To control my central heating I=92ve got a Honeywell =93Sundial RF2 Pack 2= =94 which consists of a fancy electronic programmer and radio linked wirele= ss thermostat.
The programmer has an optimisation feature that is supposed to learn how lo= ng it takes to heat up the house so for example, as I understand it, if you= set the heating to come on at 7am it should come on earlier but at varying= times depending how cold it is in order to get the house up to temperature= at 7am.
I=92ve used it for over a year and as far as I can see all it does is come = on precisely an hour before the set time and while it=92s on for that first= hour it says =93optimising=94 on the display. I think I=92ve had it long = enough for it to do its learning but it only ever comes on an hour before a= nd this does not vary with the temperature as I think it should.
Anyone got any experience of this model and what it does or what it should = do?
2=94 which consists of a fancy electronic programmer and radio linked wirel= ess thermostat.
long it takes to heat up the house so for example, as I understand it, if y= ou set the heating to come on at 7am it should come on earlier but at varyi= ng times depending how cold it is in order to get the house up to temperatu= re at 7am.
e on precisely an hour before the set time and while it=92s on for that fir= st hour it says =93optimising=94 on the display. =A0I think I=92ve had it l= ong enough for it to do its learning but it only ever comes on an hour befo= re and this does not vary with the temperature as I think it should.
Optimum start was invented long before electronic devices came in but was expensive then so it was only used for very large commercial installations. Now it is cheap. If it is working right it can knock 10%-15% off your fuelbill.
Theoretically, you tell it the occupation times of the building and it does the rest. So on a cold day it should start the heating up sooner than on a warm day. It may have optimum shut down as well. ie shuts the heating down before you leave the building.
There used to be manual set up ones but they would be too hard for the average user to set up ,it was only when they became "self learning" they came on general release.
So if it is coming on at the same time regardless of weather, it is not working.
Ba aware that most of them have a maximum length of time for the "heating up" period and this is the fallback it reverts to if faulty.
Check the various temperature sensors are still connected. Usually inside, outside and water temperature.
They are often thermistors which can be checked with a multimeter. Often they will say what resistance they should read for a particular temperature. Or maybe the handbook will.
I don't think it's quite as sophisticated as the ones you mention!
It doesn't have an outside temperature sensor or a water temp sensor. I thi= nk all it does is to learn how fast the house tends to heat up and, potenti= ally, adjust the start time when it's a bit warmer.
BUT, because in my settings I have the thing restricted to starting one hou= r before the set time I think maybe it's never had a chance to demonstrate = a varying start time. I can set it to start up to three hours early so mayb= e if I allow it to do that, I'll then see some variation in the actual star= t time based on the general temp of the house.
hink all it does is to learn how fast the house tends to heat up and, poten= tially, adjust the start time when it's a bit warmer.
Haven't come across that sort. Maybe there should be outside sensors but they're missing? Hard to see how it can work properly based purely on inside temperature.
Just your sheltered life Harry. Domestic optimum start thermostat/timers just start x mins early for a y temp below the set point up to some maximum. They aren't full commercial weather compensated control systems.
Some domestics learn how fast the house will warm up others need to be told. But the basic target of meeting the desired set point temperature at the desired time is still there, normally only the first set point time has the optimum start feature.
I have two Heatmiser programmable stats (one for C/H and H/w, the other for electric UFH in one room).
They are the learning variety, which slowly adjust the minutes per degree figure throughout the year, lacking true weather compensation they could get caught out by a cold spike, but do fairly well ...
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solid blue lines are the set temperatures throughout the day.
The orange bands are when the stat is calling for heat.
The dotted blue lines with (P) are where it's using optimum start to reach a set temperature.
The green (H) and (M) are where manual override or hold have been used.
The [T] and [t] are the timed water periods.
Dotted black line is external temperature from nearest met office station (not used by the stat, just for monitoring).
hour before the set time I think maybe it's never had a chance to demonstra= te a varying start time. I can set it to start up to three hours early so m= aybe if I allow it to do that, I'll then see some variation in the actual s= tart time based on the general temp of the house.
If I've read it correctly your system is comfortably controlling the temp within one degree and the boiler is firing for about 20mins in a
90min heating/cooling cycle (5th - 6th Dec, approx 3degC otside). It sort of debunks Honeywell's insistence that a boiler needs to fire 6 times an hour[1] to maintain an accurate room temperature.
It's saved me some time modelling my own system before junking the proportional Honeywell stats and swapping to more simple on-off control.
[1] Honeywell's default firing frequency for their programmable stats, adjustable down to 3 times per hour minimum (my chosen setting but I wish it could be lower).
There /is/ an option to control to within 0.5 degree, but I consider that unnecessary, also I suppose firing more frequently for shorter periods would be less efficient for my cast-iron lump.
Yes, though obviously the length of the cycle varies depending on temperature/wind, last Friday when it was below freezing all evening, the cycle was 20mins out of every 60mins, rather than out of every 90mins.
Yes, spotted that and again the 60min cycle at colder temps is useful. I'm trying to enhance my multizone setup and was wondering if I can get away with polling my 'slave' zones at 30min intervals (to keep demands in sync) and it looks like I can. I'll be able to tweak down to half degree accuracy too if needed.
Doesn't that point to your boiler being grossly oversized? Frequent firing leads to gross inefficiency in any boiler. Ideally it should run constantly.
That's not optimum start then, but something else that the vendors have misrepresented with some techy sounding buzz words that the purchasers don't understand..
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