Replace Horstmann H17XL programmer/complex underfloor heating

11 Dec 2022
Reaction score
United Kingdom
Good afternoon,

I was hoping someone could help me/give me advice here regarding improving our heating system at home:

We've moved into a house that we bought earlier this year and the boiler and heating controls were outdated so we upgraded the boiler to a Worcester Bosch Greenstar 8000 Life 50kW and had two Hive thermostats installed to replace the old fashioned dial ones we had before.

This all works reasonably well but nothing has been done to the underfloor heating that we have in the kitchen/family room/orangery. There are 3 Heatmiser RF Switches in the cupboard in the orangery and only 1 Heatmiser Slimline thermostat that is working, which is the kitchen one. I've now ordered another 2 Neo Air smart thermostats to pair with the remaining two Switches to get the controls running properly.
The problem is that the controller for the pump for the water from the boiler to the underfloor heating is a Horstmann H17XL at the other end of the house. Programming it is very manual and there is no communication between the Horstmann and the underfloor heating. Basically I have now switched it on from 5.30am to 10pm but this is completely inefficient as when the rooms for the underfloor heating are warm enough, it won't switch off. The underfloor heating will switch off but not the pump at the boiler - that's my understanding at least.

Now my question is how I can replace the Horstmann with something smart or ideally sth that can communicate with the Heatmiser system. I also ordered their smart integration hub. Is it possible to just get another RF Switch to replace the Horstmann?

I've added a few pictures below.

Thanks for your help.


  • 3800AB19-1466-4799-98CE-95E40246B7CC.jpeg
    287.5 KB · Views: 47
  • E88D8C02-AC8B-427C-A71A-9F743BEA2412.jpeg
    356.8 KB · Views: 39
  • 4D85BEDA-D0F6-41E7-AECF-3C1BB82CE2AB.jpeg
    303.9 KB · Views: 53
Sponsored Links

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.

Are you a trade or supplier? You can create your listing free at DIYnot Local