Wire size to well pump question.


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Old 04-12-18, 02:48 PM
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Wire size to well pump question.

This past Monday the pressure switch to my well pump failed in the on position and blew out my pressure tank and hot water heater. It was a brand new "Square D" switch. 40 to 60 psi rating. I had been having trouble with the old one sticking off and as the pressure tank emptied having no water. Id take the cover off poke the points with a well insulated rod and it would work again for a while then stick again. I replaced it with the new and almost immediately it began to stick again causing a loss of pressure until this past Mon when it stuck on causing all the damage. My wife woke me up to this very loud howling all through the house. The bypass on both the pressure tank and water heater had opened which was making all the noise. But as I was cutting power to the pump I did see that the gage was pegged at 100 psi. So I've no clue how high it really got. Anyway I've two questions. What causes the points in the controller to start sticking? And also this system was installed with 8 gage wire. The wire is way to big to be in total contact with the tiny screws in the controller. There are also walls surrounding each lug that makes getting the wire in place difficult. I don't know what HP my pump is but its at about 480 ft deep. It also has two 50 amp breakers. One at the wall box and one in the disconnect box near the pressure tank and water heater. I cant find a lug that fits 8 gage wire that will also fit the screws on the pressure switch. Anyone have any idea what might be happening? I've been in contact with Square D they want to see the switch but Id already taken it back to Lowes for replacement. I'm suppose to be getting a call from a lawyer (??) at square d, so I'm hoping they might take some of the financial load off me because of all the damage done by a faulty switch. At the same time I'm wondering if there is something wrong at my end. The old switch had lasted for about 7 years. Any help will be appreciated and sorry if I'm in the wrong forum. I wasn't sure to go with plumbing or Electrical.
 
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Old 04-12-18, 03:20 PM
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Welcome to the forums.

Not sure what "sticking off" is. Did it not pull the contacts in or it did but the pump didn't run ?

You have one problem I can readily see. You are running too large a pump on that pressure switch. Most are only rated to 1-2hp. With a 50A circuit you must be closer to +3hp. When you are using a large load.... like that big pump.... on one of those pressure switches.... it gets wired to a contactor which safely switches the high current to the pump.

You may also have a clogged line to the pressure switch. Usually it's 1/8" pipe. The inside diameter is small and can get clogged with minerals.
 
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Old 04-12-18, 04:15 PM
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An update already. The brand new one just stuck again in the cutout position. I've got cutout set to 50psi and cut in to 30 psi. I had thought the same thing about the switch. In a car, power to a high draw item like a starter, or headlights aren't directly connected to the switch on the dash. It activates another relay that directs the full power. I inspected the 1/8th pipe for obstructions prior to installing the new pressure switch the first time its brass and was clear. The rest of the manifold, is new, as is the relief valve. Can you point me to the contactor your talking about? A proper diagram, or what ever, for how it should be wired? I wish I could tell you about the pump size but it was here when I bought the place and new 14 years ago. The original switch lasted about 7 years the second about 7 years and now two failures within days of each other. The first two were branded water source. The second two Square D. I'm starting to wonder if its just a junk brand. I was careful to take lots of pictures before starting the project. (I'll try to upload some). So I'm sure the wiring is correct. But yeah, that wire size is ridiculous.
 
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Old 04-12-18, 04:51 PM
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Here's an example of a 120V coil contactor. This particular one is rated for a 40 amp load. You would wire the 120VAC output from your pressure switch to the contactor coil. The line voltage would connect to L1 & L2, while the load (pump) would connect to the T1 & T2 terminals.

https://www.amazon.com/Packard-C240B.../dp/B004Z0RLL2
 
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Old 04-12-18, 05:59 PM
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Terrible thought just crossed my mind. Could the pump be starting to fail? To much current draw rapidly burning up the points or something along that line?
 
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Old 04-13-18, 09:55 AM
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Celtic-

Iím no expert so take all with a grain of salt. I just have a few thoughts:

(1) I think sometimes really heavy wire (like #8) is used on long distances to the pump to prevent voltage drops. I donít think #8 necessarily means you have a high HP pump. I think Ė lol.

(2) Thus you would in fact have a big breaker (50 amps) to match the capability of the wire (#8 in this case). Although I thought #8 was only good to 40 amps Ė but I think there may be a case where certain type #8 can carry 50 amps (I think UF wire or something like that for a well pump. Not sure)

(3) This is a nit, but I think the pipe connected to the Square D is 1/4 inch Ė not 1/8. But you checked it out and thatís what matters.

(4) The connections from your power source (L1/L2) to the Square D should be on the two outside screws, while the connections to your pump should be on the two inside screws.

(5) I know you said it is a real bear trying to connect #8 to the terminals on the Square D. Is there any way the wires may be almost shorted? Just a thought. If the Square D contacts opened to shut off the pump, but letís say L1 from the source was a hair away from touching the wire next to it (L1 to the pump), then maybe a little vibration could cause contact and the pump would continue to run even though the contacts on the Square D were open. (and the other L2 wires were shorted also, or vice versa with L2 shorting and L1 shorted).

(6) Did you change the location of the pressure switch when you changed over to the Square D? If the pressure switch is somehow not seeing the true pressure then maybe that would explain why the pump did not turn off. Although it would be hard to explain why sometimes it turns off and sometimes it doesnít.

(7) When you noticed that the pump did not shut off but the cutoff pressure had been reached, did you look at the contacts in the Square D and confirm that they were closed?

Just a few thoughts.
 
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Old 04-13-18, 04:41 PM
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To answer a lot of questions..... the current draw of the pump should be checked with an clamp-on ampmeter or amprobe. A 50A breaker on #8 can supply a large amount of power. That breaker is protection for the wiring as well as the pump itself. An oversized breaker will not protect the pump.
 
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Old 04-14-18, 09:01 AM
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Well I broke down and pulled in a pro. Advice given was correct. To much power flowing through the Square D switch. They put in a contactor as suggested in one response. The Square D was fried so a new switch too. He couldn' speculate on the two Water Source switches lasting about 7 years. Visually looking at the innards of both switches I see very little difference. So hopefully I'm good to go now. They also had the equipment to measure current draw and all that. Thankfully pump is still good. Thanks all for the responses.
 
 

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