Replacing House Central Heating System

[DaiRees]

Is there any reason I can't fit a TRV in the bathroom?

There has to be a flow through the pump, otherwise you get a lovely water hammer sound should all the TRVs close!

Well I never knew that's the reason for not putting them in the bathroom. We've got one of those tall, chrome towel rail rads in the bathroom (and underfloor heating too) so the rooms's always very warm. One of the kitchen rads hasn't got a TRV so I could put one in the bathroom?

[Welly]

The perception is that no TRV in the Bathroom does two things; leaves an open circuit for the water flow when the other TRV's close but also warms the bathroom more than other rooms (I've never heard a woman complaining the Bathrooms is 'too warm') and helps to dry towels etc.

[steve_earwig]

I also seem to recall reading something about "thermal runaway", which I think is where the pump cuts out and the water sitting in the boiler boils (well yeah, dur). If there's no path for the pressure things can get a bit pressurised. In the dim and distant past I'm sure I saw something about the radiator in the bathroom being plumbed somehow on the back end of the boiler, so it's even on a different "circuit". I may have just dreamed that one tho.

[Doggy]

That's a fairly common approach.

For simular reasons I have my bathroom radiator plumbed into the gravity hot water circuit to reduce the risk of my wood burner boiling in the event of a power failure, (which obviously stops the pump /closes the zone valves).

My gas boiler's got a pump overrun output to get rid of the excess heat in the heat exchanger when the heating shuts down, I have this rigged to hold the heating valve open too.

[mjb]

I'm working on my central heating too... Current setup is a pretty large victorian house, massively overpowered (HELL YES!) boiler, a few TRVs dotted around, and a wireless non-timer 'stat. The house is big enough that there's really no good place for the thermostat, so my current plan is:

1. TRV everything except the bathroom
2. Introduce Honeywell Evohome TRVs

Hopefully that'll give me decent control of the per-room temperature (save dicking with open a bit, close a bit, etc) and have the lovely simple logic of "if any room needs heat, turn the boiler on, else it can be off". It's also nice and geeky

For the most part, the house is surprisingly warm, despite being 120 years old and pre-dating things like electricity, insulation, damp-proofing, etc. Got 250mm of fibreglass in the loft which is going to make using it for storage pretty expensive (boards and stilts!) and goddamn itchy.