On 07/05/2010 23:36, Roger Mills wrote:
In an earlier contribution to this discussion, Richard
wrote:

There is a manual/automatic lever on those HP2A actuators. I wonder if
the actuators motor for heater should be disconnected, and the lever
set to manual. If that means permanently open.

You can certainly keep the valve open with the lever, independent of the
motor, but you can't rely on it moving far enough to operate the auxilliary
contacts.

Anyway, I'm just taking out the cylinder, leaving the rest of the
plumbing alone, and just have the boiler run the radiators. What that
calls for in wiring changes and any lever selection on the HP2A
actuators, I'm not 100% sure.

You still need a way of having the room stat control the boiler. If the
auxilliary contacts are not doing it as the valve opens and closes, you'll
need to connect the stat output directly to M7/3 as I said earlier.

I think what I will do, is remove the connection at pin 1 in the SET 3E
timer. Then no live will ever get to the water actuator via the cylinder
thermostat. You don't want a demand for heat and the valve closed on the
cylinder pipe circuit.

Setting the switch to water of course will do nothing. But that is okay.

So, when the room thermostat closes, the heater actuator will open, and
close the auxilary contacts, producing a demand for heat, as is normal.

I think that is the solution.