Generator Sizing

[RSKY]

I have just about made up my mind to buy a Rigid 6800-watt (8500-watt surge) generator. It has a Yamaha engine and electric start.

My question is, can anyone convince me that this is too small for my uses. I have gas central heat with an electric blower, also have one of the Mitsubishi heat pumps in the sunroom. I heated for nearly three weeks during 2009 with two sets of gas logs. I have a gas hot water heater.

During the 2009 ice storm I bought the only thing I could find which was a Chinese made 3500/4000-watt pull start. With extension cords covering the floor we were able to run the freezer, both fridges, and the TV or what ever else we needed. Just could not run everything at one time. The little generator ran under nearly full load for 17 days being stopped only to refill gas and change the oil.

Can I run a 3.5 ton central unit with the Rigid 6800-watt genset?

By my calculations I can run everything else but the central air. Am I wrong?

Thanking the people in advance who are more knowledgeable than I on this subject.

RSKY

 

[Travelover]

The hard part seems to be estimating or even measuring the surge / starting load of a given device. I'm curious to see how others have done this.

 

[nc redneck]

I seriously doubt it. I have 16 KW whole house generator and had to install hard start kit to run my 5 ton AC unit. 65 amp start up load for ac and gen set would not kick it over.

 

[DonW]

In fact, the surge will probably damage the unit unless controller has safety shutdown. If your house does not have gas hot water, stove, heat, etc, you need 12K at minimum, and if house is all electric, will have to monitor the house electric hot water heater and electric stove usage (do you have own water pump or city water?). If not installing back-up generator (propane or natural gas) with weekly starts, then get a good used diesel. Today's gasoline gums-up very quickly. So when you need it, the **dang** thing won't start!!! Just bought used 12K commercial diesel with 400hrs for less than price of new gasoline unit. If your area is prone to losing electricity, get 1800 rpm diesel, not 3600rpm. Much longer life and better resale value. Many school systems used these diesel units as emergency power; now available used. Diesel fuel is considerable more stable than gasoline. Ebay has new 10K gasoline generators for around $1000 (not commercial grade). Used units can be found for much less. Remember to keep the starting-battery on good quality charger/maintainer/desulfator (disconnect when starting engine). Exercise the unit on regular schedule. Don't depend on a 6800 watt generator for much more than light duty use.

 

[techman]

Your gas heat should be okay, with the possibility that some of the newer units do not like the "dirty power" common with most gen sets of this type. Power wise should be no problem. The Mits heat pump is a mini-split which again should not pose a big problem. The only issue would be starting the blower when the heat pump is running and visa-versa. I have a 10KW diesel and run the whole house, except for the range and hot water heater. That includes 3 zones of heat pumps, 2 fridges and a freezer.

You should be able to handle the inrush of each unit individually.

paul

 

[kenmac]

That 6800 watt generator will never start that condenser. You'll have to have at least a 15 kw to do that. If you have elec range you and dryer you'll have to add the amps to see if the gen set will run them. You shouldn't have a problem running every thing that's 110

 

[grsthegreat]

Ive installed lots of gensets over the years. I have a 5,000 watt Onan hooked to a 3,800 SF house that has gas heat, gas water heater and gas stove. This 5,000 watt can light all lights on house, run freezer and referig, garage door openers, and fan unit on gas furnace, plus assorted tv's etc. What it wont do is power up a deep well or run an air conditioner. Then again, you can live without a/c. But not a well.

Generally speaking i install 15KW units when a well is used. Here in north idaho we dont worry about a/c .

 

[ModMech]

Our Hobart welder/generator can handle two of our three heat pumps, it depends a LOT on their ton rating and efficiency. If we want hot water, we need to use the gas grill if any of the heat pumps are running unless it's at night with all the lights/computers/etc off.

 

[ronjhall]

I ran our whole house on a 5000 watt Honda generator. That includes 1/2 hp water pump and furnace. We now have a 12KW whole house generator. It will run everything except the electric over. This includes a 2 ton AC. I doubt if a 6800 with power your AC or heat pump.

 

[buickanddeere]

As previously stated 15Kw may or may not start that 5HP compressor . Then there is the condensor fan and evaporator fan.
Do you own a tractor? A 20KW pto powered generator is minimum to operate your home.