Thoughts on commissioning a Vaillant Arotherm Plus 12kW

[sharpener]

18 minutes ago, JamesPa said:

I'm pretty sure plumbers connect these up if they choose to, and I'm pretty sure there is no regulation that says it has to be an electrician, its just connecting to an existing circuit via the 'wiring box'.  But then again that's why I still think an electrician may turn up and disagree with the current installation!

 

Both my potential installers had their own electrician and I gathered this to be the usual practice. (The ppl who in the end did the job are actually a firm of electricians who specialised in heating systems and then took on their own plumbers.) He turned up for a recce the previous week which was useful as we could sort out the final details without the other trades on site or any time pressure.

 

22 minutes ago, JamesPa said:

I'm pretty sure plumbers connect these up if they choose to, and I'm pretty sure there is no regulation that says it has to be an electrician, its just connecting to an existing circuit via the 'wiring box'.  But then again that's why I still think an electrician may turn up and disagree with the current installation!

 

Not sure what you mean by "wirng box". The CU they fitted has a B6 mcb for the electronics indoors - the 13A socket for the VR940F internet interface has been labelled as you can only draw 6A from it - and a C32 mcb for the 4sq mm feed to the mandatory AC isolator on the outside of the house, did your man install that already?

 

30 minutes ago, JamesPa said:

There is a switched fused spur and typical heating wiring where all the electronics will be

 

... but reckoned to be good practice to have them both on the Type B RCD that is specified in the MIs. It does not matter if either is energised when the other is not, so an indepent supply is I suppose OK if yr spur box is on a dedicated boiler cct, I would not want it on a general ring main though. Maybe I am not fully understanding your setup.

[JamesPa]

10 hours ago, sharpener said:

Not sure what you mean by "wirng box". The CU they fitted has a B6 mcb for the electronics indoors - the 13A socket for the VR940F internet interface has been labelled as you can only draw 6A from it - and a C32 mcb for the 4sq mm feed to the mandatory AC isolator on the outside of the house, did your man install that already?

By 'wiring box' I mean one of those typical central heating 'wiring centres' that many use to do all the interconnections between thermostat, valves, call for heat for the boiler etc.  Not necessary so far as I can see for the Vaillant, or indeed most ashps, as almost all wires go back to the ashp control, unless you are doing something silly with external controls (which I'm not).

 

Yes the ac isolator is fitted and wired already.  Actually a 32 A one with a 6mm feed (but a 16A MCB) just in case it needs to be upgraded in future.  I put the cable in, sparky fitted the isolator and connected to the cu.

 

10 hours ago, sharpener said:

but reckoned to be good practice to have them both on the Type B RCD that is specified in the MIs

They are.  The current boiler is run off the ring main.  I'd ideally prefer to have it separate as we do get the occasional nuisance trip, but not worth the effort until I replace the cu for some other reason.

Edited November 1 by JamesPa

[sharpener]

5 minutes ago, JamesPa said:

Not necessary so far as I can see for the Vaillant, or indeed most ashps, as almost all wires go back to the ashp control, unless you are doing something silly with external controls (which I'm not).

 

No but may provide a handy route to previous boiler or tank location if that is where the new cyl is going to be, saved me some awkward cable runs.

 

9 minutes ago, JamesPa said:

Yes the ac isolator is fitted and wired already.  Actually a 32 A one with a 6mm feed (but a 16A MCB) just in case it needs to be upgraded in future.  I put the cable in, sparky fitted the isolator and connected to the cu.

 

Sounds like you are good to go then apart from wiring the e-bus and SensoComfort itself. Best of luck!

[sharpener]

Back on the original topic some further wrinkles that have arisen.

 

1. I fitted an indicator panel with separate lights for the HW valve and each of the 3 heating circuits so I can see what the machine is doing at a glance. (Very helpful for checking all the different time schedules are set up correctly.)

 

This showed that when in Away mode the heating circuits are energised for less than a minute at 1025, 1030 and 1035 respectively every day (but AFAICS not the DHW). The installers have not responded to my question but presumably it is some kind of anti-blockage routine.

 

2. System pressure has been varying wildly between 0.6 and 1.5 bar depending on what it was doing. The label on the 25 litre expansion vessel says it is pre-charged to 1.5 bar. I don't think this was adjusted by the installers so with a nominal water pressure of 1.0 bar it will not be doing anything at all.

 

I have changed these round so with the system depressurised the expansion vessel is at 1.0 bar, and then topped the system pressure up to 1.2 when in standby. Now it works properly over the comparatively small range of 1.2 - 1.5 bar.

