to frame. this is also sized according to 250.102.(c) and should be 2/0 copper. next i need to size my equipment bonding jumper load side of my ocpd using 250.122 My se rated ats has a 400Aocpd that runs to my 400Aocpd 400A in a subpanel 400A ocpd= #3copper. finally i have my wire from my ATS to Genset frame. is this considered an equipment grounding conductor or a supply side bonding jumper? if its egc then i would size according to my ocpd on my genset... if it is considered a ssbj than i would have to size according to 250.102(C) based on the largest underground service entrence conductor in raceweay.. Any and all help is greatly appreciated!!! thanks !!!!
 
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