Adding a room thermostat

In message snipped-for-privacy@davenoise.co.uk>, at 11:03:02 on Fri, 9 Oct

Doesn't currently have a room thermostat, but I've spent whole £12 on one earlier today.

Bi-metal sensor based room thermostats have a heater and require a neutral. Many modern ones use a thermistor as the temperature sensor and don't have a heater but do need a power supply... However that might be a battery even for a wired stat as the to be a "plugin replacement" for a bi-metal stat it has to cope with not having a permenant live.

I'm not 100% sure what wiring the OP has, there is mention of two wire and two wire plus L and N.

It's a combi, *hours* to heat it's internal heat exchanger or even built in small buffer store? A decent gas boiler ought to be able to reheat a whole hot water cylinder in an less than an hour.

When I had a 2 bed flat the HW cylinder would reheat in 20 mins. When the time switch died, I didn't bother replacing it, just switched the water on when I needed it. Heating was on a room thermostat and manual on/off switch. BIG drop in gas bill...

Vaillant. But essentially that serves as a junction box for all the wiring.

Fairy Nuff.

The pump more or less goes off with the bolier. It'll probably have built in overun to remove residual heat from the heat exchanger to stop it overheating.

er, the short cycling is almost ceratinly fireing up and shutting down the boiler far more often than it will once a room stat has control.

Not experienced with modern boilers but the KISS principle applies, plumbers are not electricians... So I'd expect at a minimum a terminal block with positions for permenant L,N,E (from a SFCU) and L,N,E,Sw L for connection to external time switch/thermostas etc. If there is a built in time switch I'd expect a "SW L out" (from time switch) and "SW L in" from external controls. By default the L and SW L would be jumpered togther, like wise the "Sw L out" and "Sw L in".

Depending on the precise design of the thermostat, if your wiring is run on the surface of the wall you may need a surface fitting back box to run the wires into, especially if you have to cut both wires and need somewhere to put a chocblock or wago connector for one of them. 16mm will do.

In message snipped-for-privacy@news.individual.net>, at

Mine doesn't have buffer store nor a hot water cylinder.

In message snipped-for-privacy@news.individual.net>, at

I'll post a diagram of the status quo shortly.

In message snipped-for-privacy@mid.individual.net>, at 12:28:01 on Fri, 9 Oct

The wiring in the thermostat location is through the wall, poking out at right angles. If I need to also chisel a box into the wall, that's not a problem.

I calculate that at best I spend less than £100 a year heating water for washing

Compared with £2000 for central heating.

You must have lived in a rabbit hutch to have had your CH bills that low, that reducing the minimal losses through a hot water tank saved you anything at all...

I can hear the boiler fire up after I have had a shower. For about 10 minutes. To get the house up to temperature on a cold morning make that thee hours, and on a really cold morning its more like all morning - then I switch to 'permanently on', for the CH.

People Who Do Sums can easily prove to themselves how much the heat loss is from a small lagged tank even at 60°C, which if it is inside the house is only keeping the house warm, compared with the heat loss from four walls a roof and a floor in a detached house... ...During my divorce I stayed with a friend who should have known better, who insisted the kettle never be filled to more than the amount required for the hot drink.

I spent some time on the calculator and handed him over 50p 'that should make it up for the next three months'

Even People Who *Can* Do Sums are often too lazy or stupid to *do* them.

Having had a simple thermostat on a system installed some 40 odd years ago, I changed it to a programmable one. Very useful as most want a higher temperature in the sitting room when relaxing at the end of the day. Good way to update a basic system, and no more effort than fitting an ordinary stat.

My boiler will actually heat my fast recovery cylinder quick enough to give a warm shower continuously, I discovered.

Top floor 2 bed flat, reasonably (for 30+ years ago) well insulated. Cold to comfortable less than an hour.

HW went from fireing up twice a day (morning and evening) to reheat the cylinder to once every 2+ days.

All I know is that I made a significant reduction in the DD to the gas company...

That's worse than this place, that's high, exposed, draughty and not overly well insulated. If it's not windy it takes about 90 mins to reach the target temp on a cold morning. If it's windy and cold the boiler can barely keep up...

Ours is never off, always on the thermostat. A high thermal mass means you really don't want the place to cool down otherwise it takes days, literally, to become comfortable again.

I didn't forget, the O/P said he was perfectly happy to install a cable.

No jut two wires, it'd need a 3+E cable (perm live to stat, neutral to stat, switched live to boiler, earth)

mains

The heatmiser site itself has install manuals, the only reason I linked to the website above is that it's £20 cheaper from there.

Sounds a good idea.

But you never get back the extra minutes waiting for it to boil!

In message snipped-for-privacy@news.individual.net>, at

controller /------make-------\ | | | |

N L 1 2 3 4

| | | |

from to to mains boiler boiler

But the more I look at it, the more I suspect that either 1 or 4 is also tied to one or other of the N/L mains. Some testing required, because the documentation is s*it.

UFH. very very long time constant

exactly Not days, but about 12 hours from icy to comfortable if the heat goes off in serious winter