Help needed changing central heating timer

[WiganDobby]

I curently have a Flash Immermat timer as shown in the URL below:

http://download.hager.com/controls.hager.com/files_download/Notices PDF/9419_527_01_GB.pdf

I have previously replaced this myself, when it was faulty, with the exact same model so that it was easy to do myself. However I have been searching and cannot find this model in the UK anymore so need to change. I was therefore thinking of changing to a digital one which has a few more features, instead of just going for another basic mechanical timer. The one below seems suitable (as far as I can see):

http://www.horstmann.co.uk/download...Heating/CentaurPlus_C11-C17_installer_web.pdf

This too seems fairly basic and I believe only 3 wires are needed, would this be suitable? All of my research suggests that it will be. However more importantly it is the wiring which concerns me. I am competent at DIY but find it difficult to make head nor tale of electrical diagrams. Any ideas of what goes from the old timer to the new one?

 

[stem]

If the "Immermat" timeswitch is controlling an immersion heater, then don't do it unless you want to set your home on fire. The switching capacity of the existing timer is rated at 16A. The switching capacity of the Horstmann is 3A

An immersion draws about 13A, over 4 times the capacity of the Horstmann.

To control an immersion heater, you need a timeswitch for an immersion.

If it is being used to control your central heating (ie gas or oil boiler) then you need to tell us what wires are connected to the Immermat terminals 1,2,3 & 4 then someone will advise you.

I know your header refers to "Central Heating Timer" but I wasn't sure if this is what you were using it for, or what the Horstmann is described as

 

[WiganDobby]

If the "Immermat" timeswitch is controlling an immersion heater, then don't do it unless you want to set your home on fire. The switching capacity of the existing timer is rated at 16A. The switching capacity of the Horstmann is 3A

An immersion draws about 13A, over 4 times the capacity of the Horstmann.

To control an immersion heater, you need a timeswitch for an immersion.

If it is being used to control your central heating (ie gas or oil boiler) then you need to tell us what wires are connected to the Immermat terminals 1,2,3 & 4 then someone will advise you.

Thanks for your reply. The Immermat is used to control oil fired central heating. Would this timer then be suitable for this or should I look at an alternative?

I will check on the wires when I get home.

 

[Taylortwocities]

The Horstman programmer that you have identified wil be fine if it is just controlling the boiler and associated items (valves, pump, etc.)

You only have a single channel timer so its real simple.
Take a photo of the old wiring before you take it all apart!

Make sure the fuse in the supply to the heating system is no more than 3amps.

Good luck, the weather is getting colder!!

 

[WiganDobby]

The Horstman programmer that you have identified wil be fine if it is just controlling the boiler and associated items (valves, pump, etc.)

You only have a single channel timer so its real simple.
Take a photo of the old wiring before you take it all apart!

Make sure the fuse in the supply to the heating system is no more than 3amps.

Good luck, the weather is getting colder!!

Thanks for that, yes the weather certainly is getting colder.

By the fuse in the supply to the heating system, and this may be sound like a really daft question but I am just making sure, I presume you mean the fuse in the fuse box? If it is more do I just change it to a 3amp?

When I get home I will check the wires that are going to the old timer and take a photo.

 

[ericmark]

I would guess you also have a temperature control?

Does the boiler also do hot water?

If not then something like this may be better it controls both time and temp all in one unit.

The advantage is instead of turning off and on it changes the temperature so you don't need a froststat.

 

[Taylortwocities]

, I presume you mean the fuse in the fuse box? If it is more do I just change it to a 3amp?

No.

There will be a mains feed to the central heating system/boiler.
This mains feed should have a single fused switch that isolates the electricity to the heating system/boiler. It may just be a plug that goes into a normal socket.
The fuse for this (whatever it is) should be 3 amp.

The boiler/heating system may well be fed from a normal socket circuit.
Do not change the fuse in the fusebox!

 

[WiganDobby]

As requested the following wires are connected to the existing Flash Immermat terminals:

1 - Brown
2 - Blue
3 - Black
4 - Red

Therefore if I was to use the Horstmann C17 what wires would go to where? Also if the C17 only requires 3 wires, as it says it does, what do I do with the 4th?

Thanks in advance

 

[ericmark]

1 - Brown = L
2 - Blue = N also connect 3
3 - Black = N
4 - Red = 4

Link required L to 2.

