Electric code or UL question, SPST relay on pump

Unless I had a specific opinion from a licensed master electrician on file, I'd say no. The worst case isn't touching the motor housing, it is charge on the water going to the pond.

SFAIK, all koi ponds and swimming pools require GCFI as well. I dunno if you can just depend on that, or if neutral needs to be isolated as well.

It just makes a water jet, like fine-particled rain, not to swim in. This action can only happen while the motor is powered. When power is cut there will only be still water in the basin and that's covered.

I looked up and down the web if there is any code or other legal info about such situations but came up dry. I did find a few examples though where they tied the neutrals together and didn't switch them, like here:

More frequently I found L&N switching like here:

Hence my head-scratching.

Pool pump timers switch only the hot, and not the neutral, for 120V operation.

Those are hard wired, intended to be wired by an electrician, so there's less danger of mixing up hot and neutral.

That's true. I just had to replace GFI breaker on a pool pump panel and it was an expensive sucker.

Anything within a few feet of water, not sure exactly but if you can reach water from it, it needs a GFI or GFCI.

I a pretty sure you do not have to switch the neutral unless it is a device with a non polarized plug. Interestingly, know those Panasonic type cords that were/are used on some stereo equipment and DVD players etc. ? I notice d some players have a polarized plug yet on the other end it can be inserte d into the device either way. I wonder how the UL missed that.

Now, there could be a problem. If, when switched off, you get leakage from the neutral to Earth ground, which is possible in that situation, it could cause the GFCI to trip and cause a nuisance.

Why can't you put the relay somewhere else ? Are there lights or something there that you want to keep on when the motor is off ?

Is this a home building project, or a movable product for sale in multiple countries? If the former, you need a local building code, if the latter you need the product standards from each country where it is to be marketed.

It will depend on whether the relay is a means of electrical safety isolation for use whilst people work on the terminals of the motor, or if the relay is purely a functional item which could fail with its contacts welded shut, without any electrical safety consequence. Provided the relay contacts are not the means of safety isolation, I think that most standards would permit a SPST relay.

You would probably want to avoid requiring the relay to perform a safety isolation function. If the relay performed a safety isolation function you might need a very special relay that could never weld on, perhaps with some failsafe mechanism that blows the fuse if it does (like a microwave oven door switch), and any electronics and software that controls the relay would have to be developed under much stricter rules, as it would be a safety component. If you can arrange for the safety isolation (for working on the motor) to be performed by pulling the plug from the outlet or use a dedicated manual isolation switch designed for that job, then you avoid these restrictions on the relay.

As a separate issue, if the coil terminals of the relay are connected to electronics that can be touched, then the coil-to-contacts insulation would need to meet the IEC requirements and be UL recognised as "reinforced insulation", but that is widely available with litte added cost.

Yes. That's the way it should be done. Don't switch neutral. A GFCI is highly recommended and likely required.

Right, even in the US, you'd have to have a DPST switch for 240V split-phase.

Double insulated.

So can electrocution.

that bit is really too vague.

Each country has its own rules - except when it copies someone else's or has none. Here safety isolation requires DP switching with IIRC 3mm separation. On/off timing doesn't.

Since sealed pumps always fail in the end, I'd put some thought into the consequences of that. Eg will it kill valuable fish stock?

NT

If so, I would expect a single pole switch is fine when mounted internally to the device.

.... Phil

Yet I have seen many aquariums that aren't. People just plug them into the next available outlet in the living room.

When you ship to countries such as Germany or the Netherlands the mains plugs are not polarized. Beats me why they didn't do that.

No space. It must be in the main unit. And yes, there is other electric stuff in there that needs to rmain running.

Aha! Now we are getting somewhere. I'd have to find a more official source though so we could plead our case with UL if they flag it during review.

It's the latter. For now I only need it for the US and that is where I could not find reliable and official information. Later we can worry about other countries but it would be nice to know that at least some big ones allow it. Germany probably does because I have seen SPST relays in conjunction with water there. But this was decades ago.

It is purely operational. When anything is serviced they must pull the mains plug out of the wall outlet.

That I am not worried about and AFAIK it's not even touchable.

It's on/off timing. By "here" do you mean the US? Got any hint towards a more official statement about it from UL or so?

It won't kill anything, just make a mess. Also, the pump housing is PE-connected.

Do you know which official document spells that out?

Could be, although I have seen SPST in Germany which has 230V and non-polarized mains plugs so with portable equipment the chance of switching line or neutral is 50/50.

Yes, the pump and controller are all part of a plug-in appliance. The application is more commercial, used in businesses but operated by staff that isn't especially trained in electrical stuff.

I'd still be skeptical that you can ... understand all possible ground paths. Wouldn't it be that you could still have a ground fault in the pump housing and water ... puts current to the basin?

That's kind why I was appealing to swimming pools and koi ponds.

Which is rather beside the point - I'm not a master electrician. In order to have the proper provenance for the design, you'd need that.

That offers "galvanically separated power supply". That may be enough.

The "pump start relay" may solve that problem for 'em - it's kind of hot/neutral/ground going in, two coming out.

Understood.

What about a SSR or use a couple of triacs. I found this in my book marks. Its for a 3ph controller but might give you some ideas

Here is UK. But if it's not safety isolation it's immaterial.

So a short to case raises 'PE' voltage to nearly 240v while the fuse melts, resulting in mains voltage through the water. How does that just make a mess?

NT