Replace rotary timer and install thermostat

[Djnikon]

Hi,
I live in a really really old cottage with oil central heating. At present there is no thermostat control and the timer is an old rotary one that only has one set of timing sets (i.e. I can only set one on and one off time).
How easy would it be to replace this with a nice digital one and also install a thermostat control in the dining room - I read somewhere you should use the coldest room...?
Any advice greatly appreciated.

 

[Djnikon]

No one?

 

[OwainDIYer]

Probably the easiest thing would be to replace the existing timer with a programmable thermostat, providing it isn't in a completely silly location.

Make and model of existing timer? Make and model of boiler?

 

[Djnikon]

Thanks,
It's currently in a cupboard in the kitchen so not in a silly place.
The boiler has AVC on it, has no other details, from what I have gathered is around 24 years old and originated from Belgium.
The timer unit has no make or model information at all and is just a silver/grey box with two toggle switches and the rotary dial.
Not great info I know but its' all I have.
So a combined timer/thermostat would be best?

 

[leytonjc]

is your existing clock twin channel? (htg and dhw). or single channel?

 

[D_Hailsham]

The timer unit has no make or model information at all and is just a silver/grey box with two toggle switches and the rotary dial.

What do the switches do?

 

[Djnikon]

is your existing clock twin channel? (htg and dhw). or single channel?

Twin channel, this is what the toggle switches do. CH on/off/timed and HW on/off/timed.
Although one thing I've noticed is that if you switch CH to ON but not the HW the boiler doesn't fire. If you then move HW to ON it does. If you then switch the CH to OFF and leave the HW to ON the boiler remains fired up... Odd.

 

[D_Hailsham]

Although one thing I've noticed is that if you switch CH to ON but not the HW the boiler doesn't fire. If you then move HW to ON it does. If you then switch the CH to OFF and leave the HW to ON the boiler remains fired up... Odd.

That probably means you have a pumped heating/gravity hot water system.

If you have three or four water pipes coming out of your boiler and one or two are much larger in diameter than the others, that's another clue.

If that is the case you are restricted as you can have the HW on by itself (summer); but in the winter heating and hot water have to be on at the same time.

You can get digital timers for this, e.g Honeywell ST9400, which has to be configured as a "mini-programmer".

If you want completely separate control over CH and HW times, you either have to convert the system to "C Plan" or fully pumped.

C plan requires a mootorized valve inserted in one of the pipes between HW cylinder and boiler and a thermostat on the side of the boiler.

Fully pumped means re-piping the HW cylinder as well as a motorized valve and cylinder thermostat.

Fully pumped is the better solution, but it will be more expensive.

Your type of system is no longer permitted.

 

[Djnikon]

Ok, thanks. However... we don't have a HW cylinder. There isn't any hot storage at all.
The whole house is crazy from shocking wiring (excuse the pun) to glazing nightmares.
We got the place at a knockdown price (considering the 1.5 acres of garden land) and I don't mind fixing things as we go. It's just nothing seems straight forward.

 

[D_Hailsham]

Ok, thanks. However... we don't have a HW cylinder. There isn't any hot storage at all.

So how do you get hot water?

 

[Djnikon]

Hot water seems to come directly off the boiler, but only when the switch is ON. I did say it's a bit odd.
I have looked everywhere possible for hot water storage without any joy.

 

[D_Hailsham]

Hot water seems to come directly off the boiler, but only when the switch is ON.

It would have to be a combi boiler to do that. Can you post a pic of the boiler and the other components?

 

[Djnikon]

I will try get pictures up asap. The pump running the oil feed at the minute is a blue peter number that an engineer had to cobble together as he couldn't get the part.
It's a 24 year old Belgian ACV stamped boiler with more pipes than I can keep track of.

Thanks

 

[D_Hailsham]

It's a 24 year old Belgian ACV?

Earlier you said it was a Belgian AVC. Which is it?

 

[Djnikon]

AVC, clearly a typo. Unless there is also a manufacturer called ACV.
The whole thing is getting more weird. I switched the HW to OFF and left it off for half an hour. Yet when I opened the hot water tap I was getting boiling hot water.
There is definitely no HW storage (checked all rooms, cupboards and even the attic - as it's a bungalow, there is only a finite number of places a tank could be.