CH Timings

[Brian Reay]

I recently fitted a Hive system to our central heating. It came pre-programmed with a standard cycle- several on/off periods during the day.

Likewise, I've just fitted another 'smart' timer/thermostat to my daughter's system- the existing timer has died and this was an opportunity to both upgrade. The one we picked was designed to be a 'drop in' replacement, very easy to fit etc, but came pre-programmed with a similar series of on/off cycles.

I find if hard to believe that people use such a complex series of timings.

If you go out to work, I'd think on in the morning, off as you go to work, on for coming home, off as you go to bed etc. At weekend, on in the morning, off at bed time.

If you don't work, on in the morning, off at bed time.

I've set our Hive to this simple cycle and, using the monitoring function, the temperature seems right, I'm tweaking the times to get things right, but the basic number of cycles seems right.

So, why do the manufacturers assume people use such complex timings?

I'm not convinced it saves energy as, looking at the temp variation, the temp in our house doesn't drop much at all when the heating is off over night. Therefore, during the day (when it is warmer outside), it must drop even less.

[alan_m]

Different work patterns during the week?

Different temperatures required at different times of day. If at home and doing physical work you may want a temperature many degrees below that required just sitting watching TV,

[Harry Bloomfield]

Brian Reay formulated the question :

As I have said before, I have a weather station which logs indoor and outdoor conditions every minute and produces neat graphs. We run the heating on/offs based primarily on manually tweaking the room stat up and down, from 16C to 21C based on need. Usually I don't need to turn it up, until maybe lunchtime if we are at home, or afternoon if we are home. The heating is timed to go off at 23:00, on at 07:30, but it would never cut in between those times, because the stat is set back to

16C when we retire.

What I notice from the graphs is that even though the outside temperature increases on a morning, the house temperature continues fall, but more than it does during the night. I put this down to more activity, more opening of outside doors during daylight hours. The difference is only a matter of tenths of a degree.

Likewise, in the heat of summer, the house interior always lags some days behind the outdoor rise in temperatures.

[Brian Reay]

That could be it. I was just surprised there were so many on/off cycles during the day. I forget exactly how many Hive had but it was something like 5. The one today I'm pretty sure was 6!

It just seems needless complication- not an issue for those of us familiar with technology but not everyone is.

Otherwise, the beasts are great, I'm very pleased with out Hive system and the one I fitted today was a doddle to fit, cheaper than the replacement mechanical timer for the boiler (around £42 vs £65) and designed to be a plug in replacement. Set up was a doddle and it seems to work fine. True, unlike Hive, you can't operate it remotely(eg from a phone/PC) etc but she wasn't fussed about that.

[Brian Reay]

I've been surprised by the temp profile, as monitored by the Hive system. With the initial setting, heating going off at 10:30pm having been set to 20 C, the temp only dropped to about 19 C just before 6:30 am the next morning.

True, it is very mild at the moment.

I adjusted the off time to 9:30 pm, that changed the temp at just before

6:30am to about 18 C. It didn't drop below 20 C until after midnight.

I'm not expecting to see the same results when the weather changes and, in real terms, this tweaking probably isn't saving much energy as the thermostat would have prevented the heating turning on in most cases anyway.

(We do have cavity wall insulation and a thick loft insulation, more than the recommended, plus of course double glazing etc.)

[The Natural Philosopher]

I run my UFH 24x7

Takes too long to heat up otherwise.

But all modern products are complex. The marketing people think its makes them look more valuable and attrtactive

That's why I have a modified pre EU Henry, with no speed switch - just on and off.

Its sucks more than Dave Plowman. That's all I want it to do.

[Dave Liquorice]

Define "use". The programable stat here has set points (IIRC) at

0630, 1000, 1300 1600, 2200. With target temps of 20, 18.5, 18.5, 20,

2. Why 1300 @ 18.5? and not straight through 1000 - 1600 @ 18.5? So it automatically cancels any overide. Only very occasionally is the thing overidden. The heating is never off, its always under control of the stat.

