Archive for Alex

Hot water control

The Idratek module is now connected and working. It fails safe on HW on, so in the event of the network going down, the hot water will come on.

What I am now attempting to do is to sense whether the pipework from the boiler is heating up when the HW system calls for heat. That way, if there is a problem (boiler hasn’t fired), the immersion heater will switch on instead, and generate a warning.

After some discussion on the Idratek forum, it made sense to monitor the output of the grey wire on the 3-port valve. This goes live when either the HW is off, or the HW is on but the cylinder thermostat has reached its temperature and is therefore not calling for heat. Logically, if the above is false, and the system is calling for heat to heat the hot water, then the pipework should be getting hot.

neonMy first challenge is to sense when the grey wire is live. I have added a neon indicator (240v) to that wire and neutral, which will be on when the HW is either off or not calling for heat.

Controlling Immersion Heater – Part 3

I bought a Honeywell L641 pipe thermostat from eBay for almost nothing – and although it came with almost nothing, it does its job. It was supposed to have a cable clamp, two springs to attach it to a pipe, and a protective cover to stop anyone altering the dial. Anyway, a cable tie clamped it to the pipe, and it’s only operating on 5v!

IMG_0643This device is tied onto the flow pipe to the hot water cylinder, just after the 3-port valve (a Y-plan system). I’ve set it to about 40 degrees.

Now Cortex knows whether or not the boiler is heating the hot water tank.

The next step is to wire the relays in the QRH module to control the hot water and heating, then for Cortex to monitor that the pipe thermostat has sensed hot water, and to operate the immersion heater relay if the pipe does not get hot.