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Whole House Generators: Generac Air Cooled?

300sniper

Gun Plumber
Joined
May 20, 2020
Member Number
695
Messages
417
Loc
Greenwood, CA
It's time to get the house backed up with a whole house generator and ATS. I'm tired of dragging out the portable and running extension cords when PG&E decides it might get windy.

I've got a 400a service, but one 200a panel is the garage and the other is the house. I am only concerned about backing up the house panel. We have a 2 ton, 3 ton and 5 ton AC. I don't think it's realistic to run them all off a "homeowner" sized gen, and I'm OK as long as we can run at least one of them. We have two refrigerators and a large chest freezer that absolutely need to be backed up as is our well. I haven't done a true load study, but I am thinking I should get a 24kw.

I deal with commercial liquid cooled Generac generators at work, but I've never dealt with the air cooled "homeowner" versions. With PG&E shutting of the power, sometimes for a week plus, are these aircooled gensets up for that kind of run time? Are they reliable when it comes to more than a few hours? Is it going to be worn out after a year of running for a week straight a few times? Stepping up to a liquid cooled pretty much doubles the price of the unit and it takes up quite a bit more space, two things I'd rather avoid.
 
It's time to get the house backed up with a whole house generator and ATS. I'm tired of dragging out the portable and running extension cords when PG&E decides it might get windy.

I've got a 400a service, but one 200a panel is the garage and the other is the house. I am only concerned about backing up the house panel. We have a 2 ton, 3 ton and 5 ton AC. I don't think it's realistic to run them all off a "homeowner" sized gen, and I'm OK as long as we can run at least one of them. We have two refrigerators and a large chest freezer that absolutely need to be backed up as is our well. I haven't done a true load study, but I am thinking I should get a 24kw.

I deal with commercial liquid cooled Generac generators at work, but I've never dealt with the air cooled "homeowner" versions. With PG&E shutting of the power, sometimes for a week plus, are these aircooled gensets up for that kind of run time? Are they reliable when it comes to more than a few hours? Is it going to be worn out after a year of running for a week straight a few times? Stepping up to a liquid cooled pretty much doubles the price of the unit and it takes up quite a bit more space, two things I'd rather avoid.

When power is out for a week, would you really need to run the thing 24 hours a day?
 
24kw is decent sized... what I'm getting at is that decent sized used gensets go for pennies up here, even cheaper if you're going with gaseous fuel
you can get an 8kw diesel, or a 30kw ng unit for basically the same price
 
When power is out for a week, would you really need to run the thing 24 hours a day?

My wife works from home, and I usually do unless I am out of town. We need it to run pretty much all day. We could shut it off for a few hours at night, but more than that, the temp in the refrigerators starts getting a bit high. I don't think trying to shut it off for a few hours at night would be worth the trouble.
 
[486 said:
;n134162]24kw is decent sized... what I'm getting at is that decent sized used gensets go for pennies up here, even cheaper if you're going with gaseous fuel
you can get an 8kw diesel, or a 30kw ng unit for basically the same price

It'll be propane, and new.
 
I have had a 16kw generac with ATS for about 4 years now. We lose power often and I have run it continuously for about a week at the longest. Average is about 8 hours when we lose power and it goes out at least 12 times a year, we're really rural and at the end of the line so generally are not a priority when they get out to repair the lines. Many of my neighbors have between 16 and 24kw generacs for many years longer than I've had mine and none of them have had any issues with them so that's why I went generac. I have not had to alter anything as far as my power usage when it goes out but I don't have whole house AC units. At most during the summer I only need 2 window units to cool it and it runs those fine. I am on a well and it powers that, my electric stove, dryer etc with no issues.

Just be aware it's not a completely seamless transition when you lose power. My unit waits about 30 seconds to confirm it's an outage and not a spike etc, then the genny powers up. It will run for about 20-30 seconds to warm up and then transfers power to the whole house. So far I have only done the single required oil change for it and then the oil looked as clean as when I put it in. This is on a propane power unit.



