Replace immersion element

clvk07

Hi

need to replace the element. Are these steps correct to empty the cylinder ?

close cold feed

open hot taps

not 100 sure why from looking online also need to connect a hose to drain on cylinder if I empty via taps ?

also do I need to close valves to radiators ? As my boiler is connected to immersion ?

thanks

The Continental Op

Don't completely drain the tank. Try and leave it full to just below the element or at least check you can slacken the element with too much water then close it again before draining down further. The reason is the water helps support the tank and hold it in position. You can put more force on the element to remove it with a full tank of water. Once the water level is just below the top of the element you can remove it no need to drain down further. Rads aren't connected to the water in the tank the immersion is in.

Draining from the hot taps should leave the tank full with a few inches of water above the top of the tank in the pipe, you should see a pipe coming off the top of the tank that provides the hot water. So once the hot taps run dry you can drain off a bit off from the drain valve in most cases all you need to take out is a bucket full - drain that via a garden hose into a shower tray or bath (or outside if nothing low enough to take it).

clvk07

yes the top of the immersion has an output … sorry once the taps run dry do I still need to connect a hose ?

thought rads where connected because my boiler can also heat the immersion

clvk07

how long should take for the taps to run out ?

The Continental Op

There will still be a bit too much water in the system once the taps run dry. You probably only need to drain off a bucket full from the drain down valve (if there is one) from the tank.

The boiler will be connected to a copper coil that runs inside the tank so the water from the central heating doesn't mix with the water thats in the tank.

The Continental Op

https://www.boards.ie/discussion/comment/120619334#Comment_120619334

Not that long. At max all you should be draining down is the water that is in the header tank (assuming you have a vented system) plus a bit of water thats in the pipe. If you have a valve to cut of the header tank then very little will come out the hot taps with that turned off.

Be prepared to walk away from the job. Occasionally the immersion is so tight in the tank you can't get it out and will need a plumber. Don't force the immersion out by mad levering on an immersion spanner because you can break the fitting out of the top of the tank which means a new tank.

clvk07

ye thats I couldn’t understand I tried this morning and taps were running for 20 minutes still loads coming off

The Continental Op

https://www.boards.ie/discussion/comment/120619348#Comment_120619348

In that case the header tank is still filling up and running into the tank (again assuming vented system with header tank).

clvk07

With header tank you mean tank in attic ? I closed the valve of the feed going into the immersion is there another pipe ?

The Continental Op

There should be a pipe that goes into the bottom of the tank - often the lowest pipe attached to the tank that feeds in cold water. Thats the one that needs switching off. Its normally, in a vented system, connected to a header tank so the options are turning off the water to the header tank or tying the ball valve up, sometimes there is a valve in that pipe to save having to drain it down.

A picture of your tank with as many pipes around it as possible might help identify whats going on.

clvk07

Yes thats what I closed . I also got a pump connected for shower not sure if they did something unusual …. Currently out will take a picture as soon as I get back

clvk07

https://www.boards.ie/discussion/comment/120619408#Comment_120619408

pipe to thermostat Thermostat.jpg

Pipe_in_valve_out.jpg

Output feed.jpg

Valves.jpg

See attached. I only closed the valve on the right going in the bottom of the immersion. There is also another pipe going in on the left conected to a thermostat think that is the boiler?. also the output from the immersion seems to join pipes for the pump shower....

clvk07

289287be-3bd6-4e32-b3f6-9ff31f3b2d38.jpeg

2393d674-65fb-47c9-8ad6-5da278c0fe34.jpeg

390efc6d-d377-4ecf-9e6a-fe9bb1de98b5.jpeg

Hi additional pictures of the connection which I think is boiler radiators ?

The Continental Op

Don't worry you aren't draining down the rads. If you were the water coming out would be disgusting. It should have a corrosion inhibitor in it which is a dead give away.

You need to go into the roof and see what header tanks you have. Switch everything off first (valves in the press) and then open hot tap so you get a small flow. Then go into the roof and see which tank is refilling. There will normally be two tanks, one is the header for the hot water tank and the other for the boiler and rads. They are two separate circuits. Whichever tank is refilling is the one you want to switch off. Tie up ball valve, block the outflow in the bottom (you can get plugs to do that), or just find the valve that turns it off. If no tank is refilling see which one is emptying.

