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superstardeejay
Hi folks, hope someone can help us here, I'm struggling to get my head around a complicated electrical install of boiler & cylinders. I'm an electrician, not a plumber.
The new system has been installed by others but we've been called in to 'sort it out' after the previous people gave up.
Installation consists single sealed circuit gas boiler, Keston C55 with inbuilt pump, permanent & switched live supplies, auto-pump exercise and over-run.
Two Telford Stainless mains pressure DHW cyls, heating loops in parallel and fed off single NC motorized valve from boiler, each with twin built-in stats with volt free contacts, ie one for control and one for overtemp. Expansion spheres fitted.
Two Grundfos pumps external to boiler, each with motorized 2 port NC valves and feeding upstairs and downstairs rads respectively. Two Honeywell bimetallic roomstats, up and down.
Salus 2-channel timeclock with seperate volt free changeover relays for DHW and CH, operate independently through the programme.
All rads fitted with thermostatic valves.
Although it first sounded simple to me, I cant see how to get around the fact that:
1. The mains DHW cyl stats need by law to have overall control of the valve feeding them from the boiler, yet the boiler needs an open circuit at switch-off for pump over-run, anti-kettling and pump exercise reasons.
2. The upstairs and downstairs rads are fed via pump/valve combination so my previous point applies likewise.
3. The user wants the option of selecting via the timeclock either CH, DHW or both or neither, at will.
4. The boiler inbuilt pump is powerful enough to circulate water through any open valves and into the radiators or cylinders unless the respective valve is closed.
Can I wire this up to cover all senarios without doing damage either due to the boiler pumping against a closed circuit or overheating the cylinders?
Thanks and sorry for the rambling.
kev
The new system has been installed by others but we've been called in to 'sort it out' after the previous people gave up.
Installation consists single sealed circuit gas boiler, Keston C55 with inbuilt pump, permanent & switched live supplies, auto-pump exercise and over-run.
Two Telford Stainless mains pressure DHW cyls, heating loops in parallel and fed off single NC motorized valve from boiler, each with twin built-in stats with volt free contacts, ie one for control and one for overtemp. Expansion spheres fitted.
Two Grundfos pumps external to boiler, each with motorized 2 port NC valves and feeding upstairs and downstairs rads respectively. Two Honeywell bimetallic roomstats, up and down.
Salus 2-channel timeclock with seperate volt free changeover relays for DHW and CH, operate independently through the programme.
All rads fitted with thermostatic valves.
Although it first sounded simple to me, I cant see how to get around the fact that:
1. The mains DHW cyl stats need by law to have overall control of the valve feeding them from the boiler, yet the boiler needs an open circuit at switch-off for pump over-run, anti-kettling and pump exercise reasons.
2. The upstairs and downstairs rads are fed via pump/valve combination so my previous point applies likewise.
3. The user wants the option of selecting via the timeclock either CH, DHW or both or neither, at will.
4. The boiler inbuilt pump is powerful enough to circulate water through any open valves and into the radiators or cylinders unless the respective valve is closed.
Can I wire this up to cover all senarios without doing damage either due to the boiler pumping against a closed circuit or overheating the cylinders?
Thanks and sorry for the rambling.
kev