Programmer setting for system boiler

[Geddyboy]

We live in a late 80s house which had a boiler with two tanks in the loft which topped up the radiators and the immersion heater. There was/is a 3 port valve next to the immersion heater which would actuate on demand. The programmer was a mechanical Glowworm which failed pretty much straight away and was replaced with a Siemens Rwb9, at the time I assumed that the system was gravity due to the tanks and toggled pin 5 accordingly.
New system boiler fitted 12 years ago with the CH tank removed from the loft but retained the cylinder and tank. Programmer retained.
Another 10 years later and the programmer display has failed, therefore I have bought the newer version, RWB29Si and began to wonder whether I have a gravity or fully pumped system. It would appear that toggling between the two results in independent on status for HW and CH in fully pumped and restricted to HW on with CH or HW only on gravity. The latter is what is I was told how the system behaved in that you couldn't just have CH on. I'm not sure why I can't as the system appears fully pumped but wonder if it's due the electronics of the system?
In use, I have either the heating and/or CH pumped from the Remeha Avanta 24s boiler via the 3 port valve
I currently have a Honeywell TR6 managing the CH, the programmer is in Manual On mode for CH and HW, the issue I have is the cylinder calling for heat in the early hours.

Ideally, I would like to leave CH in Manual On and HW on timed, I suspect this may be possible in fully pumped but not sure if this is not applicable to my system type and I need to leave it in gravity mode.
All advice greatly welcome.
Edit.. Edited to say you couldn't just have CH on

 

[oldbutnotdead]

If you have a 3 port valve with one output going to rads and the other going to the hot water cylinder you have a fully pumped system. Try it (set programmer to fully pumped, set CH on and HW off, set room stat high enough to fire the boiler up and see if the primary feeds to the cylinder get hot.

 

[Geddyboy]

Thanks for the reply, I will try it tomorrow. I wonder why I have been told that you can't set on CH without HW, I seem to remember setting CH to on would pull the HW on. Could that have been a limitation of the Glowworm timer?

 

[oldbutnotdead]

On true gravity systems there were usually 2 pairs of pipes leaving the boiler- 1 pair going to the cylinder using thermal syphon only, the other pair going to the rads (usually via a pump). So if the boiler water was hotter than the cylinder water then the syphon ran, cylinder got heated usually until cylinder temp reached the boiler max temp (set on the boiler, not the room stat), the boiler would then shut down.
There might have been ancient programmers with no provision for pumped hot water but they'd be 40+ years old....thermal syphon is not a rubbish mechanism but heating the cylinder when you don't want to isn't a very energy-efficient way of proceeding.

 

[Geddyboy]

Thanks again. I will have another look at this, one thing I forgot to mention is that with this new programmer, setting the on, off, auto and once setting is within the menu setting rather than a hard button. I noticed that it has options to set the timer status for CH, HW and HW&CH. I'm not sure what will happen to the latter if I set the CH on and HW to auto. Will have a look tomorrow.

 

[Geddyboy]

Update.
I tried the fully pumped setting, CH set to manual on and HW on auto, ensuring that it was in an off timed status, as too early to enable a demand.
As the mains power had been cut, the 3 port valve was sat in the HW mode. I set a demand temperature for the CH and the port only moved to mid way, circulating both CH and HW.
One thing to note is that the wiring in the programmer backplate is missing wires on 1 and 2, also, there is a looped and joined wire within it...
I seem to remember being told that you can't have CH on without HW.
Therefore, I've reset it back to gravity which prevents my noted issue and left it in manual mode on. I like the ability to for the CH to kick in during colder mornings but the HW kicks in too, which is more than the colder mornings. Hope this makes sense.

 

[vulcancontinental]

Post a photo of the airing cupboard including pump and valve if they're in there

 

[oldbutnotdead]

It's possible the 3 port valve has been wired incorrectly (if you've never had the full functionality of the system). Pics of the wiring centre (isolate before removing cover) might be helpful also

 

[Geddyboy]

Thanks for the replies, I will try and post a photo of the airing cupboard later. For info, the pump is in the boiler, the original was removed from the airing cupboard when the Remeha Avanta was installed.
I've attached the programmer backplate which needed to be swapped as water ingress had rusted the screws, I ensured it was wired the same.

 

[JohnD]

You say it has a 3-port valve?

Some programmers have a switch or wiring option for "gravity or fully pumped."

I wonder if yours has mistakenly been left on "gravity"

BTW if you are replacing the programmer, you may find it helpful to run all the wrong into a "wiring centre"

Makes it easier to see and check how it's done, and you can test across the terminals to see what's on.

 

[Geddyboy]

Hi JohnD,
If I set it to gravity, the system will run correctly but HW needs to be enabled either in auto or manual on. If I turn CH and HW to Off on the programmer, then advance CH to either On or Auto, it will advance HW. I believe this is the feature of the gravity setting.
I was exploring the possibility of setting the programmer to fully pumped, set CH to On and the HW to auto, so it doesn't come on early morning. Whilst it is possible to set this on the programmer, the result is that when in a CH only timed event, the 3 port valve only manages to make it to mid position.
I leave CH in the On position as I have replaced the mechanical room thermostat for a wireless system and the receiver which replaced it requires it to be on 24 hours, particularly because the room the remote thermostat (Honeywell T6r) is can get a bit chilly as quite large.

 

[Mister Banks]

Hi JohnD,
If I set it to gravity, the system will run correctly but HW needs to be enabled either in auto or manual on. If I turn CH and HW to Off on the programmer, then advance CH to either On or Auto, it will advance HW. I believe this is the feature of the gravity setting.
I was exploring the possibility of setting the programmer to fully pumped, set CH to On and the HW to auto, so it doesn't come on early morning. Whilst it is possible to set this on the programmer, the result is that when in a CH only timed event, the 3 port valve only manages to make it to mid position.
I leave CH in the On position as I have replaced the mechanical room thermostat for a wireless system and the receiver which replaced it requires it to be on 24 hours, particularly because the room the remote thermostat (Honeywell T6r) is can get a bit chilly as quite large.

From what I gather reading your posts you have a pumped system that you have incorrectly configured as a gravity system to get around an issue. I think you should configure the system correctly and then investigate where the issue is.

 

[Johnmdc]

You won't be able to have CH on on it's own on a Y plan system without a wire from terminal 1 connected to the grey wire on the 3 port valve!

 

[Geddyboy]

Thanks for the replies. The only reason I have replaced the programmer is because the display has failed, I hadn't removed it since I fitted it a replacement for the faulty mechanical Glowworm, probably in 2000.
At the time, I would have puzzled over the dipswitch for gravity or fully pumped and probably set it to gravity. The system seemed to behave as it did with the mechanical programmer with respect to the automatic advancement of HW on if adjusting CH on. I retained the Glowworm and am confident it doesn't have the dipswitches at all.
We have had a kitchen extension done and a review of photographs looks like the feed from the switch from the fused spur to the boiler beside it may have been replaced.
A few years later the original Baxi boiler was replaced with the more up to date Remeha system boiler.
I don't know of anyone altering the backplate as don't have any pictures of beforehand.
As Johnmdc states, I don't have a wire on terminal 1, therefore I will abandon this and just leave it in manual on for both HW and CH and look into it when I need to replace the boiler and will probably end up with a combi as there's only two of us, we don't use the bath and have an electric shower.
Many thanks to all contributing to this thread.