Only some rads warming up, CH pump not operating (?), red light on CH pump relay

[Captain Scarlet]

Hi,

Big house with two zones (upstairs, downstairs) and many rads. Turn to manual, boiler fires up, but only about half the rads upstairs warm up, and none of the rads downstairs warm up. If I isolate the upstairs rads, some of the downstairs rads warm up, but only after a long time. Hot water (2 tanks) seems to work fine.

Just trying to rule out the simple faults before calling a plumber out...

When boiler fires up, there's no sound or vibration from CH pump - I assume it's not operating. A red LED lights up and remains lit on the pump relay (marked IMO RS2 PN 230AC). Upon closer inspection I also notice some signs of scorching (?) at the contacts (see photo below), I don't know whether this is normal or not. Does this suggest that the problem is the relay and I should simply buy a new one and try that?

Other information, in case it's relevant:
- Boiler - oil fired Worcester Greenstar Utility
- Pumps - Grundfos UPS 15-50N
- Valves - 2x Honeywell V4043H motorized zone valves (one marked upstairs, one marked downstairs)

In addition, there are 2x Grundfos UPS2 15-50/60 pumps and associated valves, I think these feed the HW tanks

Any advice gratefully received

 

[CBW]

Have you checked that the zone valves are opening correctly? If you have only 1 red led that might be the pump speed setting, which could be too low.

 

[Captain Scarlet]

Have you checked that the zone valves are opening correctly? If you have only 1 red led that might be the pump speed setting, which could be too low.

Thanks,

I moved both valves to manual 'open' position in the notch and tried everything again - exactly the same symptoms.

Then I moved levers back to auto 'off', and started CH - no movement in levers, no signs of life from pump.

 

[CBW]

I would check the zone valve wiring then to make sure there’s a switched output.

 

[terryplumb]

It your boiler is firing up ,but only some rads are heating up ,that's very likely a pump issue. Is there 230/240 volts at the pump ?