Central heating problem - radiators keep coming on!

p4u1_2

Hi

Sounds like you have a problem with the water control valve which is used to divert the hot water from the boiler to either the radiators, hot water cylinder or both. There are 3 different types of valve, the first is a diverter valve which can only select hot water or heating, the second is a mid-position valve which can select hot water, heating or both, and finally there is the zone valve. A statndard configuration will require 2 zone valves and will therefore be more expensive.

The most common setup uses a honeywell mid-position valve. I have had numerous problems in the past when using this type of valve with radiators getting hot during the summer. I would replace the valve, it would then work fine for a year or two only to fail again, usually with the radiators getting luke warm one summer and hot the next. I now use two separate zone valves and have had no further problems since. This configuration is slightly more expensive, but in my opinion far more reliable.

As for the need to use a CORGI registered heating engineer to do the work, the answer to this question is no. The work is on the heating system, not on the boiler, and therefore does not involve gas. Having said this, a central heating engineer would have a better idea of what needs to be done, and they are usually GORGI registered.

My advice would be to replace the mid-position valve I suspect you have, with 2 zone valves.

Good luck!

wonka

p4u1,

Thanks for your suggestion.

Any idea roughly how much a gas engineer would charge to implement your suggestion?

p4u1_2

Hi

Not sure about cost, I've always done this sort of thing myself. I would suggest starting by ensuring that the valve you have is in fact the problem. You can do this by ensuring both the room and cylinder thermostats are turned right up, i.e. calling for heat, then setting the controller for firstly hot water, then heating, then both, then finally hot water. Each transition should result in a whirring noise from the valve. Also check the valve type, the Honeywell V4073A mid-position valve is the type I have had problems with in the past.

Assuming you can hear the whirring noise then the valve head is working correctly and the problem is likely to be with the valve body. Normally problems with the valve head result in the boiler failing to fire up, so I suspect your problem is with the body of the valve. Also check on the valve head for a small lever which can be used to keep the valve open when bleeding the system. This lever should be free to move from one end of the slot to the other.

A replacement mid-position valve will cost about £60, and will take a good plumber/heating engineer around 2-3 hours to fit. A 2 port zone valve will cost around £45, you will need 2 of these, and depending on your paticular setup I would suggest around 4-5 to fit. I'm not a plumber, but have installed a number central heating systems, excluding the gas bit, in the past, so my estimates are based on the time it would take me minus 10-15% for a good professional doing the work.

Hope this helps!

wonka

Thanks for the detailed response!

Final question:
Where will this water control valve be located? Is it in the boiler, or likely to be somewhere near the hot water cylinder (which for me is in the airing cupboard) ?

p4u1_2

They are usually located in the airing cupboard.

Goto http://www.plumbworld.co.uk/763-0000 to see a picture of what you looking for.

wonka

Hmmmm

Just looked in the airing cupboard and found a "ACL Drayton Flowshare 2" device. A quick Google reveals that it is indeed a motorised valve.

I wonder if this is the offender?

There is a lever on a box that sits on top of the valve. It has 2 settings: "HTG" and "HWS" (heating / hot water system??).

lil_me

Tap on the radiator

p4u1_2

This is likely to the offending part. Check it is functioning as per my previous instructions, it might be that it has gone faulty and just need to be replaced. From what you say, it apperas there is a pointer on the top which indicates what the vavle is doing:
HTG = Heating
HWS = Hot Water
Looking on the Web, it is a mid position valve, so with both hot water and central heating selected the pointer should be in the middle.

sponix

jcorbygas wrote:

Yes, you should have a Corgi engineer to change it.

Corgi engineer not needed. Any plumber or handyman can do the job.

However, it could be a gravity fed system in which case the non return valve could be stuck open.

sponix

wonka wrote:

Hmmmm

Just looked in the airing cupboard and found a "ACL Drayton Flowshare 2" device. A quick Google reveals that it is indeed a motorised valve.

I wonder if this is the offender?

There is a lever on a box that sits on top of the valve. It has 2 settings: "HTG" and "HWS" (heating / hot water system??).

get an assistant to switch the system heating-hw-heating etc. The lever on the valve should move slowly from one to the other.

if it doesn't the valve (Or possibly just the valve head needs replacing.