 

 

Edited December 5 by sharpener

[JamesPa]

4 hours ago, sharpener said:

This showed that when in Away mode the heating circuits are energised for less than a minute at 1025, 1030 and 1035 respectively every day (but AFAICS not the DHW). The installers have not responded to my question but presumably it is some kind of anti-blockage routine.

My boiler, now siting on the driveway waiting to be removed, had a pump anti-seize function doing exactly this.  I imagine heat pumps do also.

 

4 hours ago, sharpener said:

I have changed these round so with the system depressurised the expansion vessel is at 1.0 bar, and then topped the system pressure up to 1.2 when in standby. Now it works properly over the comparatively small range of 1.2 - 1.5 bar.

 

Mine seems to be varying by about 0.2bar around 1.7bar

 

One thing I have noticed is very long cycle times in the mild weather - too long in fact - the heat pump can be off for more than an hour and the house cools by 0.5C in that time which is noticeable.  I thought this was governed by the 'energy integral', but it seems that the room temperature mode (inactive/active/expanded) may be dominating the cycling as the compressor doesn't switch on even when the energy integral is as low as -150 degree minutes (I have a suspicion that it comes back on at -180 degree minutes but cant prove it).

Edited December 5 by JamesPa

[sharpener]

2 hours ago, JamesPa said:

I thought this was governed by the 'energy integral', but it seems that the room temperature mode (inactive/active/expanded) may be dominating the cycling as the compressor doesn't switch on even when the energy integral is as low as -150 degree minutes (I have a suspicion that it comes back on at -180 degree minutes but cant prove it).

 

If you have it on expanded this is more likely to happen.

 

Energy integral is -90 by default, is in the Appliance Interface settings under "Compr. heat. start from", try changing it to -60. Much discussion on the Arotherm Plus FB page.

[sharpener]

44 minutes ago, sharpener said:

Energy integral is -90 by default, is in the Appliance Interface settings under "Compr. heat. start from", try changing it to -60.

 

My mistake, according to MIs default is  -60 and correct name is Compr.start heat. from.

 

There is a well documented s/w bug which affects yr ability to change this but if yr machine was mfd this year it should be OK.

 

Also you could try reducing Compressor hyster. Heat. from its default value of 7.

 

 

Edited December 5 by sharpener

[JamesPa]

46 minutes ago, sharpener said:

f you have it on expanded this is more likely to happen.

Reading the expanded mode description I think the controller may ignore energy integral if this mode is active, relying on oat to restart.  My installer has also enabled adaptive WC (which requires expanded mode).  I guess his thinking is that this will eventually sort out the WC curve, which is probably true!

[Dan F]

Expanded doesn't ignore energy integral.   Adapative WC is typically not used or recommended.  Energy integral is -60 by default, not -90.  Don't think pressure should be varying like that, mine doesn't.

[Dan F]

7 hours ago, JamesPa said:

One thing I have noticed is very long cycle times in the mild weather - too long in fact - the heat pump can be off for more than an hour and the house cools by 0.5C in that time which is noticeable.  I thought this was governed by the 'energy integral', but it seems that the room temperature mode (inactive/active/expanded) may be dominating the cycling as the compressor doesn't switch on even when the energy integral is as low as -150 degree minutes (I have a suspicion that it comes back on at -180 degree minutes but cant prove it).

 

Start with inactive and try to find your correct heat curve, you can then switch to active which is more forgiving and adjusts better to solar gain etc.   Expanded has its uses, but it's typically not a good idea.  Adaptive WC is not really recommened either.

 

Don't touch integral or hysterisis configuration until you've done the above, only then are you really in a position to understand if either of these need tweaking.

Edited December 6 by Dan F

[JamesPa]

12 hours ago, Dan F said:

 

Start with inactive and try to find your correct heat curve, you can then switch to active which is more forgiving and adjusts better to solar gain etc.   Expanded has its uses, but it's typically not a good idea.  Adaptive WC is not really recommened either.

 

Don't touch integral or hysterisis configuration until you've done the above, only then are you really in a position to understand if either of these need tweaking.

Thanks.  I was coming to that conclusion myself (and its the general approach I have been preaching for some time - get the WC curve right before you anything more sophisticated). 

 

My installer is back today to fit two rads that weren't available when he did the main job last week.  I don't want to touch too much while he is still around, but once he is gone I consider it to be open season!   That said, I can see why he has set it up the way he has.  Most wont bother with or understand the tweaking of WC curves and the way he has set it up will get somewhere close eventually I think, without human intervention.