Well pump draw creating a bit of a dilemma...

alyaz

Over the summer, with tons of solar we hadn't run into this before, but now that fall is here it has presented us with a bit of a problem.

Our well pump is a 240 volt pump. Generally (I don't have the exact voltage drop numbers or time when the pump is on) when it starts it pulls our voltage down enough (maybe half a volt or more) that the generator has started the last couple of nights. We have the start voltage for the auto start set at 24 v for 2 minutes. The pump draws for about four or five minutes so the diesel obviously starts and then runs for the set period of time.

Can you think a way around this, short of purchasing a newer/better/more efficient pump? Although that may need to be done. If I set the start voltage lower then I maybe run the risk of damaging the batteries over time. If I set the absorb run time lower then I run the risk of not giving the batteries enough of a charge when they may require it. Are my options to set the start time to a longer period, maybe 5 minutes/at or below 24 volts or is this fairly common and we just live with it?

Just a bit more background... For example today we had a fairly sunny day, so the batteries went through an absorb charge of 2.5 hrs via solar/charge controllers. Tonight, we have our showers and voltage is around 25. The pressure tanks empty and the well pump starts and the diesel gen starts. I know that once the well pump stops that the voltage would climb enough to get us through the night.

Right now the auto gen module is set using voltage parameters. Would adding a Magnum ME-BMK - battery monitor kit (so the auto gen parameters could be set up to read and operate from SOC) possibly help?

Hope this makes sense.

Looking for suggestions. Thanks.

Ralph Day

Re: Well pump draw creating a bit of a dilemma...

Your signature doesn't show your battery type. Are they flooded lead acid? If so, you should check the sg at "full" state of charge. An absorb of 2.5 hours might not be sufficient to really reach full soc. How old are your batts? With age comes reduced capacity.

Ral;ph

vtmaps

Re: Well pump draw creating a bit of a dilemma...

alyaz wrote: »

I know that once the well pump stops that the voltage would climb enough to get us through the night.

It sounds like your generator is starting because of a short term voltage sag. Setting a value for the start voltage for a generator (or low voltage disconnect) can be tricky. Too high a value and you start the generator on a brief voltage sag. Too low and you risk damaging the batteries. One thing that can cause a voltage sag is high resistance between the batteries and the inverter (undersized cables or a bad connection). If the resistance is in the batteries themselves, either they are in poor condition or you don't have enough battery capacity. For any AH capacity, an AGM battery will have less voltage sag than a flooded cell.

As Ralph Day asked: what do you have for batteries?

What to do? depends on your batteries and their SOC. If the SOC is high enough perhaps you can program the AGS to start after 4 minutes (rather than 2 minutes).

--vtMaps

waynefromnscanada

Re: Well pump draw creating a bit of a dilemma...

vtmaps wrote: »

It sounds like your generator is starting because of a short term voltage sag.

As Ralph Day asked: what do you have for batteries?

What to do? depends on your batteries and their SOC. If the SOC is high enough perhaps you can program the AGS to start after 4 minutes (rather than 2 minutes).

--vtMaps

My thoughts exactly! If you're batteries are sized for the job, are in good shape and properly charged to begin with, running a pump for just 4 minutes isn't going to take much out of them. What happens if you lock off you're generator, does the voltage come back up after the pump has been stopped for a while?

Blackcherry04

Re: Well pump draw creating a bit of a dilemma...

I use to have the same issues with a pump and pressure tank ( for 20 Years ). I finally got rid of the pressure tank and put in a 200 gallon vented storage tank with a 5 GPM ( 6 amps @ 12 V dc ) diaphragm pump to run the house. I now use the 240 V well pump as a opportunity load during sun hours. Using a well pump to pressurize a tank is a poor idea from the past, from on-grid folks.

I think this whole change cost around $200, best money I ever spent. Now I run the well pump once every 2-3 days for the same amount of time it use to run 5 times a day.

I divided the tank into thirds with float switches, so I always have 1/3 in reserve and a timer in series. Most people wouldn't need 200 gallons, the idea is to size the tank like a battery bank so you get a turn over of fresh water every couple of days.

Coach Dad

Re: Well pump draw creating a bit of a dilemma...

My System is very similar to yours... I run a 240V well pump 3/4HP that is feeding an 80 Gal pressure tank. When the pump kicks on, it runs for about 5 minutes.
I just reviewed the log data and see that the lowest voltage my battery voltage has been 24.18V...
It only dipped to 24.18 two times during raining weekends..
My normal battery dip in is around 24.58V

Here is a discussion that we had regarding load current on batteries..
http://forum.solar-electric.com/showthread.php?16082-Maximum-Battery-Load-Current
i doubled my battery bank after this discussion.

vtmaps

Re: Well pump draw creating a bit of a dilemma...

