Immersion heater

lomb

Installed a new immersion cylinder and element as ripped the boss off on the old one as someone had used jointing compound on it
Tip- Make sure the cylinder is totally full and 'under pressure' If the spanner needs anything other than the lightest taps with a hammer to loosen it then you are going to need a dremel with a metal cut off disc and need to cut two one inch slots directly opposite each other MUST avoiding cutting through the fiber washer and marking the sealing face of the boss where ALL the seal is made(none is made on the threads due to the config of them so don't bother with ptfe), it will then loosen easily. Otherwise you could need a new cylinder. Also use a rubber o ring type seal on the immersion rather than the fiber washer as no ptfe, jointing compound etc is needed so they only have to be done up hand tight and not hammered to seal.

Anyway my problem is the sink/bath selection Ive checked with a meter and Im getting 60v on the sink coil and 240 on the bath when the bath is selected and 240 on sink and 60 on the bath when sink is selected. When both switches are off obviously no voltage passes. I an checking the volts before the thermostat with the 4 core not connected at the cylinder at all. I cannot understand how this could be. Ive never heard of transformers in switches? I do have two switches in separate places wired together so can select on /off and sink/bath from two locations. Thanks for shedding any light on this strange finding.

RJF

How did you wire the two switches?

my3cents

If there is a mistake in the wiring then the elements could be wired in series so there will be a massive voltage drop across them?

RJF

my3cents wrote: »

If there is a mistake in the wiring then the elements could be wired in series so there will be a massive voltage drop across them?

OP said he wasn't connected at cylinder so element shouldn't come into it at this stage.....??

lomb

RJF wrote: »

How did you wire the two switches?

I didn't wire them they have been like that for many years. I just followed the wiring scheme. The brown wire connects to the thermostat, the black I checked was the bath neutral as 230 volts is apparent without reverse polarity and blue is the neutral 230volts for sink. All very strange.
Yes indeed I disconnected at the cylinder completely(well with the exception of earth if that means anything). Its just wired at the junction box in the hotpress where 3 cables come in, one from the switch 1, one from switch 2, one to the immersion. Im not sure where the fuseboard wire connects to presumably one of the switches?
At the junction box the wire colours match ie all 3 blues in one block, all blacks in another , and all browns in another.
The other problem is that I don't mind both elements one with less power to the sink but the immersion is rated at 3kw+2kw so if 60 odd volts goes to the sink does this mean its going to use 500 watts so that's 3500 watts total.
The wire that came with the immersion is 1.5mm heat resistant 4 core, Its 1m to the junction box is this safe? The old wire was 2.5mm probably non heat resistant and this seemed fine but is sadly not long enough as the immersion is turned a little.
Should I source 2.5mm four core heat resistant?

my3cents

RJF wrote: »

OP said he wasn't connected at cylinder so element shouldn't come into it at this stage.....??

I agree, but having worked with the general public on the phone doing tech support I know that people don't always tell it the way it is.

Another possibility is the OP is somehow measuring the voltage drop across the a neon indicator or its dropping resistor - obviously only possible if there is a neon in the switch.

With cables disconnected but power on there is also the possibility that its an induced current that is being measured, may be only a few mA but the voltage could be anything up to 220V.

lomb

It is disconnected at the cylinder yes except the earth.
There is a neon on one switch yes.

my3cents

lomb wrote: »

It is disconnected at the cylinder yes except the earth.
There is a neon on one switch yes.

Can't be 100% sure but I think the neon is causing the 60V readings. Most neons have a starting voltage of around 90V and this drops back to about 60V once fired up. If the neon is wired in a way that allows you to disconnect it then try the same tests with it out of the equation.

K.Flyer

lomb wrote: »

I didn't wire them they have been like that for many years. I just followed the wiring scheme. The brown wire connects to the thermostat, the black I checked was the bath neutral as 230 volts is apparent without reverse polarity and blue is the neutral 230volts for sink. All very strange.
Yes indeed I disconnected at the cylinder completely(well with the exception of earth if that means anything). Its just wired at the junction box in the hotpress where 3 cables come in, one from the switch 1, one from switch 2, one to the immersion. Im not sure where the fuseboard wire connects to presumably one of the switches?
At the junction box the wire colours match ie all 3 blues in one block, all blacks in another , and all browns in another.
The other problem is that I don't mind both elements one with less power to the sink but the immersion is rated at 3kw+2kw so if 60 odd volts goes to the sink does this mean its going to use 500 watts so that's 3500 watts total.
The wire that came with the immersion is 1.5mm heat resistant 4 core, Its 1m to the junction box is this safe? The old wire was 2.5mm probably non heat resistant and this seemed fine but is sadly not long enough as the immersion is turned a little.
Should I source 2.5mm four core heat resistant?

The wiring from a new pre-wired dual immersion is as follows;
Neutral Blue to the Over-Heat cut off stat then to Thermostat.
Switched Brown to Bath terminal.
Switched Black to Sink terminal.

New Dual immersion heaters come pre wired this way.

You should be using a proper immersion switch which with Brown to bath, Black to sink with the correct rated cable.

K.Flyer

A pre-wired dual immersion from today...

Sleeper12

K.Flyer wrote:

The wiring from a new pre-wired dual immersion is as follows; Neutral Blue to the Over-Heat cut off stat then to Thermostat. Switched Brown to Bath terminal. Switched Black to Sink terminal.

K.Flyer wrote:

New Dual immersion heaters come pre wired this way.

I suggested the very same thing last year in the electric forum and several of the sparks bit me head off. They pointed out that some immersions are pre wired brown sink and black bath. I've yet to see any where "sink the black" doesn't come into play but I've no reason to believe that they weren't telling me the truth.

