Mep 803 home and shop feed

[coastalguy]

Ok guys I need some input on this one. I live in south Mississippi. So after a successful load test I did a temporary test on my house before I do my permanent install. I knew this generator was a beast but my home test blew me away. Initially I turned on my inside panel and 1 central a/c system. The gen set read like 12%. So I turned on my second central a/c system. This brought me to 25%. Then I turned on my sinks so my water well would run and I turned on my dryer. This brought me to like 65%. I turned on my oven and 2 large burners. Finally I was at 100%. Just to see i turned on the last 2 burners. This finally bogged the generator. I know that in real life I will prob NEVER find myself running this many things at the same time. I was already planning on switching back to a gas stove next year anyways cause I prefer cooking on gas. My concern now is that I won't have enough load to keep the generator from wetstacking. So...... I had an idea that makes perfect sense but I'm not sure about the wiring.

My plan is to mount my generator in my pump house (10x10 building with roll up door). I'll vent the exhaust up and out the gable end. I'm going to wire over to my house panel to a 60 amp breaker with manual interlock.

My idea is to install a sub panel in my pump house with 2 breakers. 1 feeding the 60amp breaker on my main service panel to my house and the second I could run to another breaker at the panel feeding my shop. My shop will have a 2 ton central a/c system. I'm thinking that with my house lights and 2ac systems being at 25% then my shop with lights and ac system should bring it up to 37%. Even then when the shop or house hits the temp setting the ac's will kick off and the gen will basically be idling. I really like this idea because if I have family or friends that need a place to stay after a storm they can sleep comfortably in my shop.

Ok, so here is where I think this idea won't work. My house and shop each have their own utility service panel and meter from the power company. I would install a manual interlock at the shop as well BUT my house service panel has bonded neutral/ground and my shop service panel has bonded neutral/ground. I know you can only have 1 bonded neutral/ground in a circuit. So.... what's my options here if any?

 

[Guyfang]

Please write the state you live in, the Location block. Thanks.

 

[coastalguy]

Please write the state you live in, the Location block. Thanks.

Ok. I edited my post to include the location. I live in south Mississippi though.

 

[Jeepadict]

As far that my research has led me, I understand that the only legal/safe means to play the game you're describing is to backfeed one panel or the other with some sort of manual transfer like a Twistlock SO cord to separate feed outlets. I strongly recommend you retain the services of a competent licensed Electrician in your area as they know what the NEC code laws state.

As far as needing a load bank later on, keep that electric range/oven when you convert to gas...they make great load banks!

Sent from my SM-G970U using Tapatalk

 

[coastalguy]

Yeah. I did residential house wiring 20 years ago but never anything like this. Basically the generator would feed into a sub panel with 2 breakers essentially acting like a utility feed. From there each breaker would feed the main panel with interlock at my house and 1 at my shop. I know everything will work like this i just need to figure out breaking the neutral/ground bond at one service panel.

 

[Jeepadict]

I believe you have the correct theory at play. They make transfer switches that will also switch the Neutral (in place of the panel you described), but they aren't cheap. Just flipping breakers definitely won't be enough. The manual interlock at the first disconnect means will be critical.

Again, I'm a huge proponent of hiring a licensed Electrician for at least a site visit and consultation...shop around until you find someone that is well versed in backup/emergency power solutions. Even if you want to do the work yourself, the piece of mind that comes with the price of at minimum a service call is invaluable in my opinion. They can also assist you in pulling any permits that may be required by law and calling for the inspections, all while you still do the work.

Sent from my SM-G970U using Tapatalk

 

[coastalguy]

Just got off the phone with my buddy that's a licensed electrician. He more or less confirmed my thoughts and that I would have to break the neutral/ground at one end to prevent a loop. The cheapest option would be to have a separate neutral bar and ground bar in my panel at my shop that I just put a jumper between. I'd leave the jumper in place as long as we were on utility power. If we lost power and I wanted to switch over to gen power at both locations then I would have to open the cover and pull the jumper to break the bond. The only time I would even think that I would do this would be in another "Katrina" type of scenario where we'd be without power for a couple weeks. In something like that then it wouldn't be a big deal to pull the jumper. I prob wouldn't worry about it for just a simple 24 hr power outage. I'd run my home only.

