SMC twin pump(I think) cent heating problem

Niggy_2

Having read some of the other radiator threads here there seems to be a wealth of knowledge on here and I wonder if you could offer me some advice???

After doing loads of research I think I have a SMC twin pump central heating system (after searching high and low for a diverter valve ???) but I can't work out why my radiators don't work properly.  

If the heating is turned on, on the control panel, the boiler fires up when lounge thermostat is turned up, as it should, but the radiators don't get hot.

The only way i can get the heating to work is by turning the thermostat on the hot water tank up high and this seems to make water pump around the whole system regardless of whether the switch is turned to h/w on or both h/w & c/h. ???

Why should this happen?? I'm pretty sure i can hear both pumps running in garage so I don't think its the heating pump (I may be wrong though)

By the way I have recently moved into this house (my first!!!) so don't have any experience with this system or heating in general.

Any help would be greatly appreciated (My better half doesnt like the cold :-/)

plumb1_2

Has the system worked ok before this fault?,and if you can identify the controls the system has,that would help in working out how its fitted and wired up

Niggy_2

Thanks for your reply

I'm pretty sure that it hasnt worked properly since we moved in but as the boiler hadnt been serviced for at least three years we tried not to use it until the previous owners had an engineer out (long story) and we moved in during summer so didnt really use the heating but we did manage to get heating working (to test it) but this could have been under conditions laid out above.

As for controls, we have a control panel next to boiler, a thermostat in lounge and a thermostat on hot water tank.

The contol panel has a rotary timer (which appears not to work); a switch to select "hot water only" or "h/w & heating" and a knob to select "constant", "off", "once a day" or "twice a day" (dont use last 2 as timer doesnt work)

Hope this helps

budgetflyer

If in fact you have twin smc pumps then you can identify which one is working by setting to heating and hw and putting your ear to a large screwdriver against each one. You should hear the purr and feel a slight vibration.
If one appears to be dead then it should be checked for voltage.
If at this stage, you arent sure how,leave alone and get someone with electrical Knowledge to check
(although a couple of taps with a hammer may free it as it may have just stuck. )
If voltage present, then the pump is goosed and needs replaced. If no voltage then problem is elsewhere (Although this is unlikely as you did say boiler was firing)

SMC pumps used to come in 2 sizes -130 and 180 mm lenghth
Nowadays pumps are only 130mm in lenghth so 2 pump adapters will also be needed to fill the space

Niggy_2

Thanks for your help budgetflyer ;D- I'll give this a try

I have been told elsewhere that the problem might lie with a stuck non-return valve and possible lack of anti-gravity valve on the h/w circuit.

havent had much chance to look at it this week - gonna try and have a good go at it tomorrow

EP90

It could also be a faulty timer (especially as you mention some features don't seem to work and only the HW circuit is being activated)

On my system if the HW circuit becomes too hot it will open the zone valve to dump the excess heat into the central heating.

My system uses an Aga to heat the water though, so might be different to a conventional setup.