Only getting 170volts between line and neutral on shower?

[TheConduitKing]

So abit of a random one. But yesterday my Neighbor asked me if I'd be able to take a quick look at their shower as it had stopped working. I said I'd go round an take a look and see if it was something simple enough to fix and get it going again.

Checked the usual things. The solenoid was fine, microswitch was working fine, no loose connections in the shower itself.

He said that it would work occasionally then would stop and that he has had to replace the pullcord 3 times in the past year

Took a look at the pull cord and noticed that the cables were mixed up. The supply was in the load and vice versa. I didn't see any burning, again no loose connections (this was a 45amp isolator.) And that one of the earth's were disconnected and wrapped in tape. Apparently it was like that the first time he replaced it.

I turned the power back on and got a reading of 170volts between line and neutral at the shower and 230 at the pullcord itself. The shower is fed by a 10mm cable covered by a 40amp MCB with RCD protection.

I just left it at that and told him to ring an electrician I know who can come out and test it to make sure that the RCD and all that will be working fine In case it's not working.Especially with only one earth connected.

But I'm confused. How can the shower only be getting 170volts at the shower when it's getting 230 at the pullcord? Unless it's broken?

Any ideas?

 

[timhoward]

he has had to replace the pullcord 3 times in the past year

Red flag number one. This suggests more current is being drawn than the isolator is rated for, probably because of fault conditions.

And that one of the earth's were disconnected and wrapped in tape.

Red flag number 2
Someone might have found that connecting it trips the RCD.

I turned the power back on and got a reading of 170volts between line and neutral at the shower

Red flag number 3. This suggests a low resistance fault.

Someone needs to get busy IR testing this entire circuit. My long range prediction is a damaged cable between the isolator and the shower.

 

[Avo Mk8]

Just a suggestion-
If you were measuring 170V at the shower terminals, with a multimeter, but the shower was OFF, a high resistance fault (Megohms) in the circuit, say a carbonised/burnt terminal, could account for it. Turning the shower on would reduce the voltage to zero.
If you were measuring 170V with the shower running, that would indicate a low resistance fault, but with a couple of kW being dissipated somewhere, you would soon see where the fault was from the heat/smoke/flames!

 

[TheConduitKing]

Red flag number one. This suggests more current is being drawn than the isolator is rated for, probably because of fault conditions.

Red flag number 2
Someone might have found that connecting it trips the RCD.

Red flag number 3. This suggests a low resistance fault.

Someone needs to get busy IR testing this entire circuit. My long range prediction is a damaged cable between the isolator and the shower.

See, that's what I was thinking myself. Possibly a damaged cable or broken isolator again. As soon as I saw that wrapped up earth and the cable connected the wrong way around I knew something bad was up.

Glad I messaged my spark he's going round tomorrow to test it. He's local so he doesn't mind

 

[TheConduitKing]

Just a suggestion-
If you were measuring 170V at the shower terminals, with a multimeter, but the shower was OFF, a high resistance fault (Megohms) in the circuit, say a carbonised/burnt terminal, could account for it. Turning the shower on would reduce the voltage to zero.
If you were measuring 170V with the shower running, that would indicate a low resistance fault, but with a couple of kW being dissipated somewhere, you would soon see where the fault was from the heat/smoke/flames!

No if I switched on isolator and the shower I got 170. If it turned off either I got 0. If that makes sense. That's why I was confused.

I saw no burnt terminals.

Unless it's a junction box in the wall or attic or something?

 

[snowhead]

Issue on the cable from Pull switch to shower, maybe a junction box along the way with poor connections.

 

[Vortigern]

You need to do tests on the cable from the switch to the shower. It sounds like it is damaged.
EDIT: just seen that @timhoward has suggested this but the comment only loaded after I had posted.

 

[LukeD]

No if I switched on isolator and the shower I got 170. If it turned off either I got 0. If that makes sense. That's why I was confused.

I saw no burnt terminals.

Unless it's a junction box in the wall or attic or something?

Run a test cable from switch to shower. if all good ....then you know where the problem is !

 

[TheConduitKing]

Issue on the cable from Pull switch to shower, maybe a junction box along the way with poor connections.

Spark I work with is going round tomorrow to take a look. I'll report back what he finds. I might even tag along and annoy him for a bit.

 

[brianmoooore]

As Avo Mk8 has already said, with 70 volts disappearing between isolator and shower, at shower current, the location of the fault should reveal itself.

 

[nicebutdim]

As Avo Mk8 has already said, with 70 volts disappearing between isolator and shower, at shower current, the location of the fault should reveal itself.

The simplest of radial circuits with clear indication of the point at which this problem appears.

 

[Avo Mk8]

Spark I work with is going round tomorrow to take a look. I'll report back what he finds. I might even tag along and annoy him for a bit.

This doesn't make sense to me either. What was the shower doing when you were measuring 170V across it? You said it was ON, but was water flowing, and if so what temperature was it?
i.e was it on as an 8kW+ load with water flowing, or was it just 'on' (but no water flowing, so not a load), in other words 'off'!

 

[TheConduitKing]

This doesn't make sense to me either. What was the shower doing when you were measuring 170V across it? You said it was ON, but was water flowing, and if so what temperature was it?

No, that's why I was confused. No water flowing at all no matter what setting I put it on. But the indicator light was on however it was very dim.

I even shut off the mains water and checked the filter and it wasn't blocked or anything. Again like I said solenoid was reading 3.5k ohms and the microswitch was working when I checked continuity across it.

It's a Triton shower if that makes any difference. Only reason I know to check the solenoid is the solenoid broke in my own Mira shower and I was able to fix that. Apart from checking those things I know very little about showers.

 

[Avo Mk8]

No, that's why I was confused. No water flowing at all no matter what setting I put it on. But the indicator light was on however it was very dim.

I even shut off the mains water and checked the filter and it wasn't blocked or anything. Again like I said solenoid was reading 3.5k ohms and the microswitch was working when I checked continuity across it.

It's a Triton shower if that makes any difference. Only reason I know to check the solenoid is the solenoid broke in my own Mira shower and I was able to fix that. Apart from checking those things I know very little about showers.

So I'm guessing no 8kW load from the elements is activated, because they haven't been turned on, because the solenoid isn't letting the water through because there's something like a 2.5 kohm fault somewhere in the supply acting as a potential divider with the 3.5k solenoid
So if I'm right (good chance I'm not!) there's about 40mA flowing in the faulty circuit with the shower "on". About 3 watts being dissipated somewhere!

 

[brianmoooore]

So I'm guessing no 8kW load from the elements is activated, because they haven't been turned on, because the solenoid isn't letting the water through because there's something like a 2.5 kohm fault somewhere in the supply acting as a potential divider with the 3.5k solenoid

Only a minute current flowing. A much more likely scenario.