Temporary service to refeed existing panel

[jaylectricity]

Right now there's a 480V three phase service. Main panel has service disconnect and 8 circuit breakers rated 200, 400, or 600 amps. Two of the breakers feed step-down transformers. One feeds 208/120v three phase panel while the other feeds a 240/120 single phase panel. From each of these panels there are feeders to various panels throughout the building. I've eliminated the need for any of the three phase sub-panels.

We want to remove all the equipment and replace with a 5 position meter bank. The project will take a few days at least, but I need to keep power to the building for business operations. Half of the floor space is in use, but over half of that is just warehouse with LED lighting and a handful of fans and a garage door opener. The other half is office space with LED lighting, a dozen computers and two HVAC units drawing about 10kva total.

With a proper calculation would I be able to get a temporary service to a single meter mounted on the building capable of carrying that kind of load? Or is that too much demand for a temporary service? I have always thought of temp services as a pole mounted meter with a few breakers and some gfci receptacles that you install while a building is being constructed.

If I could feed the one single phase panel I could remove a lot of the equipment and allow construction to be planned for a retail space without the new service being imperative to being finished any time soon.

 

[growler]

I'm thinking that you need to be talking to a power company engineer and the AHJ (inspector) .
Sounds like there are going to be many changes to the power system and that everything needs to be planned out now.

Feeding an existing panel with temp power is possible because I have done it and it was approved. Come up with a plan and make sure it looks safe on paper. You have to sign for temp power and it's your responsibility so it had better be safe.

 

[jaylectricity]

I will be talking to the poco's engineer on site after I put in all the work order requests. One of the questions they asked me after the original request was whether we would be doing same day disconnect/reconnect or using a temporary service which gave me this idea.

This service is slightly above my pay grade, but with some process of elimination it's becoming comprehensible. I understand everything that will be happening within the building walls. Just need to find out if they'll be replacing the padmount transformer only or if they're willing to move it across the driveway.

A main part of the problem is the owner has no concrete plans for the tenant spaces we are creating.

 

[mpoulton]

This really is a POCO and AHJ issue since the real-life rules on temp services are pretty loose and it all comes down to what you can convince them to let you do. However, I will say that on large construction projects it is not unusual to have a 480V temp service with temp loads of hundreds of KVA. All the jobsite lighting, elevators, and HVAC for a large structure can often be run on a temp service. You'd try to get the final service built and activated as early as possible, but sometimes that just can't be done. But in your situation, is there any way you can build the new service separately from the old one, activate it, and then disconnect the old one and re-feed the loads after hours?

 

[jaylectricity]

This really is a POCO and AHJ issue since the real-life rules on temp services are pretty loose and it all comes down to what you can convince them to let you do. However, I will say that on large construction projects it is not unusual to have a 480V temp service with temp loads of hundreds of KVA. All the jobsite lighting, elevators, and HVAC for a large structure can often be run on a temp service. You'd try to get the final service built and activated as early as possible, but sometimes that just can't be done. But in your situation, is there any way you can build the new service separately from the old one, activate it, and then disconnect the old one and re-feed the loads after hours?

It's not feasible because the new service is dependent on the pad mount transformer being changed and a pretty sizeable distribution panel being replaced with basically a tap box. I could get the new meter bank installed, but I wouldn't be able to even run the conduit for the service conductors. Likewise on the feeders to the tap box.

The calculation for everything that needs to keep the business operational is about 166 amps at 240V. I can mount a meter/main disconnect and feed the distribution panel that houses the feeders I am keeping. Then remove the outdoor transformer, install the new meter bank with conduit to the pad, then they can replace with the appropriate transformer leaving it dead until I can make all the connections. Then during after-hours I can work on transferring each of the feeders over to their new sources.

The killer of it all is, if he had any sort of plans going into the winter there was ample time to work on it while the warehouse was completely empty. I could have just done a regular temp service and just ripped out everything all at once.

 

[mpoulton]

It sounds like even if the POCO wants to do a temp service, they'll have a hard time doing it without an outage of at least several hours. They would need to set a new transformer just for the temp, right? On a new pad or a temporary pole? That sounds expensive and time consuming. What about renting a generator for a couple days? I've seen that done for difficult service changes, but never on a project I was involved with. The weekly rate on a 40KVA quiet diesel generator is probably a lot less than what the POCO would charge to install a whole new transformer with underground primary.

 

[jaylectricity]

They should be able to give me an overhead span from the single-phase triplex that runs along the street in front of the building. It would have the necessary clearance over the lawn if they did a mid-span. Obviously I'll have to find out if they'll do that. Then they could de-energize the transformer with the 480v secondary, remove it and leave me alone until I put everything else together.

I'll keep the generator idea in mind, that's a good idea. We'll see how things go.

Thanks for bouncing some ideas around with me.