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I have an alpha cb24 combi boiler.
My problem is the boiler is knocking off on high temp after running for a few minutes. The upstairs rads are getting hot but the downstairs are only luke warm.
I've recently changed the primary temp sensor, drained system and fitted 4 trvs. When I started it up I was struggling for flow so removed flow and return isolation valves to find flow pretty blocked up. I've cleaned these out and it's a little better (the rads are heating up a bit now) but the flow still doesn't seem fast enough to take the hot water out of the boiler fast enough.
Here's how it's set at the moment:
1. Pump set to medium speed, I've tried max and min, no difference.
2. Upstairs lock shield valves opened 1/4 of a turn, tried 1/2 turn, no better.
3. Downstairs lock shield valves fully open, tried 50% open, no better.
4. Trvs all set to 5 (max).
5. All air bled out of all rads and pump.
Please can anyone give me any suggestions of things to try next, I'm at a bit of a brick wall.
Many thanks in advance.
Mike.
Edit: for info, don't know if it's relevant, when I drained radiators from downstairs, the upstairs empties completely but the downstairs do not, when I crack the bleed valves on any of the rads downstairs, water comes out and the flow to drain from my drain point doesn't increase. Am I missing something?
My problem is the boiler is knocking off on high temp after running for a few minutes. The upstairs rads are getting hot but the downstairs are only luke warm.
I've recently changed the primary temp sensor, drained system and fitted 4 trvs. When I started it up I was struggling for flow so removed flow and return isolation valves to find flow pretty blocked up. I've cleaned these out and it's a little better (the rads are heating up a bit now) but the flow still doesn't seem fast enough to take the hot water out of the boiler fast enough.
Here's how it's set at the moment:
1. Pump set to medium speed, I've tried max and min, no difference.
2. Upstairs lock shield valves opened 1/4 of a turn, tried 1/2 turn, no better.
3. Downstairs lock shield valves fully open, tried 50% open, no better.
4. Trvs all set to 5 (max).
5. All air bled out of all rads and pump.
Please can anyone give me any suggestions of things to try next, I'm at a bit of a brick wall.
Many thanks in advance.
Mike.
Edit: for info, don't know if it's relevant, when I drained radiators from downstairs, the upstairs empties completely but the downstairs do not, when I crack the bleed valves on any of the rads downstairs, water comes out and the flow to drain from my drain point doesn't increase. Am I missing something?