Pump and hot water generator question

[ayr]

I have a 5500W Generac portable generator, 30 amp. We recently had an interlock switch installed on our panel with a 50 amp reciprocal in case we upgrade our generator in the future, and purchased an adapter for our generator to plug in to that. My main question is how would I run hot water in the house with having a well pump and an electric hot water heater? I know I can run the pump on its own, but in the winter we may need hot water. I don't believe I can run them both at the same time with the power I have with this generator. And I can't find a good clear breakdown on steps, nor do I know exactly how the mechanics of my house works. Do I run the pump so the water heater fills up (is that even what happens? And how would I know when it's filled?), then turn off the pump and run the hot water for 'X' amount of time so the water in it heats up, then turn that off and turn back on the pump to use that hot water?

 

[peakbagger]

If I understand your question, you want to heat the hot water with an electric hot water heater using a generator to supply the power? That is rarely done as its big load on the generator (4500 watts typically).

In most older homes, the well pump pumps up to a bladder type expansion tank somewhere in the house until it is up to pressure, than it turns off. The bladder in the expansion tank is now pressurized liek a ballon and pushes water out of the tank to whatever household use you want including hot water. The electric hot water tank is normally always full. Heat rises so the hottest water is on top of the tank. There is a cold water line that runs into the top of the tank but is usually internally piped to the bottom of the tank. If you open a faucet, the hot water from the top of the tank is pushed to your faucet outof the ot water heater via cold water from your well expansion tank. When the pressure on the discharge of the expansion tank drops below a low set point the water will stop flowing out the faucet (unless its below the water heater). Most hot water heaters have some storage volume so you could just alternate between running the pump until the tank is full and then switching on the water heater. If both are drawing power at the same time your generator will trip.

In newer homes there is most likely a pump driven by a variable speed drive in the well. It varies its speed to supply steady pressure in the house via a special pump control in the basement. There is usually a very small expansion tank on the cold water line the size of basektball for other reasons but with this type of setup the pump would need to be powered whenever water is being used in the house. Generally power electronics like variable speed drives do not like generator power unless its a somewhat more expensive inverter generator.

 

[ayr]

If I understand your question, you want to heat the hot water with an electric hot water heater using a generator to supply the power? That is rarely done as its big load on the generator (4500 watts typically).

In most older homes, the well pump pumps up to a bladder type expansion tank somewhere in the house until it is up to pressure, than it turns off. The bladder in the expansion tank is now pressurized liek a ballon and pushes water out of the tank to whatever household use you want including hot water. The electric hot water tank is normally always full. Heat rises so the hottest water is on top of the tank. There is a cold water line that runs into the top of the tank but is usually internally piped to the bottom of the tank. If you open a faucet, the hot water from the top of the tank is pushed to your faucet outof the ot water heater via cold water from your well expansion tank. When the pressure on the discharge of the expansion tank drops below a low set point the water will stop flowing out the faucet (unless its below the water heater). Most hot water heaters have some storage volume so you could just alternate between running the pump until the tank is full and then switching on the water heater. If both are drawing power at the same time your generator will trip.

In newer homes there is most likely a pump driven by a variable speed drive in the well. It varies its speed to supply steady pressure in the house via a special pump control in the basement. There is usually a very small expansion tank on the cold water line the size of basektball for other reasons but with this type of setup the pump would need to be powered whenever water is being used in the house. Generally power electronics like variable speed drives do not like generator power unless its a somewhat more expensive inverter generator.

Yes, you understood correctly. Thank you for this breakdown. Our house is pretty old so I'm assuming it runs as you described. And it sounds like it would be possible to run one at a time to supply some hot water to the house if needed. I'm just trying to be prepared for this winter as we tend to get power outages that can last 4-5 days, and I have infants in the house. Hopefully we wont need to run hot water, and if water is needed just run the pump for a bit. But in the event we need hot water from a faucet I wanted to understand how to accomplish that and if it was possible. We have the Generac 5939 model, and it's labeled as 5500W with max ac. watts at 6875. Just learning to familiarize myself with all of this, so I believe it can handle the load from the hot water heater. Although I have read places that the generator may be running at about 80% of that capacity realistically - which may be an issue.

This might be a whole other box of worms, but do you by any chance know anything about a bonded neutral vs floating neutral generator? We had a technician come out recently and convince us that it would be better, and more cost effective, to install an interlock kit to our panel over a transfer switch. We went ahead and had that work done and there's a reciprocal on the outside of the house so we don't need to run a line inside anymore. But I came across a post on here mentioning that most portable generators are bonded neutral and will have issues if you try to hook it up to the house until you have a transfer switch. So I'm concerned our generator wont even work with the panel now, or that I'll cause an issue if I try to plug it up to test.

 

[Montanalocal]

I have got a generator hooked to my whole house with an interlock transfer switch. In an outage, before I start the generator and flip the transfer switch, I go to the main house breaker box and flip off both the well and the electric hot water heater breakers. Then when the generator is up to speed and transferred to the house, I go back and flip on either the well breaker or the hot water breaker, whichever is needed, but not both at the same time.

 

[peakbagger]

Sorry, I know basic electrical, but a pro would need to answer.

