Vaillant Arotherm in open loop, with buffer

[ectoplasmosis]

7 hours ago, BobBiggar said:

6 months of circulating with no heat demand seems like a real waste of energy. 

 

 

On the SensoCOMFORT controller, just configure the ‘room influence’ setting to ‘Expanded’. This will switch off all circulation pumps once the internal temp reaches your chosen set point. 
 

We ran like this during the summer, then switched to ‘Disabled’ mode once the heating season started, which enables pure weather compensation with the circulation pumps constantly running. 

[BobBiggar]

On 07/10/2024 at 18:31, sharpener said:

 

See the Energy Integral thread.

thanks for that, very interesting discussion in that thread. It can be challanging properly understanding control systems without detailed specifications, a bit like backwards engineering, but the essence of it seems clear enough.

or at least it is regarding the compressor. I'm still unclear about the circulation pump and even @Dreadnaught in his little summary says "There are more subtleties than I have mentioned above … such as overrun of the sum and the control of the separate building-circulation pump … but that's the essence of it." 

[sharpener]

14 hours ago, BobBiggar said:

the control of the separate building-circulation pump

 

If you have an external pump (connected to MA2) then other scenarios are of course possible depending on the Installer Settings. Configured as an HW secondary circulation pump you can make it work to an arbitrary timetable of its own.

[Peter269]

On 06/10/2024 at 12:29, BobBiggar said:

It would be great to get an update on this and how you have been getting along with the system.

Specifically, did you ever get a satisfactory answer to the question about the Arotherm ASHP internal pump. More specifically, does it keep running 24/7/52 at the minimum 9l/min even when the compressor is not operating? or is it doing something a little more energy efficient and turning off, then occasionally on to sense return temperature?

yours is the only online post I have seen asking about this behaviour and it seems relatively important when operating systems completely open loop as is becoming more common.

Sorry to say that I didn't take it any further. The whole question of controls got too complicated, plus I couldn't find anywhere really for a HW cylinder, so I gave up. Still got my old gas boiler and Evohome system. But glad to see that it has provoked some further resonses!

[BobBiggar]

On 10/10/2024 at 09:29, sharpener said:

 

If you have an external pump (connected to MA2) then other scenarios are of course possible depending on the Installer Settings. Configured as an HW secondary circulation pump you can make it work to an arbitrary timetable of its own.

@sharpener do you mean connecting an additional heating circulation pump to MA2 as opposed to the Valliant recommended MA1 ?

Connected as Valliant recommend in the attached (to MA1), the additional (post buffer) circulation pump follows the same behaviour as the HP-internal circulation pump. So basically 2 circulation pumps now running continuously. It's even a little worse than that since the additional pump is not speed controlled down when the compressor is off. 

MA2 is nominally for the DHW secondary return pump as per the attached so are you suggesting somehow highjacking the controls for DHW secondary return if that is not required and using them to somehow control the additional heating circulation pump? 

Then there's the integral calculation. This surely requires circulation during the compressor OFF time so the measured flow and return temperatures are meaningfull and the HP knows when to turn on again. This seems to be counter to any attempts to externally alter the system flow since this will distort the temps and calculation. 

The only way I have found so far to get the HP-internal circulation pump and any MA1-connected circulation pump to switch off is to set the Max Outside temperature to below the current measured temperature. This can therefore work ok for the warmer days, set to something like 16-17, but all the rest of the time, and overnight even in the summer, the pumps run all the time.

It's entirely possible I have misunderstood something and hope someone can enlighten me. I don't have the fancy monitoring capabilities of some here and cannot observe the VSW-AI all day to see what is happening when. 

I would have thought some sort of sniffing functionality, where (when the compressor is OFF) circulation is also OFF and then intermittently turned ON for a short while to enable valid flow and return temps to be measured, might be possible. The integral calculation would become more complicated but surely possible.

[BobBiggar]

On 07/10/2024 at 19:35, ectoplasmosis said:

 

On the SensoCOMFORT controller, just configure the ‘room influence’ setting to ‘Expanded’. This will switch off all circulation pumps once the internal temp reaches your chosen set point. 
 

