Would like to start gathering 20kw Gen install info...

[getpecked]

I've been following a couple other gen install threads here and picking up some useful info that can be applied to the installation of my 20kw Kohler propane fed w/ service entrance rated transfer switch. I thought I had the location picked out for the Generator, but as of this morning I am thinking of a location away from the house...approximately 120' away from the back of the house. The total length of the run from the transfer switch to the generator would be just under 150'. I really only have one spot close to the house that would work for me as far as clearances from windows and such...and if I do put it there it will kill any future plans to expand that portion of the house (if I ever hit the jackpot) lol.

I would like to size the wire in such a way that it will cover any load possibilities. The house has electric stove, dryer, water heater, central air and a well pump (small 1/2 hp). Obviously not all of that stuff will run during an outage, but I would say things like the a/c and stove could be running together in the summer. My wife is a smart woman and I'm sure would keep things at a minimum...hell she probably wouldn't even run the ac unless it was unbearable outside. During an outage I am generally not home as I am a Power Lineman in CT and get called away allot.

**With that being said...150' run...wire size for feed and controls? I know that #2 copper is rated for 95 amps and that is slightly more than this gen can put out, but with that distance I don't know if I should consider #1 which is supposedly rated at 125 amps.

**Conduit size for the 3 conductors and a ground?

Another issue I may have is the propane tank being that far from my driveway...not sure if the truck would be able to fill from there...about 175'. That is something I will have to look into.

Well...that is the biggest question at this time...more are sure to follow lol.

Thanks in advance,
Ed.

 

[getpecked]

found a pretty good calculator and it shows...120v single phase at 150ft, plugged in 75amps=#1copper

 

[Charles (in GA)]

Copper will break the bank, go with aluminum.

 

[CNGsaves]

Welcome to GJ. Best chance to get good advice is provide plenty information like your Location. Update GJ Profile with Country / State / City. Have you researched what state or local codes apply to genset install??

At 120 ft to 150 ft run, you'll also need to consider voltage drop for your electrical. +1 to go aluminum as copper is waste of money, for reality that unlikely will ever be ran with much load.

With all this expense, sure hope you're also putting in ATS (automatic transfer switch) and have genset test itself periodically to keep it running well and battery charged.

For your propane fuel line, make sure your supply line is buried deep enough for local codes (generally 18" minimum, and some states 30" depth). Sizing of LPG buried line also important so go BIG at that distance (likely 1 1/2" or possibly 2"). Buried LPG line will need to be yellow plastic polyethlene with risers at each end that transition to steel above ground. If using LPG in coastal states (Florida, etc) with hurricane risk, the propane tank will need to be buried so it doesn't wash away.

Also, be sure to call 811 or Dig Safe in time BEFORE any digging is done.

 

[pattenp]

If aluminum Mobile Home Feeder (MHF) is available where you are I'd use the MHF in 2/0-2/0-2/0-1 and use 2.5 PVC conduit. The 2/0 is a standard size in the MHF and can be used at a max of 135A. At 150ft it will give you a very good cushion on max amp draw with very little voltage drop.

http://www.southwire.com/ProductCatalog/XTEInterfaceServlet?contentKey=prodcatsheet15

 

[Stuart in MN]

found a pretty good calculator and it shows...120v single phase at 150ft, plugged in 75amps=#1copper

Make sure you're using the right voltage - most generators (particularly 20kw generators) have a 240vac output.

 

[getpecked]

Good point CNGsaves...I updated my profile info.
Also...I mentioned I want to locate the generator and the propane tank in the same area, both in the back yard. My only concern with that is the tank being so far from my driveway for filling purposes.
Yes I am using an automatic transfer switch and the generator does automatically run periodically.


"Pattenp" I am going to look into MHF you mentioned as it seems it will be able to more than safely handle any load situation I may encounter. My only thought about using 2/0 wire is if it will fit under the lugs in the transfer switch and the generator...that's why I had not really thought about using aluminum...and possibly why I really have not seen many other posts using aluminum over copper.

Stuart in MN...I see your point, but I was assuming it means voltage to be carried in one phase...it doesn't specify. If I go back and plug in all the same info, but change the voltage to 240 it actually specifies #4cu wire...no way that can be right at this distance.
edit...well Stuart...it may actually be possible. I found a post on an electrician forum with circumstances close to mine (just a slightly shorter run) and they are calling for min #4 or #3 cu

 

[pattenp]

2/0 should fit in a 20kw gen and a transfer paneled that's sized for a 20kw gen. As a reference a 100 amp breaker will take 2/0 wire.

