New, larger well pump installed - too large for current wiring

Users who are viewing this thread

Jim Goodman

JEG in Raleigh
Messages
48
Reaction score
5
Points
8
Location
Raleigh, NC
I have an 800' deep well with an 8" casing. The water level is 30' below the top of the casing. When the house was built, the well contractor installed a 230 volt, 3/4 hp well pump that put out 8 gal/minute that was set at 300'. The well pump was failing and never provided enough water. So, I just had a new well pump installed a couple of days ago....a 1-1/2 hp Grundfos, SS, 230 volt, 10 gal/minute set at 500'. It puts out plenty of volume at a high enough pressure. So, the day after the pump install, I was watering some plants with the hose going full blast, and suddenly, after about 20 minutes, I lost all water pressure. My 44 gallon pressure tank is in the house a few feet away from the main panel. It turns out there is only a 14 AWG wire running from the panel out to the well, 120 feet away. The pump installer of the new pump ran 8/2 wire down the hole to the pump....so I have a 14/2 wire coming from the panel feeding an 8/2 wire down the hole. When I lost water pressure, the thermal overload safety on the pump had tripped, protecting the pump. It is impossible, without cutting and jack-hammering my concrete carport floor and driveway, to get a new 8/2 or 6/2 wire into my panel. But, my meter base, with an existing sub-panel is remote from the house, and is about 75' from the well, and unobstructed by concrete. A trench can easily be run from the meter base to the well, and a new sub-panel can be installed by the well, so, that is what I'm gong to have done to feed power to the well with 8/2 wire.


Here is my question; my pressure tank and pressure switch are still in the house. Can the 14/2 wire currently running from the pressure switch to the pump be converted to activate some sort of relay that would turn the pump on when the pressure tank calls for it? My concern is, if the wire to power the pump is not coming directly from the pressure switch, but instead is coming from the new remote sub-panel, how does the pressure switch activate the pump to turn on? I've read about "pump start" relays. Is that what I would use?
 

Reach4

Well-Known Member
Messages
38,798
Reaction score
4,412
Points
113
Location
IL
Here is my question; my pressure tank and pressure switch are still in the house. Can the 14/2 wire currently running from the pressure switch to the pump be converted to activate some sort of relay that would turn the pump on when the pressure tank calls for it?
Yes.
  1. Your 44 gallon pressure tank may be now a little undersized.
  2. You should perhaps have a 15 gpm Dole valve to avoid upthrust, but you could reduce the potential need for that by setting your pressure switch to 50/70.
img_1.png
 
Last edited:

Jim Goodman

JEG in Raleigh
Messages
48
Reaction score
5
Points
8
Location
Raleigh, NC
Yes.
  1. Your 44 gallon pressure tank may be now a little undersized.
  2. You should perhaps have a 15 gpm Dole valve to avoid upthrust, but you could reduce the potential need for that by setting your pressure switch to 50/70.
View attachment 54316
Thank you. Couple more questions:

1. The pump you identified is indeed correct. Sorry for my ignorance, but why would my pressure tank be too small with the new pump? There are only 2 of us living in the house and our usage on average is 100 gallons per day and our daily usage is not changing. If the actual water storage capacity in a 44 gallon tank is 14-15 gallons (usable amount, maybe 8-10 gallons each time the pump cycles on?), then I think the pump would be cycling on 12-15 times per day. I have a 40/60 pressure switch that is set at 45/65. Are you suggesting I might need a bigger pressure tank because the new pump will fill the current tank too quickly and the cycle-on time will be too short and hard on the pump? According to the manual, the maximum number of starts per hour is 100, and the maximum per day is 300.

2. If I install a Dole valve, I'm guessing it would limit the upper pressure level and slow down the filling of the pressure tank, thereby allowing the motor to run longer and more efficiently during each filling of the pressure tank, is that correct? Why would I use a 15 gpm Dole valve instead of a 10 gpm one, since the pump is rated at 10 gpm? Can I install the Dole valve right before the pressure tank or do I need to be out at the well?

Thanks for your help.
 

