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!

 

[kris]

Shouldnt be nescessary if the system filled up easilly ??????? did it

 

[Nimit]

Yeah filled up no problems.

 

[village idiot]

drain down system again and backfill with cold mains through a drain valve on rad. Make sure you keep an eye on f&e tank or you may flood the place. That will eliminate any air lock issues

 

[kris]

Id defo check pump me thinks

 

[kris]

open motorised valves manually when filling via grav try n let it all fill at same time

 

[AssuredHeating]

Have you checked the pump is def spinning?? Id **** the pump valves, remove the pump head and turn it on, sometimes the impellers can wedge in place, and the pump will still vibrate like it's in action. By removing the pump head you can confirm the pump is def spinning

 

[lame plumber]

do they by any chance have trvs fitted, if your as hot as we were down here,I doubt if the trvs would open !!

 

[kris]

Lame will be right , i never thought of that as up north of scotland its never an issue lol but lames bang on the trvs wont be opening if it was that hot down with you guys

 

[Riley]

I'd def be looking at the pump

 

[townfanjon]

Did you manually open the zone valves before filing

 

[Nimit]

Have you checked the pump is def spinning?? Id **** the pump valves, remove the pump head and turn it on, sometimes the impellers can wedge in place, and the pump will still vibrate like it's in action. By removing the pump head you can confirm the pump is def spinning 

I did feel the pump to check if it was spinning and it did feel like it was. Good tip though. I will do that on my next visit there.

 

[Nimit]

do they by any chance have trvs fitted, if your as hot as we were down here,I doubt if the trvs would open !!

No they haven't got any TRV's fitted.

 

[Nimit]

Did you manually open the zone valves before filing

Yeah opened them up.

 

[kris]

Not sure if you said youd done this but id turn off most rads and leave just one on quite near the boiler and switch on heating, measure temperature on flow at boiler and after MV ( just to make sure its opening fully) then check temp at rad, if they are fine then defo air , if not then MV or pump, but make sure boiler is heating the water to appropriate temp,,

 

[Nimit]

Hi all,

Need some more help on this please.

Original issue was resolved. There was an airlock and I got rid of this by back filling via the drain off. Tested the system at the time and everything worked as it should. All rads were getting nice and hot.

Customer has called me this evening as it is now getting colder and said only the upstairs rads are getting hot.

I am going back tomorrow evening to have a look. Any ideas what could be the cause and what I can do to remedy this?

Just to recap it is an open vented s plan system.

Thanks in advance.

 

[Riley]

Did you check the pump?could be a broken impeller or just not turning freely/at all.

 

[jase158]

Pretty sure it is pump, possibly wiring issue!!

 

[Nimit]

Didn't check the pump at the time after as airlock issue was resolved and all rads were getting hot. Guess I should take a spare pump with me and try that.

 

[jase158]

usually is pump as gravity will heat upstairs rads, but not downstairs, unless its air getting in from vent (did u turn pump down after you finished the work?)

 

[Nimit]

Left the pump settings as they were from before.

Thanks for your help btw.

 

[Neil K]

Only reading this thread in full now. Yes airlock your original problem, now its the pump

 

[jase158]

Does sound like pump but i have had a couple systems that work fine and about 2 weeks later they hear a loud gushing and then half the rads don't work, usually after power flushing.

push the air out and its sorted!!

 

[Nimit]

Went to customers today. Changed pump and everything worked fine. Thanks all for the advice.