Combi Boiler

Bendy_House

This shows a wireless receiver, but I think it's the same idea as your module? You can see the by-pass link that's removed - pretty sure that would need reinstating in your case (or, if you knew what you were doing, the wires going to the Logic prog could be linked together...)

https://www.youtube.com/watch?v=cUmoT4gwxXU

kev2009

From what I can tell, the programmer (ideal electronic 7 day programmer think part is 204545, it looks identical) has 2 cables with connectors on and plug in on the left and right.

I've not seen any by-pass link.  Didn't realise I needed one tbh, I thought could just remove the programmer, clearly not.

I'd have to look into that a bit more and see what's needed, maybe it's a bypass link for each side.  

Thanks for info, at this rate it will be easier just buy new programmer.

Kev

Bendy_House

I've seen a pic, and I see it does have two cables.

One, I suspect, goes to the top-RH corner where it receives power in order to operate it. The other cable probably goes to the top-LH corner and this will be the 'switching' cable. Ie, when the timer says 'on', the two wires in that top-LH corner cable will be switched together inside the Logic so the circuit is completed and the wall stat (now a Nest receiver) will now be in the position of being able to switch the boiler on and off. The Logic and the Nest are in 'series' - they BOTH have to be 'on' in order for the boiler signal to get through. That was the same when it had the old wall-mounted 'stat. First the Logic timer had to be 'on', and this continued the signal to the wall stat, and when that also came 'on', the signal carried on to the boiler.

What happens if you turn that Logic control knob to 'CONT ON' position? That should be enough - that should allow the Nest to take over, regardless of the timings on the Logic.

kev2009

Yes, I believe the cables go to top left and right.

Previously I used cont on so it allowed nest to control it but as I've basically set Nest to be the same times as the programmer, hard to say if nest is in full control or if programmer was playing a part too.  However, with cont on, that's when boiler would come on outside of the hours i specified, which seems to be a common issue in trying to make it stick to the schedule and not come on outside of it.  It may simply be the temp settings i.e. if it drops below a given temp, it turns on which obviously the programmer ignored temps and just came on at set times, regardless of what the temp was.  I believe the boiler/programmer *may* have a safety feature built in that if temp gets below x it would come on to prevent pipes freezing etc but I'm not 100% sure without checking the manual.

Therefore by using it in Run mode, programmer would turn on/off heating and nest effectively set the temp to be at which was ideal setup for me, it worked flawless for a few months.

Kev

Bendy_House

kev2009 said:

Yes, I believe the cables go to top left and right.

Previously I used cont on so it allowed nest to control it but as I've basically set Nest to be the same times as the programmer, hard to say if nest is in full control or if programmer was playing a part too.  However, with cont on, that's when boiler would come on outside of the hours i specified, which seems to be a common issue in trying to make it stick to the schedule and not come on outside of it.  It may simply be the temp settings i.e. if it drops below a given temp, it turns on which obviously the programmer ignored temps and just came on at set times, regardless of what the temp was.  I believe the boiler/programmer *may* have a safety feature built in that if temp gets below x it would come on to prevent pipes freezing etc but I'm not 100% sure without checking the manual.

Therefore by using it in Run mode, programmer would turn on/off heating and nest effectively set the temp to be at which was ideal setup for me, it worked flawless for a few months.

Kev

Completely understand your reasoning. It shouldn't be needed, tho', and isn't a good setup.

Even if the boiler comes on during the night when it 'shouldn't', it should only be for very short bursts as your min temp should hardly ever be reached. Ditto for the frost setting. If a house has been heated normally during the day and evening, the temp shouldn't really fall below 14-odd degrees overnight even with no heating on.

I have my Prog Stat set to that figure - I can't recall it ever coming on during the night. Certainly not the past winter.

You know you have a dodgy Logic. You may also have a dodgy Nest. At the moment, you won't be able to find out which, if any, is causing the problems, or whether it's, er, user-error!

Since you know the Logic just is not required, and just should be electrically removed from the equation, then that is the correct thing to do. Then you can take your Nest to task, knowing that any remaining issues will now be down to it.

kev2009

Thanks.

Schedule should be sufficient, its on from 6:30 -10, then back on at 11 till 2pm, then back on at 4pm and goes off just after 11pm at night.

