Cold Radiators

[manicmonday]

I have a Vokera Mynute 16E Gas Boiler with 11 radiators on the system. My problem is that after balancing the system, two down stairs rads are still cold. Upstair the rads a re boiling hot, I have tries turning down the heat, reducing the flow into the upstair rads etc...Any idea very welcome.

 

[Softus]

Shut off valves to all rads except for one of the cold ones. Run system until this rad is hot. Repeat for the other cold rad. Rebalance.

 

[manicmonday]

Thanks for the suggestions but no luck..am thinking now that the pump must be knackered although it seems to be running, or its not powerful enough. On the last service, the service man suggested that my expansion vessel may need to be replaced....could that be part of the problem. Funny..all the rads upstairs are piping hot, have balanced the system and reduced flow to the upstairs rads but downstairs are only lukewarm on the top and the last rad is cold????

 

[Moz]

have you tried bleeding them ..if yes the trvs/rad valves may need replacing

 

[manicmonday]

Rads bled, no air in rads. Close rads last rad on system gets hot. TRV's seem OK. Baffled I am!!

 

[Softus]

Rads bled, no air in rads. Close rads last rad on system gets hot. TRV's seem OK. Baffled I am!!

A worn [out] pump would certainly be consistent with the symptoms you describe. Has the situation got worse slowly, or quickly?

Also, when you say that the pump seems to be running, how are you testing for that?

 

[manicmonday]

Softus, don't really know as I have only moved into the house, house and boiler are 3 years old, but there is an extension off the kitchen with one rad. Perhaps the rad in the extension has been T's off the rad in the kitchen, although the rad in the kitchen is not great.

Thanks for you help

 

[Softus]

Softus, don't really know as I have only moved into the house, house and boiler are 3 years old, but there is an extension off the kitchen with one rad. Perhaps the rad in the extension has been T's off the rad in the kitchen, although the rad in the kitchen is not great.

Thanks for you help

...when you say that the pump seems to be running, how are you testing for that?

 

[manicmonday]

Can feel it running but wouldn't the presence of hot water upstairs indicate that it is working?? Maybe I need a more powerful pump to push the water around the house...will try to source one over the weekend. Thanks for your help!

 

[Softus]

I'm trying to lead you down the path of fault-finding, instead of diasnosis by conjecture, and I would say you (and I) don't have information to say with any certainty that the pump is not powerful enough, especially as the pump is contained within the boiler casing (as is my understanding anyway).

The fact that the upstairs rads are hot doesn't mean that the pump is running - this can happen by convection. Moreover, hot upstairs and cold downstairs is a classic sign of failed, worn, or inoperative pump.

With 11 rads, I presume that you have 6 up and 5 down, but how many downstairs rads are becoming what you would call hot?

If none, then the pump is number one suspect, but before you replace it it would be sensible to check that it's actually running. If is isn't, you'll need to check that pump has an electrical supply, because the failure could be elsewhere.

You say that it feels as though it's running - again, how are you testing for this?

 

[Moz]

to test the pump ...
get a long scewdriver an place the metal end on the pump casing an ear on the other, turn on your heating,can you hear the pump impellor motor working ?
if yes its not the pump

how old is the system (pipework ?) you may have sludge in the downstairs heating flow an return pipes ,
to test ,is the water bled from these rads a dark brown colour