Replacing analogue timer help please

Hi, new here although have lurked for several years so I owe you all a thank you for helping me in the past.

I recently had a Heatline Monza 24 boiler fitted which so far has been excellent however I'm feeling the limitations with the mechanical dip-switch timer and would like to replace it with a digital one so that I can have weekend programmes and override. The existing timer is a Grasslin FM1/STUH and I've found a Grasslin Digi20 on ebay for £15. Physically they are exactly the same and have the (edit)same pin-outs(/edit) so should just swap over (in theory) however there are a couple of discrepancies that I don't understand, namely the resistive load and inductive load are higher on the existing timer (16A and 8A respectively vs 10A and 2.5A) and the contact type is "volt-free changeover" vs "volt-free normally open". I've attached images of the data sheets for clarity.

Does anyone know if the Digi20 will work OK?

Thanks in advance.


Edit: Just noticed that the existing timer has 5 actual contacts and the Digi20 has 4 (no pin 5) although the existing timer still only uses 4 connections.

Heatline I love those timers.

yes just change it wiring the same

Thanks ade2k, when you say wire it up the same, do you mean to wire up the new one on pin 4 since there isn't a pin 5?

Your existing boiler appears to use the normally closed contact to call for heat when it opens, which is a little odd.

Are you sure the existing is wired the right way round, i.e. I turns boiler on and O for off?

mfarrow said:

Your existing boiler appears to use the normally closed contact to call for heat when it opens, which is a little odd.

Are you sure the existing is wired the right way round, i.e. I turns boiler on and O for off?

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Yes, 100% sure. Is that bad from a compatibility point of view?

Yes it's very bad from a compatibility viewpoint, it means the electronic timer won't be suitable unless you have it set to on when off and vice versa.

Plenty of others out there I'm sure which have the N/C contact you need, I think we've got a Grasslin.

Look out for changeover or NC (normally closed) in the spec.

mfarrow said:

Yes it's very bad from a compatibility viewpoint, it means the electronic timer won't be suitable unless you have it set to on when off and vice versa.

Plenty of others out there I'm sure which have the N/C contact you need, I think we've got a Grasslin.

Look out for changeover or NC (normally closed) in the spec.

Click to expand...

Thanks for that, this helps a lot. The Grasslin Digi 42 looks like it supports NO on pin 4 and NC on pin 5. Looks promising but more expensive.
http://old.lscontrol.dk/LS_pdf/fm1digi42oi.pdf

Rather than change the timer I would consider a new thermostat. You can get a smart one that will allow timer programming. You just set your current timer to 'on' and do everything via the smart thermostat.

nickjb said:

Rather than change the timer I would consider a new thermostat. You can get a smart one that will allow timer programming. You just set your current timer to 'on' and do everything via the smart thermostat.

Click to expand...

Hadn't thought of that, thanks. Would I need any additional wiring though? I suppose the 42 should be easier if it's a straight replacement.