Downstairs rads taking ages to heat

[Frosty7]

Hi there I’m brand new to this forum and really need some help.
my downstairs radiators can take an age to heat up. Sometimes they just don’t heat up at all. Other times they do heat up and all is good. Until I turn the heating down at night and the issues begins again the next morning. A heating engineer has suggested a power flush. Any help/advice would be really appreciated.

 

[Aquarius]

What type of system do you have? Do you have any motorised valves?

 

[Frosty7]

What type of system do you have? Do you have any motorised valves?

Hi thanks for the reply.
move got the water tank type. Not a combi boiler. Sorry that’s as much as I know about the type of system. I do have a 3 way motorised zonal valve. The pump is definitely running.

 

[Frosty7]

Hi thanks for the reply.
move got the water tank type. Not a combi boiler. Sorry that’s as much as I know about the type of system. I do have a 3 way motorised zonal valve. The pump is definitely running.

What is confusing me is that then downstairs rads do warm up just never as hot as the up stairs ones and it’s a lottery as and when they heat up. As if this moment i have turned the heating off. Opened all rads to fully open. Then turned the heating on. Within minutes the upstair rads are proper hot. Nothing downstairs though

 

[SJB060685]

Could be the system needs balancing and would be my first approach.

 

[Frosty7]

Could be the system needs balancing and would be my first approach.

Ive tried that many times unless I’m doing it wrong. I’ve opened the shield valves half a turn on the upstairs rads. They get roasting. Just now I’m I’ve closed them all up stairs to see if this does anything. Also just tried bleeding the downstairs rads. A steady flow of clean water comes out

 

[SJB060685]

Yes turn off all the upstairs rads and see if that makes a difference.

 

[Frosty7]

Yes turn off all the upstairs rads and see if that makes a difference.

 

[Frosty7]

Right. Just done that. 10 mins ago. Still not heat in the slightest.

 

[Frosty7]

Right. Just done that. 10 mins ago. Still not heat in the slightest.

The pipes going into the pump from the boiler and out the other side of the pump to the radiators at roasting. To hot to touch

 

[SJB060685]

Could be a pump problem, the upstairs radiators heating up through gravity circulation.

 

[Frosty7]

Could be a pump problem, the upstairs radiators heating up through gravity

 

[Frosty7]

I think you could be right. It’s a Grundfos 15-50. It’s been quite noisy for sometime. I just tried bleeding it by undoing the centre bleed screw and the pump stopped. As I tightened it up it was struggling to turn (the pump I mean)
Had to find a sweet spot where it doesn’t leak out of the bleed screw hole and the pump turns. That’s not right is it?

 

[Frosty7]

Could be a pump problem, the upstairs radiators heating up through gravity circulation.

think you could be right. It’s a Grundfos 15-50. It’s been quite noisy for sometime. I just tried bleeding it by undoing the centre bleed screw and the pump stopped. As I tightened it up it was struggling to turn (the pump I mean)
Had to find a sweet spot where it doesn’t leak out of the bleed screw hole and the pump turns. That’s not right is it?

 

[Ben-gee]

No. Time to replace the pump then you’ll be fine.

 

[Frosty7]

No. Time to replace the pump then you’ll be fine.

Ok. Thanks everyone. Couple of final questions. Where is the best place to get a new Grundfos 15-50 pump? And I take it I will only need the pump. No need to replace the housing with the unions? Also how much? I see them ranging from £160 - £250

 

[SJB060685]

If the pump is rotating sometimes then you MIGHT and im not saying do but might have a weak capacitor.
Probably best to replace the whole pump though to ensure future function.
I would change the pump valves at the same time.

 

[Frosty7]

Ok. Thanks everyone. Couple of final questions. Where is the best place to get a new Grundfos 15-50 pump? And I take it I will only need the pump. No need to replace the housing with the unions? Also how much? I see them ranging from £160 - £250

Ok. Thanks everyone. Couple of final questions. Where is the best place to get a new Grundfos 15-50 pump? And I take it I will only need the pump. No need to replace the housing with the unions? Also how much? I see them ranging from £160 - £250

Ok. Thanks everyone. Couple of final questions. Where is the best place to get a new Grundfos 15-50 pump? And I take it I will only need the pump. No need to replace the housing with the unions? Also how much? I see them ranging from £160 - £250

If the pump is rotating sometimes then you MIGHT and im not saying do but might have a weak capacitor.
Probably best to replace the whole pump though to ensure future function.
I would change the pump valves at the same time.

Sorry but what it the capacitor?
And the valves your are talking about are they the ones directly above and below the pump?

 

[SJB060685]

A capacitor is a device that helps start and run the motor. Yes the valves above and below the pump are best changed as well, they're notorious for leaking if you touch them.

 

[Aquarius]

Probably a Grundfos ups pump might be needed now, as they’re all energy efficient products now. About £85-100

 

[Frosty7]

A capacitor is a device that helps start and run the motor. Yes the valves above and below the pump are best changed as well, they're notorious for leaking if you touch them.

I just want to update.
my heating is now working fine thanks to all who replied.
the problem was a few things.
1. the heating engineer closed the bypass valve completely as with a 3 way zonal valve there is no need for a bypass as the valve is never closed.
2. The return pipe is 28mm. He said the return is not required to be so big so he closed if the valve on the return a little therefore restricting the return a bit.
3. The pump. The pump was replaced.
I’m now getting roasting hot radiators all round the house and they get to heat well within half an hour.
Result
Cheers

 

[Ric2013]

Glad to see you got it sorted and thanks for coming back to us. Hearing whether our speculations are correct is what makes our time on this forum worthwhile.

 

[Frosty7]

Glad to see you got it sorted and thanks for coming back to us. Hearing whether our speculations are correct is what makes our time on this forum worthwhile.

No worries I completely agree.
the pump alone may have fixed it but good to know about the other issues which help to fix. I’d never have known them