Generator install, sizing, location

[s219]

We're moved into our new house out in the country and I need to get a generator installed. The electrician wired an interconnect to the main panel with a power grid lockout, so I can manually switch the whole panel off the grid and over to the generator, then control individual circuits to tailor my load. The interconnect and lockout is setup with a double pole 100A breaker (so it can run 100A at 240V, or run two 100A legs at 120V).

From the breaker panel, we have a length of 2-2-2-4 aluminum wire run into our crawl space, and spooled up into a loop. Once I decide where to locate the generator outside the foundation, I can route the wire through the foundation where it needs to go and button everything down. There's at least a 70-100 ft run no matter where I go, which will cause about a 5V drop but that's tolerable.

Based on the wiring and breaker, the largest generator I could install would be 24kW, but that's on the ragged edge at full load so I'd probably never be able to run it 100% without tripping the interconnect breaker. So I'm eyeballing diesel generators in the 14kW to 21kW range. I still need to do a final circuit audit to figure what I can and can't run reasonably, and what to prioritize (well pump, fridge, HVAC blower are my top priorities). Trying to get current or power draw specs for the geothermal system to see if it's even within the realm of possibility. I'm definitely keeping an eye on fuel consumption rates too, as I'd like to be able to run for 4 days on a tank if possible.

I want to go diesel since it has (by far) the smallest footprint for the generator and fuel tank for a given run time, and we don't have natural gas out here or a reason to have propane. I'm looking at a 60-100 gallon diesel tank that mounts right under the generator itself.

For those who have installed diesel generators, what did you do for location relative to the house? Code says at least 4 feet from the foundation. I'd like to locate it where noise and exhaust are going to be the least offensive. Can the exhaust be modified to move it farther away or higher?

In addition to running the main wire through the crawl and mounting the generator next to the foundation, I also have a possible option of running the wire from the main panel out through an external wall and then under my driveway to a spot about 50 feet away. We're not pouring the driveway pad for another 2 weeks, so I could have some conduit ready to stick under the forms before they pour.

 

[Pete Judd]

I would have that transfer switch between the main panel and the grid. That way you control all the loads at the panel inside the house.. Since you don't have nat gas for heating, I assume you have a heat pump for heating and cooling or just an electric furnace. Do you have a wood stove for back up in the winter? How long are your outages? I just put up a 275 gallon tank with 125 gallons of diesel that I got for free, and plumed it both for the gen and a fill point for the tractor as well.

We handle power outages flooded in right now with a 2kw honda, Sonds like 25kw is fine if you don't want to adjust your life stile durring the outage, but 12KW will make most things work is mannaged.

 

[techman]

24 KW is a big gen set. I have a 10 KW and can run my two geo heat pumps and everything in the house, except for the stove and hot water heater. On an outage I charge the HW heater once a day, shutting of the heat pumps. It is an 80 gal HW heater, so it easily lasts the family for a day. For cooking we can run one burner, but more often use the convection/microwave to the cooking. On average we burn about 0.3 gal/hr.

Bigger means more convenience, but higher costs to buy and higher fuel consumption. You may look at:
Kubota 12 kW Diesel Generator
or
Kubota 15 kW Diesel Generator
units. They also have a 21 and 25 KW units.

I put my genset in my shed (12' x 20') and ran the feed underground. I purchased it with a 2 wire start control, but have manual transfer. Look at: Generator InterLock Kit - Introduction as a low cost, code compatible transfer, since you already have the feed breaker installed. I also have a 50 gal barrel of diesel fior the genset, as well as a second 50 gal barrel in the shed for the tractor that I can use as well, if needed. With the start control, there are all of the engine protections and I can start the genset from the house when needed.

Paul

 

[s219]

I would have that transfer switch between the main panel and the grid. That way you control all the loads at the panel inside the house.. Since you don't have nat gas for heating, I assume you have a heat pump for heating and cooling or just an electric furnace. Do you have a wood stove for back up in the winter? How long are your outages? I just put up a 275 gallon tank with 125 gallons of diesel that I got for free, and plumed it both for the gen and a fill point for the tractor as well.

We handle power outages flooded in right now with a 2kw honda, Sonds like 25kw is fine if you don't want to adjust your life stile durring the outage, but 12KW will make most things work is mannaged.

We have a geothermal system for heat/AC that also provides hot water in the summer. Fireplace for backup heat in winter (with ducting that will distribute hot air through the whole house as long as we can power the HVAC blower). Around here, outages from hurricanes or winter storms normally run 4-5 days, but could last up to 8-10 days. Being further out in the country at our new place, I expect we'll be on the longer end of that range now.

In winter we can definitely skate by without the geothermal system. In summer, we could manage if the temps stay moderate, but normally its hot and steamy after hurricanes and new houses just do not do well trying to stay cool with open windows and fans running, so I have some concern that we really might need to run the geothermal system. Or get backup window units for a couple of the rooms.

 

[s219]

24 KW is a big gen set. I have a 10 KW and can run my two geo heat pumps and everything in the house, except for the stove and hot water heater. On an outage I charge the HW heater once a day, shutting of the heat pumps. It is an 80 gal HW heater, so it easily lasts the family for a day. For cooking we can run one burner, but more often use the convection/microwave to the cooking. On average we burn about 0.3 gal/hr.

Bigger means more convenience, but higher costs to buy and higher fuel consumption. You may look at:
Kubota 12 kW Diesel Generator
or
Kubota 15 kW Diesel Generator
units. They also have a 21 and 25 KW units.

