programmable thermostats

[Fred]

Hi,

I've just replaced the thermostat with a programmable thermostat. The idea being that I can set one temperature during the day and another, lower temperature at night just to keep the chill off in this cold weather. As a result of this, I have switched the central heating to "always on" on my CH programmer.

I'm wondering whether to remove the programmer completely? What would you do? Do brand new installs that use programmable thermostats have a programmer at all?

The programmer is a Horstman digital affair. One good thing about it was that you could set the times for Monday and then press a button to copy those times for Tuesday, Wednesday, etc.

The thermostat I have bought is a Salus and I could not find a way of copying programmes, so I've had to enter each day separately, which was tedious. Too late now but are there any programmable thermostats that allow you to copy programmes?

My other criticism is the thermostat has five programmes per day and I didn't need too use five, so I had to set the "unused" ones all to late at night to use them up. On the Hoprstman you could set unwanted programmes to begin and end at the same time. The thermostat doesn't have start and stop times; it just has a start time and it stops when the next programme begins.

I'm just wondering what to do about the hot water. Is it best to leave that on the timer so that it comes on briefly morning and night, or since there is a cylinder stat, can that be left on continuously? My feeling is that the latter might be wasteful as even an insulated cylinder will cool. Or am I wrong?

TIA

[Martin Pentreath]

The Honeywell CM927 lets you do that, but unless you have an exciting and unpredictable life you'll probably never be changing the programme again, so I wouldn't worry too much.

The Honeywell version also has five (possibly six?) which you have to use up. I find them useful for regular re-affirmation of my prescribed temperature during the day to thwart members of the household who sneakily try to set it to 30 degrees when I'm not looking.

[Usenet Nutter]

Is it a Salus RT 500RF with it's companion connected beside the Boiler ? That's all you need ..you don't need a separate programmer .I had one before but when I got the new combi fitted the programmer got dumped .

As for setting the programmes I agree it is a bit of a pain ..you just have to scroll through them all day by day and set the temp you want or do what you did .

[Dave Liquorice]

Ours still has the programmer in series, easy means of switching the heating off rather than having to faff about with the stat. I think that has a "holiday" mode but it's not as simple a pressing a button the face of the programmer until it says OFF.

The Danfoss TP75 does, superceeded now but I expect it's replacement does as well.

I think you haven't quite got your head around how a programable stat works. It sets a temperature for a particular period of time not a specific time. The TP75 has 6 set points/day and up/down buttons to overide the set temp until the next set point. If for example you had

18.5C set from 0630 to 1700 but you over rode that at 1000 to 20C it would stay overidden temp until 1700. But if you put in a set point at say 1200 and 1500 but with 18.5C as the temp any overide would only last to the next of those set points.

The hotter something is the faster it looses heat... If I was on my own and the water heated fast I'd use a manual "on demand" system. I have had such a system in the past when the time switch broke and there was a marked reduction in the gas bill... Mind you I was living on my own and the tank would stay hot enough for washing and washing up for a couple of days and it would reheat from stone cold in about

45 mins and from warm in less than 30.

[Mike Clarke]

You can disable individual time periods on the CM927. In programme mode select the desired period with the < and > buttons then press and hold the big "i" button on the right for at least 2 seconds, the word "DISABLED" should appear on the display. It's a toggle process so just do the same to re-enable it when needed.

[Usenet Nutter]

Although the Salus 'stat does have a "Frost" button which sets the temp to 5 deg so it's virtually the same as an "off" button.

[John Rumm]

You may want to retain it to control the hot water heating.

Not surprisingly the Horstman centaustat will let you do that (as will others)

Unless you routinely use a large proportion of the hot water at varying times its probably best only recharging at a couple of set times each day.

[Roger Mills]

Yes, that's standard practice - let the programmable stat do the timing for the CH

You'll need it for the hot water - so keep it. Also, if you've got more than one heating zone (or if you subsequently add more zones) it provides a central point for turning off the complete CH system.

I've got a couple of Honeywell stats - one wired and one wireless - and they both allow the programme to be copied from day to day.

My Honeywell stats have 6 time settings per 24 hours - which I use for (effectively) 3 on-off periods. My 3 'on' periods are 6am-10am, noon-2pm and

5.30pm-midnight. Generally speaking, the house remains warm enough during the morning and afternoon 'off' (actually just lower temp setting) periods - but I can use the 'Party' function to over-ride those and maintain the full temperature during the day if SWMBO complains of feeling cold - such as in the current cold spell.