We ran like this during the summer, then switched to ‘Disabled’ mode once the heating season started, which enables pure weather compensation with the circulation pumps constantly running. 

thanks @ectoplasmosis, this may become an option if I upgrade our current older VRC700 to the Sensocomfort.

[ectoplasmosis]

1 minute ago, BobBiggar said:

thanks @ectoplasmosis, this may become an option if I upgrade our current older VRC700 to the Sensocomfort.

You have access to the exact same settings on your VRC700 already: “Room Temp Mod”. 

[BobBiggar]

13 minutes ago, ectoplasmosis said:

You have access to the exact same settings on your VRC700 already: “Room Temp Mod”. 

the options given under "Room Temp Mod" are
- None (current setting)
- Temp. mod
- Thermost.

not sure which would correspond to expanded

Also, the VRC700 is in our warm utility room. If the functionality relies on a temp sensor within the VRC700 it might be challenging. Nevertheless i'll certainly give it a try and hopefully can find some setting which work.

[ectoplasmosis]

13 minutes ago, BobBiggar said:

the options given under "Room Temp Mod" are
- None (current setting)
- Temp. mod
- Thermost.

not sure which would correspond to expanded

Also, the VRC700 is in our warm utility room. If the functionality relies on a temp sensor within the VRC700 it might be challenging. Nevertheless i'll certainly give it a try and hopefully can find some setting which work.

“Thermost.” would be equivalent to Expanded I would have thought. 
 

You would need to have the VRC700 in a habitable space however; the temp sensor wouldn’t be doing much stuck in a utility cupboard. 

[BobBiggar]

Just now, ectoplasmosis said:

“Thermost.” would be equivalent to Expanded I would have thought. 
 

You would need to have the VRC700 in a habitable space however; the temp sensor wouldn’t be doing much stuck in a utility cupboard. 

yep, I feared that. 
we have the winter coming up so this only starts to be really annoying when the warmer weather arrives. By then I hope to have the sensocomfort fitted. thanks for the pointer in the right direction

[ectoplasmosis]

2 minutes ago, BobBiggar said:

yep, I feared that. 
we have the winter coming up so this only starts to be really annoying when the warmer weather arrives. By then I hope to have the sensocomfort fitted. thanks for the pointer in the right direction

If you get the wireless version, then you can stick that anywhere you like, even move it around depending on how you use the house. 

[BobBiggar]

9 minutes ago, ectoplasmosis said:

If you get the wireless version, then you can stick that anywhere you like, even move it around depending on how you use the house. 

yes, that's the plan. This should address a big chunk of the problem

I still think Vallient controls should do more to minimise wasteful circulating pump operation. Pumps are a well known energy waster

[sharpener]

2 hours ago, BobBiggar said:

MA2 is nominally for the DHW secondary return pump as per the attached so are you suggesting somehow highjacking the controls for DHW secondary return if that is not required and using them to somehow control the additional heating circulation pump? 

 

Yes but IIRC one of the options is to have it work to its own separate weekly schedule so you can then program it how you like, you do not have to use it in connection with DHW at all. It doesn't seem to be in the sensocomfort simulator on the web so I will check this in the flesh on Thursday.

 

1 hour ago, BobBiggar said:

I hope to have the sensocomfort fitted. th

 

You do not need a whole new sensocomfort to measure living room temp, there are wired or wireless thermostats ?VR92+/-F, you just need to assign that to the heating zone instead of the sensocomfort.

[MechanicalBuilder]

On 14/09/2023 at 14:06, JohnMo said:

Well done you.

 

But you do add complications, you possibly need or have a buffer

In and out quite a lot, good thing about airtight houses, opening a single door doesn't cause a draft.

 

I actually operate two WC regimes, shoulder months use floor as a storage heater, charge up at a higher temp for an out 6 to 7 hours instead of running all day with very little load. Then when it's really cold outside that run time extends across the day. But so the house is the right temp at bedtime, the heating is generally off about 6pm anyway. Still all done single zone. One thermostat/timer in the hall. 

John does this help stop cycling? Sorry to revive an old thread but I’m trying out WC over a fixed flow temp and I can’t stop the heat pump from cycling. It’s a daikin altherma 3 and at 10’c OT 30’c flow temp the house is overheating. I try to turn down the flow temp and the compressor is short cycling every 20 mins or so. I’m really trying to use the ‘low and slow’ method of heating but I’m finding the ashp doesn’t really need to do much. 
 

