Well, a hundred quid is about 165 litres at today's BoilerJuice quote (including VAT), and 165 litres would be about 82 hours of burning by my Wallstar, according to consumption rates specified in the manual. (Boiler is seven years old.)
MM
When my CH system was fitted it included a Drayton RF3. I moved the cooker box, wired in the fused, switched spur and the receiver and set up the 'stat so, although the labour costs were included in the installation there would have been none for the control side if it had been a retrofit. Just as well that I did it, 'cos the fitters couldn't seem to understand the setting up (it's far from intuitive at the start).
Shouldn't be. Any stat worth it's salt will be digital and use a unique ID that requires pairing. The intermittent nature of transmission is such that interference between stats will not be an issue.
Mathew
My Honeywells have that (CM907 and CM Zone) and I am not convinced it works well, it heats up the house much much earlier than you want it to, so I play silly games with the time I want it to achieve the temperature. Maybe if it learns with time and I get cold I will trust it more.
Kostas
Overall, after reading these and other comments I'm beginning to think that a retrofit stat isn't worth the hassle. I only switch the heating/hot water on anyway as and when. The only time I run the boiler on the timeswitch is when I go away and then only if it's expected to be cold (like over Christmas).
Otherwise I just decide on the day whether I shall have a bath and switch on the hot water accordingly. 20 minutes for only the washing up. Or 30 minutes to have a really hot bath, plus some left over to do the washing up. As for the CH, it's rarely on. I heat just the room I'm in, using a small oil-filled electric radiator, and the kitchen gets residual heat from cooking anyway. For example, the temp in the annexe (next to kitchen) this morning was approx 9 deg C. In the kitchen it was 17 deg, which is slightly below what I find comfortable. In my workroom right now (15:21) it is 17 deg, which is mainly residual heat from the two PCs. I have, however, just switched on the oil-filled rad for half an hour to bring the temp up to 19 deg, then it'll be turned to lowest setting on thermostat while the PCs come up to temp. Seems daft to switch on the CH and adjust all the TRVs just to get the same effect from burning oil. I don't like CH. I grew up without it and would rather have open fires (or stoves). As a kid I was used to scatching patterns in the ice on the INside of the bedroom window when I awoke.
MM
It makes adjustments on a day-to-day basis to the base rate-of-rise assumption - out of the box this is 3C/hr. Thus, within a few days it ought have settled to as close to actual as it will ever get. My CM927 works perfectly in this regard and reaches target temperature within
10 minutes (max) of the target time. I monitored mine for a few weeks using a webcam taking a photo every 10 minutes and found it worked very well at accomodating a wide variety of external temperatures.Whilst the optimum start feature has been available on the Chronotherm stats for a number of years now, right back to the CM60 series (amongst others), I do have a feeling they've tweaked it on a number of occasions. Certainly even within the current CM900 series they've made changes such as reducing the maximum advance of time from 3 hours to 2. Perhaps yours is one of the earlier models?
Mathew
As Mathew has said, it should settle down after it's had a few days to learn how your house responds. Mine does it very well and saves having to guess how much earlier to set it as the weather gets colder.
If you really can't stand the optimum start feature there's no need to play silly games with the time, just disable the feature by going into installer mode and setting the appropriate parameter. The details are in the installation guide which should have been supplied with it. If you had someone install it for you then they might have only left you the dumbed down user guide but the installation guide is available on the Honeywell website (or it was when I got mine a few years ago). If you can't manage to find a copy I think I've got a PDF copy somewhere that I could email to you.
I got one for about £12.95 this January.
I wired it near the CH programmer (which happened to be in the kitchen), in series with the control cable.
But, I suppose it could go anywhere where the ambient temperature is typical of the rest of the house (or it can always be set a bit higher or lower to compensate), and is easy to connect to the boiler (but not right next to it).
(My TRVs are almost totally useless; they go from 1 (or is it *) to 5. If set at 2, the radiator never gets hot. If set at 3, it never gets cold! If by some miracle the temperature of the rad is just right, then as soon as the weather changes a little, it needs adjusting again. Why aren't they calibrated in degrees?)
Calibrated markings would be meaningless as you're wanting to set the temperature of the room for the main occupancy space on something that sits 6" above the floor next to a radiator. Relative markings (hence 1 to 5) therefore make far more sense: if the current setting doesn't heat the room up high enough, turn it up - and vice versa.
Yours sound like they've almost certainly failed and no longer responding to the variations in temperature (hence they are for all intents and purposes manual wheelhead valves). Indeed, they don't last forever - cheap(er) ones particularly - do you know what make/model/ age they are?
Mathew
My TRVs are Honeywell -- the boiler engineer who came on Friday said they're good quality kit -- and I find them just as much a PITA as BartC does his. My house was built in 2004. Trying to adjust the TRVs to give exactly the right results is an exercise in futility.
MM
They are susceptible to the temperature of the pipes, so if the boiler is firing infrequently the TRV will open up due to being cold for some time. In less cold weather, this causes an overshoot; in cold weather an undershoot. TRVs need to be turned down and up to adjust for what the boiler's doing, IME. Last year, as I removed and replaced each radiator in turn, I turned the TRVs to the horizontal position and that seems to have stabilised them significantly.
"will not" rather a definative statement. B-)
There is an awful lot of other stuff using the same frequency as wireless stats. In a crowded urban area it is perfectly feasable for something else to transmit at the same time as the stat and corupt the received signal. AFAIK stats only transmit once for each state change.
Has the heating system ever been balanced? To do properly takes a quite a while so it's rarely, if ever, done by builders/installers.
OK when the TRV's start to shut down rads it'll screw the balance but in the general heating from cool the system would perform better.
I hope you don't buy via boiler juice. Suppliers based 20 to 30 miles away *always* beat their quotes by a 0.5 to 1p/l, the local supplier anything up to 10p/l or more!
2l/hour = 20kW *input* so something over 15kW out. What a tiddly boiler. B-) The rating for ours is 7l/hr with a 38kW output but I've had a smaller jet fitted as the connected system (now it has zones) can't dissipate that amount of heat fast enough and it trips the overheat stat...
I doubt it does that, it would require the receiver to have some smarts and be told what the set points and time is that you set on the stat. Far more likely to just send a turn on or turn off signal when the stat state changes.
That's pretty much exactly what it (the CM927) does. The stat sends the cycle period and proportional on time (0-100%) to the receiver which then takes responsibility for demanding heat as required. This is why the flame symbol on the stat remains on even when the call for heat is off (i.e. the receiver is sitting in the off-period part of the cycle).
The drawback with that approach is that if a change signal is missed then it'll sit in the wrong state until the next changeover period.
Mathew
No it won't - the pressure increase across the rest of the system will rise uniformly (remember: balancing is down to relative resistance, not absolute).
Mathew
That's why they use digital identifiers and repeated status transmissions. See my other reply... ;-)
Mathew
...I should point it it does this regularly - not just when something changes.
Mathew
I find that their close proximity to the radiator makes them almost useless, beyond a very crude form of wet finger stab.
Even the digital wiresless stat needs a couple of degrees up in really cold dry weather. I feel cold when the air is dry in the house.
But they are better than nothing.
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