As some one esle has said you don't need the place as warm during the day whilst active and not slobbed out in front of the telly.

Your box must be fairly well insulated and don't forget the "waste heat" from appliances and the occupants. ISTR that a resting human is chucking out several hundred watts.

This box will be back down to 18.5 not long after midnight if it's cold (below freezing) and blowing a gale outside.

[Harry Bloomfield]

Maybe 50w max.

[Roger Mills]

The way the programming information was presented by Hive when I bought mine (may be different now) was that you could have three on/off periods per 24 hours, with Off meaning the frost setting of 7 degrees.

I soon discovered that you could change each Off temperature to anything you liked so as to have six switching events per 24 hours.

I actually wanted four different temperatures per 24 hours - a set back of 12 degrees overnight, 20 degrees for about 4 hours in the morning, to warm the house up, 18 degrees for most of the day while we are active or out, and 21 degrees for sitting around during the evening. I effectively got rid of two potential switching events by adding them to the overnight period. The shortest interval between events is 15 minutes. I wanted the heating to come on at 6am - so I ended the main overnight period at 5:30 and then had two more 12 degree periods at 5:30 and 5:45.

One advantage of having multiple short periods at the same temperature rather than one long one is that if you've got someone in the house who keeps over-riding the heating every time they feel cold, you can reduce the amount of energy wasted by having the stat automatically reverting to its programme fairly frequently.

[Brian Reay]

I thought ours was set for more cycles but perhaps not. Certainly the 7 C is right.

Changing it in Hive is a doodle, one of the delights of the system.

The one I fitted yesterday, while cheaper etc, and I didn't spend long studying the instructions, seemed a faff. While, all in all, I'm impressed with the cheap one, it was the idea that the manufacturers assumed people wanted a complex default set up I was questioning.

At the moment, I'm finding the house is dropping only a couple of degrees (20 to 18) overnight. I started with the heating turning off at

10:30 and on at 6:30. Now it is set for 9:30 off. As I went for a drink of water this morning at about 6:15, I checked and the temp was 18.5.

Of course, it is very mild just now.

I don't mind my wife doing that, the idea of having heating is to be comfortable. Having been raised in a house with no ch and just a coal fire in one room in the frozen north, we both enjoy the comforts of ch ;-)

[Dave Plowman (News)]

Yup - that's how I have it. Nice and warm to get up, then slightly lower during the day when I'm likely to be doing things and in and out. Then the best temperature for relaxing in the evening. But this is an old house with not brilliant insulation, so every little helps. ;-)

[Pamela]

On 17:03 13 Nov 2018, Brian Reay [e-mail] wrote in news:psf04d$i81$ [e-mail]:

I would be suspicious of such a small drop overnight even in mild weather. Maybe the thermometer is close to a warm wall.

Currently I see a swing of something like 5 degrees C on my max/min thermometer in a downstairs room which has only one outside wall.

[Harry Bloomfield]

Pamela wrote on 15/11/2018 :

No, it seems to be fairly accurate and representative. The sensor is mounted on an internal, low thermal mass wall (plasterboard). The wall is behind you and over your head, as you climb the stairs - so it will get a good airflow passing it as heat rises past it.

I have a second thermometer in the main bedroom, a bedroom who's temperature I deliberately set to be a couple of degrees cooler than the rest of the house and its door is kept closed all day to prevent it acquiring surplus heat, but remains open over night. On a morning, it registers the same temperature as the other thermometer over the stairs.

As already said, the house has a large thermal mass and I made sure long ago, that it was very well insulated, properly ventilated and very efficient. It is very different to the cold, drafty inefficient place I moved into in the 1980's. Once the place is up to temperature, the radiators fall back so they are only slightly above ambient to maintain it.

[Roger Mills]

My heating is off (well, set to 12 degrees so effectively off) between midnight and 6am. For the last two nights, the temperature only dropped about 2 degrees - from 22 down to 20 - before it was time to come on again. My stat is on in inside wall in the downstairs hall. I'm sure that drop would be more in really cold weather, but it's mild at the moment.