However, I have still seen nest where it has said it has turned heating on at 1 or 2am right up till 6am.... madness.

The heating on temp is always 21 and lower so it goes off.

Maybe I should set the eco and safety temps to the lowest they can go, think its around 4 degrees? and then see? However, I'm a bit dubious of setting to these temps but maybe that's all i can do? My eco temp from memory is similar to your 14 and it has come on this past winter of a night but i can't get the history and Nest only seems to keep last week or so and obviously I've had it set to Off so it not been trying to heat etc.

Kev

Bendy_House

My current Prog Stat is an old Heatmiser, so it's just set to give the temps I want at the times I want it - essentially 20oC at 6.30am, and down to 18oC at 8am for the day until 5pm. Back up to 20oC at 5pm, and then down to 14oC at 10pm for overnight.

I have recently installed a Hive for someone, and have to admit I was confused by the programming as it wasn't as intuitive as expected - it seemed to not let me do what it 'should'. Anyhoo, I eventually got it to do what I wanted, which is a background 10oC at all times except for a few set hours during the day (it's for a village hall).

I am not familiar with programming the Nest, but it must surely allow the same setup? If you write out what it is you want for each day, and then go through the process of programming it for that, then you can monitor whether it's actually carrying it out. If it isn't, go on a forum for advice; ask them, "This is what I want - xyz - please tell me step by step how to do it?!" (which is what I had to do at one point... :-(

If you do this, but the Nest doesn't, then you go back and describe what's happening.

(If you mention that you also have a Logic timer also set to go on and off, I suspect you won't get any replies...)

I don't understand, "The heating on temp is always 21 and lower so it goes off." What's 'lower'?

If you write out exactly what you want, we can take it from there, and so can 'experts' on the Nest forum.

Eg:

06:30 to 10:00 - 21oC

10:00 to 11:00 - 16oC

11:00 to 14:00 - 21oC

14:00 to 16:00 - 16oC

16:00 to 23:00 - 21oC

23:00 to 06.30 - 14oC

Each set of timings must have an allocated temp.

(Unless the Nest is different).

Good chance this is easier to program via the App - that's what I've read about most 'smart' systems.

kev2009

Sorry lower as in I set temp lower so heat goes off, here is schedule I have, might be easier to understand

06:30 -10:00 = 21C (heating turns on unless temp in higher than 21C)
10:00 - 11:-- = 15C (so heating goes off)
11:00 - 14:00 = 21C (heating turns on  unless temp in higher than 21C)
14:00 - 16:00 = 15C (so heating goes off)
16:00 - 23:00 = 21C (heating turns on unless temp in higher than 21C)
from 23:00 = 15C (so heating goes off)

However, with this it still come on in night or at times outside the heat on windows programmer using continuous on boiler as i played with it before in continuous and decided it was costing me more than using old method of programmer.

I setup the programming on nest via the nest webpage, found it easier than the app and it appears in app virtually instant so i know schedule is right etc, it just Nest decides to do what additional stuff to what I've asked i.e. turning heat on during night or turning heat on earlier than I asked it to.  Will take another look when i can, still 50/50 between buy new programmer and prob have no issues or buy blanking plate & the loop connector and use Nest only and put up with it coming on at times I don't want and additional cost.

Thanks for all your help so far btw

Kev

kev2009

actually its 16:00 - 22:00 not 23:00

Sorry misread it on nest page

Kev

Bendy_House

Cheers, Kev.

It looks as tho' you are doing things correctly. That leaves either a faulty device (I suspect it isn't, as it would be a weird fault) or else the settings aren't as you expected.

For instance, when setting up the Hive from scratch, the first thing is asks is something like "Do you want the ON times to be when the heating comes on, or when the required temp is achieved?" Ie, for your 06:30 / 21oC, the first option would be that the boiler comes on at 06.30, and the latter would be that it would already be 21oC by 06:30, so it would clearly have come on much sooner.

I'm sure you know all this, but could the setting be wrong on the Nest?

Also, to ensure it stays effectively off during the night, try it at a lower 12oC after 22:00.

After trying this for a couple of days, note down exactly what is happening - you look back on your App for this? Write that down too, and that's what to ask about on the forum, or direct with Nest.

And post it here too, please

I'm 99.9% certain that your Nest can be 'normal', and not do this extra stuff.