Stationary Genset Install

[OKCMoparGuy]

Need advice on installation of a stationary 16kw Onan w/ weather enclosure behind my shop. I'm going to have an electrician involved to ensure everything's done right and to code but wanted to discuss my options for my particular install. I'm an automotive technician by trade not an electrician so any advice/feedback you can provide is appreciated.

Here's my current setup:
- Cutler Hammer Type BR Loadcenter(s)
- 400 amp service at the house (2 panels)
- 125 amp breaker in the house panel feeds the shop (1 panel) (200' away)

Here's my plan:
- Genset approx 4' from shop to allow complete access for repair/maintenance and as close as possible to service panel entrance
- #4 gauge wire from genset to disconnect switch then to shop panel
- Shop panel backfeeds 80 amp breaker at house panel
- Cutler Hammer Type BR Interlock Kits on each loadcenter at the house

I'm ok with manually controlling the load at the service panel and like the flexibility the interlock kit provides. Should I be concerned that I don't actually have a manual transfer switch on this setup. My main reason for omitting this is room, or lack thereof, between the meter and my loadcenters.

I'd also like to be able to monitor wattage at my home's service panel (Whole Home Power/Watt Meter). I'm looking for a product that uses inductive clamps around both mains and has an LCD monitor near the service panel. I think this would allow me to better manage generator load without trekking all the way back to the generator itself. Striking out so far searching on GJ and google, any recommendations.

Thanks

 

[Chilliwack Murray]

How do you prevent connecting two sources together? If you have interlocks, they would prevent power ever getting to your shop.

In this scenario, if the shop feeder breaker were on (to allow backfeed to the house) the utility breaker would have to be off and vice versa... If the utility breaker were on, the shop breaker would have to be off.

You should sketch this out and post a picture but there really is no safe way to backfeed a system. The installation manual available online will cover everything you need to install the unit. What is the model? Most current products will allow some sort of remote monitoring.

 

[OKCMoparGuy]

Thanks Chilliwack I added a pic to my original post to help me clarify. The manufacturer specific interlock installed on the panel(s) prevents the 80 amp generator breaker and main breaker from both being turned ON at the same time. The generator breaker has to be located in specific relation to the main breaker to accomplish this. The 125 amp shop breaker (on the house panel) will be left in the ON position.

An error and oversight in my original plan:
- Since I have (2) 200 amp panels in the house and only 1 of the panels is feeding the shop I'll have a dead panel.

What's the best way to distribute to the other panel?


The generator I'm trying to purchase is a used Onan DNAE (liquid cooled Lister Petter Alpha series diesel engine) (pic from internet attached to first post). It does not come with an automatic transfer switch. I was considering an ex-military 10kw MEP003 (skid mounted diesel Onan) but I'd rather not have to deal with dragging a 1000lb generator next to my house in an ice storm or after a tornado. The initial electrical installation of the MEP003 sounds like it would be easier though. If there's not a safe way to accomplish the install of the the stationary Onan I'll default to the MEP003. From what I've read both are great gen sets, fuel usage is similar and parts are still available for both.

 

[Mustang51js]

Seems ok to me, like you said you will only be able to use one panel unless you put a j-box and went to each panel. But then it's one more thing to worry about if your not home and had someone else turn gen on. I never understood why some people have to have everything on in their house with the generator, it's supposed to be for the basic stuff. If you do decide to power both panels you have to make sure the phases are matched up to each other just in case someone does turn on the breakers when gen is not in use, the interlock kits should prevent that but you never know.

 

[malibu101]

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I'd also like to be able to monitor wattage at my home's service panel (Whole Home Power/Watt Meter). I'm looking for a product that uses inductive clamps around both mains and has an LCD monitor near the service panel. I think this would allow me to better manage generator load without trekking all the way back to the generator itself. Striking out so far searching on GJ and google, any recommendations.

Thanks

I too would like the same thing.
I too have looked without much luck other than a mix of expensive industrial C/T's and meters.

I wish you luck with everything but I am selfishly watching for an answer to this question in particular also.

