need to add info about
- differences in wiring of spring-return & non-spring valves
- how 3-port mid-position valves work
Re the orange picture, it took me some puzzling to work out what it was, a text label would really help. NT 08:01, 10 January 2007 (GMT)
But there _is_ a text label under the picture - ?
--John Stumbles 19:15, 10 January 2007 (GMT)
I think the reference to Hydronic wrt a 3 way valve is a spelling mistake perhaps you mean hydraulic, certainly it doesnt make any technical sense as its the tradename if the Smiths fan assisted plinth heater (a finned coil with axial blower)
The original Honeywell spring return 3 way valve with mid position was a curiously convoluted solution which has been shrouded in mystery untill the description provided (tkx btw) - personally as a professional engineer i hate it aand regard it as a nasty bodge. But a million homes probably still have this device in their Y plan systems.
I think it worthwhile to discuss the earlier system where a TRV was installed on the outlet of the HW heating coil to give a praticular DHW temperature.
As I recall - some 30 years ago - there was no zone valve and I think the pump only came on when CH was demanded and only pumped through the radiators. The HW tank was mounted above the boiler and the heating coil was gravity circulated and had 28mm tubes
The controller (similar to the Honeywell st699 but and earlier model?) had a mechanical interlock on the sliders controling CH and HW.
you could have
All off HW on 1x 2x HW + CH on 1x 2x
CH on by itself
Come to think of it, I dont remember a HW coil bypass gate valve being fitted (not very kind to the boiler (a potterton 40,000 Btu model) but I dont remeber any operating problems.