If no domestic hot water is required as I said before I would not use this type of timer. However much depends on if there are radiator thermostatic valves fitted etc.

 

[WiganDobby]

1 - Brown = L
2 - Blue = N also connect 3
3 - Black = N
4 - Red = 4

Link required L to 2.

If no domestic hot water is required as I said before I would not use this type of timer. However much depends on if there are radiator thermostatic valves fitted etc.

Thanks for that. The existing timer does the central heating and hot water. There are also no TRV's. Does this change things?

 

[ericmark]

With no TVR's the combined thermostat and timer I linked to would do a better job.

The timers you have do not discriminate between central heating and domestic hot water. The older boilers normally follow one of the plans. It's been a while since I have worked on older systems but I think the W plan had thermosyphon for domestic hot water and so there was no way to either control the temperature or independently control it.

However most the other systems have the domestic hot water and central heating independently controlled. However with a well insulated hot water tank likely there is little need to control the domestic hot water.

With the combined thermostat and timer it will change the temperature rather than just switch on and off so no need for a frost stat and you can set it so if it gets really cold in the night it will still fire up. Plus daytime and evenings can have a different temperature set.

One disadvantage is battery needs changing once a year. Does last longer but I change every year.

However what you have got will work so if you can't take it back then if it were me I would fit it.

 

[WiganDobby]

With no TVR's the combined thermostat and timer I linked to would do a better job.

The timers you have do not discriminate between central heating and domestic hot water. The older boilers normally follow one of the plans. It's been a while since I have worked on older systems but I think the W plan had thermosyphon for domestic hot water and so there was no way to either control the temperature or independently control it.

However most the other systems have the domestic hot water and central heating independently controlled. However with a well insulated hot water tank likely there is little need to control the domestic hot water.

With the combined thermostat and timer it will change the temperature rather than just switch on and off so no need for a frost stat and you can set it so if it gets really cold in the night it will still fire up. Plus daytime and evenings can have a different temperature set.

One disadvantage is battery needs changing once a year. Does last longer but I change every year.

However what you have got will work so if you can't take it back then if it were me I would fit it.

Ericmark thanks for all your help. I have not bought anything yet so am open to suggestions, I was only thinking about the Horstmann C17 as that is what a few retailers mentioned as a replacement when I was looking for the old timer. No doubt that is because it was what they stocked!

A combined thermostat and timer may well do a better job and be a better match. The thing that puts me off though is it being dependent on a battery. Do you know of anything similar that is mains powered? Sorry for all the questions!

 

[WiganDobby]

After taking Ericmark's advice on board would this be better, as it is connected to the mains which is what I would want, and would it be suitable to replace the Flash Immermat?

http://www.screwfix.com/p/danfoss-tp4000-24hr-programmable-room-thermostat/90659?_requestid=2373793

 

[ericmark]

Yes it will do the job. However it still uses batteries. Wiring diagram http://heating.danfoss.com/PCMPDF/050v03.pdf
It is the same as one you selected except also does temperature.

My daughter, son and myself all use the type I listed so I know they work OK. There is only one fault in that the battery warning light does not always work. It should last a few years but I always forget when changing batteries every two years so I change every year.

The one you have selected has more events than the one I use so it will be better. You can just connect the wires where old clock is together with chock block and fit a blank or a switched fuse connection unit on the back box and then replace the existing thermostat with new one. There is also a radio controlled model for the one you have selected.

 

[WiganDobby]

Yes it will do the job. However it still uses batteries. Wiring diagram http://heating.danfoss.com/PCMPDF/050v03.pdf
It is the same as one you selected except also does temperature.

My daughter, son and myself all use the type I listed so I know they work OK. There is only one fault in that the battery warning light does not always work. It should last a few years but I always forget when changing batteries every two years so I change every year.

The one you have selected has more events than the one I use so it will be better. You can just connect the wires where old clock is together with chock block and fit a blank or a switched fuse connection unit on the back box and then replace the existing thermostat with new one. There is also a radio controlled model for the one you have selected.

Silly me, I must have misread as I thought it was mains powered

What about this then which I think is main powered and seems similar to the one you suggested?

http://www.horstmann.co.uk/downloads/ElectronicDocuments/ThermoStats/AS1Installationguide.pdf