 

[offroadsteve]

Thanks Chilliwack I added a pic to my original post to help me clarify. The manufacturer specific interlock installed on the panel(s) prevents the 80 amp generator breaker and main breaker from both being turned ON at the same time. The generator breaker has to be located in specific relation to the main breaker to accomplish this. The 125 amp shop breaker (on the house panel) will be left in the ON position.

The problem with this setup is that the interlock is designed to only allow you to use one source of power at a time, so when you are on generator power, the shop panel is isolated from the house, therefore no power back to the house. But, you'll be sitting pretty in the shop

The only way to correctly do what I undestand you would like to do is run a seperate set of conductors back to your main house panel and install the interlock in your main house panel. You could theoretically do this using the conduit (assuming you have conduit) from the house to the shop.

I've been thinking about the same thing and always came back to the same problem... no way to safely backfeed through the shop service and keep both the house and shop powered up!

 

[Rookie2]

There are alot of current transformers on ebay from $25-$65.00 but this is the simplest solution ebay #171117365394

 

[FJ 432]

First you may want to check your distances to your home, I think you need 5 feet.

Secondly, IMO a automatic transfer switch is a better solution given the 2 panels scenario. I understand the space issue but I think for safety concerns I would consider a nema 3R ATS placed at the generator if needed.

 

[Paul1956]

At our data center we have a large diesel generator, automatic xfer
switch and a couple of large UPS units.

When the city power cuts out the UPS units carry the load temporarily
until the generator kicks in and stabilizes.

 

[malibu101]

There are alot of current transformers on ebay from $25-$65.00 but this is the simplest solution ebay #171117365394

NICE!
That is exactly what I am looking for at a great price.

Of course I would need 2 of these. One for each phase.

THANK YOU!

 

[BigGMC]

Secondly, IMO a automatic transfer switch is a better solution given the 2 panels scenario. I understand the space issue but I think for safety concerns I would consider a nema 3R ATS placed at the generator if needed.

Wouldn't matter in this case as his main service goes to the house and he wants to feed the generator (back up service ) into the shop's panel.

 

[PRH44]

I am guessing you really do not want the gen-set next to the house? In which case you could feed your house and shop with one transfer switch.

 

[Mustang51js]

You have to look at the manual of the generator, but for the most part it's 18 inches from combustibles and 5 feet from a window on the exhaust side.

 

[Chilliwack Murray]

The best solution is a service entrance rated automatic transfer switch ahead of the main panel. If the load exceeds the generator capacity you can leave it off and start it manually when you have switched off the excess loads. When you start it, the transfer switch will transfer, when utility returns it will retransfer to utility.

To operate the system with the interlocked breakers you are proposing you would need to make the the second 200A panel a sub-fed panel of the one with the shop (generator) and utility feeds. Do you actually have 400A load and or a 400A service or are these just the panel sizes that are installed? If you have a 200A service than there is no difference having a 200A main with a 200A sub since that is all the power you have anyway.

 

[theoldwizard1]

You have 2 issues.

1. 2 load centers at the house
2. trying to "re-use" the feed wire to the shop

There is no simple, safe way of using 1 set of wires to send power from the house to the shop or from the shop to the house.

If you can not move all of your "priority" circuits to one load center, you need to install a 400A DPDT safety switch "in front" of them (between the meter and the 2 load centers), like a Square D DU325. This assumes you have a dedicated line coming directly from the generator to one of the feeds to the DPDT.

There is only one way that I can think of to "re-use" the wire from the shop to house as a "feed", but it requires a 4PDT switch (or 2 linked DPDT switches). It would require some "interesting" wiring, likely approved by an engineer and of course your local building inspector. It would probably be cheaper to install another line directly from the generator behind the shop to the house.

 

[Chilliwack Murray]

The interlocked breakers he posted the link for would work just fine IF the second panel was a sub-panel to the main panel but not otherwise.

 

[CoopVA]

I am guessing you really do not want the gen-set next to the house? In which case you could feed your house and shop with one transfer switch.

^ This ^. +1