I put my genset in my shed (12' x 20') and ran the feed underground. I purchased it with a 2 wire start control, but have manual transfer. Look at: Generator InterLock Kit - Introduction as a low cost, code compatible transfer, since you already have the feed breaker installed. I also have a 50 gal barrel of diesel fior the genset, as well as a second 50 gal barrel in the shed for the tractor that I can use as well, if needed. With the start control, there are all of the engine protections and I can start the genset from the house when needed.

Paul

Paul, your strategy is about what I was figuring we would do -- I just need to work out the start/run load for our geothermal system to see if it's even in the cards. Otherwise a 14kW unit will be more than enough.

So how far is your shed from the main home, and what wiring gauge did you run? Did you add an exhaust pipe running out of the shed, or just leave a door open?

The interlock we have is very similar to what you show, but it's a GE part made for the GE panel. As shown, it prevents you from engaging the generator feed breaker when the main (grid) breaker is on, and vice versa. Nice and simple.

I had been planning on a Kubota generator (since I have a Kubota tractor and trust them) but that same company now sells Isuzu units that have notably better fuel economy, so I am thinking Isuzu now....

 

[s219]

One other question Paul -- I see you have a service light to show when the grid is energized, which I also want to do. Can you give details on the type of lamp and how you wired it in? I assume it has to be fused? Thanks.

 

[grsthegreat]

Im not sure of your actual total connected load on your panel, as i dont know the particulars of your situation. I hook up lots of generators here in Idaho, and it depends on so many variables, such as
1. is there a well pump
2. elect or gas heat, cooking appliances,water heater,a/c
3. what do you NEED to have operate
4. what can you do without
5.How long is a usual outage and do you have access to extra fuel. A LARGE 24KW diesel genset will eat the fuel.


I have found that a smaller propane generators (10-14kw) can handle a fairly heavy demand unless you want to include air cond or deep water well applications. Then i usually bump to 20KW or better. .


Personally, i have a 10KW propane on my 4,000 SF home that runs everything i need. I have gas heat, gas WH, gas cooktop. Dont care if i cant use a/c cause our summers are never too bad anyways. Im on community well that has its own generator. so i have a small need of supplemental power.

We have needed to use it more times than i can remember, and almost always in the dead of winter. I would not want to be without it. They tend to take longer to fix down lines here in the sticks.


Now, as far as how far from the house, youll have to check with your local codes,as they all vary. Our local codes require a diesel storage tank to be 5 feet from the residence. have no idea about yours. There's also codes as to how close you can be to an operable window or door.

 

[grsthegreat]

One other question Paul -- I see you have a service light to show when the grid is energized, which I also want to do. Can you give details on the type of lamp and how you wired it in? I assume it has to be fused? Thanks.

all automatic transfer switches have a fused 20 amp (actually 2 of them) circuits that tell the transfer switch when utility power has been restored. youll need the wiring diagram from your unit. This applies to auto units only.
Pauls system is a manual transfer switch, so im really not sure how he did his unless its hooked to the mains, and i that test light would have to be rated at 200 amps, which it isnt.(but im sure it works fine...)

Personally my system uses the eyes.... i see the neighbors house light up, i turn my unit off haha


Actually, i have a utility room thats not hooked into my gen panel, so i turn that light switch on. When the light goes on, i know utility power has been restored.

 

[doxford jim]

Hi guys,

I too have a dedicated standby generator at my property. I have a 12kW Kubota that sits in a wooden shed about 40ft from the house. The power cable is run underground and is connected to a manual disconnect switch. When standby power is needed I disconnect the house from the grid, go out and start the standby generator, then return to the house and connect to the generator at the main disconnect switch (disconnect has grid in and generator in - you can only use one or the other). It works fine for me.
The house has geothermal heating/cooling, electric cook stove etc. The 12kW provides 100 amp service to the house with no problems. We are in an area where the winter temperatures go down to -40C on occasion, though the coldest I have started it was at -28C. The generator has glow plugs in the heads and fires up well - even at low temperatures. The starting battery needs to be well looked after of course or no starting ability. The exhaust is vented outside through a proper exhaust through the side of the shed. There is also a grill in the side of the shed that directs the warm radiator air out of the shed through a louvered opening with an outside door.
The fuel tank is next to the wooden shed and is a household 275 gallon tank. Originall left unprotected, I built a shad around the tank to keep out the weather and it works just fine. The fuel in the tank was new when the generator was installed in 1999. I have treated it and topped up with new fuel as needed and have never had any problems.
I generally run the generator on house load for three or four hours every two months or so. This gives the engine a good workout and charges the battery properly.
The generator is adequate for our needs and has been great when we have been without power. I watch the load we use when on backup power and usually have a meter connected to watch the voltage doens't get too low (indicating dirty fuel filters).
For backup heating we have a propane furnace that is connceted to the air handling system for the house. I have had the geo unit down and used the propane to keep our house warm. It works but uses a fair bit of propane.
This setup works for me. Diesel is probably the easiest to get and store safely - winter or artic diesel fuel only. Propane would work too but in extreme cold conditions, uses a lot more fuel and then there is the problems of insufficient gas boil off at - 40C temps.
I can get some photo's and post if needed.
HTH
Jim

 

[grsthegreat]

Hi guys,
. The 12kW provides 100 amp service to the house

Jim

errr. actually this provides 50 amps, 240 volts.


but is sufficient for most uses you described