Heating/boiler problem

[MyCatLovesMeSometimes]

Got a strange problem with my boiler and wondered if anyone could offer any advice?

The central heating doesn't seem to be switching off but this only happens intermittently. It seems to be related to the hot water as when I turn that back on again and then off (on the timer unit says it's a model Lp241) the heating then turns off finally.

Had the plumber out once who couldn't find anything wrong but this is now happening every other day or so.

The boiler is a 20 year old Baxi Solo 2 (which the plumber has also advised won't be worth replacing if anything major goes wrong with it).

this is an ACL Drayton programmer, quite old, but they are a very good brand. If you are sure it is the programmer at fault, it would be very easy to swap it for a new one. IIRC it has a standard backplate, and by undoing the retaining screw underneath, you can swing the box out and off, and it unplugs leaving all the wires connected to the backplate.

see here www.draytoncontrols.co.uk/homeownerzone/products/timecontrol/LP722programmer/

the LP722 is more advanced and widely available at good prices, for example.

The only other brand I would recommend is Honeywell.

Unless you are unusually handy, it would be safest to have your heating engineer fit it for you. IIRC it has a gravity/pumped switch on the back, and he can also verify that all the connections on the new one are exactly the same as on the old, and change them if not. If you currently have an old "knob" dial wall thermostat, ask him what it would cost to fit a Honeywell CM907 Programmable Thermostat, because my preference would be to go for a very simple HW timer, and control the heating with that, it is probably the best on the market. The labour cost will be very similar. The CM907 will not control the hot water, though.

I gather you do not have a combi.

p.s.

It might also be the three-port valve. This has a motor which is operated by the thermostats on the wall and on the cylinder, and as it moves, it operates a switch that turns the pump (hence the boiler) on and off. I can't remember, but I think it may keep the boiler running if the motor has not rotated correctly to operate the switch. An older engineer should be very familiar with it and should be able to meter its terminals or turn it by hand.

It looks like www.screwfix.com/search?search=port+valve and is probably next to the pump and/or cylinder and/or boiler. If you stand next to it while someone turns the timer and the thermostats on and off, you will hear it whirr open and closed. It should take 1-2 seconds, no more. If it is working correctly, when the system should be heating the radiator, the leg and one of the arms will be hot, and when it is heating the cylinder, the leg and the other arm will be hot. Unless it is very old, when heating both the cylinder and the radiators, the leg and both arms will be hot. If either arm gets fully hot when it should be off, it is worn out.

Drayton and Honeywell are the good brands, they last about 20 years. There are also some cheaper brands.

Apologies for not coming back sooner.

Many thanks for the advice and the links, it's really appreciated.

Dh and I have been talking about replacing the boiler next year so hopefully this will keep it going till we can afford to replace it.