Oil Boiler not heating the water tank in the airing cupboard

[David195757]

Sorry to bother everyone. My brother in law sadly passed very young last year and he was always the person to sort problems of this nature.

I have been asked to take a look at this problem. I checked the tank today and it is not being heated by the boiler. I do not know how long this has been going on for.

The oil boiler is working fine and all rads heat up as normal. Regularly serviced.Please assume the immersion is working fine for now. I took some photos and the only thing I can see is there is a shortish pipe coming out of the right side of the tank which has a red round handle attached to it. That is in the off position. There was a leak affecting this pipe I believe several years ago, note the dried up water stains.

If anyone has time to look at this and make any suggestion from the info provided it would be appreciated. thanks.

 

[ericmark]

The valve seems to be to a capped pipe, so a red herring. There are three popular systems.
C Plan, often no motorised valve.
Y Plan, single three port motorised valve.
S Plan, two or more two port motorised valves.
My C Plan the DHW can't be turned off, today C Plan only seems to be found with old oil boilers. With my system, cheaper to use the immersion heater in the summer, mine will not thermo-syphon in the summer, some will, and with those, there is often a valve to close for summer use.

 

[CountryFan]

As above, likely a motorised valve (if fitted) at fault. On a separate note, there’s no insulation on that copper cylinder, so when it’s heated, don’t expect it to last long. You can get a hot water cylinder jacket though.

 

[David195757]

Thanks for replies. It’s my very elderly mother in laws boiler, I’ll check if immersion works and then after that I’ll ask plumber to take a look. I assume unlikely a layman like me would be able to fix valve problem.

 

[Hugh Jaleak]

Short, capped pipe I'd imagine was the original cold feed to the system, this has been removed, how is the system supplied/topped up with water now do you know?

 

[David195757]

Thanks, I believe water is supplied through a separate small tank in the loft

 

[oilhead]

looks like a gravity circuit with the vent/feed on the vertical extension from the top cylinder pipe. Have you checked that there is water in the small header tank?

 

[David195757]

I haven’t. I will get opportunity to check that in a couple of days. All rads in house are heating normally, but would that still happen if there was no water in small tank?

If there was no water in small tank, should it still be possible for the immersion to work via the switch?

Assuming your diagnosis is correct what should I say to plumber when explaining the issue?

Many thanks

 

[Hugh Jaleak]

Water in the small cistern feeds the Primary circuit, that is the Boiler, Radiators and the Coil inside the Cylinder. The Hot Water you draw from the taps is the Secondary Circuit, fed from the larger Cistern above the cylinder, this is totally separate from that in the Primary Circuit, heat is transferred from the Primary water as it travels through a coil of pipework inside the cylinder, into the Secondary, Domestic Hot water. So, in simple terms you have 2 lots of water, that cannot mix. The system keeps them separate.

The Immersion will heat the Secondary water as required regardless of what the Primary Circuit is doing, but if the Radiators are working, then there has to be at least some water in the Primary system.

Possible issues are, there could a Valve on the Primary circuit preventing the water from the Boiler reaching the cylinder, or, if the Primary circuit from boiler to cylinder is still reliant on gravity circulation, the pipework could be blocked with sludge. Can you trace the capped off pipe and the one adjacent going into the Cylinder, back to the boiler?

 

[dilalio]

Look for a couple of motorised valves.
These are normally close to each other and are boxes mounted to valves on pipes. One will be on a pipe going to the cylinder.
You can usually manually open and latch this to stay open, and whilst you have the heating on, it will allow heated system water into the cylinder to provide you with hot water.

This is a temporary measure and the actuator on the motorised valve needs to be replaced. You can DIY it if you have some knowledge of wiring.

Look up YouTube videos on replacing a motorised valve power unit/actuator.

 

[David195757]

Many thanks for that.

 

[David195757]

Water tank is heating normally now. They got the boiler serviced recently and hadn’t actually checked the tank since they started to switch heat on. So far so goodthanks