Immersion not heating from CH

Seth Brundle

We had work done a year ago that involved moving the boiler and ever since then the rads are fine but the immersion doesn't heat up from the CH. Does something need bled and if so (haven't checked) presumably the valve is near the immersion tank?

ART6

kbannon wrote: »

We had work done a year ago that involved moving the boiler and ever since then the rads are fine but the immersion doesn't heat up from the CH. Does something need bled and if so (haven't checked) presumably the valve is near the immersion tank?

The hot water tank is on a separate circuit from the central heating. Generally on the tank there are two valves, one low down on the side of the tank but not at the bottom, and one about 18 inches higher up and immediately above the first. these supply the flow and return to the heating coil inside the tank. On many systems there is also a bypass valve that connects the two pipes to the valves. So, the flow and return valves should be open and the bypass should be closed. If your system is atmospheric (that is not pressurised) then you shouldn't need to bleed it since the tank has a vent pipe. If it's pressurised system check the pressure is around 1 bar -- it might need topping up.

copper12

kbannon wrote: »

the immersion doesn't heat up from the CH.

Do you mean that you have no hot water when you have the central heating on
Or do you mean the emersion is not heating the hot tank when the heating is off but you have the emersion on ?

Seth Brundle

The central heating does not heat the tank since the boiler was moved last year. If I use the electric immersion heater its fine (irrespective of the CH).
The CH pipes going into the tank don't seem to be heating up despite that these seem to branch off (downstairs & possibly under the floorboards for the upstairs) for the CH which is fine (upstairs rads were hot this evening when I checked).
The two CH pipes going into the immersion tank branck off pipes that head up to the attic. These are cold about 2 foot above the immersion outlets (around the immersion they are warm but this could have been because the immersion switches were on).
There are no taps/valves that I can see to isolate the immersion but there is some form of valve downstairs (behind the feckin fridge so akward to see) but surely if the rads upstairs are fine then this is irrelevant?
Could the pipes inside the immersion be blocked? (I added corrosion inhibitor about two years ago)
I haven't checked the small tank in the attic - I'll do it tomorrow.

BostonB

I've never heard the hot water cylinder called an immersion tank before. Its very confusing.

Maybe theres a valve not working. I can heat my hot water cylinder separately from my radiators, just using the boiler.

copper12

if you could post a pic it might help of the hot water cylinder

Seth Brundle

It seems to be like the indirect cylinder pic here!
http://www.diydoctor.org.uk/projects/domestic_hot_water_systems.htm

copper12

I meant of your cylinder and the pipe work around it?
Usually there is a gate valve that balancing the hot water’ I am thinking’ this might have been closed or blocked
You would seldom have trouble with the hot water coil in a cylinder’ but anything is possible
This valve behind the fridge’ any idea what this is for’ could it be used for isolating the rads for summer hot water

Seth Brundle

I'll get a pic tomorrow - opening the hot press can wake the kids. There isn't much to see though tbh!
The pipe that the 'valve' is on seems to serve the entire upstairs (rads and cylinder) after it branches off the downstairs pipes - it looks similar to an air valve in my folks house - that kind of cover - its not a tap valve from what I can see.

copper12

If there’s three pipes most likely ¾ going up then one of these could be the flow to the hot water cylinder
Place your hand above this valve and turn it anticlockwise until you feel it getting hot don’t open it to much

byte

Funny, Ive noticed the other day that I'm experiencing the same problem. I've the "indirect cylinder" setup also. There's a stopcock where the pipe leaves the bottom (No 3 in image), but even having it open full has no affect.

Where the pipe enters the "flow from boiler", its actualy a Tee, with main pipe making its way up into the attic. Presumably it continues as an overflow into the tank.

Seth Brundle

Downstairs (behind the fridge where the pipework splits) two pipes head upstairs. These may branch off under the floorboards for the upstairs rads - I don't know yet but presume so. However above the floorboards (in the hot press) they branch off into the cylinder. The main pipes keep heading north right into the attic.
There are two other pipes in the attic - the water pipes going in and out of the actual cylinder (feeding the hot tap).

The valve is behind the fridge which is in a kind of alcove and a bitch to get in/out - I'll try and get a pic but I honestly think its not really relevant.

BTW I do appreciate the help!

Seth Brundle

The attached pic shows the setup behind the fridge. Looking at it I presume its a form of pressure relief valve - maybe you can confirm.
I'm not sure where the pipe on the left goes - possibly to the back of a fireplace?
Anyhow, the two northbound pipes are visible there.

JamesM

Make sure that there is water in the header tank in the attic - and that it is getting down to the system. When there is not enough water in the system, the hot water circuit is usually the first to be effected.
Jim.

SoldOut

I had this same problem a few weeks ago after being away for a month so there was no heating on. The immersion is upstairs so I turned off all the radiators upstairs for about half an hour then when I could feel the immersion getting hot I turned them all on again and everything has being working perfect since.

Seth Brundle

Attached are the CH pipes linked to the cylinder. These are the pipes I previously mentioned three posts up. There are three other pipes in the hot press (on the other side of the tank - a mains going up to the attic & hot water pipes (which also go up to the attic and down under the floorboards).

I tried turning off the rads upstairs this evening but 'er indoors had already had the immersion on before I came home. However, I'm fairly sure that the pipes in the attached pic were hot (and not from the already hot cylinder).

The header tank in the attic seems to be working perfectly. Water up to its max and pushing the float down lets more water in.

copper12

Has the problem developed from when you moved the boiler
If this is the case then it’s something you done or didn’t do; that is tie the pipe work properly
Easily done if it was a DIY job' you need to check around where the tie in was done around the boiler or there’s a valve shut off somewhere

Seth Brundle

It has happened since then but the boiler was in an outside shed which was knocked and moved to a different shed.
The pipework going from the boiler is the same as before and there are no valves to isolate the CH from the cylinder - the cylinder is effectively on the same network as the rads! Thats why I'm stumped!

copper12

There may be an air lock turn off all the rads then turn on the heating
Turn off the heating and on a couple of time in quick succession this might move the air lock also there may have been some debris got into the pipe work and may be stuck in the tee’s have you bleed the rads is there water coming out of the bleed holes

Seth Brundle

The rads are all fine.
I'll try turning off the rads agin tomorrow evening and see how it goes - hopefully the pressure with the rads off will sort it out whatever it is.

copper12

With the pump running water will find the easiest path there is usually a valve that balances the hot water going to the hot water tank otherwise you would have the hot water tank getting all the hot water and the radiators very little there is something either blocking the water getting to the coil or there’s a valve turned off

Seth Brundle

I'll check under the floor when I get home but the builders definitely didn't touch anything inside the house.