Use "solar ready" CSED as a three main service?

[hmspe]

I do load calculations for many houses that have a calculated load for the whole house significantly less than 400 amps but where the panel calculations for the two panels available for a typical "all in one" do not leave enough capacity in the panels for pool equipment. These are in Arizona so EUSERC applies. The usual solution is to go to a wall hung service with CTs, but the lead times for those are typically over a year.

The Siemens MC3042S1400 series has an integral panel and a second main like a typical CSED, but also has a third space for a breaker tied to the internal bus that is meant to be an input from a parallel energy source. Would it be NEC compliant to use the third main position as a service disconnect to supply a pool panel?

 

[wwhitney]

I do load calculations for many houses that have a calculated load for the whole house significantly less than 400 amps but where the panel calculations for the two panels available for a typical "all in one" do not leave enough capacity in the panels for pool equipment.

Are you saying that the 220.82 Optional Load Calculation is significantly less than 400A, but that there's no way to divide the loads into two groups so that the Part III Standard Load Calculation for each group is under 200A?

Cheers, Wayne

 

[kkyyllee]

I would say not permitted 110.3 B. This was not the intended use by the manufacturer/;abeling of the equipment.

 

[hmspe]

Are you saying that the 220.82 Optional Load Calculation is significantly less than 400A, but that there's no way to divide the loads into two groups so that the Part III Standard Load Calculation for each group is under 200A?

Cheers, Wayne

It is common that the 220.82 calculation is in the 260 amp range but the panels are each in the 175+ amp range. The feeders will be 250MCM AL SER cable. Since this is in Arizona ambient temperature derating is required. I generally use 122 degF for ambient so the cable limits at least one of the panels to 188.6 amps.

Pool permits are pulled separately by others and I generally can't get information on the pool equipment. The pools for these houses tend to have heaters, coolers, and multiple pumps. I normally provide a 100/2 breaker or fused pull-out for the pool people.

Kyle posted 110.3(B), but I'm not sure I agree. 110.3(B) does not mention "intended use". I'm a big fan of "Charlie's Rule". I'm not sure what labels there actually are, or whether the labels limit the third main to ONLY parallel source input. I did not find an installation manual other than the drawing I linked. The lack of clarity (at least to me) in the requirements in the Siemens drawing is why I started this thread.

 

[kkyyllee]

here is a label from a panel i have encountered for reference. The third main is labeld as "Parallel Energy Source Disc." M1 and M2 are labeled as service disconnects

 

[hmspe]

here is a label from a panel i have encountered for reference. The third main is labeld as "Parallel Energy Source Disc." M1 and M2 are labeled as service disconnects

Thanks. The actual label is much clearer than the drawing I linked.

The long lead times for the services we normally use are not popular with clients and they are asking for alternatives.

 

[curt swartz]

What NEC year is AZ on? Keep in mind that the panel in the picture does not comply with the 2020 or later NEC.

 

[jaggedben]

..
Kyle posted 110.3(B), but I'm not sure I agree. 110.3(B) does not mention "intended use". I'm a big fan of "Charlie's Rule". I'm not sure what labels there actually are, or whether the labels limit the third main to ONLY parallel source input. I did not find an installation manual other than the drawing I linked. The lack of clarity (at least to me) in the requirements in the Siemens drawing is why I started this thread.

I think it is ambiguous. The NEC allows the total service overcurrent devices to exceed the service conductors rating if the calculated loads do not (230.90 Exception 3) but I'm not sure if UL permits that for a meter main. I have connected solar/battery backup systems that include loads to the parallel energy disconnect, but that is more like the 'intended use'. I think Siemen's labeling is fairly silly and CYA, but if an inspector cites 110.3(B) I don't think there's any slam dunk counterargument. It depends how you interpret the label.

 

[hmspe]

What NEC year is AZ on? Keep in mind that the panel in the picture does not comply with the 2020 or later NEC.

Arizona is a home rule state. Most jurisdictions are 2017. A few are 2020. I occasionally see 2014, 2011, or older.

I'm not sure whether the barrier requirements in the 2020 are being enforced. State law requires that a PE do the load calcs for 400A and over or 600 amps and over, depending on how a jurisdiction reads a run-on sentence in the Administrative Code that was obviously written by someone with no electrical background. I don't see the final installations unless the EC redesigns and the inspector takes exception.

