I need to set a house at a specific temperature (15 deg C, for insurance purposes). There is no thermostat.

A bit of googling suggests that the markings on TRVs don’t correspond to specific temperatures, though some suggest they do. I’ll keep googling, but does anyone have anything to input?

Drayton TRV4s (which is what I have on the rads here) state that the settings of 1-5 and Max will be in the range of 10-30 degrees approximately. So I guess it’s not that accurate otherwise they would have published a table.

you can get electronic thermostatic radiator valves which will be more closely prgrammable
http://www.uswitch.com/energy-saving-products/radiator-valves/terrier-i-temp-i30-programmable-thermostatic-radiator-valve?variant_id=220

al – check out this.
stick with it and it shows what the danfoss settings correspond to.

http://www.radiatorcontrol.com/how_a_trv_works.aspx

Your best bet is probably to do some experimentation and recording.

thats 26.5 degrees kryton…..

i suspect its for an uninhabited house !

From what I understand, a TRV is in effect a variable control. It won’t correlate to a specific temperature, as it doesn’t know what size radiator is attached, nor how big the room is.

Id suggest, testing over a few days with the door closed and slowly increasing the setting of the TRV until it’s where you want the temperature to be.

From what I understand, a TRV is in effect a variable control. It won’t correlate to a specific temperature, as it doesn’t know what size radiator is attached, nor how big the room is.

Id say that applied to a normal rad valve, not a TRV one.

They operate by the expansion of a medium (wax, oil or gas) pushing on the valve head pin according to the temperature of the medium.

If you’re going to leave the house uninhabited for any length of time, even with the trvs all set, you’ll still be running the boiler pump, and wasting heat on the radiator that has no TRV.

External thermostat is a 20 minute job to fit, and they cost about fifteen quid for a wired one, or £40 for a cheap wireless one (we have an ECO ET-4, and it works okay). You don’t have to go into the gas bit of your boiler (the sealed box bit), so as far as I know it isn’t covered by gas safe regs (don’t quote me on that obviously, but I can’t see why you’d need the training to to connect two wires to a switch).

Pretty sure that the Honeywell TRVs that we got last yr had a temp range for each number on the rad. No idea how accurate they are though…

…can’t post a link easily from my phone (being lazy) but Google Honeywell UK & then under heating products/TRVS/VT117 – select the vt117 and download the reference guide.
It has a temp range per number on the dial…

does the house have TRVs already installed ?

if not its easier to fit an external thermostat !

you’ll still be running the boiler pump, and wasting heat on the radiator that has no TRV.

You have to have some heat coming out of a certain amount of non-TRV radiator.

they might be just what I need. A simple thermostat switch won’t work so easily on my boiler as it needs to be on to feed hot water to the taps.

if I don’t have a radial circuit for my radiators (there is a 4 way split just below the boiler), I don’t need to worry about boiler lock right? at present each rad has a TRV on it and the boiler on fires when one or all of these opens up.

Thanks all, even you Kryton.

TRVs already in place. I’d forgotten about the “always on” rad 🙁 so a Thermostat may be the way to go, even if I can find accurate temperatures for the TRVs.

TR has it – unoccupied property, heating MUST be on 24/7 @ 15 deg C October -> April 🙁

It’s only £550 more pa for a Policy requiring no heating (thanks Nobby) so that may be better – if the old dear can be convinced.

does the house have TRVs already installed ?

if not its easier to fit an external thermostat

That.

Too slow al, sorry

You have to have some heat coming out of a certain amount of non-TRV radiator.

That was my point. If you have a thermostat, you don’t have any heat coming out when the house is warm enough, and the moment the temp gets high enough, you aren’t wasting any energy the pump.

If you just run the boiler, even on a daily timer, then you waste heat on the non-TRV radiator. You have to set the timer to be on for a long time each day in case of a cold spell when it’d cool down quickly.

they might be just what I need. A simple thermostat switch won’t work so easily on my boiler as it needs to be on to feed hot water to the taps

So do all combi boilers. They usually have a separate switch wiring for this. Assuming it’s some kind of combi boiler. Thermostats don’t wire into the main boiler electrical connection, they go into the switching circuit which turns the heating on and off, the boiler has a place to run a 4 core wire into, and terminals to screw the right wires into.

Check the manual for your boiler (online if you don’t have it), should show the wiring.

TRVs already in place. I’d forgotten about the “always on” rad

Actually, it is possible you don’t have an always on rad. There is one place where I have worked on the heating which didn’t have a thermostat, but rather the boiler had an external sensor and controlled the water temp itself with all of the rooms having TRVs. Boiler was an ELCO.