Reach4

Well-Known Member
Messages
38,798
Reaction score
4,412
Points
113
Location
IL
1. The pump you identified is indeed correct. Sorry for my ignorance, but why would my pressure tank be too small with the new pump? There are only 2 of us living in the house and our usage on average is 100 gallons per day and our daily usage is not changing. If the actual water storage capacity in a 44 gallon tank is 14-15 gallons (usable amount, maybe 8-10 gallons each time the pump cycles on?), then I think the pump would be cycling on 12-15 times per day. I have a 40/60 pressure switch that is set at 45/65. Are you suggesting I might need a bigger pressure tank because the new pump will fill the current tank too quickly and the cycle-on time will be too short and hard on the pump? According to the manual, the maximum number of starts per hour is 100, and the maximum per day is 300.
The actual drawdown in practice is about 25%, or 11 gallons. You could test this. Stop using water while the pump is running. When the pump stops, see how many 5 gallon buckets you can fill before the pump kicks on again.

Your pump will be filling at about 14 gpm. Rule of thumb is that you size the tank at about 4x that or larger. 44 is not that much smaller than 56, but if you ever need a new tank, then consider upsizing.

2. If I install a Dole valve, I'm guessing it would limit the upper pressure level and slow down the filling of the pressure tank, thereby allowing the motor to run longer and more efficiently during each filling of the pressure tank, is that correct? Why would I use a 15 gpm Dole valve instead of a 10 gpm one, since the pump is rated at 10 gpm? Can I install the Dole valve right before the pressure tank or do I need to be out at the well?
It would not limit the maximum pressure. When the water level is at 30 ft, the pump is going to be pumping a lot more gpm. Look for upthrust. I am not a pro, and I have no relevant experience. Somebody may tell you that you have no need to worry about upthrust. In that case, don't worry. A Dole valve is a flow limiter, for preventing that upthrust. Search out the term with regard to submersible pumps. Dole valves come in 13.5 and 15 GPM around your area of pressure interest.

If your pump kicks on at 50 psi rather than 40, then there would be less upthrust. That does reduce the drawdown of the pressure tank some, however.
 

Jim Goodman

JEG in Raleigh
Messages
48
Reaction score
5
Points
8
Location
Raleigh, NC
That helps, thanks a lot. I will raise the pressure on the pressure switch to 50/70 I did talk to the well pump installer today after receiving your email and he said my pressure tank was large enough. FYI, here is his response:

PUMP GUY - Your 44 gallon tank is enough. You shouldn’t need any dole valve at all. Unless you put one in that restricts the flow to exactly what the well produces. That way you only pump what the well produces.

ME - So the water column above the pump is 470’ high. Just making sure that’s OK with regard to upthrust

PUMP GUY - It will work no problem. The water level is most likely lower than that. It would be best to have a variable speed pump in that well to mitigate some of that.

ME - Well, I can’t do that now. This is why I was asking about a Dole valve.....would it mitigate some of the pressure differential

PUMP GUY - It would. The problem is if the water level is high and you are restricting the pump to low flow then you will be on the right hand side of the pump curve. As the water level goes down you begin to move to the left of the pump curve. We mostly plan for the worst case scenario when we size pump. Being we figure the water level at whatever the lowest point is. There really is not an ideal pump for a low yielding well except if you could, like I said, put a variable speed pump in.
 

Reach4

Well-Known Member
Messages
38,798
Reaction score
4,412
Points
113
Location
IL
PUMP GUY - Your 44 gallon tank is enough. You shouldn’t need any dole valve at all. Unless you put one in that restricts the flow to exactly what the well produces. That way you only pump what the well produces.
The first two sentences are perhaps right. Last two, no.

It is possible that your line from the pump to the pressure tank is small enough that it is not going to be pumping enough for upthrust problems anyway. Plus the pumps can put up with some amount of upthrust.
ME - So the water column above the pump is 470’ high. Just making sure that’s OK with regard to upthrust

PUMP GUY - It will work no problem. The water level is most likely lower than that. It would be best to have a variable speed pump in that well to mitigate some of that.
You don't want a variable speed pump.

Wait until some actual pump guys comment. Don't go out and get a Dole valve right now. I may well be overly-concerned, but concern may be reasonable. But cranking up the pressure switch to 50/70 (about 3.5 turns CW on the 3/8 nut on the big spring adds about 10 psi to both cut-in and cut-out) is free. Then up your air precharge to 48 psi. Air precharge is set with water pressure near zero.
 

