rads not working

[CXR100]

hi all , got a job in work tommorrow , rads not heating up in a property, none of them . i visited this property a week maby ago , and a etra rad has been added on to the system a few weeks ago i thaught that it could be an airlock, but the boiler engineer had visited before me and advised me to replace the 3 port vavle ond the open vented system , so i did, wired it up , but the pump would still not run , but it ran fine when i turned the cylinder stat up , so i replace the room stat wich solved the problem , pump running , rads heating up but not great, (system is in a bungalow . and all piped in atticc and drops down to rads) anyway , had a call back today , rads all cold again , but when i close they bypass i can feel the heat going up the heating pipes to the atticc, but rads still not heating up. a guy in work rekons it the ball in the 3 port that has come loose and blocking the pipe or something??? never heard of this happen before. anyway im going back tommorow. im 95% thats its an air lock on the return from the heating or something have tried to close all off and leave one on , then that one gets really hot so close that one off and open another ect, but when they are all on they are only getting lukewarm if the bypass is closed . im going to try and fit manual air vents on the pipes in the atticc tommorow to see if it will work , anybody got any other ideas?? system is really old, thanks guys, and sorry for the long post!!

 

[Killy Bing]

Blockage on the flow or before the common return? Take a magnet.

Assuming this is an open vented system?

 

[CXR100]

why was it working fine before fitting the new rad then? have you had this before?? its a local authority house wich i work for, house completly refurbished, re wired , plastered , painted, kichen , bathroom , but they dicided on leaving the old open vented system!!!!!!!!!

 

[Killy Bing]

Re filling can dislodge crud.
key part you have said is old!

who fitted the new rad then?

 

[armyash]

Had something similar the other week. Bypass valve was shot. Swore it was an airlock but new bypass sorted it.

 

[CXR100]

another guy in work , the bypas is only a gate valve!!!

 

[carrpaul]

get system hot as you can then drain from furthest point with tank still on and see witch way the water is going , then back fill off mains to the path with most resistance .

 

[jtsplumbing]

What about the pump ? as that been changed ? just because its making a noise doesn't mean its doing anything