Gravity to fully pumped and CH zoning

[mutchie]

We have recently had our heating system upgraded (new radiators and conversion from gravity hot water to fully pumped system). In doing this we took the opportunity to have the heating zoned for upstairs/downstairs.
Everything works well but I would welcome thoughts on the following:
1. No room stat was installed for the upstairs zone! Stat downstairs controls downstairs zone only. Upstairs is either on or off at the programmer, rooms controlled with TRVs
2. The existing 28mm HW flow pipe was converted to combined feed and vent (with approx 4m horizontal run.) 28mm HW return retained as such. New HW flow pipe added (15mm). Is this OK? Does it compensate for the 28mm return? Is it to prevent the HW ‘robbing’ the heating supply (22mm)?
3. Pump overrun can be 20-30 minutes? Would this be due to the short bypass circuit (boiler instructions recommend min 4m – actual length is just over 3m)

Potterton Profile boiler. Horstmann 3 channel programmer. 3 x 2 port valves. TRVs on all radiators.

 

[clearhead]

We have recently had our heating system upgraded (new radiators and conversion from gravity hot water to fully pumped system). In doing this we took the opportunity to have the heating zoned for upstairs/downstairs.
Everything works well but I would welcome thoughts on the following:
1. their is no reason you should not have a room stat upstairs
you are the client did you request one
2. sorry im not understanding this-are you saying its had a 15mm pipe put into the hw cylinder
3. pump overun should be for a minute or so too take excess heat form the boiler

 

[mutchie]

1. When we discussed the initial installation, they pondered how to do it and suggested programmable stats for up/downstairs. I was happy with this. Final instal had new 3 channel programmer and no upstairs stat.
2. Yes, 15mm pipe to cylinder. Eixisting 28mm gravity cirulating pipes retained (old flow now used combined feed/vent , old gravity HW return kept. New 15mm pipe added as HW flow.
3. What could cause the extended overrun?

 

[clearhead]

personally i would of had a stat upstairs considering you have zoned it

i don't know why anyone would put a 15mm pipe into a cylinder if i wanted to throttle down the flow i would of put in a lockshield valve in (a gate valve without the head - primaraly to stop people tampering)and also the hot water does'nt normally rob the heating supply much-cylinders only take a few kw output and normally recover pretty quickly
i have seen it done and will research for my own piece of mind

pump over runs are normaly a control (stat) within the boiler to take an adequit amount of heat away until satisfied- depending on boiler - you might have to check boiler liturature
have you got an automatic by pass valve on system (system bypass)this opens when motorised valves shut down, excess heat and pressure circulate via bypass valve
and allows it to circulate around boiler primary pipework allowing boiler to cool

 

[mutchie]

Thanks for the reply. The bypass has a gate valve on it.

Re stat: I am happy enough to instal this myself but just wandered if there was any reason not to have one.