Got home 'earlyish' yesterday (Friday), to be greeted with the details of a 'lady in distress' only a few hundred yards 'up the road' from me. "No hot water". Thinking the obvious I ring her and explain that I will check it (the immersion), but if it needs replacing she will need a plumber.
Get shown to the airing cupb., mains pressure cylinder with immersion. Follow flex to partition wall, other side (landing) is a 20A. D.P. switch in the OFF position. I ask about this (being switched off) and she knows nothing of the switch, never used it........
Anyhow, I test at the head of the immersion. Everything working correctly, 'stat o.k., load test correct. So far - so good!
Looking further into things and because she knew nothing of the immersion switch I realised that, in the cylinder, there was a heating coil (from a boiler) with a cylinder 'stat.
She only has a programmable 'stat on the landing and one on the ground floor AND she explains that "the boiler is in the roof-space". There is NO 'central' programmer for the system. I discover that the fused spur (for the heating system) is the only control for the domestic hot water, ie. with switch ON - power is permanently direct to cylind. 'stat. Each 'room stat' controls a heating zone.
By turning 'off' the cylind. 'stat I hear a motorized valve 'spring back' - under the cupb. floor. I pull back the carpet and lift a 'trap' - there are the 3 motorized valves!
Deterrmining that each valve was being activated correctly by it's individual 'stat I thought it's time to have a look at the boiler. Up in the roof-space I go, and there it is. Flashing (warning) light and display showing .4 Bar water pressure. Obviously pressure too low to operate boiler.
Looking around the wall-hung boiler (and inside the casing) I can find NO water top-up 'link pipe'! Now I am stumped! Ring a heating engineer contact I know and he explains that the 'top-up link' could be in the airing cupb. or perhaps even the kitchen sink, and should have a pressure gauge by it.
Lo and behold, there it is...........in the airing cupb. Re-pressurise the system - turn back on the power - turn up the cylind. 'stat, valve opens and - hey presto - IT WORKS! Hot water circulating!
Try each of the two zones' programmable 'stats in sequence.............luvvly jubbly............now, at least 2 hours later, I am a central heating diagnoistic engineer :43: