Solid state relay questions

========================

Nice and cheap - right ?

Triacs cannot take over current surges that last more than a cycle or two.

Why use 2 in series ? I can only see that causing problems.

.... Phil

This is water for your house. That means that it is a critical function.

Cut the crap about what you 'can' or 'cannot' do. It is only money, and you owe it to yourself and any (possibly unfortunate) family as may also need reliable water on rare occasion. Start over, do it right and sleep well. Do anything else, and be prepared for the worst possible scenario.

Keep in mind that this forum exists so that the uninformed may provide the least appropriate, most complicated, least reliable solutions for establish ed problems with established (and reliable) solutions such that the request er of such information may be relieved of taking responsibility to do the r ight thing in the first place.

Peter WIeck Melrose Park, PA

Line drop. Bullshit. Use #6 copper UF cable, and the line-drop for a 400-foot run is 2.53 volts at 8 amps (1920 watts).

Repeat: cut the BS and do it right.

Peter WIeck Melrose Park, PA

MY well is powered from the shop line as well as your well. The shop/garage is on a separate 100 amp line from the service point. The house is a 200 amp line from the same service point.

Why do you need to change the source of service to the pump?

Paul

The house has a generator for when the power goes out. The shop does not. This is why the change in power source. Eric

Pete-I already have the wire in the ground. It is sized correctly for the length of the runs. I am not going to dig more ditches. And what is wrong with using the existing switch to control a relay instead of the pump directly? Would it be dangerous? Not meet code? Would a different relay be better? Eric

The below was in the can when your next message came through. There are any number of bad reasons to do it the way you suggest. Relays have their issu es, and they tend to fail at the worst possible time under the worst possib le conditions. I understand that you are not in downtown Seattle, nor even close to it, so surety and/or redundancy is a big concern. So, if you must use a relay-switch, use one rated for short-cycling and for heavy currents. Also known as a Definite-Purpose Contactor-Switch.

Of many, many options. This will let you control a 240 VAC line from a 120 VAC line. The activator coil options are many, from 12V to 240V. One bit of advice - DO NOT cheap out on these parts.

Peter Wieck Melrose Park, PA

___________________________________________________________________________ _______________________________________ And you do understand what happens to SS (any, actually) relays when they g et stuttered power? Such as when a transfer switch kicks in and out? Nothi ng solid-state likes to be short-cycled unless designed specifically for th at. And even mechanical relays wear heavily if short-cycled.

Repeat: Bite the proverbial bullet, run a new heavy-gauge line to the well system, and be done with it. The first time you do not have to go schleppin g out to the shop in a howling windstorm you will bless that decision.

Peter Wieck Melrose Park, PA

I'm not gonna cheap out on components. And I'm not gonna run 400 feet minimum of #6 wire. Nor am I gonna dig more ditches in my finished yard. I am gonna have an extra relay in the control box, just like I have an extra pressure switch at the pressure tank. Could you please explain why a relay controlled by a remote switch is a bad idea? BTW, thanks for the links. I have decided to not use solid state devices but instead will use a sealed realy. Eric

a) Because a relay is _NOT_ typically rated for motor-start loads. b) Because a relay is not designed for the purpose you suggest. c) Because a relay does not accept abuse very well.

Whereas: a) A definite-purpose contactor _IS_ rated for whatever motor load you ch oose (it's only money). b) A definite-purpose contactor _IS_ designed to turn motors on and off, a s needed and as often as needed. c) A definite-purpose contactor _MAY_ be designed against any number of c oil voltages. d) A definite-purpose contactor _IS_ quite reliable if installed correctly . e) A definite-purpose contactor will take a great deal of abuse. In point of fact, they were developed for exactly the sort of scenario you suggest.

Again - this venue may often get used as a means to avoid the safe-and-corr ect solution in preference for the Kluge solution - but that does not make that solution correct, nor safe, nor reasonable.

Keep in mind that any problem with electricity, motors, and controls for sa me has, at some point in the last 130 years or so, been addressed and manag ed. Most, quite elegantly. Reinventing a simple wheel only for the sake of that reinvention is always futile, often silly, and all too often, dangerou s.

Peter Wieck Melrose Park, PA

I guess I should have said contactor, which is just a special type of relay. Eric

Much as a Ducati or a Triumph or a BMW is a special sort of Scooter.

Peter Wieck Melrose Park, PA

Or use a boost transformer to compensate for the drop, but only to power the pump.

Why isn't the switch at the pump? How are you going to get power from the house to the pump, without new a new power line?

After all this confusion - I expect that the OP means to "control" the pump from the house. If I can interpret the issue (risky, always). a) The house has a back-up generator. b) The line to the pump is from the house, but the power to the tank is from the shop, not backed up. c) The pressure switch is at the tank.

I interpret this to mean that a 120V pressure-switch is controlling a 240V pump, powered by two different sources. Which is flat-out nuts.

I am interpreting (again, risky) that the OP wants the controls at the pump.

So, the 120V source at the shop will control a 240V (hopefully) contactor at the pump.

All the while forgetting that if there is a power-failure, that 120V source will be dead - so, no water.

Clue 1: The tank does not care where it is in the system. Clue 2: The tank will be perfectly happy staying where it is, with all controls, pressure-switch, contactor and so forth at the pump - in suitable enclosures, of course.

Peter Wieck Melrose Park, PA

The tank and pressure switch are at the shop and have been so for over 20 years. The pressure switch has two contacts. The 240 volt power from the shop, where the tank and pressure switch are, is switched by the pressure switch. The pressure switch has a completely mechanical action. The pressure switch switches both legs of the 240 volt power. When the house was built and I was digging ditches I put conduit in the ground from the house to the well so that I could eventually power the well from the house. Now that I have the generator panel and transfer switch installed and bought off at the house I want to power the well from the house so that the generator will be able to power the well when the power goes out. I pulled wire from the house to the well to supply power, so now power from the house is at the well head. The pressure switch must be located at the pressure tank for proper operation. I am not going to move the pressure tank. So all I want to do is to use the existing pressure switch to switch the power to a contactor coil. The power for the contactor coil that the pressure switch will be switching will be coming from the house. The contactor will be switching the power coming from the house. There will no longer be any power coming from the shop. Nowhere did I say any switch was 120 volts. What is wrong with doing this? Eric

he house to the pump, without new a new power line?

mp from the house. If I can interpret the issue (risky, always).

rom the shop, not backed up.

V pump, powered by two different sources. Which is flat-out nuts.

mp.

at the pump.

ce will be dead - so, no water.

ntrols, pressure-switch, contactor and so forth at the pump - in suitable e nclosures, of course.

He could have easily buried a new power line to the tank when he installed the plumbing, as well. I am rebuilding my pumphouse and rewiring it. It wil l have a couple AC Ammeters and a line voltage meter to monitor the pump's health, along with a one minute lockout between pump cycles. Te old pump fa iled, but All I could check was the voltage, since there were no current tr ansformers in place. One till monitor the current to the run winding,, the other will show total current. The voltmeter's use is obvious. The timer is to prevent overheating of the start capacitor, if the potential relay fail s, again. I have a new submersible pump, and two pump control boxes, so it an be swapped out without waiting for spare parts. The old pump lasted 22 y ears. That is a long life, with Florida's very hard water.

I have never seen one installed that way. Why not just put the pressure switch at the house, if you insist on not locating it at the pump? That would eliminate all of the jury rigged crap that wouldn't pass an inspection.

Comments:

1. use a definite purpose contactor.

1. the pressure switch might have a minimum load, so if those contacts are used to switch a relay coil, they may fail.