Watts needed for generator to run a 1/2 HP sump pump?

[sixdogs]

I have a 10K/12K surge generator but there are times when I might only want to run my Wayne 1/2 HP sump pump off a smaller generator. I'm not sure if I can do this with a smaller portable Honda.

In searching the net, one site says a 1/2 hp sump pump needs 1050 watts to run and 3200 to start. I had planned to get the Honda 3200/2600 watt portable but now I'm not so sure that if that will work. I don't want to burn up the generator overloading it. There is no info with my pump.

Can anyone offer any insight on watts or generator to run a dedicated 120 line for a sump pump for power outage?

 

[coldsteelva]

You can reduce the in-rush peak current hit to your generator if you can wire a hard-start kit into the pump circuit. The same tech works to run AC systems off generator also.

 

[sixdogs]

You can reduce the in-rush peak current hit to your generator if you can wire a hard-start kit into the pump circuit. The same tech works to run AC systems off generator also.

Thank you. Can you explain more? This is over my head.

 

[coldsteelva]

Hyper Engineering | Single Phase

AC motors can require 6x the rated power to start up from a locked motor position. So for that first instant, the draw of power is much more than your small generator can supply and it will trip. Hard start kits are in-line capacitors to overcome that surge. There are also soft start kits, that spread that surge out, by starting the motor at a lower speed and then ramping up to 100%:

 

[sixdogs]

Hyper Engineering | Single Phase

AC motors can require 6x the rated power to start up from a locked motor position. So for that first instant, the draw of power is much more than your small generator can supply and it will trip. Hard start kits are in-line capacitors to overcome that surge. There are also soft start kits, that spread that surge out, by starting the motor at a lower speed and then ramping up to 100%:

How does this wire in? What do I do to switch back to plugging back in the wall to run normally?

 

[LittleBill21]

How does this wire in? What do I do to switch back to plugging back in the wall to run normally?

its a permanent modification, it doesn't hurt anything, just expensive

 

[ponytug]

Getting a soft or hard start added to your well will do you and your generator a favor. Your generator will live longer if it runs more than 50% or so load, as low loads tend to have both diesel and gasoline generators over fueled, which tends to foul engines.

So while your 10k can probably start your well just fine, the well alone probably is not going to be enough of a load to keep the engine rings in good shape. As @coldsteelva points out, that 6-10X surge implies a much larger generator, but isn't enough of a load to keep the bigger generator in good shape.

The only downside is the upfront cost, but the soft start will probably help the longevity of your well pump motor, and the hard start will help reduce any voltage drops around the property when the well pump kicks in.

All the best,

Peter

 

[MAX-24-Dean]

I have a 10K/12K surge generator but there are times when I might only want to run my Wayne 1/2 HP sump pump off a smaller generator. I'm not sure if I can do this with a smaller portable Honda.

In searching the net, one site says a 1/2 hp sump pump needs 1050 watts to run and 3200 to start. I had planned to get the Honda 3200/2600 watt portable but now I'm not so sure that if that will work. I don't want to burn up the generator overloading it. There is no info with my pump.

Can anyone offer any insight on watts or generator to run a dedicated 120 line for a sump pump for power outage?

For small inverter generators, in general the guidelines out of some of the older inverter generator manuals typically stated the following.

Pure resistive loads can be run at 100% of generator rating.
Incandescent lights or electric resistance heater fall under this catagory. No inductive loads.
So a 1000 watt inverter generator can run 1000 watts of these type of loads as there is no start up surge.

Power tools with can be used at 80% to 90% of the generator rating.
Depends on how the motor is wound, which effects the magnetic coupling ability of the power tool.

Motors can be used at 40% of the generator rating, this is dependant on how they are made. Motors loads are typically around 85 percent efficient.

To find the motor load that a 1000 watt inverter generator can safely start, we would use some simple math from the older manuals.
1000 watts x 40% = 400 watts.
400 watts x 85% (Motor efficientcy) = 340 watts.
The 1000 watt inverter generator can safely start a 340 watt motor load (according to these older manuals).
I would not try to start any motor under load using this math.