 

[WWRD99]

I gotta ask if you checked how much start up amps your ac takes. Unless they're under 2 ton they probably pull 50 amps on start up. Have your electrician friend stop over quick and test it. Some have the start up amps on the panel that covers the switches. Unless you're watching the load meter when the compressor kicks on you won't know if the meter pegs.

Sent from my SM-S906U using Tapatalk

 

[coastalguy]

Yessir I've watched the meter when both units started. My whole house is spray foamed. Right at 2400 sq feet and is heated and cooled by (2) 2 ton units.

 

[Scoobyshep]

For the 2nd panel you could install an isolation transformer, that would prevent the ground loop issue

 

[WWRD99]

Yessir I've watched the meter when both units started. My whole house is spray foamed. Right at 2400 sq feet and is heated and cooled by (2) 2 ton units.

Ok, but the start-up for those 2 could be too much to start the units start-up load. It won't hurt the genset, in theory, but could damage the compressor. It won't start properly. Could damage the capacitor for the fan or compressor as well. I'd check each leg load to make sure they're close to the same with them running. If both ac units are on the same leg it could over load that side. Easy fix is to move the fuse to the other leg. A soft start will fix the start up load. They drop the start up load to about a third.

Sent from my SM-S906U using Tapatalk

 

[coastalguy]

Ok, but the start-up for those 2 could be too much to start the units start-up load. It won't hurt the genset, in theory, but could damage the compressor. It won't start properly. Could damage the capacitor for the fan or compressor as well. I'd check each leg load to make sure they're close to the same with them running. If both ac units are on the same leg it could over load that side. Easy fix is to move the fuse to the other leg. A soft start will fix the start up load. They drop the start up load to about a third.

Sent from my SM-S906U using Tapatalk

Funny you mentioned the soft start. I've been researching them quite a bit. I think they are great regardless of you're using gen power or not. Seems like a no brainer that me ac systems should have them from the manufacturer

 

[WWRD99]

Funny you mentioned the soft start. I've been researching them quite a bit. I think they are great regardless of you're using gen power or not. Seems like a no brainer that me ac systems should have them from the manufacturer

The new micro air one is very nice. I put one on mine. My lights never dimmed before, but I have put them on homes that did. Usually a home with a 100 amp service. Pulling 80 amps starting the ac did dim the lights. Older homes. If the load can't be supplied to the compressor and other components, it lowers the efficiency of them at start up. From what I've found, on average, it won't lower your electric bill but can extend the life of the compressor and the other components in the ac system. Some electric companies charge more for high amp loads, which the ac is probably the largest one on start up, so it could lower it on peak times if they do. The industry answer for a long time was a hard start kit that added a capacitor to help boost the start. Soft start does everything different as it starts the fan then ramps up the compressor. You could put one on system that cools the house you use the most and see if you need the other system. Only reason I harp on this is I'd hate to see a failure in the genset or your ac system when you need it most.

Sent from my SM-S906U using Tapatalk

 

[coastalguy]

Yeah I def agree with you. I honestly don't think I need them for gen set purposes but I still want them just to hopefully extend the life of my compressors. I mean for $250 each if they get me 5 more years than I would have normally got without them then I think it's money well spent.

 

[WWRD99]

Yeah I def agree with you. I honestly don't think I need them for gen set purposes but I still want them just to hopefully extend the life of my compressors. I mean for $250 each if they get me 5 more years than I would have normally got without them then I think it's money well spent.

The new flex is 379 list price. It's the one that does any size up to 6 tons. If you can find the older models for the 2 ton ones, they were right at that 250 price. I did the flex just because it had a bunch of goodies that I can look at how it's working plus a surge protector. On a side note, I'd open up the side panel and see what capacitor you have in there and buy a few. I put new a new on every year. Only 20$. It's the part ac companies get 300$ to replace on that 90-degree day when the ac quits. If you get the exact one that's in there, it's a wire for wire replacement and no guessing.

Sent from my SM-S906U using Tapatalk