Can I replace a TP9000 thermostat with a simple fused switch?

9 Mar 2021
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United Kingdom
Hey all, this may sound like an unusual question - I asked here about my particular setup before and people here helped me understand it, so now I have a concrete (DIY) plan here and need a sanity check.

I have a Danfoss TP9000 thermostat for both my hot water and heating. However, the heating valves are actually controlled via 3 separate Emmeti CS11 thermostats (one for each room). In fact, upon further inspection, it turned out the TP9000 is "hacked" to always keep the heating always on (red light on the right is always on and the temperature is always 5°). Effectively, its only purpose is to control hot water.

I'm considering replacing the Emmeti thermostats with Hive ones and replacing the TP9000 with a simple fused switch like this to control the hot water. There's already a switch like that next to it that turns off heating as a whole (including the TP9000) so it's unnecessary to even have a switch for heating - I'd just wire that to be always on.

In principle, it seems unnecessary to have a "smart" controller for hot water, so I'd really only flip the switch off if I'm going to be away - whereas the heating would be controlled via the smart thermostats anyway.

This seems like a straightforward thing to do, but still, would appreciate if people could chime in if there's something about this that's a bad idea that I'm not seeing?
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