No heat in downstairs radiators

[mattwood22]

Hello,

We have an issue with our downstairs radiators not warming up. Upstairs working fine. Boiler has been serviced and all fine. Boiler man said we needed a power flush. System has been power flushed. Radiators get warm with the power flush machine active but not with the boiler. Tried turning all upstairs radiators off but still no heat reaching downstairs.

The Powerflush guy suggested there is a number of things this could be, the first thing to check being the three way diverter valve, but having read online about how this works it doesn't seem to differentiate between upstairs and downstairs and is clearly supplying part of the heating system?

Pump is working. Rads are bled. Open vented system (I think that's the name? We have a tank in the loft that feeds the system and a hot water cylinder)

10mm pipes which isn't ideal, but they've worked fine up until now.

Am I missing something or is there suddenly a complete blockage between the last upstairs radiator in the loop and the first downstairs one?

Thanks in advance for any help

 

[Stuckinarut]

Is this a new issue? Is this a new build problem? Do you have dual zones?

 

[mattwood22]

Thanks for the reply. Yes we've been in the house 10 years and this has happened this winter. The house is about 30 years old I think. And the heating isn't zoned it's either all on or all off (when working!)

 

[mattwood22]

[Deleting double reply]

 

[Stuckinarut]

Ok, so although the pump is working, it could be weak. If you’re confident and capable o can talk you through a process to test. How old is the pump and is there a bleed screw?

 

[mattwood22]

I'm unsure of the age, so over 10 years. It's a Grundfos 15-50N and does have a bleed screw. A walk through on how to test would be great!

 

[Stuckinarut]

So, with the pump running (heating or hot water demand or both) place a suitable container, if not just an old towel, remove the bleed screw and there should be a dribble of water from it. Using a screwdriver apply a small amount of force, if the pump stops it’s weak, if it takes a bit of effort or doesn’t stop it’s ok.

 

[mattwood22]

I can stop it really easily by pushing the screwdriver down the side. Less easily when pushing into the middle of the spinning 'thing'.

I can't seem to attach a video, I'll try find somewhere external for it

 

[mattwood22]

Not great but hopefully an indication of ease...

 

[Exedon]

The 15 50n is a bronze pump also the yellow colour gives it away. That was a very expensive pump to be on a heating system.
You absolutely sure that it is the heating pump?

 

[mattwood22]

I'm not 100% sure, but I can't think of anything else it could be for. It feeds the three way diverter, comes on with the heating/ hot water. Pipes either side get hot...

 

[mattwood22]

I've replaced the pump today and 2 of the 5 downstairs radiators have sprung back to life. I'm going to leave the pump on full power for a few days and see how the last three get on

 

[mattwood22]

This morning I've turned off all rads (with TRVs) except the three cold ones. Two are now warm! So I suspect either an airlock/blockage has been pushed through or balancing is needed.

The final radiator is still stone cold as are both pipes. This also happens to be the radiator taken off for power flushing. I'm wondering if the radiator itself is air locked (as opposed to the pipes)?

Thanks all for your help @Stuckinarut . 3 plumber visits and none got to the diagnosis of weak pump.

 

[Stuckinarut]

The warm ones might just need a balance, obviously difficult to tell without being there. As for the cold one - could be an airlock elsewhere affecting it or something else.

Depends on who you're dealing with and I wouldn't want to cast aspersions without anyone being able to defend themselves, however some things are perhaps suggested to generate income?

 

[mattwood22]

I've removed and flushed the final cold rad with the garden hose. While it was off I opened the TRV and lock shield and both spluttered a bit with water and air coming out. Refitted and bled. Turned the heating on and it's warm!

@Stuckinarut I owe you a pint