Buying Advice What is the best generator for our needs?

[Carl_NH]

catdiva,

If you have natural gas then Generac makes a decent 8-15KW whole house generator that is automatic and probably would be $3-5K installed.

But before you go any further you need to calculate your total amperage load. What concerns me is your well pump - 3-5 HP is a huge starting load and may be 3Phase as well.

The rest of your loads can be likely handled by a portable genset 6-8KW probably.

You should have a label on your pump control box stating the HP and amperage draw if you dont then have an electrical contractor that does generators come out and spec a system for you.

Mickey - OP said they have natural gas - that would be my first choice - its inexpensive and doesn't "run out"

Joshua - that was the first critical things they need to consider - I really find it hard to belaive too that they have a 3 or 5 HP thats huge and maybe 3 PHase too.

Carl

 

[BobRip]

I think the most important single thing to do first, is to find out what you really have for a deep well pump. If you do realy have a 3 or 5hp pump that totally changes what you would need for a genny.

I agree. My well pump is 1.25 HP and my 8 kw generator could not start it. I had to pull the pump and install larger wire. Well pumps take a lot to start since the pump must accelerate a long column of water. How deep is your pump? A shallow well is usually lower HP than a deep one.

 

[dave1949]

Grundfos makes some "soft start" well pumps that can help initial high amp. draws. They are also used in solar pumping applications for that reason.
SQ | Grundfos

Bob, have you ever had your generator output load tested? Do you know if does actually produce 8 kW?

 

[BobRip]

I agree. My well pump is 1.25 HP and my 8 kw generator could not start it. I had to pull the pump and install larger wire. Well pumps take a lot to start since the pump must accelerate a long column of water. How deep is your pump? A shallow well is usually lower HP than a deep one.

That is an 8kw continuous.

 

[BobRip]

Grundfos makes some "soft start" well pumps that can help initial high amp. draws. They are also used in solar pumping applications for that reason.
SQ | Grundfos

Bob, have you ever had your generator output load tested? Do you know if does actually produce 8 kW?

We tried an identical generator at the well head and it would start it. Of course the wire was shorter there. After upsizing the wire a 5kw generator will start it. Of course a better grade generator might work better.
My pump is down about 300 ft and the run to the house is about 100 feet. The chart the well guy had showed that 400 feet was the maximum allowed to run to my pump. So we were right on the edge. Just pointing out that there are many variables. To your point the quality of the generator is one of the variables.

I have not had the generator tested and I would love to have the soft start well pump. It seems silly to have to size the generator for the single load of a pump.

 

[dave1949]

We tried an identical generator at the well head and it would start it. Of course the wire was shorter there. After upsizing the wire a 5kw generator will start it. Of course a better grade generator might work better.
My pump is down about 300 ft and the run to the house is about 100 feet. The chart the well guy had showed that 400 feet was the maximum allowed to run to my pump. So we were right on the edge. Just pointing out that there are many variables. To your point the quality of the generator is one of the variables.

I have not had the generator tested and I would love to have the soft start well pump. It seems silly to have to size the generator for the single load of a pump.

Yep, there are variables. At my old house, if I used a 12 ga 50' lead cord on my table saw, it would trip the breaker when starting. Using a 14 ga 25' lead cord never tripped. Sam saw, same outlet, same breaker. I've only had my generator load tested once, it checked out. I have heard some brands/models do not meet their ratings, but how often do they get tested, probably hardly ever.

 

[Carl_NH]

BobRip,

There is no 1.25HP pump unless you have a unique pump/motor. Either its a 1 HP or 1.5HP. We have a 1.5HP set at 365' with #10 wire - it draws 22 amps 240V starting and 10 amps running.

Our 5700W running 7500W starting with 238V@60HZ would run it but struggled with other loads present, so I upgraded to a 7500W/10000W that has a voltage regulator and it runs at 237V @62HZ and seems to manage the load better.

So the power quality and wire size is important to run the heavy 240V loads and I decided to upgrade the generator to protect the pump ultimately as its more $$ to replace.

Carl

 

[meburdick]

I agree. My well pump is 1.25 HP and my 8 kw generator could not start it. I had to pull the pump and install larger wire. Well pumps take a lot to start since the pump must accelerate a long column of water. How deep is your pump? A shallow well is usually lower HP than a deep one.

Something was wrong if an 8kW generator couldn't start a 1.25 HP pump. That pump would require about 1kW to start.

OP - The best things you can do are as follows:

- Understand how much you'll need to operate the generator. Some areas are prone to power loss, some are not. The more it will be in operation, the more of a concern you will have for things like fuel efficiency and size.
- Do some online research for sizing a generator as it will help you to estimate what sorts of power consumption to expect.
- Write down the start and continuous operation needs for all of the equipment that you'll want in use while the generator is in use.

I have a very large house (2600 sq ft) and am able to run my garage door opener, most lights, well pump, oil-fired water heater, circulating fan for the wood stove, refrigerator, ceiling fans, and even some of the televisions off of a hard-wired 6250 continuous operation gasoline generator.

 

[meburdick]

BobRip,

There is no 1.25HP pump unless you have a unique pump/motor. Either its a 1 HP or 1.5HP. We have a 1.5HP set at 365' with #10 wire - it draws 22 amps 240V starting and 10 amps running.

Our 5700W running 7500W starting with 238V@60HZ would run it but struggled with other loads present, so I upgraded to a 7500W/10000W that has a voltage regulator and it runs at 237V @62HZ and seems to manage the load better.

So the power quality and wire size is important to run the heavy 240V loads and I decided to upgrade the generator to protect the pump ultimately as its more $$ to replace.

Carl

Carl,

That 62Hz will do a number on your pump. The voltage can be off by 10, 20, 30, even 40 volts without doing any major damage. But the Hz needs to be 60 dead-on to prevent damage to the items being run.

 

[BobRip]

BobRip,

There is no 1.25HP pump unless you have a unique pump/motor. Either its a 1 HP or 1.5HP. We have a 1.5HP set at 365' with #10 wire - it draws 22 amps 240V starting and 10 amps running.

Our 5700W running 7500W starting with 238V@60HZ would run it but struggled with other loads present, so I upgraded to a 7500W/10000W that has a voltage regulator and it runs at 237V @62HZ and seems to manage the load better.

So the power quality and wire size is important to run the heavy 240V loads and I decided to upgrade the generator to protect the pump ultimately as its more $$ to replace.

Carl

I checked the old pump and it is one horse power. Sorry for the error. It does seem strange that a one HP pump would not start on an 8 kw generator. I originally had a 4 kw and upgraded because it would not start the pump. The 8 kw worked fine until Isabel. The well guy did not find it strange that I had trouble starting it. I changed the pump at the same time I changed the wiring, so perhaps the old pump had issues.