I allow the original programmer to control my HW heating - with 3 on periods per day - timed (in general) not to coincide with times when the CH is running full chat - then there's no need to worry about CH vs HW balancing.

[Piers Finlayson]

I have the Horstman digital stat and do what you suggest - have the regular programmer on 24/7, and control the CH via the stat. As the house is usually occupied I only use a single setting all day, and use up the other programs at 10pm (when the heating goes down).

I have hot water controlled by the programmer on twice a day. One problem I do have is that my programmer has no "boost" or "one hour" feature in case you want the HW on for a short period of time (e.g. cos someone had a bath at an "unusual" time). If/when I replace the programmer I'll definitely get one with this function.

[Fred]

I have two CH zones: upstairs and downstairs. One uses the wired version, the other uses the wireless one.

I wondered about removing it but as others have said it would allow control of HW and allow me to switch everything off easily.

Thanks.

[Fred]

Thanks. I guess I should have asked about makes and models before I bought what I did ;(

Sorry for the confusion; I understand how they work, it's just on mine there is no way to "switch off" unwanted programmes, the point I was trying to make is that on a timer you can set the on time to equal the off time on any unwanted programme slots. In another reply someone mentioned that their model allows you to do this, so I guess this is another reason I should have done more research before I went shopping. Still, these are minor niggles and as someone else replied, hopefully it is a set and forget installation that I won't need to touch again.

[Fred]

[and later (sorry to quote out of order)]

Yes, I will keep the programmer to do exactly as you suggest.

I did buy the Horstamn from Screwfix but took it back and bought the Salus instead. IIRC the Horstman displayed the set temperature rather than the room temperature (unless I didn't RTM and was using it wrong!) and I changed it because I felt the Salus display was better.

[Dave Liquorice]

But you don't have any "on" or "off" times you only have a set of points in time after each one and before the next a particular temperature is selected. Just set any unused ones to the same temp as the period before and you have, in your langauge, turned it "off".

If the Salus has an overide feature setting some of the unused points through the day should cancel the overide at that time, instead of leaving it overidden all day for example.

[Roger Chapman]

snip

I have had a Horstman centaurstat as my upstairs stat for several years now and that has both room temperature and set temperature in the display. I believe it may have a holiday setting as well but I had wired a switch in series before I found that out and flipping a switch is so much easier than the looking up instructions that precedes setting holiday on the downstairs stat.

[John Rumm]

There may be a couple of options for the display, but ours is set to show the target temp and the room temp.

[Usenet Nutter]

That is the way the Salus works but it is a bit of a PITA to go through all the periods each day/night to set the temps .

If you override the Salus at any point the overide temperature remains only until the next period when it reverts to the temp that has been set for that period so if need be you have to overide it again .Is that what you meant?

[Piers Finlayson]

let you do that (as will

Ours only displays the room temp (or, while changing it, the set temp). I don't remember there being an option to configure but it was a while ago.

[Dave Liquorice]

Does it not come with sensible defaults? Though you if you want to adjust those you still have to work your way through them...

Yes. If you have set points at say 0600 and the next at 1800. If you overide that at 0900 then it will stay overidden until 1700. But if used one or two of the "spare" set points during the day but with the temp set as the 0600 "normal" one then the override would cancel at those times. I think I have at least one such constant temp set point at about lunch time. Personally I don't want to have to remember that the heating is overidden when I go out for the afternoon... I'd rather set the overide again, *if* needed.

[Roger Mills]

But a manual switch cannot possibly duplicate the function of the holiday setting!

Your switch will stay off until you come home to a cold house and switch it on again.

Using the holiday setting, you can tell it to come on on the day of your scheduled return - so that you come home to a *warm* house. May not matter in the summer, but it does in the winter!

Quite apart from that, most programmable stats double as frost stats - so the heating will come on if the temperature drops below (typically) 5 degrees - *even* in holiday mode. With a switch in the OFF position in series with the stat, the heating will *never* come on no matter how cold the house gets.

[Roger Chapman]

Did you miss the bit about the downstairs stat?

But the downstairs should come on when programmed and the upstairs will get some warmth from that. It won't take very long to give the bedrooms that last lift before bedtime.

Yes indeed. I came home after Xmas to find the batteries low in the downstairs stat and the stat reduced to frost stat status. Seeing that it takes 2 days to get my house fully up to temperature in the depths of a cold winter that was a bit of a blow.

Now that would depend whether or not there was more than one stat controlling the boiler.