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Hi all. Has anyone come across this before where an unvented cylinder has been put on the end of a radiator circuit of a combi with a zone valve and cylinder stat?
Discuss Unvented on the end of heating circuit in the Plumbing Jobs | The Job-board area at PlumbersForums.net
Yes. In a very expensive house 'designed' by a, so called, qualified architect who built sheds for Tesco... It was mostly DIY and utter rubbish.
It continues to 'work' because I rewired so the UVC had its own timer and I altered timings so that water was heated only when there was no heating demand. The UVC feeds bathrooms & the combi feeds the kitchen and cloakroom.
Hi all. Has anyone come across this before where an unvented cylinder has been put on the end of a radiator circuit of a combi with a zone valve and cylinder stat?
This is pretty much the worst arrangement I can think of. Have you looked at its paperwork? My money says that it was installed by an amateur...
My explanation would be along the lines that unvented cylinders require a lot of power from the boiler when they are reheating. They also need the flow temperature to be as high as possible. These requirements together mean that they have be on their own zone and benefit from being as close to the boiler as possible. Your current system is the opposite of what's best.
This is pretty much the worst arrangement I can think of. Have you looked at its paperwork? My money says that it was installed by an amateur...
My explanation would be along the lines that unvented cylinders require a lot of power from the boiler when they are reheating. They also need the flow temperature to be as high as possible. These requirements together mean that they have be on their own zone and benefit from being as close to the boiler as possible. Your current system is the opposite of what's best.
He has said it was all working fine until I serviced his boiler. In June. A month later I get a call saying he has no hot water and that it has gradually diminished since me being there. I go there and discover the zone valve is knackered and the immersion programmer and tell him this design is a bodge. He says he wants a cheap fix for now and so I put a new zone head on.
So a call this morning saying he cannot keep on having issues with his system and paying me to come out to temp repair it.
One possible explanation for this history, is that until the summer they were actually using electricity to heat their water. In June you fixed/changed things so that the boiler was being used instead. This worked, just about, until now when the weather's colder and the radiators are drawing power from the shared zone.
Make sure you really understand the details of the current system before making modifications. Any modification short of separate zone with independent flow and return piped back to the boiler is going to risk reverse flow problems. I.e. it'll be okay in this winter but the customer will call you in the summer saying that their radiators get hot whenever the hot water is on.
This is what I told them.
Reply to Unvented on the end of heating circuit in the Plumbing Jobs | The Job-board area at PlumbersForums.net
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