 

[curt swartz]

I'm surprised that AZ requires a PE for Class 320 residential services. In CA they are a very standard service and seldom get asked for load calc's. Whoever came up with that requirement must have been a PE.

You mention going with a CT service. Yo can also get Class 320 CSED's with a single 400 amp breaker. That is cheaper than CT's. You could feed a single 400 amp panel board or drop into a wire way with multiple MB load centers or individual disconnects.

 

[hmspe]

Whoever came up with that requirement must have been a PE.

I tend to think it was a lawyer.

R4-30-302. Electrical Plans
A. A registrant shall prepare and submit drawings and specifications for a new electrical system or an addition or modification to an existing electrical system provided the service and associated electrical feeders exceeds 600 amperes 120/240 volts, single phase or 225 amperes 120/208 volts, three phase and the fault current exceeds 10,000 amperes.

 

[curt swartz]

I tend to think it was a lawyer.

R4-30-302. Electrical Plans
A. A registrant shall prepare and submit drawings and specifications for a new electrical system or an addition or modification to an existing electrical system provided the service and associated electrical feeders exceeds 600 amperes 120/240 volts, single phase or 225 amperes 120/208 volts, three phase and the fault current exceeds 10,000 amperes.

That states exceeds 600 amps single phase 120/240 volts so would not apply to a 120/240 single phase Class 320 panel.

 

[hmspe]

Curt,

That is a reasonable reading, but it is not the way local jurisdictions parse the sentence. Most seem to key on "fault current exceeds 10,000 amperes" rather than the voltages.

I think R4-30-302 needs to be re-written to make the requirements clear, but making that happen would be an uphill battle.

 

[jaggedben]

Seems like the fault current criterion would apply to even some 200A services. That's a really effed up law.

 

[wwhitney]

That is a reasonable reading, but it is not the way local jurisdictions parse the sentence. Most seem to key on "fault current exceeds 10,000 amperes" rather than the voltages.

The text says "A or B and C." That's ambiguous, and it could means "(A or B) and C" or it could mean "A or (B and C)". Since A and B are both about voltage and current ratings, while C is about fault current, I favor the former reading.

But either way, if not A (i.e. 120/240V single phase and 600A or less), the clause is not met, and it is not necessary that "a registrant shall prepare . . ."

Cheers, Wayne

 

[hmspe]

It depends how you interpret the label.

Agreed, but I'd have to convince both the AHJ and the utility that it was OK. 30 years ago I would have taken on the challenge. Not so much today.

You are correct that almost all 200 amp services would technically require load calcs by a PE since the utility fault current tables we are required to use show over 10KA for 200 amp single phase services, with some showing over 10KA at 125 amps. Plan review in most jurisdictions does not enforce this for 200 amp services.

 

[curt swartz]

I don't think I have ever done a 200 amp residential service where the current exceeded 10K. Even though its higher at the transformer the service lateral will drop it. The largest lateral used for 200 amps is 4/0 AL.

Class 320 services are frequently over 10K but less than 20K.

 

[wwhitney]

You are correct that almost all 200 amp services would technically require load calcs by a PE

Not per the text you quoted. There are only two logical readings of "the service and associated electrical feeders exceeds 600 amperes 120/240 volts, single phase or 225 amperes 120/208 volts, three phase and the fault current exceeds 10,000 amperes."

(1) (A or B) and C: the requirement kicks in whenever the fault current exceeds 10,000A and further the service is either OVER 600A 120/240V single phase or OVER 225A 208Y/120V.

(2) A or (B and C): the requirement kicks in whenever either the service is OVER 600A 120/240V single phase, or the service is OVER 225A 208Y/120V and the fault current exceeds 10,000A.

Either way, any 400A or 600A 120/240V single phase service is exempt.

Cheers, Wayne

 

[curt swartz]

Since you are a PE i can see why you don't want to fight any local jurisdiction misinterpreting the rules. You make $$$
As a contractor or homeowner I would definitely fight it.

 

[hmspe]

Most homeowners don't want to delay their projects or spend the money to change the AHJ's interpretation. Getting Phoenix to change would not change Mesa or Tempe or Scottsdale or....

After 34 years in AZ I moved to Texas about 6 years ago to "retire". I'm not well situated to try to change the local interpretations in AZ. I'm not sure I want to in any case. AZ does not license electricians so the calcs would come from the residential designer with no electrical training or certification.