On 15/05/2021 22:30, Theo wrote:
ARW wrote:
On 15/05/2021 11:27, Theo wrote:

I never investigated but I imagine there was just on/off control for the
boiler (gas valve only, since there was an always-on pilot that had a piezo
spark-button to relight it if it went out), and an additional time clock
output that was in series with a thermostat to run the pump for the heating.

How was the boiler turned off in this system, when the thermostat said the
house was hot enough and so was the water? If the heating called for heat
and the hot water was up to temp, surely that would overheat the water?

https://assets.danfoss.com/documents...6en-GB0201.pdf

Were the common programmers of the time

This was the one:
https://www.amazon.co.uk/LANDIS-GYR-.../dp/B072FSJP2N
which was just a simple 1 rev per day motorised dial plus some cams to
operate switches.


On the back of that programmer there is a switch that allows you to
choose between gravity or fully pumped.

What this switch did was link the HW and CH sliders. So if both were off
and you moved CH to timed or ON it also moved the HW slider across to
timed or ON.

However moving the CH from ON to OFF left the HW slider where it was but
moving the HW from ON to OFF also turned off the CH.

Being on gravity makes a lot of sense - the neighbours moved their cast iron
boiler into the garage and 'it never worked properly after'. Which would
follow if the tank is suddenly further away from the boiler.

Yes they would have needed to put a pump in for the HW.


--
Adam