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How to diagnose this immersion problem

Spocker

I have a standard dual-element immersion controlled with a Timeguard digitial timer, set to come on only once a week.

Recently I discovered that the timer was activating no problem, and the neon indicator on the sink/bath switch comes on for a second or so, and turns off again. The MCB does not trip.

I thought it was the thermostat, as it had slight burn marks:

so I replaced it, but still the same issue.

Another check of the element and all the connections are sound and clean:

and the high limit switch isn't popping (I know the water in the tank is not hot enough)

At this point I'll either replace the high limit switch (do they go faulty?) or bypass the timer unit (do they go faulty?). Am I missing anything else?

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[Deleted User]

You are checking things that come after the sink/bath switch. If all or none of these were working you should still have a working sink/bath switch. I'm guessing the issue is with the sink /bath switch or the timer. Have you put a multi meter on the switch or timer to check the voltage?

Edit: personally I think this would be better in the electrical forum. You'll get advice from electricians there rather than DIY people

Spocker

Sleeper12 wrote: »

You are checking things that come after the sink/bath switch. If all or none of these were working you should still have a working sink/bath switch. I'm guessing the issue is with the sink /bath switch or the timer. Have you put a multi meter on the switch or timer to check the voltage?

Edit: personally I think this would be better in the electrical forum. You'll get advice from electricians there rather than DIY people

Good point on the electrical forum, I just defaulted to DIY.

I haven't metered the voltage (yet - I'll try tomorrow) but you might be right that the timer could be the culprit - it still has power all the time, but seems to be what resets after the second or so.

A quick check of the Timeguard site doesn't give any information on the whether the timer (NTT-04) has any overload (or similar) protection in place. Its reasonably new, only installed in Aug 18

my3cents

It won't make a difference in the way it works but is the immersion wired correctly? Obviously I've no idea whats at the other end of the blue wire but if its the neutral would it be normal to have the thermostat and cut out switch working on the neutral side of the circuit?

Spocker

I didn't wire the immersion, it was the local plumber. This all worked fine until I discovered it wasn't a couple of weeks ago, which is why I'm trying to trace a faulty part, rather than starting from scratch

punisher5112

Check all the connections 1st and check for burns or melting in switch and cables...

Cerco

If you provide a photo of the On/off & bath/ sink switch wiring it would be helpful.

Spocker

No obvious signs or burn/melting, other than on the thermostat in the tank, which I already replaced. Heres a shot of the back of the timer and switch

and this is the wiring guide

my3cents

So how is this supposed to work?

So the timer is working all the time making the the main immersion switch sort of redundant on a day to day bases apart from the sink/bath option?

Wheres the other junction box? You've a blue, RED and brown leaving the immersion switch (plus earth) and blue, BLACK and brown cable going to the immersion element (plus earth).

You do seem to be switching the neutral on the thermostat btw which isn't a good idea but at least the main immersion switch (the one with the neon on it) breaks both the neutral and live so if the switch is off a swapped live and neutral won't lead to a live wire in the immersion heater when its switch off.

Spocker

my3cents wrote: »

So how is this supposed to work?

So the timer is working all the time making the the main immersion switch sort of redundant on a day to day bases apart from the sink/bath option?

Thats correct, the main immersion switch is indeed redundant

my3cents wrote: »

Wheres the other junction box? You've a blue, RED and brown leaving the immersion switch (plus earth) and blue, BLACK and brown cable going to the immersion element (plus earth).

Good catch, heres the junction box in the hot press:

my3cents wrote: »

You do seem to be switching the neutral on the thermostat btw which isn't a good idea but at least the main immersion switch (the one with the neon on it) breaks both the neutral and live so if the switch is off a swapped live and neutral won't lead to a live wire in the immersion heater when its switch off.

OK, again thats the way the plumber wired it; is it more common to switch the live?

[Deleted User]

First thing I'd do is check the sink/bath switch with a multi meter. See if you have 230v going in & coming out. The fact that the red light comes on & goes out again suggests that the issue is with the switch or timer. There is no point testing it with a phase tester because all that will tell you is that the bulb in the tester is working.

Skihunta13

Everything is connect grand, the common nuetral should be broke through the stat.
I suspect the timer. On the timer connections you have a brown link wire going from your incoming live to the common of you timer. If you turn off the power and move that link so you are linking the incoming live to the outgoing live, you would effectively bypass the timer. If all works grand from the immersion switch then the timer is faulty.
Be sure to turn off the immersion circuit from the fuseboard.

Spocker

This is it wrote: »

If you use the boost option does the neon stay on? Have you a meter to check voltage?

Only stays on briefly, and I get a spike on the voltage to 240v

Sleeper12 wrote: »

First thing I'd do is check the sink/bath switch with a multi meter. See if you have 230v going in & coming out. The fact that the red light comes on & goes out again suggests that the issue is with the switch or timer. There is no point testing it with a phase tester because all that will tell you is that the bulb in the tester is working.