Sounds mad but true

So do all combi boilers. They usually have a separate switch wiring for this. Assuming it’s some kind of combi boiler. Thermostats don’t wire into the main boiler electrical connection, they go into the switching circuit which turns the heating on and off, the boiler has a place to run a 4 core wire into, and terminals to screw the right wires into.

Check the manual for your boiler (online if you don’t have it), should show the wiring.

hot water demand is whenever the boiler is on.

heating is controlled by a timer panel, can be on/off timed. There is also a radiator temperature dial on the front of the boiler. There are TRV’s on every radiator and the boiler stops firing when the rooms are warm. always been that way since i moved in.

its a Worcester something or other.

Cheers Rik et al. Pretty sure there’s an “always on” rad.

This is all to comply with insurance. I spoke to them earlier about the situation, they said it was “up to me” how I ensured the temp was 15 deg, which isn’t really satisfactory IMO, I think I need to call them back and hassle them.

Maybe I just put a TRV on the “always on” rad given the whole system is going to be always on.

a couple of cheap oil-filled radiators? they have thermostats on them.

Do you know the make of the system? What I did was change a couple of parameters in the boiler so the room with the always on rad was above the set temp. The parameters changed the water temp in the pipes according to the outside temp. The rooms with the TRVs were always above this because we turned down the fixed valve (without the trv)

We used a min/max thermometer as above to make sure that it worked

heating is controlled by a timer panel, can be on/off timed

So when you turn that off, you don’t have hot water to the taps either?

If not, and you have a timer panel that switches the heating independent of the hot water, then the timer panel is going into the switching circuit. You can go into that with an external circuit, which is what the external thermostat does.

Al,
Could you fit one of these wireless thermostats and fit the digital controller bit which has the thermostat in it by the always on rad. Set the controller to 15 deg 24/7 and then the rest of the radiators to 1.

The heating is then set to 15 degrees and you should avoid any pipe freezing incidents. Also that controller has a frost stat (built in override if it gets too cold)as that was one of the main concideration when fitting it at my girlfriends flat.

Maybe I just put a TRV on the “always on” rad given the whole system is going to be always on.

Not that I’m an expert on these things at all, but when I asked why that existed (the always on radiator), I understood it was that if all radiators had TRVs, on an old boiler (without a separate bypass circuit), you would be stopping circulation and the pump would blow.

Even with a modern boiler with a bypass circuit, you’ll still be running the pump and wasting energy anyway. And a TRV costs almost as much as a cheap thermostat, and fitting it will probably mean draining the heating system, compared to connecting 4 wires to the boiler.

Essentially, your original question is ‘how do I efficiently and simply do what a thermostat does’. And the answer is ‘fit a thermostat’.

joe its not that simple

i had a similar system i just ripped out

the way it was plumbed up meant that for the hot water tank to heat up the heating system had to be on as it was in paralel with a pair of motorised valves.

piece of crap.

i could walk round and turn all the valves round to zero and have water only but that was a chav.

rusty mac – if its frosty enough in the house to activate the rf500s frost function you have issues already. My boiler has frost protection at anything below 5 degrees – its located outside.

OK I can see the thermostat makes sense, if I can wire one in on my next 2 1/2 day trip, and work out what to set all the TRVs to to get 15 deg C!

In the meantime I have to get a neighbour to get it going on 1 October 😐

Might be easier draining it 😡

This place is weird. I was about to post my own dippy question about fitting a wireless thermostat after getting fed up with poor performance from TRVs.

I’ve got a basic system with motorised valves controlling HW and CH, linked to a Honeywell programmer. Should I be looking at wiring the ‘receiver’ into the programmer, or another part of the system?

T_r boiler at my girlfriends is also outside, would agree that if it is tripping the frost stat inside there are bigger problems.

not read all of ther above but if you put some max/min thermometers in each room you can keep an eye on things.

only cost a few quid each.

OK, all that can be done for now is put CH on TRVs to 2 or so.

Gas fitter reckons there may be thermostat on the boiler for the output temp, so may be able to lower that (I have to ask a neighbour to go in and do all this, while if is helpful, he’s a bit clueless). I’m visiting in 2 weeks, am I being paranoid that 24/7 boiler operation may cause it to break down?

And I am assuming the fuel bill is gonna be collosal (thermostat or not) …is that reasonable?

Been there somewhat, similar empty house, left the heating on low. With all doors and windows shut and most curtains closed, plus no hot water used and little opening of outside doors the bill didn’t seem to bad. But I wasn’t paying.

That min/max thermometer above is borked.

Constant on and off more likely to break dowm ime.