Replacing a mechanical boiler timer with digital - Help!!!!

[wealthjd]

I thought the faulty mechanical timer on my boiler would have been an easy thing to replace with a digital one as the device does exactly the same thing, however when putting getting the new digital device there are a few problems. Can anybody help?!

This is the old timer. As you can see there are 5 prongs.

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• wealthjd
• 31 Jan 2015
• 1

This is the new digital timer. What i don't understand is that there are only 4 prongs?

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• wealthjd
• 31 Jan 2015
• 1

Am I missing something obvious here?

Thanks!

 

[Dan Robinson]

Ignore the 5th Prong that isn't being used on your old one.

You only have 4 wires anyway.

Simples.

 

[wealthjd]

I should have also said that I have tried to plug it in by ignoring the missing prong but it did not work and the boiler stayed on constantly.

Thanks

 

[denso13]

Get one with 5 connections such as the FMD120. Can you get a better photo of the back of the old one?

 

[wealthjd]

Is that any better?

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• wealthjd
• 31 Jan 2015
• 1

 

[Dan Robinson]

Clue is in the voltage.

 

[wealthjd]

Care to elaborate?
How this affect the prongs?
How can this be corrected?

 

[Dan Robinson]

You need to buy the right clock.


Old one is Dc, new one is mains AC

 

[wealthjd]

Damn. So is there a way of converting this simply?

Also from looking about all the timers seem to be AC and not DC. Anywhere where they sell them?

 

[Dan Robinson]

How about telling us what boiler it is?

 

[wealthjd]

It's an ariston boiler but there isn't any model number on it. However it looks like this...
http://www.upperplumbers.co.uk/imag...on_MicroGenus_II_28_MFFI_mechanical_clock.jpg

 

[stardanny]

Replacement timer still available.

http://www.heatingcontrolsonline.co...-027601261-999599-mechanical-timer-p-968.html

Daniel.

 

[mfarrow]

Also the old timer had a Normally Closed contact, which was used by the boiler. The new one has no Normally Closed contact, and wiring the boiler to the Normally Open contact naturally caused the boiler to be on constantly.

So you need a timer operating from 3VDC and having a Normally Closed contact available to boot.

 

[DP]

Also the old timer had a Normally Closed contact, which was used by the boiler. The new one has no Normally Closed contact, and wiring the boiler to the Normally Open contact naturally caused the boiler to be on constantly.

So you need a timer operating from 3VDC and having a Normally Closed contact available to boot.

Do not see how. Page 22, figure 2.24 shows otherwise. Short circuit fires the boiler for CH. Only explanation to what the label on programmer shows is that convention used is incorrect. All contacts in electrical diagrams normally shown in 'unpowered' position. Another clue is that the thermostat shown in the diagram also shown as operated i.e. calling for heat. _/_ a contact shown thus is less confusing

OP, plug the 'new' timer in again and then short the two contacts with a screw driver (DO NOT SHORT THE M TERMINALS). See if the boiler starts up.

 

[stardanny]

Do not see how. Page 22, figure 2.24 shows otherwise. Short circuit fires the boiler for CH. Only explanation to what the label on programmer shows is that convention used is incorrect. All contacts in electrical diagrams normally shown in 'unpowered' position. Another clue is that the thermostat shown in the diagram also shown as operated i.e. calling for heat. _/_ a contact shown thus is less confusing

OP, plug the 'new' timer in again and then short the two contacts with a screw driver (DO NOT SHORT THE M TERMINALS). See if the boiler starts up.

Yes, but still useless.
The new timer isn't suitable for that boiler, the new timer is 240v ac version, that why it didn't work.
The old timer is 3v dc version. Use this like in my earlier post, the same type suitable for that boiler.
http://www.heatingcontrolsonline.co...-027601261-999599-mechanical-timer-p-968.html

Daniel.