Edit: The power transition back to grid power is seamless. The only way I know it's back on grid is if I go outside and the genny is off.
 
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I have a 20kw air cooled generac on propane that came with my house. The PO had just installed it before she decided to sell so it was basically new when I bought the place. It's been trouble free and has come in handy quite a few times in the ~6 years I've been here. I had to run it for like 6 days straight one year when a tornado took down half the power lines nearby.

I had to talk the propane company in to giving me a 330 gal tank....their calcs only said I needed like a 120, but that doesn't leave a lot of reserve when you need to run it for extended times...and then you're stuck paying their outrageous winter rates.


One thing I'd recommend is getting the complete generac load panel replacement if it's an option. Mine was installed as a subpanel and it's just retarded. They took her for ride on it apparently...left the old zinsco panel and installed the generac sub panel next to it and extended all the circuits on the generator over to the sub. Stupid. You can get the whole house panel that has the transfer switch built in to it for like $400.
 
WARNING: THREAD HIJACK :grinpimp:


Timely thread to ask you generac people a question. I'm helping a buddy's daughter with a new prefab house shitshow (no planning-----they must have figured the house was just gonna fall into place).

What do I have to run between the generator and the transfer switch? Seems like about 7 conductors I think. Three for load sense and a few more for the generator to talk to the switch and tell it what to do.

Can all those wires be in the same cable or does the load sense ones have to be separate from the others?

What type of cable did you use? I've got to cross the entire 60 feet of house between the generator and the switch. I'm running the cable inside the house.

END HIJACK (thanks)
 
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It's time to get the house backed up with a whole house generator and ATS. I'm tired of dragging out the portable and running extension cords when PG&E decides it might get windy.

I've got a 400a service, but one 200a panel is the garage and the other is the house. I am only concerned about backing up the house panel. We have a 2 ton, 3 ton and 5 ton AC. I don't think it's realistic to run them all off a "homeowner" sized gen, and I'm OK as long as we can run at least one of them. We have two refrigerators and a large chest freezer that absolutely need to be backed up as is our well. I haven't done a true load study, but I am thinking I should get a 24kw.

I deal with commercial liquid cooled Generac generators at work, but I've never dealt with the air cooled "homeowner" versions. With PG&E shutting of the power, sometimes for a week plus, are these aircooled gensets up for that kind of run time? Are they reliable when it comes to more than a few hours? Is it going to be worn out after a year of running for a week straight a few times? Stepping up to a liquid cooled pretty much doubles the price of the unit and it takes up quite a bit more space, two things I'd rather avoid.

Read the specs carefully. That 24KW likely will only power up about 120 amps at full load. You'll have to do some load management most likely.
 
I have had a 16kw generac with ATS for about 4 years now. We lose power often and I have run it continuously for about a week at the longest. Average is about 8 hours when we lose power and it goes out at least 12 times a year, we're really rural and at the end of the line so generally are not a priority when they get out to repair the lines. Many of my neighbors have between 16 and 24kw generacs for many years longer than I've had mine and none of them have had any issues with them so that's why I went generac. I have not had to alter anything as far as my power usage when it goes out but I don't have whole house AC units. At most during the summer I only need 2 window units to cool it and it runs those fine. I am on a well and it powers that, my electric stove, dryer etc with no issues.

Just be aware it's not a completely seamless transition when you lose power. My unit waits about 30 seconds to confirm it's an outage and not a spike etc, then the genny powers up. It will run for about 20-30 seconds to warm up and then transfers power to the whole house. So far I have only done the single required oil change for it and then the oil looked as clean as when I put it in. This is on a propane power unit.



Edit: The power transition back to grid power is seamless. The only way I know it's back on grid is if I go outside and the genny is off.

Ours takes about 30 seconds once the main power is off. The engine fires up within 15 seconds of the power shutting off, gets up to speed in about 15 seconds and the transfer switch kicks over.
 