Valveman

Cary Austin
Staff member
Messages
14,599
Reaction score
1,296
Points
113
Location
Lubbock, Texas
Website
cyclestopvalves.com
I don't think the #14 wire will cause the overload to trip. You can actually run a 1.5HP on #14 wire as long as 190'. It will work like a reduced voltage soft starter and should not trip the overload. If it did trip the overload, it would be on start up. Since the pump was running when it tripped the overload, I am guessing it is a flow issue and the motor is not getting cooling. If the pump is set below where the water comes into the well, it is top feeding the pump, and the motor will get hot. Do you know if the well is cased, or where the water is coming into the well?

Upthrust will be a problem. It doesn't matter that the pump is set at 500', it is still only lifting from the water level of 30'. So you have a pump designed for 500' with only 145' of head on it. The only time it will see 470' of head is when the water level has been pulled down to 370'. Having such a deep set pump is such a shallow well means there will be 230 PSI on the CSV and the pipe before the CSV.

Yes a CSV helps with upthrust. But you have gotten such an over sized pump it will take two CSV1A valve to bring it down from 230 PSI to 50 PSI. And yes a CSV works with a pressure tank.

Explanation for a second grader is to find out why it is tripping the overload, because the #14 wire isn't the problem. I am thinking the pump is set too deep to get cooling from below the motor.

Also see our video as to how a CSV works here.
 

Jim Goodman

JEG in Raleigh
Messages
48
Reaction score
5
Points
8
Location
Raleigh, NC
Cary, thanks for your reply. I don't understand what you are saying in your comment about upthrust.....I don't understand the math. I have an 8" well casing for my house. The well had recently been bored when we purchased the property. A developer was going to try to develop it into 10 building lots, and they bored the well intending for it to be a community well. It did not produce enough water for that, but according to the well report, the well is 815' deep and the 8" well casing depth is 63'.

Other notes on the well report:
1. WATER LEVEL BELOW TOP OF CASING = 33'
2. WATER ZONES (depth) from 645' to 646' and from 740' to 741' (I don't know what this means)
3. YIELD - 10 GPM

Back to my not understanding what you are saying about upthrust; the water level below the top of the casing is 33' and the well pump is at 500' from the top of the casing. Doesn't that mean the head is 500'-33'=467'? Could you please explain or point me to a link that explains why there is only 145' of head? And you comment that its such a shallow well.....isn't there 300' of water below the well pump that would be cooling the pump? I was thinking that there is a continuous column of water from the bottom of the well at 815' all the way up to the water level below the top of the casing at 33', which would be a column of water 782' long. And with an 8" hole, that would be ~782 x 2.6 gallons per LF = 2000+ gallons of water in the well being replenished at 10 gallons per minute per the well report. If water is entering the well above the pump, wouldn't gravity cause it try to flow downwards towards the bottom of the well and be filling up the 300' space between the well pump and bottom of the well, thereby keeping the pump bathed in water, unless the pump depleted the well? And with the well replenishing at 10 GPM per the well report, and the pump having an average output of 10 GPM, wouldn't it be hard to drain the well? When I had the problem the other day with the pump turning off, I was running one garden hose for about 20-25 minutes and no other water was being used in the house.

How would two CSV1A's work instead of just one? Would one be set at a higher pressure and the second at the target pressure? I want to understand the mechanics of what would be happening. The pump I have is a Grundfos 10S15-21

Thanks very much.
 

Reach4

Well-Known Member
Messages
38,798
Reaction score
4,412
Points
113
Location
IL
The next time your pump is pulled, get a flow inducer (shroud) on it. It is cheap. Can be kinda homemade out of 4 inch PVC. The fact that your 4 inch pump is in an 8 inch well makes that flow inducer more important for cooling than if you had a 5 inch casing.
 
Top
Hey, wait a minute.

This is awkward, but...

It looks like you're using an ad blocker. We get it, but (1) terrylove.com can't live without ads, and (2) ad blockers can cause issues with videos and comments. If you'd like to support the site, please allow ads.

If any particular ad is your REASON for blocking ads, please let us know. We might be able to do something about it. Thanks.
I've Disabled AdBlock    No Thanks