Determination of Existing Load

[iwire]

I am involved in a service upgrade for a condo building, I recommended recording meters be installed to determine the existing load.

What has prompted this is one units 100 amp main keeps tripping, that person wants to upgrade to 200 amps. The issue is the main for the entire building is only a 400.

Now the Condo owner has questions.

"Since the new Unit 1 breaker trips at 100 amps and the service needs to be increased to 200 amps to accommodate the heat, electric stove, TV, computers and general lighting, the demand analysis will not and cannot reflect Unit 1 drawing more than 100 amps. As proposed, Mr. Badger's approach cannot accurately "determine the existing service load for the entire building." The new breaker works as a bottleneck. If the demand analysis erroneously concludes that 400 amps is sufficient for the building and the building's service is not upgraded, the existing FPE 400 amp breaker will be overloaded when my service is upgraded to 200 amps. It seems to me as a layperson that this situation would fly in the face of Rule 3 since it WOULD "increase the magnitude of an existing violation."

(Rule 3 is a local rule that allows new work without fixing existing problems)

What I am looking for is a good way to explain to the layperson that the recording meter can do an adequate job.

On the other hand I am also willing to concede this layperson may be correct.

How would you do it?

Thanks in advance, Bob

 

[tallguy]

What I am looking for is a good way to explain to the layperson that the recording meter can do an adequate job.

On the other hand I am also willing to concede this layperson may be correct.

How would you do it?

Thanks in advance, Bob

Never would've figured I'd be able to answer a question for you Bob... but being closer to a layperson than most on this forum, I feel well qualified

I would tend to see it the same way that the HO sees it, but more info would be helpful.

1) How many units are we talking here?

2) What does a standard load calc yield?

3) What is the story on this particular unit -- size, etc? Why would it be so different than the others? Is it just a matter of time & the right HO before other units are tripping?

4) Sounds like they have electric heat. The amperage draw in February in CT/RI/MA will be a whole lot more than in August.

That being said, here are a couple points to share with your over-involved HO:

1) You would see more than 100A on the recording meter since it does not trip at 100A instantaneously, right? He seems a fairly bright individual and should grasp a trip curve if you explain it.

2) His neighbors may be drawing much less than him. I can't see how it would be dramatically different unless he is the only one with electric heat or has a much larger unit, but something must be going on.

An example for this guy (gal?), assuming 4 units and peak usage:

Unit# 1 = 125A
Units# 2-4 = 65A each
Total = 320A (80% of 400)

3) Is the new 200A service going to suddenly be drawing 150A?? I doubt it, unless the HO is enduring massive inconvenience (like can't run the toaster without turning off the heat and the dryer).

Ultimately though it sounds like someone who wants to upgrade "just in case" and is going to argue their case no matter what. Might be best to just take the business with a smile.

Egad... just noticed the magic letters "FPE"... Time to upgrade!

 

[Pierre C Belarge]

Bob
One way to look at this is to have the utility monthly bills for the last 3 months to be examined. This will give you an idea of the load he/they are drawing. I would also test the unit without the AC running to get a general idea without that load. Then I would have an AC company check the AC to make sure it has been maintained and that it is not the cause of the overload.

Has this unit owner had any work performed to the unit in the near past that may have contributed to the overload?

Sometimes it is not possible to teach someone who has just enough info to understand exactly what a professional is trying to accomplish.

I would also compare his unit to some of the other units that are off of the same service.

 

[cschmid]

Here the POCO can actually give you a continuous amperage usage if you ask nice. This could narrow down a pattern for you and with this proof. You should be able to sell the Land lord on monitoring the panel that is the problem. The land lord is paying the electric bill I presume...so appeal to his pocket book land lords are all about profit show him you can save him money in the long run. Don't know if this is any help but it is my contribution.

 

[tallguy]

Bob
One way to look at this is to have the utility monthly bills for the last 3 months to be examined. This will give you an idea of the load he/they are drawing.

That would only give you the average, not the peak -- which is what's really relevant to tripping the CB.

You should be able to sell the Land lord on monitoring the panel that is the problem. The land lord is paying the electric bill I presume...so appeal to his pocket book land lords are all about profit show him you can save him money in the long run. Don't know if this is any help but it is my contribution.

Bob had referred to it as a condo, and that would seem to fit with the degre of concern the HO is expressing regarding the service drop. If it is a true "condo" there is no landlord. The HO would be a member of the condo association.