Gas central heating timer

I have a Horstmann Channel Plus which has an internal battery

Honeywell ST699

Been on the market for over 30 years

Yes, we have one, and very happy with it. Unsophisticated: two on-off periods per day, or one on.....off covering both times, or continuous. CH and DHW both follow the same time settings. No individual day sets, nor week day / weekend stuff. Battery back-up, although ours failed a year or so ago and had to be reset every time we had a power failure, so I got a replacement. Just slotted it into the original base unit; no rewiring.

There are cheaper programmers, but whether they have battery back-up, I don't know, although I'd have thought it pretty standard these days as it can't be that difficult to implement.

Does it need to time hot water as well?

If not, then doing away with the programmer and using a prog stat is probably easier.

For a simple programmer with battery backup, then the classic honeywell models are quite simple:

The nicad on the PCB can be replaced (with a near identical NiMh)

It *might* be this one

There are two or three types that look very similar in the photos but are significantly larger (mainly in height)

Such as this

More recent timers from Honeywell (and others?) might have battery backup but they carry their own set of problems with poor LCD glass to flexible PCB bonding.

The Other Mike presented the following explanation :

We had one of those, which soon had the display fail and the battery backup didn't often work..

We got this about 5 years ago..

CP715 Si

- Service interval function

- 7 day, 5/2 day or 24 hour programming

- Permanent back lit display

- AM/PM or 24 hour display

- Built-in programmes

- Automatic BST/GMT time change

- Convenient user overrides

- Holiday function

- Industry standard wallplate

- Factory set clock

It is rather more sophisticated than we absolutely needed, but the display remains good and it has a neat 1 hour program override for heating and hot water. It has twice given problems though...

It twice crashed, where the display went blank, plus both heat and HW were turned permanently on. It was easy to spot, both LED's on, when they shouldn't be and the display blank - Cycling the power, restored normal operation.

When you say less useful are you just getting too much commercial advertising up front? You hopefully have an ad blocker and also you need to mask out things like graphic results and sponsored links if possible by the terms you look for. Its the classic needle in a haystack issue, the haystack is now getting so large that finding the needle is a lot harder. You also need to realise that to stay free, internet services see the user as the product, so they need to be able to track you and also advertise to you as well. Of course in the future Foresee a paid account for freedom from all of the above as being the only affordable way for sites to continue. We are still living in the honeymoon period when commercial interests can actually still pay for data and as we all get better at denying them the data so their revenue dries up. Brian

Many modern ones have a built in back up battery including

(Water only or heating and hot water) Just click on one of the pictures to get the description and a link to the manual.

Thank you for all your replies, I now just have to decide which is most suitable for me.

My Danfoss TP9 does not lose time or its settings in a power cut.

I think my Heatmiser Smartstat must get its time from the Internet. It has not lost its settings when the power has been switched off.

Do you want to run your heating during the power fail? If so you'll need to power the pump too, which might point to a UPS.

Andy

No, I just do not wish to reset the timer every time we get, a not infrequent, power cut here.

As a broader question to the group, bearing mind that these devices are often fitted for 10, 15 possibly 20 years or more how long (I mean in years not hours of a power cut) would the backup battery typically last?

Rechargeable batteries used in radios, drills and laptop computers don't seem to last anything like this long.

You should more think about light duty backup batteries used in e.g., computer motherboards like Apple Macs of the power PC era which usually needed replacing after 10 years or so.

In fact a supercapcacitor might be te way to go rather than a battery..not sure how long they last tho.

Primary cells MIGHT last longer.

That looks somewhat similar to the timer a neighbour had a few years ago when I was called to assist after a power cut maybe around 2010 ish.

Even with the user guide scanned, enlarged and printed out on A4 it was almost impossible to understand how you ever programmed it up. One of the switches under the cover used a word or phrase, I can't recall what, it was quite clearly from the english language but of such obscure relevance to any intended functionality as to make the labelling pointless.

I came to the conclusion you had to be off your head on class A drugs to properly understand the instructions. What the design brief was I shudder to think.

Unlike those radios drills and laptops you are not cycling them through a full charge discharge cycle, all you are doing during a mains power supply failure is keeping the processor supply in sleep mode together with the timer setting and a real time clock. It could amount to no more than a few micro amps of current draw. A low capacity trickle charged Nicad or in more recent times NiMh or Lithium cell could easily cover power failure of several days or longer.

The AA duracells in our standalone Honeywell programmable RF thermostats (CM61 & CM67 series) last at least two and maybe three years essentially doing the same thing plus permanently driving a time display and squirting out a coded 868MHz RF message several times an hour to the base unit during the heating period.

Of course if APC did the charging circuitry for heating timers then the thing would be massively overcharged and then expand to twice its size and fall off the wall every 6 months requiring a crowbar to remove the battery.

The Other Mike formulated on Monday :

I agree, but with a bit of effort reading the instructions, I can get a handle on it. Trouble is, it needs so little attention and each time I might need to adjust anything, I have then spend time re-reading it all.

Chris B was thinking very hard :

That working life varies a lot, depending on the quality of the charging circuit. In my case, when we go away for a while, I just isolate the power until we get back, which isolates the timer. It maintains itself happily for 14 days and works as normal as soon as powered back up.

I have seen the same oval PCB mount NiCads survive 20 years or more.