Can a motorised valve develope a mechanical problem that can cause a flow restriction causing the boiler to short cycle?
- posted
5 years ago
Y Plan Heating Valve
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- posted
5 years ago
A three port valve is always open in some respect - either to port A or B or some combination of the two. So the basic mechanism can't block the flow totally. It might be a place some other blockage could get hung up though.
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- posted
5 years ago
Since your title is Y Plan heating valve, I assume that you are asking about the type of 3-port valves used on Y Plan systems?
These valves are not on/off valves in the way that 2-port valves are, and have 3 position - HW only, CH only, and both together. In theory there should always be a flow path one way or the other. However, if you've got TRVs on all your radiators and if they are all closed, the water have have nowhere to go in CH-only mode - which could potentially cause the boiler to short cycle.
I can't envisage a mechanical problem which would cause this to happen - unless there was a blockage in the valve.
What are the actual symptoms? Are the radiators and HW getting hot?
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- posted
5 years ago
Roger Mills snipped-for-privacy@gmail.com wrote in news: snipped-for-privacy@mid.individual.net:
It is not mine - it seems erratic - the boiler is short cycling. It has just been replaced - the heating eng thought the old one had a blocked heat exchanger(!!) but as it was 15 years old it was pobbibly worth replacing for a more efficient one.
Nothing seems consitent. Sometimes upstairs radiators are working - sometime the hot water isn't - there seems to be a circulation issue.
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- posted
5 years ago
A 3 port Y plan valve can't block with its own parts. The blocking device h as to move a fair distance to block one of the ports, it can't block 2 at o nce.
What have you tried so far? Checked the pump impellor? Done a clean of the system? Is there at least one rad with no TRV? I assume you've checked the rads aren't all turned off & that the primary circuit is full :) Might also be worth asking how short the short cycling is.
NT
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- posted
5 years ago
Sure it's a y plan valve, not a diverter?
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- posted
5 years ago
Not seen it for myself - he has had the pump replaced. He has has a new boiler - there is a flow problem somewhere. He has an engineer (?) working on it. I wonder if a radiator may have been put in the flow - ie, in series.
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- posted
5 years ago
maybe a clogged pipe or jammed trv. When I had a clog I couldn't shift I added drain points dotted about & drained from each one. It got a bit of flow going, the chemicals & filter then did the rest.
NT