Page 1 of HELP...dodgy central heating

Plumbing boffins
We`ve got an ancient boiler (not a combi... obviously) which we are waiting to pack up so we can get a new one for nowt from those wonderful Warm Front people. Anyway, we are still getting hot water and the boiler is firing, but the radiators are not getting hot (the downstairs ones are stone cold and the ones upstairs get ever so slightly warm, which they always do when the water is on). Heat exchanger? Pump? You decide...
Thanks

I`m no boffin but maybe there is air in the system and needs bleeding/draining?

We had a problem at one of my old rented places where the T valve would not open so the radiators never came on.. Basically water enters from the boiler and can either go to a circuit for the hot taps, a circuit for the heating or both depending on the position of the valve. (in my basic understanding of it) I had to remove the electrical motor unit (switch off of course) and manually open the valve with a pair of mole grips.

I think air normally means they heat up very slowly or perhaps only paritally.

This item was edited on Monday, 30th April 2007, 16:31

As Sashendon sez, its likely to be the diverter valve..... but there could be other reasons for your problem - depending on the system, you will have whats called a 2 or 3 port diverter valve, (check the obvious first by bleeding the rads at the highest point in the system just to satisfy yourself there is water in all of them) - post back and let me know if you have a time clock or programmer on the wall, also can you have the heating on seperate from the water? i.e is the clock mechanical and u have to slide switches or toggle switches over to select the mode? - water only or water and heating - or water or heating seperately controlled.... if the former u are likely to have a 2 port valve, if the latter it will be a 3 port valve - 2 many variables to go into without some more info :B

Not an expert, but could it be a)air in rads/system b)sludge in rads, c)pump not working properly? But if the pump was dead, I think you`d find the boiler lights won`t come on, in order to prevent over heating in the system. d)thermostat fault. Sorry don`t know about the T tube.

We recently had to get our heat exchanger replaced because it was leaking, even though we could get hot water and the rads worked. British gas tried to blame our agressive water that was damaging the 3rd heat exchanger in 3 years! Fortunately they took a water sample which came out in our favour and no powerflush required :), Otherwise they`d have made us have a £750 power flush.



Niteowl

It will more than likely be the flowshare (diverter) valve - they get clogged up and stop working, we have had ours changed about 3 times.

why take life so seriously..its not like you are going to make it out alive

Thanks for the feedback.
Where do I find the diverter-valve, flowshare, pump etc? Are they usually hidden away somewhere? If so, I`ve no idea where they are, as the system was there when we moved in and any work that needed doing before was done by a plumber. If the fault is one of the things mentioned is it mendable or, considering the age of the system, is a new boiler required sooner rather than later. Are we okay using it at the moment for hot water only??

Ramshackle: We used to have a digital programmer but that went kaputt a couple of years ago so we`ve now got a 24-hour, rotating dial, mechanical click on-and-off type thing. You can have just the water on or water and heating, but not heating only. This is set by slide switches which also set it for "once, twice, all-day, off".

Right that narrows it down considerably then - you will have a 2 port valve then not a 3 port - you should also more than likely have a Domestic hot water tank stat as well, though this isnt always the case, I will try and make it as simple as possible to help you fault find but there are many reasons for the fault you have!

if you have a hot water tank stat this plays a major part in the system as it is the changeover switch in their that allows the diverter valve to move and let the water flow through the rads and the hot water tank at the same time, your type of system is usually whats called water priority or "W plan" - unless the stat changes from "call" to "satisfied" you will not get water round the rads....

So you have 2 possibilities so far...

1. The diverter valve motor itself has failed or the valve has seized.

2. The domestic hot water tank stat has failed / is switching over but the contacts inside have failed and failing to send a "call" to the diverter valve which in turn fires up the boiler...

You should find the diverter valve in the same cupboard as the pump and domestic hot water tank - i would rule out the pump as if this has failed the Boiler would have come out on the internal over temperature stat and gone into "lockout" due to the excesive heat generated when a call for hot water was recieved.

To be honest unless you are handy with a mains tester and can confirm the integrity of the hot water tank stat / diverter valve switches theres not much else you can do.

Also please be aware that many older 2 port diverter valves are NOT designed to be taken apart in situ and any attempt to do so will result in lots of water everywhere.... (although if the motor has failed you can usually remove this safely in situ) newer models have removable heads leaving the valve body in place.

You shud however be able to just remove the cover plate or access the manual lever on the valve, if its just the valve stuck, you may be lucky and be able to free it up by moving the valve from auto to manual via the lever..

Do the lever test with the power to the system off or you will be fighting the actuator if the motor has already swung over..

Sorry for the long reply, and hope you can sort it from the info above... and yes i am a plumber.... ;)

This item was edited on Wednesday, 2nd May 2007, 20:23