Rads not getting hot!

[Nimit]

Hi all,

Need a little advice please. A customer said his radiators were not getting very hot like they used to.

I checked the zone valves (s plan vented system) and replaced the hot water zone valve as it was faulty. Also manually removed all the rads and flushed and cleaned them in the garden. System was filthy. It hasn't had anything done to it for ten years. I did put in Sentinel X400 and left it in for two weeks before I did this.

Now when the boiler is on the zone valves and pump all work as they should do but none of the rads get hot. I can feel water is going around on the flow and return pipes in the loft. I have tried closing all rad valves apart from one rad and still that is not even getting hot! Any ideas what I can do to resolve the problem?

 

[Simon F]

is the boiler overheating??
new pump

 

[Dotty]

Do the pipes to and from the cylinder get hot?

Also check that a muppet hasn't installed a loop between flow and return.

 

[Nimit]

Boiler isn't overheating. Pump is working fine. The pipes to the cylinder are not getting hot. It was a problem before but is ok now the zone valve has been changed. There was a by pass with a 15mm ballofix which was half open. I've closed it but has not made any difference. Although it could be broken. Will change that next time I go there.

 

[kris]

I would measure temp on the flow pipe leaving the boiler and that will eliminate or point you in right direction of where heat is going if theres heat atall

 

[Nimit]

I would measure temp on the flow pipe leaving the boiler and that will eliminate or point you in right direction of where heat is going if theres heat atall

The boiler is in the kitchen and the cylinder, pump and zone valves are all in the loft. The flow and return pipes for the rad circuit is hot. Would measuring the temp on the flow pipe by the boiler still apply here?

While I was there I tried hitting the valves on one radiator a few times to see if anything was blocking it to no avail. Also I tried letting water run through the bleed vent which allowed some how water to come through but it seems to not be circulating and cooled again.

 

[kris]

Theres a difference between a pump thats turning and u pump thats turning but lost all it uumph, sounds like air , or sludge or pump, defo a circulation problem, is it pressurised system or gravity fed,, i know you cleaned rads but with emptying system its maybe moved dirt in pipes possibly, maybe pockets of air,

 

[kris]

Measuring temp at boiler will simply eliminate the boiler , at least its heating the water satisfactory, so problem defo circ

 

[kris]

Do as croppie says there maybe a loop and the water simply traveling the simplest root if struggling

 

[Nimit]

The system is gravity fed. I was thinking next time I go back I will connect the the cold mains straight to the flow pipes and try and flush through any remaining sludge. Good idea? Also if it is air pockets how would I go about getting rid of them?

I did notice that the pump there was a 25-80 set at the highest speed!