I have 2000 watt Yamaha and Honda inverter generators and use them on a 1/2 HP trash pump. They will start the pump with the outlet valve closed (no load). I then open the valve and it is not a problem to add pumping load to the motor.
I can't start the motor if the valve is open, which places to much load on either generator and they will stall out. Not good for longevity of the motor or the generator. Voltage sag=higher amps in inrush current.

I would never reccommend a 2000 watt gen. to start this load for a customer. I would tell them 4000 watt gen. is what they need as it will start the motor under load.
1/2 HP = 373 watts continuous. 373 x 10 = 3730 starting watts needed.

Some of the cheaper inverter generators do not start motors using the 10 times inrush rule of thumb. So your mileage may vary depending on quality of gen. set.

 

[tractortroof]

8500 watt generac gas generator will run that and much more. That’s the peak watts. It will not need a start assist on such a small motor. I run that dirt my whole house including 4 ton heat pump (definitely use start assist on that)

 

[masscity]

The well here is 85 feet deep with a 220V 3/4 hp pump. I bought a Champion 3500/4000 watt generator in 2008. It will run my well pump.

I think they quit making this generator, because 3500/4000 is too small for 220V in most cases. My neighbor and brother bought 3500/4000 right after, but they didn't have 220V anymore. The ones they bought had the RV plug.

 

[Deere Dude]

I run 2 submersible sump pumps at the same time, 1/3 HP each with my 3200 watt generator with no problems. I use them to fill tanks from a pond. 1/2 HP won't even slow it down even if starting under pressure.

 

[sixdogs]

I run 2 submersible sump pumps at the same time, 1/3 HP each with my 3200 watt generator with no problems. I use them to fill tanks from a pond. 1/2 HP won't even slow it down even if starting under pressure.

Do the two of them ever start at the same time? Is that the Honda generator?

 

[ponytug]

@sixdogs, Since there are substantial variations in starting draw amongst different motors/manufacturers, and especially with different loads (in this case the back pressure from the depth of the well and the house plumbing), and in the generator winding and overload control circuits, can I suggest that you borrow or rent a generator of the size/type you want to use to see if it meets your needs?

It just seems to me that once the discussion moves beyond "is it possible, at some point for one time?", the devil is going to be in the details, as above, and as well as other factors such as whether you have adjusted your generator to get the right voltage and frequency at the well pump.

I know enough cases where someone did manage to start a well pump a few times on their generator, only to burn out the generator windings after a half a dozen or perhaps twenty starts, so to me it is a horses for courses thing. Do you want to have this new generator start the well pump a couple of times, or do you want to be able to rely on it? What would be your backup if the generator that you are thinking of buying fails?

Just my $0.02... Good luck!

Peter

 

[sixdogs]

@sixdogs, Since there are substantial variations in starting draw amongst different motors/manufacturers, and especially with different loads (in this case the back pressure from the depth of the well and the house plumbing), and in the generator winding and overload control circuits, can I suggest that you borrow or rent a generator of the size/type you want to use to see if it meets your needs?

It just seems to me that once the discussion moves beyond "is it possible, at some point for one time?", the devil is going to be in the details, as above, and as well as other factors such as whether you have adjusted your generator to get the right voltage and frequency at the well pump.

I know enough cases where someone did manage to start a well pump a few times on their generator, only to burn out the generator windings after a half a dozen or perhaps twenty starts, so to me it is a horses for courses thing. Do you want to have this new generator start the well pump a couple of times, or do you want to be able to rely on it? What would be your backup if the generator that you are thinking of buying fails?

Just my $0.02... Good luck!

Peter

I want to rely on it to cover temporary and unexpected power loss when I don't want to fool with the bigger generator. I also don't want to burn the gen out, having done that years before.

I don't know where to borrow one but I'll look around and on Monday will call the maker of my sump pump just to see if they can offer any numbers. Thank you.

 

[Deere Dude]

Do the two of them ever start at the same time? Is that the Honda generator?

I have 2 submersible pumps in a pond in a couple feet into the water. When I ran them to pump water into tanks for watering our garden I would just plug them into the 110 port on the generator and switch on the 17 amp circuit breaker and they take right off. It is a 3200 watt John Deere generator maybe 30-40 years old. Valves were open at start-up.