 

[ayr]

I have got a generator hooked to my whole house with an interlock transfer switch. In an outage, before I start the generator and flip the transfer switch, I go to the main house breaker box and flip off both the well and the electric hot water heater breakers. Then when the generator is up to speed and transferred to the house, I go back and flip on either the well breaker or the hot water breaker, whichever is needed, but not both at the same time.

Can I ask what capacity generator you have? This was the process I was thinking of doing, but thought I'd need to turn off all breakers before turning on the generator. Just so the fridge and other items weren't kicked on first. I need to walk around and jot down numbers on what each device is going to need, but I imagine I could only run the pump and something smaller at the same time. And maybe only the hot water heater by itself.

 

[Montanalocal]

Can I ask what capacity generator you have? This was the process I was thinking of doing, but thought I'd need to turn off all breakers before turning on the generator. Just so the fridge and other items weren't kicked on first. I need to walk around and jot down numbers on what each device is going to need, but I imagine I could only run the pump and something smaller at the same time. And maybe only the hot water heater by itself.

I have a 9 Kw generator. I only turn off the pump and the hot water heater. Both because they are large loads, and because the come on and off automatically by themselves. I leave all the other breakers on. When I throw the double-pole double-throw transfer switch, the generator motor rpm reduces slightly for an instant when the load hits it, but then comes right back up. Been doing this for years, it seems to work fine.

 

[EbS-P]

5kw generator IMO is not big enough to run the water heater with out manually managing the load. Ie turn everything off but a light or two and then turn the on the water heater. Once it’s up to temp flip it off and the pump on.

You could consider upgrading to a heatpump hot water heater. Those run 600watts in heatpump only mode. Pay back time for them is quite quick if you use a lot of hot water.

 

[mcdougy]

There are some big generators for sale at Costco and the price is hard to beat....

 

[maple1]

How big is your water heater? If it's up to temp when the power goes out, you will still have hot water stored in it. Be sparing with it and it should last a couple days. Otherwise, you will likely need a bigger generator. 5500 would be marginal with just the water heater going and everything else off at the breaker. You might get by doing it like that but might be close. May possibly be able to do it, then turn heater breaker off once up to temp and turn the pump on. I'd likely try it first before upsizing the generator. You could get a thermometer with a remote probe/sensor and tuck the sensor against the tank under insulation where you can get at it, to give you and idea how water temp inside is doing.

If you have a deep well submersible water pump, you might also be marginal on starting that too.

Big generators are very thirsty. Bad news in an extended outage.

 

[EbS-P]

I do think one must decide if a power outage is an inconvenience or an emergency. And that decision/designation can change during the event. You just need to know what the the criteria are and respond accordingly. Hot water during an outage would be a luxury for us. Just like AC would be in the summer. But if you get a water leak inside sure the summer any outages more than 2 days post leak probably would be an emergency as mold could become an issue. And at some point emergency becomes disaster and that’s why we carry insurance.

 

[rwhite]

Is your cook stove electric as well? We have an electric hwh but propane cook stove. During outages we heat pots of water on the stove or wood stove and just do hobo baths.

 

[Highbeam]

Almost all electric water heaters are 4500 watt and 240 volt. It’s a straight resistance load with no surge. Any generator rated for 4500 or more watts “continuously” is adequate. The trouble with an interlock is that unless you turn off all of the other breakers, something could come on like a refrigerator so I prefer an extra couple thousand watts above the 4500.

I just looked at a Costco firman generator. Tri fuel and 6400 watt continuous rating on propane. That’ll do it.

I also have an interlock and an electric water heater. I don’t need hot water badly enough to keep a big 6400 watt fuel hog running. I would like the big fuel hog for occasional hot water heating and the rest of the time a little 2000-3000 inverter for quiet, efficient, powering of low wattage essential loads like refrigerators and televisions and charging the teenage daughters’ phones!

 

[Highbeam]

As far as pump and hwh, you make sure you have pressure in the plumbing and then “charge” the water heater. Then shut off the hwh and flip on the pump for your shower. You have 40-50 gallons of hot water before the hwh tank needs a recharge.

My hwh goes from 50 degrees cold to 120 degrees in about an hour.

 

[maple1]

Almost all electric water heaters are 4500 watt and 240 volt. It’s a straight resistance load with no surge. Any generator rated for 4500 or more watts “continuously” is adequate. The trouble with an interlock is that unless you turn off all of the other breakers, something could come on like a refrigerator so I prefer an extra couple thousand watts above the 4500.

I just looked at a Costco firman generator. Tri fuel and 6400 watt continuous rating on propane. That’ll do it.

I also have an interlock and an electric water heater. I don’t need hot water badly enough to keep a big 6400 watt fuel hog running. I would like the big fuel hog for occasional hot water heating and the rest of the time a little 2000-3000 inverter for quiet, efficient, powering of low wattage essential loads like refrigerators and televisions and charging the teenage daughters’ phones!

I ordered a Champion 4500 inverter gennie from Costco during Fiona. Took a couple weeks to get here. Then a couple more weeks for me to get to unboxing it. Found the plastic bottom on it had a big crack in it. No box damage. Tried to get a replacement but out of stock. Dang it, I really wanted that gennie. They took it back no questions. Tried to talk them into letting me keep it 'as is' at a discount, but they didn't want any part of doing that.