I think the timer might indeed be the problem, as the "on" indicator goes off there as well

Skihunta13 wrote: »

Everything is connect grand, the common nuetral should be broke through the stat.
I suspect the timer. On the timer connections you have a brown link wire going from your incoming live to the common of you timer. If you turn off the power and move that link so you are linking the incoming live to the outgoing live, you would effectively bypass the timer. If all works grand from the immersion switch then the timer is faulty.
Be sure to turn off the immersion circuit from the fuseboard.

Thanks, bypassing the timer would be a way to rule it out alright. It's only 12 months old, so I've shot an email to Timeguard to see what they say

This is it wrote: »

Bypass the timer and see if the immersion works. What you need to know is if there's power at the immersion or if the immersion switch or timer are fecked.

Tomorrows test

Skihunta13

There is also a reset button on the front on the timer you could press. It may resolve you problem.

my3cents

Spocker wrote: »

...

OK, again thats the way the plumber wired it; is it more common to switch the live?

Not so much more common but the rule. The reason the live is switched is that way when the switch is off (be it fuse, wall switch, timer switch, immersion thermostat or immersion cut out) the circuit is no longer carrying live current.

In your case the heating element is always connected to live current when the immersion heater is on even if the water is hot and the thermostat has tripped off. Its not a big deal as the switch with the neon in it disconnects both live and neutral wires. However in a lot of circuits, your timer being an example only the live is switched on and off leaving the neutral always connected.

If you switched the neutral in a lighting circuit then the bulb holder would still be live when you change the bulb.

But none of that is the reason your immersion isn't heating. Skihunta13 has indicated the simplest testing solution.

Skihunta13

my3cents wrote: »

Not so much more common but the rule. The reason the live is switched is that way when the switch is off (be it fuse, wall switch, timer switch, immersion thermostat or immersion cut out) the circuit is no longer carrying live current.

In your case the heating element is always connected to live current when the immersion heater is on even if the water is hot and the thermostat has tripped off. Its not a big deal as the switch with the neon in it disconnects both live and neutral wires. However in a lot of circuits, your timer being an example only the live is switched on and off leaving the neutral always connected.

If you switched the neutral in a lighting circuit then the bulb holder would still be live when you change the bulb.

But none of that is the reason your immersion isn't heating. Skihunta13 has indicated the simplest testing solution.

What you say is always the way, however as an immersion has 2 lives you would need 2 thermostats to break the lives.

dodzy

Does boost work?

Disconnect the link/bridge wire and test again. My money is on the switch. Timeguard will replace I’m sure. They make decent products.

Cerco

Skihunta13 wrote: »

What you say is always the way, however as an immersion has 2 lives you would need 2 thermostats to break the lives.

That depends on how you wire it. Immersion elements are resistive therefore they do not have polarity.so you can have one live through the thermostat and two neutrals. Always refer to regs and manufacturers instructions. If in doubt get an electrician to resolve.

my3cents

Skihunta13 wrote: »

What you say is always the way, however as an immersion has 2 lives you would need 2 thermostats to break the lives.

I see your point, my mistake,

you'd have to switch the neutrals on sink/bath switch if you were to wire a single live to the thermostat.

Hotblack Desiato

Cerco wrote: »

That depends on how you wire it. Immersion elements are resistive therefore they do not have polarity.so you can have one live through the thermostat and two neutrals.

Then you'd be switching two neutrals instead of one!

Always refer to regs and manufacturers instructions. If in doubt get an electrician to resolve.

No worries here as long as they replace components like for like and wire it up the same way as it was before.

Cerco

Hotblack Desiato wrote: »

Then you'd be switching two neutrals instead of one
No worries here as long as they replace components like for like and wire it up the same way as it was before.

Yes you would switch between sink and bath neutrals.

Yes, if it was wired correctly initially.

Cerco

Spocker

dodzy wrote: »

Does boost work?

Disconnect the link/bridge wire and test again. My money is on the switch. Timeguard will replace I’m sure. They make decent products.

Boost didn't work either, so I've bypassed the timer altogether, and just wired the switch direct. The neon is staying on, so I'd be pretty sure the rest of the circuit is ok (just going to wait for an hour to make sure I actually get hot water).

I shot an email to Timeguard who said "based on your description it does sound faulty, send it back"

On a side note (because I don't have the tool to take it out) and just fro my own knowledge, which connections are for each of the elements in this picture:

Is the shorter element connected via the black wire? And the other side of the short element is the connection with the red/brown cap?

Patches oHoulihan

Sorry for the bump.

I was looking at one exactly like this today. No timer just a dual switch tripping RCD instantly when switched on. No new stuff done in house.

Looked at cables at back of switch and at cylinder pot and all OK. Not a sign of any damage or melt etc. 230v at supply side of switch.

Hard water area. Maybe it's the element has corroded.

Is there a test that can be done?

whizbang

Multimeter on Ohms setting, test from Earth to any of the element connections. You have to have both Live and Neutral connections disconnected first.

anything less than a few Meg Ohms means element is gone.

The Continental Op

@Patches oHoulihan you'll have to disconnect it to do any tests. Disconnect at the switch (take pictures so you know what wire goes where) then close it all up again with wires out. Make sure everything is safe and switch back on, if nothing trips then its the immersion. If it still trips its the switch. I've seen switches with "tracking" that means they short out every time they switch. By tracking I mean an electrical pathway created by moisture and mains voltages.