Baxi Solo 3 pfl 8mm micro bore

[holy85]

Hi All,

I've been trying to help a friend out with his central heating issue. He has a wall hung Baxi Solo 3 pfl 60 regular boiler with a vented f&e in the loft. The pipe work to the radiators are 8mm micro bore.

The boiler works good for about 30mins then switches off, then it will restart again and run for 5mins, switch off for 5mins etc.

If the temperature on the boiler is set high the boiler will go into over heat, and will need manually resetting.

Just over the weekend the system was power flushed, F & E taken out cleaned. A fair bit of iron oxide and muck was cleaned, now the water in the system is clear. In the passed month the PCB board, fan and air pressure switch have been changed.

The radiators have been painted, and so my feeling is the boiler is good, but the heat isn't radiating away from the radiators efficiently causing hot water to go back to the boiler, causing it to switch off.

I can't seen any by pass valve fitted which i though could have been the cause.

All radiators valves are fully open up stairs and downstairs, if i close the upstairs and quarter turn them back the system overheats faster.

Lastly the pump is working and looks new.

Any help on this would be great, have we missed something obvious? which is causing the boiler to keep swiching off, and flow pipe to become extremely hot?

 

[muggles]

Radiators don't radiate, they convect. Who did the powerflushing? Was it a properly trained person, or someone who thought they'd have a go because it looked easy? Sounds to me like you still have circulation problems

 

[holy85]

I did the power flush, i've been through the training and worked with others in the passed who have done it, it's not something i would recommend anyone to go out do if they don't have any experience or training of doing it. A whole day was spent doing it and using the products etc. may be there is some still left in the system that didn't free up, but from what i can see its come out clean.

Another issue is the radiators have twin entry valves on one side, the flow isn't the best i would imagine. I don't have much experience with working on micro bore systems so i'm not too sure.

 

[muggles]

Sounds to me like there are a fair few holes in your knowledge generally, not just with microbore systems. Were the parts thrown at the boiler in the hope that that would cure the problem, or was there a different problem that required those to be done?

The old twin-entry valves may be causing at least some of the problem - the injection pipe tends to fall off eventually, and then you get a short-circuit through the valve, effectively bypassing the radiator. Some microbore systems can't be powerflushed either, and trying to powerflush with twin-entry valves isn't going to get you anywhere at all with cleaning the rads, especially if the valves are knackered. Time for a re-pipe to a standard BBOE pipework configuration, and you need to find out whether the pipework is teed off 22mm F&Rs or run from a manifold

What's the temperature differential between flow and return when the boiler cuts out?

 

[45yearsagasman]

You cannot power flush a system with twin entry valves. Do you know if the system has a manifold?
Solid blockages will not be removed by flushing.
You will need to start disconnecting various sections including the pump and physically look for blockages.

 

[holy85]

Thanks for the reply muggles. Those parts were needed the pcb board went because it kept over heating, which ended up burning the board. After that the fan went, so decided to change the fan and switch at the same time.

I could feel the rads warming up midway, but then again the rads do look old and could have holes along the start of the pipe. A good starting point will be remove a rad and give it a flush, and inspect the vlave and rod for damage.

Agree changing to bigger bore would be best, but changing them will require alot of work as they run down the wall and in the skirting. Also they just decorated recently.

The aim is to get it working like it is, and last resort get the whole system changed possibly.

I tried measuring the flow and return using infrared, due to being limited on space and measuring the corner elbow of the pipe I don't think I was getting the correct reading. The reading I got was around 50 by the time it would overheat.

We also changed the cut off switch when the pcb was changed, incase it was faulty.

 

[holy85]

They recently moved into this house, so no floor boards have been lifted yet. A manifold must be under the floor. The pump was taken out and taken apart to inspect, all seemed fine. The rads all get hot, from top to bottom, but take some time in doing so. must still be clogged at the rads. Thanks for the help guys, will start to disconnect, and inspecting further will keep you posted.

 

[muggles]

I wasn't suggesting a wholesale repipe, just removing the old twin entry valves and re-piping the rads with conventional valves

 

[holy85]

Thanks Muggles

Microbore is still a good system, just needs maintaining.

 

[AGAS]

just a pita to flush

 

[petit_pablo]

Power flushing twin entry lol, if the spreader tubes weren't blocked by the flush they have probably fallen off now instead.
I can think of a few things that could be done but it would need a GSR'd guy to do some of it.
Flushing 8mm on manifolds is a waste of time.