1HP Pool pump motor relay-need advice

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snappy
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1HP Pool pump motor relay-need advice

Post by snappy » Mon Jun 11, 2007 9:10 am

My PIC will be controlling a 1HP pool pump motor. I have two 50A solid state relays (optically isolated), and a large mechanial relay. My question is will the Solid state relays (Potter-Brumfield) pose any operational problems with the motor? Will leakage current in the shutdown state cause any problems other than safety? I was thinking of having both solid states controlling each "hot" line since it is a 220VAC pump...or have one solid state relay actuate the DPST mechanical relay. any suggestions?

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bigglez
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Re: 1HP Pool pump motor relay-need advice

Post by bigglez » Mon Jun 11, 2007 2:10 pm

snappy wrote:My PIC will be controlling a 1HP pool pump motor. I have two 50A solid state relays (optically isolated), and a large mechanial relay. My question is will the Solid state relays (Potter-Brumfield) pose any operational problems with the motor? Will leakage current in the shutdown state cause any problems other than safety? I was thinking of having both solid states controlling each "hot" line since it is a 220VAC pump...or have one solid state relay actuate the DPST mechanical relay. any suggestions?
Greetings snappy,

Good to see a swimming pool question on this forum! (I don't play a pool boy on TV, but I do look after our backyard pool in real life).

A solid-state relay would be ideal, and any leakage current trivial for a motor circuit. Our main pump is on a clockwork timer (relay) and our booster pump is on a second timer, but also connected through the solar panel controller (to kill the boost pump for three minutes when the panels engage).

Sounds as if your pump is configured for 220V, so you need to break both lines (L1, L2) to turn it on and off. Most if not all pool pumps use capacitor-start, single-phase, induction motors, which can be strapped for 120V or 240V operation.

The solid-state relay (even if you use two single poles) will last longer than a mechanical DPDT relay. It would be easy to set it up for testing.

Final note, try to keep the pump running as long as possible, instead of turning it on and off frequently. Most pumps are happy when run up to temperature with a steady load.

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Philba
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Post by Philba » Tue Jun 12, 2007 6:45 am

Interesting question as I have a pool with a 120 VAC 1HP circ pump that I want to put on a timer. I don't need it running all the time (eats electricity). I have been advised to use a contactor driven by a smaller relay. Though I'm still researching, I'm a little skeptical of that advice as being overkill. Given that my pump appears to be rated for 10A, anything over a 20A relay should be ok. Right?

In your case, I would think 50A SSRs should be just fine as long as they are rated for 400 VAC.

snappy
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Post by snappy » Tue Jun 12, 2007 9:27 am

Relays are Potter Brumfield SSR-240D50 rated @ 50A datasheet is http://relays.tycoelectronics.com/datasheets/SSR_DS.pdf, 240VAC. I am going to try two relays- one on each of the HOT lines, although I only really need one. I was told not to worry about surge currents on startup because the SSRs trigger at the zero crossing of the AC sine wave-thus a gentle current increase. My only worry is using the SSR and damaging the motor somehow. Nobody I know has seen this type of relay on a 1HP motor before. If this is a problem I will use the large mechanical relay I have.
FYI: What the PIC does is read a pressure sensor 0-5V and PIC is setup with a high and low trip point and one input for a leak detector to shut the pump down on any abnormal condition such as a blown hose, plugged up skimmer(squirrels), or leak. On pump start up, the internal timer will disable the low trip for 30 sec until pressure builds up then enter the main prog loop, and my store-bought 120VAC timer will shut the system down at night by switching my 5 VDC supply off for the PIC control circuit. Most of the circuit is prototyped and working good except the 30 second delay timer in the PIC.

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Post by Philba » Tue Jun 12, 2007 10:22 am

sounds good. I'd also consider sensing the current drawn by the pump. When it runs dry, the current consumption goes down. You could use that to prevent burnout. I have a commercial controller for a water tank pump that does that. Works pretty well.

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bigglez
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Post by bigglez » Tue Jun 12, 2007 10:30 am

snappy wrote:Relays are Potter Brumfield SSR-240D50 rated @ 50A datasheet is http://relays.tycoelectronics.com/datasheets/SSR_DS.pdf, 240VAC. I am going to try two relays- one on each of the HOT lines, although I only really need one.
Snappy,

Not so. The link you supplied is to a "1 Form A (SPST-NO)" relay. You must break both hot lines (L1, L2) to stop the motor, so two relays are required!

Don't over-think this one. Pool pumps are mature technology, operate well from mechanical clock timers, and seldom fail from abuse due to pool conditions (leaks, obstructions, operator error).

Extended motor operation with no water flowing is not wise, as the pump relies on the water to cool the windings (indirectly through the metal housing).

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snappy
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Post by snappy » Tue Jun 12, 2007 3:03 pm

One SPST N.O. relay should stop the pump since the neutral wire is not used. This has been done in the past by using a regular light switch and is how I found the system originally, but the windings are still live from the other unswitched HOT, there's just no current flow. This may be a safety issue if someone thinks the pump is electrically isolated and removes the rear cover to work on the wires. Using two SSR's still has leakage current in the OFF state and may also cause a hazard if the pump is not running and someone assumes it is isolated (there is water in close proximity). Also all the fancy features have real functions, since the last owner had his sand filter plug up and he blew a hose off and emptied the pool into the garage!!!- thats where the pump / filter is-WOW eh? I have all new hoses and all double-clamped good. Also the PIC will eventually communicate to my PC home automation PC so I can see the pressure and setpoints from the net. But what I am really worried about and need advice on is what the leakage current will do to the motor and internal components when shut down. I had a new fan motor quit working on me using an SSR once and am not sure if using one is OK.

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bigglez
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Post by bigglez » Tue Jun 12, 2007 3:38 pm

snappy wrote:But what I am really worried about and need advice on is what the leakage current will do to the motor and internal components when shut down.
Snappy,

Use a good quality DPST (or DPDT) relay spec'd greater than the "handle rating" of the breaker that feeds the motor's branch circuit.

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Nihing19
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Re: 1HP Pool pump motor relay-need advice

Post by Nihing19 » Wed Jun 13, 2018 11:32 pm

Hey,

Is it conceivable? my pool pump seized up amid the winter and I needed to supplant it...bought one on line and I some how wound up with a one speed 1.5 HP Waterway pump. while introducing it I saw that the power line would not achieve the clock.
I chose to take the line off the old one and supplant the new one's...when I expelled the back cover to the pump I saw that the new direct seems to have the same electrical associations and the old two speed pump.., the just distinction appeared to be the wiring associations and the two way switch. The electrical posts were even numbered the same,

What do all of you think? is this feasible?
Thank you in advance.

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