cold rad

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cold rad

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PaulRB

I have 1 cold rad in a downstairs cloakroom.
I have flushed it, tested the valves ( not trv ) and connected a hose from the o/side tap to each valve to blast any air-locks.
I have turned off all other rads and it still won't work.
I have replaced rad with a length of 15mm pipe and the pipe gets hot immediately! Put a new rad back on and it works for 2/3 days then fails.
If I draw 1/2 a bucket from the return pipe, hot water is drawn thru the flow pipe and the rad works for 2/3 days.
I know it could be a blockage, either air or sludge, but how come I can always draw hot water thru if I drain from the return pipe?
It seems as if there is something stopping the free flow thru the system which I can by-pass by encouraging the flow when draining.
I would be interested in advice as to what should be my next step.
Someone must have come across this before!!
Thanks
 
What you have is a regular pumped Y plan system, these are very common. Your problem is not so common though, every system is full of air when it gets filled but 9/10 are vented easily. So lets hope for your sake it is not drawing in air or air catching somewhere.
 
Ok Guys,
I have done exactly as described by Paul and still something not quite right.
My kitchen rad has a lockshield with bleed valve on return and wheel type on flow. I have shut off both valves, put bucket under bleed valve opened bleed and no water has come out!! but if i open the flow valve water starts flowing out lovely and the hot water starts coming thru the flow pipe....rad then starts warming up. Filled about half a bucket shut off flow valve and refilled the F+E tank. There were small small splutters of air so did the same thing 2-3 times more by opening the flow valve again.
Now with the flow valve off i open the lockshield fully and open the bleed valve............a trickle of water coming out!!!!
BLOCKAGE?????? As i am writing this the bleed valve is open fully and the water is still trickling out.
 
1 more thing.
Thought i would try the rad with the heating on again.
Shut all other rads off at there lockshields, turned on the heating, boiler fired and lasted for about 60 seconds then went off. Boiler fired again a further 2-3 times then eventually cut out on the boiler overheat thermostat. Could this be due to the blockage there is a build up of heat at the blockage and circulation is affected????
 
067256 said:
Ok Guys,
I have done exactly as described by Paul and still something not quite right.
My kitchen rad has a lockshield with bleed valve on return and wheel type on flow. I have shut off both valves, put bucket under bleed valve opened bleed and no water has come out!! but if i open the flow valve water starts flowing out lovely and the hot water starts coming thru the flow pipe....rad then starts warming up. Filled about half a bucket shut off flow valve and refilled the F+E tank. There were small small splutters of air so did the same thing 2-3 times more by opening the flow valve again.
Now with the flow valve off i open the lockshield fully and open the bleed valve............a trickle of water coming out!!!!
BLOCKAGE?????? As i am writing this the bleed valve is open fully and the water is still trickling out.
Click to expand...

is the pump on?
 
067256 said:
1 more thing.
Thought i would try the rad with the heating on again.
Shut all other rads off at there lockshields, turned on the heating, boiler fired and lasted for about 60 seconds then went off. Boiler fired again a further 2-3 times then eventually cut out on the boiler overheat thermostat. Could this be due to the blockage there is a build up of heat at the blockage and circulation is affected????
Click to expand...

heat not getting round, is pump working? rad vales open? valves on pump open? history of sludge?
 
pump is working,
rad valves open,
no history of sludge as far as i am aware, only been in the house 18 months.
heating on, pump running, open bleed valve on return...just a trickle of water coming out. Rad has a new valve aswell.
 
dont vent when pump is on, make sure its off or could actually suck air in

make sure vales is open, sometimes if new and dpendant on type the washer can be stuck on seating, leaves valves shut, take off rad and slowly open valves to check
 
Do you have microbore pipe anywhere? 10mm or less.(Sorry, but I couldnt be bothered reading 10 pages!)
 
Pump switched off.
Closed both valves on rad and removed the rad in question. Opened flow valve and get a good flow of water.
Open lockshield valve and only a trickle, there is nothing wrong with the valve as i have actually tried it on another rad when i fitted a TRV.
I'm just convinced now that it is a blockage.
 