The amount of water in that tank will be the amount you are draining down (plus a bit in the pipe work) if you switch the water off to it.

Escapees

I'm feeling nervous after reading this thread. With all due respect, a good DIY tip is to not take on a job or project that you're not competent to do. We're talking both water and electricity in this case. And even if the replacement appears successful immediately, that doesn't necessarily mean it will be problem free going forward.

clvk07

https://www.boards.ie/discussion/comment/120619987#Comment_120619987

got it thanks a lot. The valve wasn't closing properly, tried again and water out the hot taps stopped within few seconds. Too late now to drain it as I will have to get a replacement element, (not sure how long it is etc) will try during the week. So I will close the valve, open the hot taps, open the drain valve and drain a bucket of water, close the valve and loose the element?

The Continental Op

https://www.boards.ie/discussion/comment/120620038#Comment_120620038

Thats about it. Very slowly unscrew the immersion and check for any water weeping out around the threads as it comes loose. If that happens wind it back in and drain a little more. Have a load of old towels/sheets handy to soak up any seepage. Provided you have the immersion loosened with the tank nearly full you can then drain down as much as you want. I normally just go to the edge of the immersion thread so its quicker to fill back up to check if its leaking. Don't forget to get a good immersion spanner, not the pressed metal rubbish a nice deep box spanner is often the best (one with a notch to take the immersion cable is handy) and a washer for the immersion. You should get a new washer with the immersion but check. Don't worry about wiring it all back up until you have checked its not leaking. Nothing worse than having to undo the wiring to take out or retighten the immersion heater.

btw you are 100% sure the immersion needs replacing? Its nothing simple like the thermostat in the immersion that needs replacing?

clvk07

thanks for that. Switch is sink bath , when on bath water heats up same as sink , has been like this since last year was working fine before …

The Continental Op

https://www.boards.ie/discussion/comment/120620248#Comment_120620248

Hmmm that sounds a bit strange? You'd need to do some rewiring or have some very serious fault for that to happen. Check the switch or replace it when you wire up the new immersion, perhaps the contacts got stuck in which case worth checking the switch now in case its borked and the immersion is OK.

clvk07

Thought my immersion element has two coils when on sink only top heats up and when on bath both ? Is not the case ?

clvk07

Just measured on sink drains 2.1k and on. Bath 2.8k

John.G

https://www.boards.ie/discussion/comment/120620298#Comment_120620298

No, when sink selected, short element heats ~ 35L of water, when bath selected, long element selected which heats ~ 80% of the cylinder total contents, whay are you cheanging it? it may only be the thermostat that needs changing as it serves both elements, can you post a photo of the wiring at the top of the element by removing the cover with immersion switched off.

What do you mean by 2.1k and 2.8k?, do you mean the element resistances which seem OK if they are bath,21 ohms and sink 28ohms.

Immersion Wiring Schematic.jpg

clvk07

Sorry meant kw on sink drains 2kw of power and bath 2.8kw I have installed a smart switch in front and can see total power consumption

The Continental Op

https://www.boards.ie/discussion/comment/120620611#Comment_120620611

So what is wrong with the immersion heater(s).

John.G

You said rcbo tripping g probably earth leakage so more than likely immersion replacement required. What is the load rating of the RCBO?

clvk07

When on bath doesn’t heat water more than sink. Just changed the thermostat got one for tenner

clvk07

IMG_2690.jpeg

Here you go new one in

The Continental Op

https://www.boards.ie/discussion/comment/120620731#Comment_120620731

The temperature of the water should be the same but on bath it should heat more of the water in the tank - enough for a bath ;-) On sink obviously should heat a smaller amount. If you test by switching between them you'll get odd results because the sink will have heated the water at the top of the tank enough for the thermostat to go off and it will still be off when you then switch to bath. You need to use some hot water before the thermostat will close again and the bath part of the system will start.

clvk07

Is the thermostat temperature ok ? Think is around 60 , old thermostat was set to 55

John.G

https://www.boards.ie/discussion/comment/120620731#Comment_120620731

Correct but the bath heats more water than the sink, if wired correctly.

clvk07

https://www.boards.ie/discussion/comment/120620933#Comment_120620933

Wiring is correct and the fact when is on bath uses 2.8KW and sink 2.1K shows more current drawn...... Will try with new thermostat for 1 hour tonight.... Also have temperature set to 60 now, (was 55)