Ideal Classic NF50 not heating radiators?

[Alec200]

Hi all.
I'm new to this forum and afraid I don't know anything about boilers, which is a shame as mine is playing up!
I had a look through the FAQ section but didn't see anything that helped.

The central heating hasn't been used since last winter apart from firing it up about twice during the warmer months to check it still worked. I went to put it on yesterday and had the following problems.

The boiler fires and heats the hot water fine. But when I have just the central heating on with the control unit, the boiler doesn't light. The radiators obviously remain cold.

I've checked the very, very basic things. Thermostat is set to very high and I've reset the mains power to the house to clear the control unit.

Any ideas?

 

[shambolic]

Won't be the boiler. As it's a heat only so if boiler was fault you would have no hw as well
It will either be clock not sending power to room thermostat or room thermostat not sending power to zone valve(silver or White box near pump) or zone valve stuck.
Tbh it will probably be the zone valve. You will have a Y plan one 3 port or an S plan 2 valves.
Check this out first

 

[Alec200]

Sorry for being clueless, but where would I find the zone valve and how should I check it?

 

[shambolic]

They will be small boxes on the pipework near to pump possibly at hot water cylinder one will be on hot water pipes one on heating or a central 3 port version.
Turn on heating and hw look for these valves/valve and if lever on side that you can manually put in open position(used if you are draining or filling system). If you put it in open position and rads heat then test to see ip power on brown wire (for two port valve) if power but not opening then valve head faulty
Google honeywell zone valves or sunvic zone valves to give you an idea of what to look for.

 

[Alec200]

Thanks for the quick replies
I've Googled the zone valves but can't find them in the air cupboard around the hot water cylinder. There are four cables around it. Two lead to water pumps, one to the immersion heater(I think) and the other to what looks like a temperature probe in the hot water cylinder.
Would these valves failing cause the boiler to not fire then?
I've looked around the boiler and no sign of valves there. Where else could they be installed?
Thanks again.

 

[45yearsagasman]

Do you have 2 pumps or any of these View media item 38425 View media item 30391

 

[Alec200]

Here's some pics of what's around the hot water cylinder.

I couldn't see anything that looked like the valves I Googled

 

[45yearsagasman]

Thats a thermal store and the pump bottom right is the CH pump.
Check that it has power to it and is running. Could well be damaged by the look of the crud on the top.

 

[Alec200]

Ok. I've just checked the pumps.

The cruddy looking one on bottom right of hot water cylinder:
1. Small amount of air escaped when I loosened the screw
2. Water soon began to drip quickly out
3. Makes a hum which changes in pitch when the 3 speed dial is rotated.

The better looking pump on top left:
1. Air escaped for over 3 minutes and would have continued if I didn't tighten the screw.
2. Water dripped extremely slowly compared to first pump
3. No hum and no change when speed varied with the on pump dial

Could the pump on the left be the CH pump? Should I test it by disassembling as described in FAQ section or is the CH pump definitely the one on bottom right that seems to be working?

Thanks again for any help.

 

[Alec200]

Any ideas if the pump on the right is definitely the CH pump?

 

[Alec200]

Tested the pumps today. Tens out that the CH pump is the one on the left. Took the pump out from the housing. The jiggling about must have kick started it as it randomly started working again. It's a little noisy so will keep an eye on it.