 

[getpecked]

2/0 should fit in a 20kw gen and a transfer paneled that's sized for a 20kw gen. As a reference a 100 amp breaker will take 2/0 wire.

I may have to check an electrical supply store, I looked at homedepot.com and it is not offered in my area online or in store

 

[pattenp]

You may have to go to the actual store. My HD and Lowes carry it but is not shown on the web that they have it.

I may have to check an electrical supply store, I looked at homedepot.com and it is not offered in my area online or in store

 

[CNGsaves]

Recommend you call your local propane companies as to location of propane tank. Personally, I would NOT want a big propane truck driving across 175 ft of my back yard to fill up LPG tank. Are there buried sewer lines or other utilties that truck could damage by driving over?? Also may be setback rules on your land that forces you to install the tank in particular spot.

You should also inquire about BUYING vs LEASING the LPG tank if you end up going with propane.

Do you have access to Natural Gas . . . it would be much cheaper fuel in the long-run and even cheaper to install as you wouldn't need LPG tank.

 

[getpecked]

Recommend you call your local propane companies as to location of propane tank. Personally, I would NOT want a big propane truck driving across 175 ft of my back yard to fill up LPG tank. Are there buried sewer lines or other utilties that truck could damage by driving over?? Also may be setback rules on your land that forces you to install the tank in particular spot.

You should also inquire about BUYING vs LEASING the LPG tank if you end up going with propane.

Do you have access to Natural Gas . . . it would be much cheaper fuel in the long-run and even cheaper to install as you wouldn't need LPG tank.

I'm not a big fan of a truck driving across my lawn either, but a large tank off the back of my house may not work for me either...plus I think it has to be 10' away after a certain size and that definitely won't work at my house. There is nothing the truck would damage in my back yard except for the grass...plus the hose must be able to reach half of that distance anyway...I'll have to call and find out. I do not have access to natural gas.
I will have to look into the cost and advantages / disadvantages of buying vs leasing. I figure buying would give me the freedom of choosing the best price out there and not being locked in with the leasing company.

 

[getpecked]

You may have to go to the actual store. My HD and Lowes carry it but is not shown on the web that they have it.

will do.

 

[pattenp]

Ooops.. I'm not thinking right... it's the #2 MHF that Lowes and HD carry not 2/0. You will probably need to go to a electrical supply.

You may have to go to the actual store. My HD and Lowes carry it but is not shown on the web that they have it.

 

[wyliesdiesels]

found a pretty good calculator and it shows...120v single phase at 150ft, plugged in 75amps=#1copper

Good point CNGsaves...I updated my profile info.
Also...I mentioned I want to locate the generator and the propane tank in the same area, both in the back yard. My only concern with that is the tank being so far from my driveway for filling purposes.
Yes I am using an automatic transfer switch and the generator does automatically run periodically.


"Pattenp" I am going to look into MHF you mentioned as it seems it will be able to more than safely handle any load situation I may encounter. My only thought about using 2/0 wire is if it will fit under the lugs in the transfer switch and the generator...that's why I had not really thought about using aluminum...and possibly why I really have not seen many other posts using aluminum over copper.

Stuart in MN...I see your point, but I was assuming it means voltage to be carried in one phase...it doesn't specify. If I go back and plug in all the same info, but change the voltage to 240 it actually specifies #4cu wire...no way that can be right at this distance.
edit...well Stuart...it may actually be possible. I found a post on an electrician forum with circumstances close to mine (just a slightly shorter run) and they are calling for min #4 or #3 cu

First off since your generator is rated 20kw, you would have to use 90a rated feeder. #4 would be too small because its rated for 85a. Second, the generator is rated for 240v so thats what u use.

When I did the calcs by hand, i came up with #1 AL or #3 CU.

If u end up using individual conductors, use 3 #1 AL or #3 CU, and #6 AL or #8 CU for the EGC/ground.

Dont forget to size the conduit for the feeder and the control wires!

 

[soj]

My only thought about using 2/0 wire is if it will fit under the lugs in the transfer switch and the generator...that's why I had not really thought about using aluminum...and possibly why I really have not seen many other posts using aluminum over copper.

Per the Kohler RTS automatic transfer switch install book, the emergency (generator) lugs will take up to 250 MCM wire for the load and neutral, up to 1/0 for the ground. This is assuming a service entrance rated switch, 100A or 200A.

For install details on all Kohler RTS switches (the recommended switch for 14 and 20 RESA and RESAL generators), see here.

The install manual for the 14/20 RESA/RESAL generators does not give the lug capacities for the line, neutral and ground terminals. It refers you to the decal next to the terminals. I am not at home, and my 14KW may have smaller lugs anyway.