cold heating system

[kettle]

apologies if this has been asked before, i have found similar probs but not quite the same.
i have a open vented mini bore system,two zone valves, grunfoss 15/60 pump and a baxi boiler with cast iron heat exchanger, about 15 years old.the system has been power flushed very recently, the zone valve on the heating side is new ,as is the pump. only problem is, i have no hot rads. a couple of flow pipes to the rads get hotttish but not the rad itself.with just the heating on, the boiler fires up for a minute and then cuts out.the pump is very hot. the only thing i can think of i that the manifold(s) are blocked. but wouldnt the power flushing sort that?
any suggestions greatfully received.

regards

Chris

 

[Bamber gaspipe]

It sounds like a blockage to me. When you said you had a powerflush was it done properly? usually if there is a problem regarding circulation, every rad with a problem is targeted with powerflush machine, I actually remove the problem rads & flush them manually with a hosepipe & then powerflush. If the machine was just connected to the flow/return on rad it`s not a guarantee of a proper flush especially with large build up of sludge at bottom of rads. Microbore is notoriously prone to blockages. Was a sludge remover introduced into system before it was flushed? I normally bang it in a week before I Powerflush. By the way, if you have paid for the powerflush the engineer should have resolved any problems after he/she had finished the flush if not get him/her back.

 

[kettle]

Hi Bamber,thanks for the reply.two rads were removed and washed manually by me, and neither of these gets warm at all. the flush was done today,through a flow and return and this rad doesnt get hot. No previous visit for sludge remover. i thought of a blockage some where but dont know where.the guy that did it could only suggest replacing the mini bore with 15mm pipe which i can do,but not if i dont have too.
Chris

 

[Bamber gaspipe]

Hi Bamber,thanks for the reply.two rads were removed and washed manually by me, and neither of these gets warm at all. the flush was done today,through a flow and return and this rad doesnt get hot. No previous visit for sludge remover. i thought of a blockage some where but dont know where.the guy that did it could only suggest replacing the mini bore with 15mm pipe.
Chris

If your boiler is firing up & then shutting down then it would seem to be overheating, the pump cannot shift the hot water so it is a blockage in my opinion. I don`t know what else to tell you really, without being there I cannot pinpoint the blockage. Have you checked your feed & expansion tank in loft? is there any water in it?
You may have a blocked cold feed supply to your heating system. The easiest way to check this is to attach a hose to one of the drainoff points on a radiator downstairs. Open the drainoff & observe the water level in your tank in loft, if the level drops & cold water starts to fill up the tank then you don`t have a blocked cold feed to your heating system.

 

[kettle]

there is water in the f/e cistern and it was used to refill the system today.so i think that side of it works ok.

 

[Bamber gaspipe]

there is water in the f/e cistern and it was used to refill the system today.so i think that side of it works ok.

The last time I went to a rad that was not working ( piped up in microbore) I chopped the pipe under the floor & the hot water came rushing through (it was all furred up). If you can, drain down a rad & disconnect the valves, open up the valves into a bucket & observe the flow rate if any, if you are getting a strong flow rate at both ends the pipework to this particular rad is not blocked. Unfortunately you will need to repeat this wherever there is a problem at each rad.

 

[kettle]

ok , i will do that. should there be an equalish(is there such a word?) flow from both valves?
just another thought,wouldnt the rad that had the flushing machine connected to it be clear? neither pipe gets warm at all

Chris

 

[kettle]

right.drained a couple of rads and tried the flow from the valves.not good on return,fast dribble on the flow.