Priority Switch Woes

Seth Brundle

Just looking for thoughts on an issue we've been having.

We have two electric showers: one in the main bathroom and one in the en-suite. About six years ago, we had a priority switch installed giving priority to the en-suite (up till then, the electrician who put in the ELCB board had put them both on the one switch. Both showers have a pull-cord switch.

Anyhow, over the past few years we were having issues whereby the bathroom shower wouldn't be getting power when you'd pull the pullcord. Usually turning on and off the en-suite shower would get the bathroom shower working again. We had an electrician look at it about two years ago and he replaced (If I recall correctly) a relay and a contactor.

Anyhow as this wasn't an ideal solution we had the electrician take another look. He didn't seem to be sure about the cause of the issue and eventually reckoned that one of the contactors was not working and replaced it. The electrician checked all the wiring and is satisfied that it is all correct.

We went on hols a day or so afterwards and since we returned, the problem we're seeing is that the en-suite shower isn't available. I've found that the contactor marked ES [en-suite] gets quite warm (not hot) - much warmenr than the second contactor. If I knock off the main power on the left for a few hours to let it cool down and turn it back on, the en-suite shower works fine again for a while (it allows my wife to get a shower but I can't get one after her).

I've received the invoice from the company for the recent work done but as it's not working, I told them and they're arranging another visit. However, I am wondering if anyone here has seen the likes of this issue before and how did you manage to overcome it? Is it likely that another contactor is faulty? What might cause them to fail?

Note that I'm not loooking to do any of this myself - I just don't want the electrician coming and spending a load of time doing trial and error because they haven't a clue of the actual problem.

Strangely, one of the things we discovered recently was that the priority switch only really works in winter when the showers would be set for full power - during the summer, their thermostat would be at a lower setting, the shower is not drawing as much power which apparently isn't enough to trigger the priority switch.

John.G

That set up looks like non priority interlocking, I think Priority switching has only one sensing relay and one contactor, in your case the sensing relay should be on the ES shower supply with the contactor on the Bathroom shower?. You have two sensing relays and two contactors so whichever shower is on means that its current sensing relay opens the off shower (NC) contactor so it can't start up. Maybe the system was set up as non priority and has been converted to Priority.

Only other thing is that one contactor is a Hager ESC 240S and the other a Hager ESC 240.

Seth Brundle

Thanks. I'm still waiting on the electrician to call out to resolve this.

I had noticed the two different contactors when looking online for known issues the other night. I think the 's' is a non-humming version.

As for the ES contactor - would the current set up cause it to heat up or is this just likely to be a fault contactor?

In terms of the current setup (two contractors and two relays), it's been like that since the original electrician installed it. In your limited remote view, is it ok?

John.G

I don't think there is necessarily anything wrong with the set up, its just non priority interlocking which you probably have no problem with?

I think those two contactors are normally open (NO) so assume that they are energised closed (with both showers off) until one of the showers sensing relays opens the other ones contactor, the contactor coils probably draw ~ 10W or so at all times, whether this is enough to cause overheating or not I just don't know, if the contactor gets very hot with the shower in service then one could definitely say IMO, a contactor fault. I think the ability to use both showers on 1/2 power in the summer is normal as the sensing relay is probably rated to operate at ~ 4.5/5kw shower element load.

John.G

Contactor, looks like maybe 12.15W during showering time but only 0.5W with contactor closed which shouldn't do much harm as high current flow through the contactor only for say 40 mins/24hrs.

Total power loss under IN, 12,15W, Power dissipation per coil 0,5 W

kirk.

https://www.boards.ie/discussion/comment/119425846#Comment_119425846

Ya the non priority is both contactors normally energised and contacts closed

Shouldn't be much to it if the problem is present when u go to shower , should be easily diagnosed

kirk.

Low heat in summer the board should still work as normal

Low heat is circa 20amps and should operate the relays no issue

John.G

Ie both showers should operate together if either relay not sensing > 20A ?

kirk.

https://www.boards.ie/discussion/comment/119429620#Comment_119429620

First in to operate shower with heat the n/c contacts on a sensing relay open and break supply to second showers contactor

1/2 heat or full heat makes no difference to operation of board(or shouldn't)

if I recall the sensing relays operate at about 5 amps I think

kirk.

https://www.boards.ie/discussion/comment/119429620#Comment_119429620

Sorry ya to clarify only 1 shower should operate even on half heat

Same as full heat operation

Seth Brundle

So if both of mine can operate when on half heat, what would that indicate in terms of the setup I posted above?

John.G

Don't know but I think I can see Ires 5.5A on the sensing relays which suggests something not right as 1/2 load on either shower is ~ 20A.

kirk.

https://www.boards.ie/discussion/comment/119430375#Comment_119430375

Check your sensing relays and contactors operation

Fault is present while showering so should be easy diagnosis