the feed and vent arrangement should only be like that on a gravity system not pumped. If its not sorted the system will end up with corrosion problems. If the op plans to fit a MV on the hot water it will need to be on the return assuming the diagram is correct, and if the boiler has pump overun a bypass will be required.
what heating plan??
- Thread starter cpm25
- Start date
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I have probably drawn it wrong, there have been no corrosion problems and system got to be twenty years old. I just want to stop the scalding water so i will put mv on the return and wire it as splan, which should give me the option of adding a room stat and cyl stat, thanks guys for making it clearer. I was always able to have heating off and hot water on, so the mv must control the heating side of things.
G
gaswizzard
Install the MV on the horizontal piece of pipe going into cylinder , this will ensure an open path from boiler to expansion cistern.
i thought that was better option too, thats what i will do.
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M
mysteryman
You need to be careful with that. You may end up pumping over, or sucking down. Conversion to a Y Plan [mid-position valve] is best. No bypass is then needed. The Y Plan valve costs little more than an S Plan valve, so the on-cost is minimal, and a better job is done. Check very carefully that your layout is as shown - it is odd if so.
The diagram might not be exactly as drawn it was from memory as to get to the mv pump and pipes i have to crawl under floor to under the boiler, but i have a gate valve on the return from the cylinder and when i turn that off, the cylinder stops heating with no adverse effects, understandably if the pump was running with both circuits closed this could be a problem, (BUT THE OVERHEAT STAT WOULD PROB JUST CUT IN), but wired as splan this could not happen because if the valve which you demand to open doesnt the pump would not run. This is my understanding anyway. With that said could i not just swap that gate valve on the return side?? be alot less cable and hassle. Like i said i will have the boiler and relevant pipe work replaced soon so dont want to be converting etc, as it is nearly there i can have hot water only in summer months but there is nothing other than the boiler to control water temp and i think it gets to around 90 degrees which is dangerous and a complete waste.
M
mysteryman
Yes, point taken. Fine especially for a short-term job. A Y Plan is better for a permanent fix.
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