K.Flyer

Unless the immersion manufacturer is wiring them wrongly, thats the way I get them and thats the way they go in.
The above image is one I fitted today, the brown went to the longer element (Bath) and black went to the shorter element (Sink) and blue went to the thermostat. And thats the way I have seen them for many years. So who am I to argue with the manufacturer's instructions?

lomb

I changed the wiring around in the cylinder to my old wiring scheme, brown to thermostat black to bath(30 ohm resistance) , blue to sink(20 ohm resistance)

I see no reason to follow the new wiring scheme.I could change it at the junction box but why bother?
All working well now anyway.

Bruthal

my3cents wrote: »

With cables disconnected but power on there is also the possibility that its an induced current that is being measured, may be only a few mA but the voltage could be anything up to 220V.

This is the likely scenario. Capacitive coupling.

The impedance is so high in capacitive coupling, that it is only measurable with very high impedance multimeters, which digital ones are.

lomb

Thanks another question. There is a small leak maybe one drop an hour from the return central heating connection on cylinder. Ive removed and added more ptfe and its tight at the angle of exit required. Without ptfe it wants to screw down 3/4 of a turn in the wrong direction. Should I add jointing compound to the ptfe or scrap the ptfe and use hemp or can I buy a swivel connector so I screw down and ensure its turned the right way. The flow doesn't leak.

my3cents

Non plumbers reply, try using gas one wrap ptfe tape, its much thicker and seals better, you may need more than one wrap. ptfe is like teflon, non-stick you can't mix it with a sticky sealer. You may just not have used enough ptfe tape in the right place on the tread first time around, you don't have to stick with a couple of wraps, if it takes ten then thats what it needs, but ideally no more than needed. Try wrapping ordinary tape really tightly in the threads twisting the tape so its NOT flat then go back and put a couple of extra wraps on the middle of the thread thats in the middle of the joint when its made then finish off with a flat layer form the end backwards to hold the hole lot in place. You should just still be able to make out the threads at the end of the fitting but not in the middle. If you feel you need to apply too much pressure to make the final part of the joint then you can stop take the joint apart and tape it again with a bit less tape. Apologies to real plumbers but that works for me.

I know a lot of plumbers rightly condemn the over use of ptfe tape (I often laugh when I see it on surfaces that aren't part of the seal like nut side of olives) but for an amateur its clean to use and if you do make a mistake you don't have a joint that is stuck solid or the problem of cleaning the sealer off a failed joint before starting again. One of the dangers of ptfe tap is that its in effect a lubricant on the joint so it make it easy for amateurs like me to over tighten a joint.

Robbie.G

lomb wrote: »

Thanks another question. There is a small leak maybe one drop an hour from the return central heating connection on cylinder. Ive removed and added more ptfe and its tight at the angle of exit required. Without ptfe it wants to screw down 3/4 of a turn in the wrong direction. Should I add jointing compound to the ptfe or scrap the ptfe and use hemp or can I buy a swivel connector so I screw down and ensure its turned the right way. The flow doesn't leak.

Best thing on that is hemp and jointing compound
Done right it will never leak

lomb

Ive added hemp and jointing compound boss white to the ptfed thread . I know not the correct way but access is very poor now without taking the whole lot out again. No leaks so far under pressure for an hour so we will see. The connector has screwed down properly tight at the right angle.
The old cylinder was hemped and compounded and there way no leak at any of the 4 connectors for many years.. If I was to do it again I wouldn't bother with the ptfe. I suppose these type of connections are far more critical than olive type where the olive is forced into the taper.
ps tried gas ptfe and to be fair it worked on the other 3 connections fine but no ordinary ptfe as a string that's a thought for the future thanks

Jimibo

Hi, does anyone know if you can de-scale an immersion heater using the drain valve?

Sleeper12

Jimibo wrote: »

Hi, does anyone know if you can de-scale an immersion heater using the drain valve?

If you go to the trouble of draining down to descale why not just replace the element. Haven't bought one in years but Im guessing 20 to 30 euro. Descaling might run the risk of blocking a pipe or fitting. Then how sure are you that you have flushed the system? You will be bathing / showering in this water afterwards

Jimibo

Sleeper12 wrote: »

If you go to the trouble of draining down to descale why not just replace the element. Haven't bought one in years but Im guessing 20 to 30 euro. Descaling might run the risk of blocking a pipe or fitting. Then how sure are you that you have flushed the system? You will be bathing / showering in this water afterwards

Hi, I think the issue might be the element has a small hole and the water is boiling on it. It's making a strange noise, kind of like a ticking and rattling noise.

I've made a video but I can't post it yet (only after I've joined for 24 hours) so I will tomorrow.

I've never replaced a element before. It doesn't look too difficult (if you use a box spanner and can actually get it out). But might be something better to get a plumber to do. I just wanted to make sure that the element is broken before I replace.

Sleeper12

Jimibo wrote:

I've never replaced a element before. It doesn't look too difficult (if you use a box spanner and can actually get it out). But might be something better to get a plumber to do. I just wanted to make sure that the element is broken before I replace.

Trust me here. Get a plumber. It's not uncommon to damage the cylinder while replacing the element. A 150 euros job can become a 450 euro job very easily.

Jimibo

Sleeper12 wrote: »

Trust me here. Get a plumber. It's not uncommon to damage the cylinder while replacing the element. A 150 euros job can become a 450 euro job very easily.

Yes, I think so.

I guess with an issue like that it can be tricky to diagnose. But I reckon it's probably a broken element.

Anyone knows a good one let me know