It can get rather cool in the bedrooms in the winter with the wind blowing. Down to 11 or 12C but rather an extra thick duvet and unbroken sleep rather than a warmer room but broken sleep because of the clunks and groans from the CH coming on at 0345...
I bought the Danfoss TP75 in the wirefree version for >=A3100 but from other posts it looks like the budget market is catching on, all be it with restricted facilties. The TP75 will do 6 set points/day with 0.5C resolution at 10 min intervals every day for 7 days and each day can be different. It also features "chrono proportional control"(1) and an "anticipator"(2) for the first set point of each day.
(1) Controls the boiler in relation to the calculated demand for heat. If only 50% of the boilers output is required to maintain the room temp the boiler is only fired for 50% of the time.
(2) Fires the boiler a variable amount of time before the first set point of the day to ensure that the setpoint temp is reached by the required time.
I've got the TP75 and I don't like the fact that although you can set different times for each day, the set temperatures have to be the same for all days.
There I was about to start a new thread, when I spotted this active topic.
I have a Horstmann Centaurstat7 which I bought from Screwfix. I have wired my heating so that is always on and the feed to the thermostat is always live. So the stat has total control of the heating system.
It has 4 periods and rather than weekdays and weekends which many controllers have it has work days and non workdays. This is a great feature as my wife works part time therefore need the house to be warm some of the weekdays. So far so good...
However in practice it is not so good. It is far too sensitive, meaning that the system frequently gets switched on (ie cold starts) for 5 minutes or so then switches off. My boiler is fairly old, so takes a while to heat up its cast iron cylinder, so it scarcely starts heating the water sometimes, then it switches off! I shudder to think how innefficient this is and need to do something about it quickly.
I must say I am suprised really - I thought Horstmann was a good make. Has anyone else:-
- got one of these?
- noticed similar behaviour?
- come up with any solutions?
- come across any optimisations/installers settings like those mentioned for the Honeywell CM67 previously in this thread?
I'd rather not go to the expense of replacing the controller. If I do would have to make sure it has the workday/non-workday feature explained above rather than straight weekday/weekend settings as many controllers do.
I don't know this model but I noticed in a simple Landis programable thermostat there is a small switch inside which is something to do with short cycling. Maybe yours has something similar.
I chose the Centaur stat particularly because it has got a small hysteresis. I used it for 8 years (it was made by Eberle then) with an ancient boiler and no complaints. The short cycles mean that the boiler never gets chance to get too cold before it starts up again so no long warm up periods. It keeps our house at a nice constant temperature, better than starting to feel chilly before the heating comes on again.
Following on from what Bill says, there may be settings to change this: the Honeywell CM67 has 20 or so 'engineers' settings including sensitivity, cycles per hour and minimum on time. Worth checking the installation (not user) instructions
As frequent readers of uk.d-i-y know this is a control that I use and (I confess) rather like. I have one in my own home and have fitted one with just about every heating system I have done substantial work on.
The fact that you have the thermostat clicking off after short while means either the house was very nearly warm enough already or you have a bad position for it. Too near to a source of heat or sunlight?
I have also had no complaints from customers about the heating not coming on or remaining on long enough.
Thanks for that Ed. I infer that you have substantial experience in matters CH, so its reassuring atleast that the Centaurstat has your seal of approval.
In repsonse to your comments, this is what I have tried so far: 1] the thermostat is in the hall about 4ft from a rad on the opposite wall. Unfortunately I don't have a TRV on this rad, but I have turned the valve right down, so its very nearly off. This rad is logically near the boiler - one of the first on the flow side and last on the return side, so I was concerned intially that the flow was choosing the path of least resistance, through this rad and the hall reaching temp b4 the rest of the house. But this hasn't made any difference. Very often its obvious the boiler just hasn't got up to temperature, by feeling the flow pipe out of the boiler just after it has switched off. 2] removed the 'stat cover from the base and covered the vent holes with cellotape, to try to make it less responsive - no change here either.
The external door into the hall is south facing, but is about 15ft away from the 'stat, so I don't see direct/indirect heat from the sun being a problem.
The only other thing occuring to me as I write is that the 'stat is located on single-skin wooden panelling alongside the staircase. On the other side of this are steps down to the basement. There could be
2 issues here: temperature fluctuations conducting through the wood - perhaps unlikely as wood by nature is relatively insulating. The more likley cause is small draughts coming into the back of the 'stat. The wire to the stat disappears through a hole the panneling down into the basement, where the boiler is. At the moment the basement is otherwise unheated and there is permanent fresh-air ventilation. As I write I am unsure whether that hole is totally air-tight... Could have hit the jackpot - will check it out when I get home tonight...
The only other thing I had thought of doing - a nasty low-tech effort
- would be putting a bit of fibre-glass lagging inside the 'stat, again to try and make it less responsive.
Anyway - I'll check that hole tonight and post back if I've cracked it
Something is making the Thermostat slightly warmer? Why not try a slightly higher or lower temperature. In fact my general rule for programming heating is: "Programme low and override up whenever as needed."
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