Seeing as this is the right time of year to attempt DIY on our Central Heating without freezing to death, I thought I'd delve into a little project to upgrade our system.
The house that we bought towards the end of last year has a CH system that could only be described as 'crude' at best! The boiler is in the garage, and sports a gravity hot water system, with pumped central heating. There was (until recently), a naff old Randall 102 timeswitch, which totally failed to either keep good time (typically losing up to 1 hour per day) or to switch on/off at the defined times.
So, phase 1 of my upgrade project was to replace the CH programmer. I chose an ACL Drayton unit, a Tempus 7. Good programmer, looks much better, and with jumpers set correctly, behaves as I would expect - i.e. allowing HW control on its own, or CH AND HW together (turning on HW pulls up the CH also).
But here's the weird thing: our CH cylinder also has a tank 'stat, but there are NO motorised zone valves anywhere in the system. Now this, to me, is rather odd. I also stripped and rewired the 'wiring centre' at the same time; as all the power to the boiler in the garage was old and flaky, I have installed a double socket, a fused spur (with appropriately rated 3A fuse) and a 'wiring centre' which in this case, is a blanking plate over a ton of cabling in a flush-mount box, suitably earthed!)
As far as I can tell, the mains from the fused spur feeds the timer. The 'HW On' signal from the timer goes via the Cylinder stat and fires the boiler if the Cylinder stat says 'Go!'
The 'CH On' signal from the timer goes via a Room stat in the living room, and fires the water pump, if the room stat says 'Go!'.
To cap it all, there's a Honeywell Frost stat in the garage, which connects the boiler directly to the mains, if the temperature drops to +5 deg C. In this circumstance, this ensures that the boiler always fires, if the Frost stat says 'Go!'....
So my questions are as follows:
1. The Drayton Tempus 7 seems like a good choice of programmer. But there's also a similar model, a Lifestyle LP722, which seems similar BUT it does have a fancy-looking backlit display, which might look funky in the dark! Are there any differences between these two 7-day programmers? Recommendations?
2. I'd like to replace the crusty old Honeywell room 'stat in the lounge with a new Programmable Thermostat. But is there any point now that I've installed the Tempus 7 programmer?
3. Should I install a pipe-stat as well as the Honeywell frost stat in the garage, to protect the boiler? Or would this be unneccesary with a properly installed Room stat in the living room (probably still required for boiler protection, I guess).
4. How the hell does my HW system manage to regulate its temperature without any zone valves? The Honeywell Cylinder stat certainly seems to be doing something....
5. Can I bang a 2-port motorised valve into this system to upgrade it to a C-plan? I understand that there are venting safety issues with doing this.. FWIW, the Water Pump is sited directly beneath the boiler in the garage.
The whole thing really does seem like an odd bodge, although I'm guessing that I could upgrade it to a properly split CH/HW system, with a bit of extra effort.
All advice would be welcomed, particuarly around the Programmer / Digital Room stat issue.