Tepid Radiators - losing the will!

[TiSwAs]

Hi,
i have a problem with a tepid radiator in our single story extension.
The central heating was fine all radiators heated nicely, since the new extension (2 years ago) the radiator never gets hot only tepid half way up the rad, I know from the build that the radiator in our unstairs en-suite was tapped into to feed the new radiator in the extension and that a rad in the kitchen was taken out and capped (both pipes had brass caps fitted and hidden behind skirting board) is this causing my problem?!?

I've tried the following -
Had the central heating off and closed all the valves - turned CH on and then opened the radiators starting from the furtherest way (now this is where i might have gone wrong) i presumed that the furtherest was the new extension radiator it came on hot the main on/off valve pipe was cold but the other side was hot and obviosuly feeding the rad (is this an issue?) then i proceeded to do what i thought was the next and so on.... it turns out that last rad to be turned on never got hot only very tepid.
The next test i peformed was to turn off the first rad (extension) and the last rad (small bedroom) whilst the heating was on - turned on the last rad (small bedroom) and it got warm-ish, then turned on the extension rad - never got hot only tepid half way up the rad

To add i was getting some wired gurgling noises from our Ensuite rad turns out that the rad was only HOT 2/3rd's way up - so i bleed it and there was obviosuly 1/3rd full of air - got that out and now that rad seems ok - i then proceeded to bleed the other rad's but they were all fine.
I bleed the tepid ones for a while too but it was only bleeding cold/tepid water out of them.

To me it seems like the system/pump doesnt have enough power to pump the water round to all rad's, I've recently had the pump (very noisy) and zone value (motor packed in) replaced (system was drained down only).i didnt tell the plumber that i was having the heating issues as i thought the replacements would solve it (maybe i should then he could have investigated it) i rang him the next day to tell him the issue he said the pump i purchased was sufficient enough for all the rads in my house.
The other tiny issue which i thought i'd mention just incase it's related is that the hot water pressure is very very poor, it's bearable in the upstiars main bathroom sink but the bath and kitchen hot water trickles out.

My boiler is a conventional system

Many thanks for your time in reading - hope someone can give me some ideas on how to resolve.

Kind Regards
Dave.
　

 

[RoryD]

Too much for me to read m8. Can't work out if it is one or load of rads playing up and if they are upstairs or down...all this is relevent

 

[TiSwAs]

Too much for me to read m8. Can't work out if it is one or load of rads playing up and if they are upstairs or down...all this is relevent

after the last attempt at fixing it does seem like 2 tepid radiators now... but no matter which 2 radiators it is it seems to follow the ones i've turned off and back on again so that could be 2 upstairs or 2 down stairs or 1 up and one down!

 

[patreed]

Too much for me to read m8. Can't work out if it is one or load of rads playing up and if they are upstairs or down...all this is relevent

Agreed, way too much narrative 🙂

Have you tried a powerflush and then re-balancing of the rad valves using an infra-red thermometer?

 

[WHPES]

Sounds like airlock and / or out of balance to me but I can't be bothered to read it all!

 

[jcbstuart]

I Have the same problem. I bled all the radiators and got them to work fine.
I replaced the bathroom taps on the bath. Turned the water back on, and now the 2 toilet`s up stares wont fill up. I have lost pressure on the cold tap for the bath and no cold water on the sink. If anyone can help that would be great. Thank you from jcbstuart

 

[Howsie]

What Kw boiler do you have?

 

[M.Joshi]

We had a similar problem with a pump in a new boiler failing after a couple of years. Your system may be clogged up with sludge. If you don't want to pay for a Powerflush, try running Sentinel X400 through the system for a few weeks. Then drain it out. Remember to flush the system through with clean water and then fill adding inhibitor.

 

[M.Joshi]

I replaced the bathroom taps on the bath. Turned the water back on, and now the 2 toilet`s up stares wont fill up. I have lost pressure on the cold tap for the bath and no cold water on the sink. If anyone can help that would be great. Thank you from jcbstuart

You have an airlock in the system. If you have a combined mixer bathroom tap (hot & cold), turn both taps on and block the tap outlet (i.e not allowing water to come out). Water from the hot tap should push the airlock out from the cold pipe. Don't do this for too long as you may contaminate the cold water supply.

 

[doitmyself]

i have a problem with a tepid radiator in our single story extension.
I know from the build that the radiator in our upstairs en-suite was tapped into to feed the new radiator in the extension

Turn off all rads except the one on the extension.

Does the extension rad now get hot? If it does, you have a balancing problem. Read How to balance a CH system

the main on/off valve pipe was cold but the other side was hot and obviously feeding the rad (is this an issue?)

It's not important. If the main valve is a wheel valve (not a thermostatic valve), just swap the wheel top with the plain top the other end (assuming they are the same make).

You adjust the lockshield (plain cap) valve when balancing, whichever end it is on.

 

[Roger Welton]

Assuming its all piped up corectly (did the builder do this himself or get a plumber in?) then it must be a balance / air lock problem.