I have a 20kw air cooled generac on propane that came with my house. The PO had just installed it before she decided to sell so it was basically new when I bought the place. It's been trouble free and has come in handy quite a few times in the ~6 years I've been here. I had to run it for like 6 days straight one year when a tornado took down half the power lines nearby.

I had to talk the propane company in to giving me a 330 gal tank....their calcs only said I needed like a 120, but that doesn't leave a lot of reserve when you need to run it for extended times...and then you're stuck paying their outrageous winter rates.


One thing I'd recommend is getting the complete generac load panel replacement if it's an option. Mine was installed as a subpanel and it's just retarded. They took her for ride on it apparently...left the old zinsco panel and installed the generac sub panel next to it and extended all the circuits on the generator over to the sub. Stupid. You can get the whole house panel that has the transfer switch built in to it for like $400.

Ours is the 22kw on propane. I ran the calculations on the gallon per hour burn and checked that against the BTU per hour and it come out to 3.9 gallons per hour at full load. Also checked against cubic feet per hour. I also did that to size the gas line. We are close enough to the genset to only need 3/4" pipe. 10 more feet or two more fittings and that would jump up to 1".

We had them set a 499 gallon tank which holds 400 gallons. 500 puts us in an entirely different set of restrictions we couldn't deal with.


We checked the new panel with the built in TS. It was far cheaper albeit a fair bit more ugly to surface mount the transfer switch panel and gutter.
 
There are hundreds in Nevada County and not one complaint.

A dedicated 250 gallon tank isn’t out of the question.
 
We are a Generac dealer. The air cooled units are very reliable. In a case like yours where the load is questionable we’ll typically put in two air cooled units instead of one liquid cooled commercial unit. It’s not only cheaper to go that route, but the liquid cooled generac’s are not as reliable as the air cooled. If we do go the liquid cooled route, we typically steer the customer to a different brand.

For example, in a 2500 sqft house with geo we’ll install two 22kw air cooled units. One for the house and one for the geo.
 
WARNING: THREAD HIJACK :grinpimp:


Timely thread to ask you generac people a question. I'm helping a buddy's daughter with a new prefab house shitshow (no planning-----they must have figured the house was just gonna fall into place).

What do I have to run between the generator and the transfer switch? Seems like about 7 conductors I think. Three for load sense and a few more for the generator to talk to the switch and tell it what to do.

Can all those wires be in the same cable or does the load sense ones have to be separate from the others?

What type of cable did you use? I've got to cross the entire 60 feet of house between the generator and the switch. I'm running the cable inside the house.

END HIJACK (thanks)


I just run conduit and pull #12's because it's what I keep on the truck.

I think you can get away with #16 or #18 at that distance. You can get 7 conductor cabling at a supply house. Conduit will be cheaper though.

Read the damn install manual, it tells you exactly what to do.

I'm coming to hate all this new homeowner crap with WiFi and Bluetooth to do the start-up and config. Give me simple with a few jumpers I can set and forget and the homeowner can't fuck up.:flipoff2:
 
Ours is the 22kw on propane. I ran the calculations on the gallon per hour burn and checked that against the BTU per hour and it come out to 3.9 gallons per hour at full load. Also checked against cubic feet per hour. I also did that to size the gas line. We are close enough to the genset to only need 3/4" pipe. 10 more feet or two more fittings and that would jump up to 1".

We had them set a 499 gallon tank which holds 400 gallons. 500 puts us in an entirely different set of restrictions we couldn't deal with.


We checked the new panel with the built in TS. It was far cheaper albeit a fair bit more ugly to surface mount the transfer switch panel and gutter.

Mine has a high pressure (1/2"?) line from the tank to a main regulator at the house, and then splits off (still at higher pressure) to the various appliances, each with their own regulators. I'm assuming that because it's such a long run from the tank, they didn't wan't to run a new bigger low pressure line. Seems to work. Also makes adding new stuff easier since the HP line has plenty of capacity.


I did the same calcs. and I think mine had roughly the same burn rate. I figured I could run mine for a little over a week on a full tank as I'd rarely have it at full load.
 
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