Blackcherry04 wrote: »

I use to have the same issues with a pump and pressure tank ( for 20 Years ). I finally got rid of the pressure tank and put in a 200 gallon vented storage tank with a 5 GPM ( 6 amps @ 12 V dc ) diaphragm pump to run the house.

How do you figure out what is the maximum size storage tank to use? If it is too large, the water may go bad. I imagine the answer depends somewhat on the water itself and the temperature of the storage tank (basement temp, room temp).

--vtMaps

alyaz

Re: Well pump draw creating a bit of a dilemma...

Thanks for all the feedback. I've added my battery bank details to my signature.

The batteries consist of twelve - 2 Volt Davidson flooded batteries. They are about 6-7 years old and have performed well since we bought the place about a year and a half ago. We hadn't run into this issue before because the previous owners did not have the pump running off the inverter. They would simply wait until one was having a shower and when the water pressure stopped they would yell to their spouse to turn on the Honda generator they had. Well the yelling here didn't last long and we had a cable pulled down from the inverter/house to the gen shed where the pressure tanks and well pump connections are located. We didn't even have this issue until we added the auto gen start module, as we would just watch the battery monitor when the well pump came on and (during summer and up until now) the draw never registered lower than about 24V on the monitor. This morning the batteries are at 25.4 V, which is quite typical of their voltage after a night. Soooo, other than the voltage sag during the pump draw last night, the voltage does bounce back to normal / operable levels.

I may call Davidson today and ask them about the four or five minute draw on the batteries (I'll actually time it today). Davidson's battery literature shows to recharge at 23.7 (I believe). I know that would not really help once we get into the winter months when the solar performs less and the battery voltage decreases. One more thing, battery voltage readings under load and at rest are quite different right? In my limited understanding, that suggests you could let the voltage drop under load - to say 23.7 V, safer than to the same level at rest, for short periods?

And is there any merit in this scenario? Setting up my gen parameters to start say at 24 V but once absorb mode is reached to cycle off after cool down? And then ensure that I run a proper / full absorb cycle at least once a week?

Blackcherry04

Re: Well pump draw creating a bit of a dilemma...

vtmaps wrote: »

How do you figure out what is the maximum size storage tank to use? If it is too large, the water may go bad. I imagine the answer depends somewhat on the water itself and the temperature of the storage tank (basement temp, room temp).

--vtMaps

If you store it in the dark, 10-12 days would be fine. If longer you'd probably want a dosing pump or Ozone or UV system to keep it safe. I turn mine over every 2-3 days. I also have a dump valve in the bottom of the tank, when in doubt, I dump it and start over.

It's all about payback and cost over time. A Well pump just uses to much of the energy ( 60-70 % ) creating pressure in the system and starting it's self in off-grid for me. It took a long time for me to figure it out ( hard head ).

Here is the usable volume on a 80 gallon bladder tank . Do the math on your GPM flow.

80 gallon tank at 30/50 pressure holds 26.58 gallons.
80 gallon tank at 50/70 pressure holds 20.31gallons.

techntrek

Re: Well pump draw creating a bit of a dilemma...

Sounds like you need a delay timer. If your current system doesn't have a setting for this you could add one between the genset controller and the genset. Find a timer that will delay the start by 5-10 minutes, and reset the countdown if the start signal is lost (assuming your controller sends a constant "on" signal).

alyaz

Re: Well pump draw creating a bit of a dilemma...

Here's where I'm at with the well pump issue...

The Magnum ME-ARC remote when hooked to the Magnum ME-AGN -N (network version) through the Magnum PAE4024 inverter/charger allows setting the gen to start based on amp draw, voltage, time, temp, and even SOC if you have the Magnum Battery Monitor. Anyway, seems you can set parameters in more than just one area. So I have it set up now so that the genset will start if either:

voltage drops below 24V for two minutes - then the gen will start and go through a full absorb; or
if amp draw exceeds 45 amps for 15 seconds (well pump seems to draw about 85 amps for about six minutes) then gen will start and only run until amps drop below 30 amps for two miinutes.

Anyone have a similar setup and/or see any issues with this?

thanks...

BB.

Re: Well pump draw creating a bit of a dilemma...

Part of it depends on how long you want the genset to run and how much "help" your solar panels need...

A 1,065 AH @ 24 volt battery bank should be able to discharge very nicely at C/8...

1,065AH/8H rate = 133 Amps

So, if your total load on the battery bank is less than 133 amps--I am not sure you would want to start the generator--Especially if it is only for 6 minutes at a time.

85 A * 24.5 volts = ~2,083 watts

You have a ~2kW of solar panels connected anyway--So if the pumping is done during daylight hours, the load on the battery bank is much closer to 500-600 watts (if you assume ~0.77 solar array derating).

