Horstmann 425TIARA Programmer, Black

Product Information

Anyway, I've been looking at the wiring diagram for the H27XL and comparing with the H37XL, and I'm trying to work out if I can use this 3-channel unit with my 2-channel system. We're sorry but this product has now been discontinued by Horstmann Controls and can no longer be purchased. Thanks for the reply, I have got a friend checking it out tuesday and he diagnosed exactly what you said, he said that it will be the motorised valve more than likely. Offers 16 programmes for fully pumped systems incorporating motorised or mid-position valves and 10 programmes for gravity H. I am after a wiring diagram for it as would like to replace with a Horstmann H21XL two channel timer but am unable to find this particular model online.

In principle the 3 channel will work if you alter the pin layout but since the original wiring is suspect one would need to be on site to make any sense of it. If you are poking around with a screwdriver, make sure the system is isolated - there are live terminals near the top edge.

The whole idea is that the expansion of the hot water in the radiator / boiler pipework is taken up by an air pocket in the primatic hot water cylinder.

I am exactly at the same stage of trying to remove the same panel and only see it being stuck solid to the backplate. Sounds like you have gravity circulation for the energy supply circuit to the hot water which can be stopped with the valve. i just would like to be able to programme at least 3 times aday and what exactly does using the existing backplate mean. I'm sure it's not that complex but I like to know how things work in my head before I spend the cash.If the "plate" were slightly out of alignment and just hooked on the main unit, it should have come away by now. Ideally I would still like to replace the timer as I would like different times for the weekends etc. This was supposed to be a direct replacement, simply clipping onto the identical backplate and giving me new functionality, with the ability to set different times for different days.