Have you a rule of thumb for when your heating season begins? I’d like to try and leave the heat pump on all the time but as I’m off grid I can’t afford the excess power consumption of this 

 

 

 

[JohnMo]

10 hours ago, MechanicalBuilder said:

John does this help stop cycling? Sorry to revive an old thread but I’m trying out WC over a fixed flow temp and I can’t stop the heat pump from cycling. It’s a daikin altherma 3 and at 10’c OT 30’c flow temp the house is overheating. I try to turn down the flow temp and the compressor is short cycling every 20 mins or so. I’m really trying to use the ‘low and slow’ method of heating but I’m finding the ashp doesn’t really need to do much. 
 

Have you a rule of thumb for when your heating season begins? I’d like to try and leave the heat pump on all the time but as I’m off grid I can’t afford the excess power consumption of this 

 

 

 

I say embrace the cycling, rapid on off as not good, but cycling on a controlled manner is generally good. There is a lot of miss information out there, that heat should not cycle, they do and will when heat demand is below min output, and even if the condition doesn't suit the refrigeration side they will manage by cycling. Mine rarely gets down to 4kW output on a 6kW ASHP.

 

I am back to WC mode but in essence doing exactly the same as you comment you referred to but just leave to do it's own thing over a longer period.

 

Couple of givens, at temp where you just start to heat the house almost every heat pump is way over sized, they cycle to manage heat delivered.

 

The lower the flow temp the more difficult the heat pump finds it to control and run for extended periods.

 

I fiddled with the compressor start stop hysterisis to get a 10 to 15 min run in mild conditions. That was a figure I found some useful heat was being added to the house, any less than that the house temp slowly dropped. Some will implement a control strategy where at higher OAT they use the controller thermostat combined with WC.

 

I would drop your flow temp a couple of degrees and monitor.

 

For reference this is mine at 9.5 Deg OAT. About 12 to 15 mins on and 30 mins off. Max flow temp was 29, min power output 5kW.

[sharpener]

On 15/10/2024 at 14:29, sharpener said:

IIRC one of the options is to have it work to its own separate weekly schedule so you can then program it how you like, you do not have to use it in connection with DHW at all. It doesn't seem to be in the sensocomfort simulator on the web so I will check this in the flesh on Thursday.

 

Sorry but I can't find this again either in the manual or in my own installation. It may be one of those menu options which appears/disappears depending on what else you have got installed or configured. A bit like Room 13 in the M R James short story of the same name.

[sharpener]

On 18/10/2024 at 16:59, sharpener said:

It may be one of those menu options which appears/disappears depending on what else you have got installed or configured

 

Finally found it while looking for something else @BobBiggar

.

On the SensoComfort go to Control | DHW

Set to Time Controlled

Circulation Weekly Planner then appears in the available options:

 

 

Then you can set up to 3 time periods per day:

 

 

If you set HW to Off or Manual it disappears again. But the Weekly Plan is stored in the memory so is still there if you enable Time Controlled once more.

 

AFAIK you can then configure the MA2/MO2 output as Circulation Pump and use it for any purpose or indeed as an independent timer.

 

If I had worked this all out earlier I would not have needed to re-use my old Honeywell timer for the Thermal Store!

 

HTH

[BobBiggar]

thanks @sharpener I'll look into this as another tool to try and control the circulation pump. I don't have the sensocomfort and cannot see this functionality on my VRC700 but it may be hiding there somewhere.

so far I am looking at 3 functions that might help reduce so much circulation pump activity when no space heating is required

- maximum outside temperature - this is a bit of a blunt instrument but can be useful as an upper threshold. 16 or 17 deg seems like a decent starting point
- @ectoplasmosis suggestion to use the sensocomfort thermostat reading in "expanded" mode. This seems like a good mechanism. I haven't been able to try it properly yet as I still have the VRC700 in the plant room with an unrepresentative temperature reading, but it works, functionally
- the possibility to highjack the DHW scheduler to control MA2 as a heating circulation pump. Again, seems like a blunt instrument, but might be useful