Controlling gravity HW, pumped CH that does not have room thermostat

[tonyo]

Hi,
I have CH system with pumped CH and gravity HW. It consists of
Ideal Mexico boiler
V4043H 2 port valve
Lamdis & Gyr RWB2 controller
Pump
The CH has no room thermostat or hot water thermostat and allows for hot water only or hot water and CH.
!. Can the system be changed to have separate control of the CH and hot water
2. Is it possible to be able to control the CH by using a programmable thermostat.
3. Is it advisable/possible for the boiler to be automatically turned off if both the HW and house have reached the desired temperature according to the thermostats
4. Should the pump carrying on running for a short time when the boiler is switched off due to the room thermostat reaching the required temperatue
5. Is it best to have a new CH controller and if so can you recommend one
6. Can you recommend a medium priced programmable thermostat
7. Have you any other recommendations

Thanks
Tony

 

[Hugh Jaleak]

Yes, simple answer would be to convert to a Honeywell 'C' plan. This incorporates a motorised valve on the cylinder return, coupled to a stat on the cylinder for HW control, and then fit a roomstat on the CH circuit to activate pump and motorised valve when CH is required. http://www.honeywelluk.com/products/Systems/Sundial-C-Plan/

Unusual to have a valve on the CH in your setup, whilst there might be slight gravity circulation on the CH when HW is working, usually the lack of pump is enough control. Boiler should shut off when both stats are satisfied with the C plan set up correctly.

Pump overrun is usually controlled by the boiler, if your doesn't have this feature its probably not required, and would be difficult to set up externally.

RWB2 is a decent programmer, ultimately they all do the same job, I wouldn't replace for the sake of it, might be better to look at programmable roomstats if you want more control on the central heating.

 

[tonyo]

Hi Hugh

thanks for the reply, one thing I do not understand is it looks like the pipe to the CH water tank which is 15mm is between the pump and the V4034 valve. How would the hot water get to the tank if the pump is off.

Thanks again for your help

Tony

 

[Hugh Jaleak]

Not quite sure what the is pipe is, but it's possibly the cold feed to the system. HW circuit is gravity, wont need the pump. Needs looking at to determine best position to fit a valve, as there must be a clear path from the boiler to above the feed and expansion cistern maintained at all times. That's why valve is usually fitted on the return.