Restarting a Horstmann 425 timer

[charlie3110]

Hi
I have a boiler that has a Horstmann 425 as the timer. This was fitted many years ago when the integral timer gave up the ghost. It works well when it works but I live in the country and prone to power cuts. After about 2 years the Horstmann will not start on its own. I replaced it about 3 years ago with a new one but after a all day power cut the clock now does not run again. I am loathe to keep buying a new timer just to get the clock running. Is there a way of getting it started again? Electric house clocks have a little flick to get them going but I can find nothing in the manual or on line about starting the Horstmann like this. Is is time to upgrade to a digital timer that I could reset after after every power cut? If so could you recommend and equivalent to the Horstmann 425 that will give me two timings on and off a day?
Thanks

 

[OwainDIYer]

Horstmann (and others) do electronic replacements for the electromechanical timers, that use the same backplate so no rewiring required, eg

http://www.gil-lec.co.uk/products/H...+24hr+2+Channel+Digital+Programmer/2005970180

Battery backup means they do not need resetting after a power cut.

 

[charlie3110]

for some reason I cant follow your link but what you have recommended is just what I need. Can you tell me on here what the particular Horstmann I need to replace the 425? Is it a C27?
Thanks

 

[OwainDIYer]

the link is to a Horstmann H21XL

http://www.tlc-direct.co.uk/Products/HOH21.html

there is also the Channel Plus H27XL which is a 7-day version. TLC have a helpful link to compatibility information.

And the backup battery life is 10 months continuous. Should cover most power cuts.

 

[charlie3110]

Thnks I will get right onto it

 

[charlie3110]

Sorry to be a pain but when I click on the Horstmann H21XL
it says it is a direct replacement for the 425 Diadem. However on checking mine I find that it is a 425 Coronet. Is this still the replacement item?

Thanks

 

[OwainDIYer]

IIRC:

Coronet was the single-channel one (with 1 slider switch).

Diadem was the 2-channel one

Tiara was the 2-channel one with neon indicators

There are similar products from other manufacturers which you may prefer and which will mate with a Coronet/Diadem/Tiara backplate.

If it's only for heating (combi boiler?) then you could replace it with a single channel programmable thermostat to give you different temps at different times.

Hortsmann single channel 7 day programmer (a bit cheaper than 2 channel)
http://www.tlc-direct.co.uk/Products/HOH17.html

programmable stat eg (battery powered with replaceable battery)
http://www.tlc-direct.co.uk/Products/SMTRT035.html

 

[charlie3110]

I have to thank you Owain for your patience but hopefully one last question? I realise now that it would have helped you if you had all of the information on my first question. A combi boiler? Pass. I have a Myson Velaire PJ 50/70 Pressure Jet Oil Fired Boiler. It was working with a Horstmann 425 Coronet that replaced the integral boiler timer when that gave up the ghost.
If you could narrow my needs down to one or two suitable replacements then I would been so appreciative. My needs are for the c/h to come on and off twice a day and the hot-water to come on with that or on its own if the timer allows. You might have guessed by now that I am a silver surfer but one who feels that he can still do the simple DIY such as replacing this timer especially if I can plug in a like for like albeit a digital one.
My sincere thanks again Owain for your patience and help

 

[OwainDIYer]

whether you can have different settings for heating and hot water depends on how your system is plumbed and wired.

How do you currently control the hot water to have the hot water on but the heating off?

Any of the ChannelPlus H -- XL should be a drop-in replacement for the Coronet, but if you want the possibility of having separate CH and HW control then it would be cheaper to buy the 2-channel now rather than have to replace it later. Then it's your choice of whether you want 24-hour or 7-day timer.

Just remove from the backplate any connections to terminals 1,2,3 on the backplate which were not used by Coronet but are used by Diadem/Tiara. They may have been used as 'spares' - if they have been you will need to use chock block connectors to provide 'spare' connection points.

 

[charlie3110]

There are two switches on the Myson one for central heating that will only work if the hot-water switch is on but you can have just the hot water switch on. These switches are on the casing face plate of the boiler. The Coronet only controls the time. In the summer I have it on 24 hours and just switch the hot water on for an hour a day. In the winter I usually get it to come on at 0500 for two hours and that heats the house and lets me get the wood burner roaring! Then in the evening it comes on for about an hour at nine to heat the bedrooms.
I think I know what you mean about the wiring and once I determine which replacement timer I need I can follow the wiring round.

Thanks again Owain you are very kind

 

[OwainDIYer]

The manual for the boiler with the wiring diagrams is here
http://s000.tinyupload.com/index.php?file_id=07201939164674791426

It should be possible to wire the programmer in to replace the 'deluxe control panel' with the CH/HW switches and timer to give you separate CH and HW settings - although you will still have to have HW on for CH to work. However, it's a bit complicated. The boiler itself only requires one 'call for heat' command from the programmer. You would wire the programmer directly to the pump, zone valve etc.

The programmer will have an 'interlock' in its installation settings which ensures that when CH is on, HW is also on.

 

[Boilerman2]

I think you'll have some rewiting to do Charlie,
The last one of those I changed (Myson Velaire) I used a Siemens RWB2E
which needs a new base plate the programmer should be set to the "Gravity" position to enable the correct firing of the boiler when selecting heating only

 

[charlie3110]

Thanks to Owain and Boilerman for your help. I have enough information to go away and draw out the wiring needed to replace my Coronet. I like a challenge!