Do you have programmed cycling for your genset--I.e., once a week for 10-20 minutes--Do some well pumping/irrigation/washing/etc. at the same time as your generator cycling so you are not "wasting" fuel.

Note--I am "on grid" and no wells... So this is my two cents worth on the issue.

-Bill

alyaz

Re: Well pump draw creating a bit of a dilemma...

Great info, thanks Bill.

Coach Dad

Re: Well pump draw creating a bit of a dilemma...

BB. wrote: »

A 1,065 AH @ 24 volt battery bank should be able to discharge very nicely at C/8...

1,065AH/8H rate = 133 Amps

So, if your total load on the battery bank is less than 133 amps--I am not sure you would want to start the generator--Especially if it is only for 6 minutes at a time.

I agree with Bill...
You should use your SOC % to determine when to start your generator...
For example if you get below 70% SOC...
Since the magnum has a 105 Amp changer you can get the batteries back to a reasonable SOC in an hour and then let the Solar take over when the sun comes out.

alyaz

Re: Well pump draw creating a bit of a dilemma...

Coach Dad wrote: »

I agree with Bill...
You should use your SOC % to determine when to start your generator...
For example if you get below 70% SOC...
Since the magnum has a 105 Amp changer you can get the batteries back to a reasonable SOC in an hour and then let the Solar take over when the sun comes out.

My new ME-BMK is sitting at the USA/Canada border and I'll be picking it up later this week. Once it's installed I see this 'pump' thing a lot easier to manage. :-)

Blackcherry04

Re: Well pump draw creating a bit of a dilemma...

I don't think anyone would argue with using SOC as a basis to start a recharge, but not always. Knowing your loads, their timing, the amount of re-charge potential you have and the amount of generator current available are all factors of when you recharge. If your generator is maxed out just trying to recharge it's one thing, if a recharge only uses 50% of your generators potential, it's another. Sure it's a dance to keep up with your energy use and it all goes out the window when your mother in law arrives for a week visit. I found that anticipating loads in advance a smart strategy. Running a generator for 30 minutes in the early evening may be better than having it run when your trying to recharge and wasting power at the wrong time. If your at 100% of SOC it's one thing, If you get out of Bulk and have 85% to start with it's another. Being at 60% at 6:00 in the morning, may not be a big deal depending on the anticipated weather for the day. If it's a no sun day, it might be a big deal. Seems like with a 10 KW generator you have power to spare and should use it to it's full potential. The AGS systems do not have enough perimeters to keep up with all factors. I'd use it as my fail safe and try to balance all I had. As your batteries age it all changes and so must plan.

What I did was track on a spread sheet my hourly use for a few month's and came up with a hourly usage numbers against the SOC and adjust it seasonally. Some of the loads will surprise you over time, early evening is the highest in my house with early morning second. When my kids were around, it was a killer as soon as they got home. Parasitic loads that run 24/7 is a area that you can trim some if you figure them out, of course the Refrigerator is the largest, with the TV and Satellite second for me. Anything with a " Remote " should be on a power bar and cut off when not in use.

Having a good idea of the cost of run time on your generator is a factor that you need to work out. I have a 20 KW and it's was planed at $10 a hour with some maintenance figured in. Replacement and catastrophic failure is hard to figure. I also have a smaller back up that will carry my full battery recharge load.

Heating is a huge factor that has go into figures as winter is closing in. Short days and limited sun. Working out a plan is a good idea.

Remember, if it was easy, everyone would be doing it.

alyaz

Re: Well pump draw creating a bit of a dilemma...

wrote:

Remember, if it was easy, everyone would be doing it.

haha... copy. yes, as i get to know my system better, i'm starting to understand that it's a living breathing thing and one setting isn't going to cut it. thanks.

Blackcherry04

Re: Well pump draw creating a bit of a dilemma...

alyaz wrote: »

haha... copy. yes, as i get to know my system better, i'm starting to understand that it's a living breathing thing and one setting isn't going to cut it. thanks.

You'll learn overtime, a lot is trial and error. One thing here, most of us have made all the errors, so you won't have to. There so many variables from system to system, you can take two identical systems 10 miles apart and they can act very differently. Your loading and attention to detail will make a huge difference in the performance of your system. I have a system and a half, if my main goes down or is running behind I can shift loads to the other system and take up the shortfall with the flick of a switch. I did that instead of adding to one system that would have been larger, but not as flexible and dependable. Gas was a $1.00 a gallon when I designed my original system, if you make changes, make the ones that make sense, my 20 kw generator doesn't run much these days, if at all. It did teach me good load management. Good Luck to you as you learn about your system.