10mm microbore drops down to the rad in question. Microbore behind 'dot and dab' plasterboard.
Could i force mains water up the return pipe via the bleed valve and 'hope' the blockage shifts?
 
067256
At the start of my troubles I took off the rad and attached a hose to the flow valve, connected to the outside tap ( but any mains tap will do ). Then I opened the valve and opened the outside tap. The mains pressure should force water into the pipework and hopefully shift the blockage.
I then repeated the process for the return valve.
BUT only run the mains for 5-10 seconds or it will back-fill the F + E tank ( you will know this because water will start coming out of the overflow!!! )
Also, it can be fiddly trying to attach a hose to the valves but worth persevering.
It might clear the blockage.
Good luck.
 
067256 said:
Pump switched off.
Closed both valves on rad and removed the rad in question. Opened flow valve and get a good flow of water.
Open lockshield valve and only a trickle, there is nothing wrong with the valve as i have actually tried it on another rad when i fitted a TRV.
I'm just convinced now that it is a blockage.
Click to expand...

sounds like it mate, maybe force mains pressure back up
 
Microbore is well known for being soft and getting squashed easily. It is also prone to blockage being of narrow bore.
I wonder if there is a squashed bit behind the dot and dab?

Its like a garden hose being kinked. Water may well flow through, but will be unable to reach top flow rate.
 
if its worked before and no works been done its unliekly to have become kinked
 
Ok, so today i have traced as much of the pipework as possible by taking up floorboards etc....
i cannot find any kinks. squashed bits. It goes 22mm down to 15mm down again to 10mm for about the last 2 metres.
I have taken off the rad in question and connected a washing machine hose between the flow and return...opened both valves, turned on heating briefly to check and now i have a good flow and the washing machine pipe is getting hot!!!
Why dont i get this when i connect the rad back up???????????????????????????????????????????????
 
maybe a restriction in the radiator? take it outside and put your garden hose on it and flush it out
 
067256 said:
Ok, so today i have traced as much of the pipework as possible by taking up floorboards etc....
i cannot find any kinks. squashed bits. It goes 22mm down to 15mm down again to 10mm for about the last 2 metres.
I have taken off the rad in question and connected a washing machine hose between the flow and return...opened both valves, turned on heating briefly to check and now i have a good flow and the washing machine pipe is getting hot!!!
Why dont i get this when i connect the rad back up???????????????????????????????????????????????
Click to expand...

take rad outside and flush it out
 
must be greater resistance, the system needs balancing

when rad off did you open both valves for split second to check they both run well?
 
Again as the previous one, i reckon biggest problem here is the need to balance the system correctly. I bet less than 10% of fitters balance a system correctly or even know how to.
 
its often not needed with powerful pumps and well designed systems, but when something like this happeneds its required
 
Stupid question.
Shall i open the valves and check for flow with the heating switched off?
Should i get a good flow of water from the flow and return??
 
Ok, so i now have taken off the washing machine hose and both valves are closed. HEATING TURNED OFF.
Open wheelshield(flow) lots of water coming out and good flow, no air spluttering. Close wheelshield.
Open Lockshield(return) bleed valve closed.........a trickle of water coming out.....constant but trickling, no air spluttering.
Opened bleed valve aswell...the same result
WHY IS THIS HAPPENING ON THE RETURN??????????
 
Why have i only got a trickle of water coming out of the return pipework?
 
067256 said:
Ok, so i now have taken off the washing machine hose and both valves are closed. HEATING TURNED OFF.
Open wheelshield(flow) lots of water coming out and good flow, no air spluttering. Close wheelshield.
Open Lockshield(return) bleed valve closed.........a trickle of water coming out.....constant but trickling, no air spluttering.
Opened bleed valve aswell...the same result
WHY IS THIS HAPPENING ON THE RETURN??????????
Click to expand...

have you tried valve open on return with rad off?
 
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