Problems with Vented Thermal Store

[past3bar]

Problem where some radiators do not get hot on system with Worcester CBi 19/24? heat only boiler.
Thermal store has 2 pumps one for primary and one for ch with by-pass valve fitted.
Checked offending rads- trv's fitted but valves checked and no evidence of sticking or blockages (ptfe etc) Some debris in system.
Rads supplied by 10mm hep pipe.
Tried balancing system.Then tried shutting all other rads to force through.
Both in and out tails get warm but rads don't.
tried re-setting by-pass to no avail.
Upped pump speed to 3 (max)on ch pump also checked flow direction away from store.
Then noticed leak in boiler casing. On further inspection cast iron heat exchanger appears to be leaking.(Burst)
Have I done this by upping pump speed?

 

[ChrisR]

No!.
Most of the problems you have could be attributable to corrosion and the resultant sludge.
What store is it?

 

[DP]

Are you sure both the tails at the rads are getting warm?

Remember, water enters the rad via the flow pipe (hot) and leaves the rad via return pipe (minus heat given off by the rad). Water could be at similar temperature if rad needs to be bled and also major chunk of pump power is pushing the water through the radiator.

Check the temperature of water flowing through the central heating pump and compare it with water flow into the radiator. If different I would be looking for a blockage. I have in the past had to replace plastic as it seems to be prone to blockages on a sedimented system (plenty will be found in the heat bank if system not treated properly)

 

[past3bar]

There are no markings on the cylinder except a sticker indicating Fernox Protector was added in 2002. (When I think system was installed)
I thought the flow and return temps were similar because I drained the offending rads then opened the valves to check and possibly clear any minor blockage. What I think is the flow side gets hot to the rads. The return side is, after a slight volume of water passing, equally hot. I suppose this means it's the rad that is blocked!
The house is built with chipboard floors laid after 1st fix so I cant check much of the pipework.
Can these systems be power flushed ? I think a new boiler is required because leaking water has now damaged PCB. and I don't want to fit a new boiler to a dirty old system.