rads not getting hot, but hot water is!!!

[mattytheplumber]

hi guys, just need some advise on this one.....

I got called to a job today and when i asked for the heating to come on the boiler fired up and the pipes round the cylinder were all hot and both sides of the pump!! I tried bleeding the rads to try drag any air out the system but this didnt work. the man said he would be happy for us to do a power flush to get rid of this problem and also any sludge in the system. i just want to know if you guys think that the flush would cure the problem.

thank a lot.

 

[Mbear]

You'll need to fault find on the ch/hw elect circuit, check the programmer/stats and zone valves are functioning correctly b4 u charge for a p/flush.

Have u done any fault finding at all?

 

[mattytheplumber]

There is power going to the programmer and it is turning the heating on. The two port valve is working corectly too! one rad got warm closest to the boiler but that was it. so with the one rad getting warm i thought there must be a block????

He has no room stats anywhere in the house just one thermo rad valve downstairs.

 

[Mbear]

Is the pump Circulating?

Checking for blockages or airlocks would be my next step aswell. Do u know about the fridge magnet trick when checking for chokeages?

 

[mattytheplumber]

fridge magnit??? no ha


The pump is running yes, and what would you advise the best way to check were the block could be??

If it is a block, witch it sound like, i assume a flush would do the job?? I know its not the most cost effective but i think the guy would like one anyway.

 

[Mbear]

fridge magnit??? no ha


The pump is running yes, and what would you advise the best way to check were the block could be??

If it is a block, witch it sound like, i assume a flush would do the job?? I know its not the most cost effective but i think the guy would like one anyway.

Yes but is it circulating? Take the bleed screw out the pump and check it's rotating.

Take a normal fridge magnet and check it against sections of copper pipework where u suspect the blockage may be, parts of the return or maybe the cold feed, the magnet will stick to copper pipework choked with magnetite, it will not stick to areas that are not blocked. If it is completely choked in a certain area then I doubt a p/flush will clear a choked pipe on it's own, it would usually need cut out and replaced.

 

[marleyco]

nice trick, never tried it myself. atleast you can probably say the blockage is either flow or return before first radiator. bit of a nightmare locating blockages, can see why your thinking power flush

 

[plumbitism]

Is the header tank full? Check that the ball valve hasn't got stuck. I assume that you have tried manually opening the motorised valve?

 

[tamz]

Taking the screw out and checking the pump is rotating is not sufficient to prove the pump is circulating properly. I have had a few cases where the impeller is worn or broken and although it may circulate somewhat it does not provide enough head.

Matty
Check the water quality and you will know if it needs a flush.

 

[mattytheplumber]

yes the motorised valve is working corectly and the header tank is full. The pump is working but if your saying you had cases were the blades have worn, i have spare pumps in the van so will try a new pump and see if this resolves the problem. thanks