ECN Forum Forums General Topics of the Trade General Discussion Area Upgrading 3 Phase system

Exsisting 3phase 100amp 240v delta system.
Upgrade 3phase 150amp 240v delta system.

This service is underground and I have already requested a work order with the Utility Company. It appears the exsisting underground feeders are of a sufficient size and
will confirm with them.

The exsisting panel is rated for 150amps. There are:

2 pole 240v arc welder 30amp

3 phase 240v air compressor 50amp

3 phase 240v sub panel 60amp
The equipment from the
subpanel is feeding a
paint booth and uses
approximately 23amps

Interviewing the owner of the Auto Body Shop I was able to determine the typical use of the equipment on this service.
I used an amp probe to take readings at different times during the day to find out what the actual load was on the service. The load averaged between 20 and 60 amps evenly distributed between phases.

The new equipment will be 3 phase 230v 50amp breaker.

Would anyone be able to give me some feed back on whether or not I am correct on thinking this upgrade will handle the exsisting load and the new load. I am assuming 60amp exsisting plus 50amp max on new for a total of 110amps on the 150 amp service. 80% being 120amps.

Thanks for any help in advance.

2 pole 240v arc welder 30amp

3 phase 240v air compressor 50amp

3 phase 240v sub panel 60amp
The equipment from the
subpanel is feeding a
paint booth and uses
approximately 23amps




What about the loads from lighting & heat / cooling & ventilation & receptacles (microwave, etc)?

What you have adds up to 163A.... In Canada, If I am not mistaken, the service in a garage must be rated at least 100% (not 80%) of all loads

Also, what if they want to add equipment in the future?

A 150A panel should be the same price as a 200A panel...

They have service for other equipment.

Don't you have calculated loads in Canada?

The exsisting panel is 150 with a 100 breaker.

Any thoughts would be appreciated.

The ampmeter, is not going to give you the calcuated load.

dont want to bog this down with too many CEC references, but for a garage, there is a 10watts per square meter value from table 14, and based on 8-210(b) the loads described are "special loads" and as such the rating of the equipment must be used for service ampacity with demand factors permitted in other sections of the CEC. In other words, 150 amp service could be okay, depends on the loads on the sub panel,the square footage of the garage, and the nature of this new 230(?)volt 50amp breaker. Most likely a 200 amp service will be required, but that means new feeders, possibly existing conduit size could be a concern.

Unless it's a tiny ark welder 30 amps seems a bit low. Ark welding in an auto body shop is not an acceptable repair by todays standards. Are you sure it was not a MIG welder? I could see the nameplate on that being 30a.

What do you mean they have service for other equipment?
Is there is 2 services for the same unit and one service your talking about is only for the equipment you listed?

Besides lighting, office, breakroom, bathroom, HVAC, there are receptacles in the shop? Is there some kind of exhaust fans in the shop? Things might be used like battery chargers, power tools, hydralic pumps, stud welder, portable heaters, work lights, fans, resporator pumps, and even computers.

Loads to come might be a frame rack, spot welder, plasma cutter, TIG welder, paint mixer, etc.

Paint booths have lighting, a large fan(s), and a heater that can bake the paint. 23 amps sounds a bit low for FLA.

This might not be a paint booth for cars, just for making parts look new.

I appreciate everyones input and maybe I'm not making the circumstances clear enough. I will try again here.

There are two services to the building. It is an exsisting Body Shop that has been in business for many years. The single phase 200amp service handles most of the electrical requirements such as general lighting and power.

The three phase system only handles the equipment I mentioned and the commercial HVAC company wants to install a 3phase, 42amp, 230volt unit. The name plate says max. 50amp overcurrent protection per phone conversation with the HVAC contractor.

I have performed actual readings several times during the day with confirmation from the owner who is completely hands on with regard to equipment use as to when what equipment is operated. The load is constantly 20 to 60 amps throughout the day on the 3 phase service.

The Utility company has already given the okay to perform upgrade however I wanted to confim that with the additional load of the HVAC system would the demand be within tolerance of a 150amp service upgrade from 100amp.

Therefore:

Would anyone be able to give me some feed back on whether or not I am correct on thinking this upgrade will handle the exsisting load and the new load. I am assuming 60amp exsisting plus 50amp max on new for a total of 110amps on the 150 amp service. 80% being 120amps.

Thanks again and I hope this clarifies my situation.

Let me try my math with your numbers.

Largest load air compressor 50 amps x 1.25 = 62.5
Welder 30 amps
Paint booth 23 amps
RTU 42 amps
Total 157.5 amps

I don't believe you can derate the other loads.

Thank you for your input Active 1.

Does anyone else agree/disagree.

I was under the impression that if I have an actual sevice load investigated that that takes precedent over calculated load. Therefore :
60amp exsisting plus 50amp max on new for a total of
110amps on the 150 amp service. 80% being 120amps.
If this is acceptable it would save the customer the
installation of a new panel and a 200amp upgrade which the
exsisting service lateral and meter could handle according
to the Utility Company.