Baxi / CH pump problem

[LFR]

Hello all. Some advice would be very much appreciated!

I have an old Baxi solo 3 40 boiler, HW tank. F&E system. Old system.

A couple of weeks ago the boiler kept struggling to heat the rads, particularly downstairs. I removed the Grundfos pump and cleaned A LOT of solidified gunk from the impeller and all looks great. Refitted. Worked for a few days and then boiler seems to be kettling, banging, and regularly overheating.

I replaced the 3 port motorhead yesterday. Valve itself seems ok. With motorhead off it turned freely. I also drained down the whole CH system and added cleaner.

Now the boiler will fire up for the HW and heat it nicely, but the CH will only heat upstairs rads and the boiler overheats after a while. Much less banging and no real kettling sounds. The pump is on full speed as the auto setting brings the wattage down to about 3 and would do nothing. Full speed approx 26-33w.

I don't really want to replace the boiler as I am planning on selling the house this year.

Any thoughts would be much appreciated!

 

[dilalio]

Blockage, air or both.
Plus pump could have weakened through age and/or dirt.

 

[LFR]

How might I unblock if it is air? All rads bled. And HW return valve.

A sludge blockage will probably require a pressure clean/flush but I'm pretty sure that will destroy all my pipework etc! I am hoping the cleaner (sentinel x4000) will help with that.

 

[ianmcd]

A sludge blockage will probably require a pressure clean/flus

you wont clear any blockage with a pressure/clean/flush

 

[LFR]

So how would it be cleaned if it needs to be?

 

[MeldrewsMate]

...the wattage...

Any thoughts would be much appreciated!

Firstly, appreciate that the watt is a unit of POWER, so you turned up/down the power.
Rant over....try cleaning out the pump impellor again. When you're sick and tired of doing that, consider installing a system filter.

 

[LFR]

I know it is a unit of power. My point was that on auto, trying to heat the CH, that 3w is not going to do anything.

I checked the impeller and its clean as can be. No damage. No nasty noises when running.

Could I remove the pump, keep it plugged in and turn on the HW or CH to see the impeller spin without water?

 

[ianmcd]

So how would it be cleaned if it needs to be?

clearing a blockage and cleaning a system are not the same thing, only way to clear a blockage is rod it or cut it out