Vaillant Arotherm Plus 7kW never low and slow

Hardware Heatpump
1

Hello. I’ve been reading a lot about how a heat pump should best be run low and slow. I’ve never had that with my system ever since it was installed.

System Details:
Install date October 2021 (yes i have the dodgy firmware, only just read about it)
7kW, 8 radiators, no buffer, weather compensation, 145L hot water tank.

It was installed under the Scottish government heat pump install scheme (can’t moan too much here was made redundant and got it for free to replace old storage heaters)

Over the lifetime of the system so far I’m getting an average of 1.96 cycles per hour

I don’t use the weekly planner, just have it on setback and have desired temperature set to 21 degrees C. My sensocomfort is mounted in the vestubule where the balance radiator is fitted.

During spring / summer it doesn’t come on as much obviously but winter, especially this one has me concerned. Not that it isn’t heating. It is. My house is not cold.

I have attached a picture of my Circuit 1 display taken at 08:35 this mornng when the temperature was -6 degrees C

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Heat curve is low as temperatures in the house are fine.

Also the flow temperatures.

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This confuses me as which module is determing when flow temerature is reached? Not only that one shows the flow temp way overshot maximum.

I tried having room temp mod. on active only and the compressor just kept running but not low and slow. According to my smart meter it was running at full pelt. (worked by multiplying the max kW rating of the compressor x the pence per unit of my tarriff) so i switched back to expanded.

Any ideas what to do? I’m looking into getting the control board replaced as that seems like a good bet.

Apologise if this has been covered before. Just want to get my system working most efficiently.

1 Like
2

Any other circuits? Are you 100% sure DHW wasn’t running when you saw 47C flow temp? Having you called Vaillant renewables helpline (they are very good)?

The overshoot may be down to a VF1 sensor being connected. Check to see if you have a sensor on flow pipework that is connected to a connector called “VF1”. This was in a lot of Vaillant schematics, but is now not recommended as it can cause overshoots.

To get the best efficiency from the system you should ideally be using “active” room mod instead of “expanded” and adjust your heat curve down if possible. There will be a bit of trial and error needed, but by doing this you may be able to reduce the flow temperature and in turn improve efficiency,

3

‘Expanded’ mode will turn the heat pump and circulation fully off once the indoor temp reaches your set point, then back on again. I would only use Expanded mode in the summer months, when it makes sense for the entire system to be off, except for hot water runs.

‘Active’ mode will aggressively ramp up power to quickly reach your indoor set point; this is why you’re seeing high initial consumption. It does settle after a while.

‘Inactive’ ignores all indoor temp readings, and runs using pure weather compensation based on outdoor temp only; this will be the most likely to run ‘low and slow’ as you’re intending.

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4

Hi thanks for the answers. DHW wasn’t on as that is programmed to come on between 1pm and 2:30PM. I’ve just run a little experiment. Set my room temp. mod to Active, below is the result

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Now not too long after i took these pictures my heatpump did throttledown for a few minute, smart meter was down to a few hundred watts (no other major sources of energy use were on)

I will look at the other temperature sensor.

5

Quick update. Left the house for half and hour, came back and system had throttled back up to full, flow temperatures above target on both flow temperature readings. For the time being gone back to expanded mode as i can’t afford to have the compressor running full tilt when flow temperatures reached

6

There is a sensor connected to VF1 loathe to disconnect it though. Where else does the controller get a flow temperature reading for control? If you could point me to latest Vaillant installation document omitting this would be appreciated

7

Can easily reconnect if you want to. This is a recurring issue, others are also concerned about removing it, but they never go back. Unsure re: doc but you can rry to find latest schematics or easiest thing is to call Vaillant renewables and ask them.

If you remove, hit the reset button after. Same if you replace it. Ignore error on sencomfort, it will go away.

8

OK will try that. I set room temperature modulation to inactive, and compressor was running full pelt, even though way over target temperature. Will keep this thread updated.

Blockquote

9

Removed VF1 reset controller. No fault messages, have room temperature modulation to inactive. Target flow temperature : 36 deg C current Flow temperature 50 deg C. That is also the max target temp. Compressor running at maximum not throttled back at all.

At a loss what to do now.

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10

It’s hard to make an assessment from random snapshots of flow temperature. If your house is warm enough, and not too hot, then it’s probably working fine as it is. What would really help here is to be able to plot the temperatures over time, and collect data over longer periods.

I can do this for you remotely - can send me a private message on this forum and we’ll work out some details. (Click on my picture, then look for blue [Message] button)

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11

If house is getting two hot on inactive/active, heat curve is likely too high. Being on expanded simply hides this issue.

If the ASHP flow temperature is overshooting (above when the heating circuit wants) then you have a seperate issue. It’s almost always one of these three reasons:

  • DHW is running
  • There is another heating circuit asking for higher flow temperature.
  • Flow/BufferTop sensor is connected (either to VF1 on heat pump controller or S1 on VR71)

But if could also be a fault or an issue with a sensor.

Nothing wrong with using expanded is this is what is working best currently, but ideally you want to get to the bottom of the overshoot issue and tune your heat curve to enable you to run it more efficently on active.

12

Hi

DHW isnt on
I only have one heating circuit.
VF1 sensor i disconnected on the heat pump control interface module.

I agree i want to get to the bottom of it, but I’m sure you understand why i won’t want the compressor running at full tilt for hours on end.

I’m beginning to think my system has an issue that can’t be seen just looking at the controller and to be honest no point going back to my original installer.

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13

Call Vaillant Renewables Line, they are very good.

14

Will be calling tomorrow. Appreciate all the advise btw. Just a touch frustrated, as it heats so i know the pump works. Beats storage heaters anyday.

15

Suprised you didn’t get an error on sensoComfort when you disconnected VF1. Make sure it’s fully disconnected and reset (or even power down few). It should show a missing sensor error once reset, and then overshoots stop. Other things is, if you have a VR71 wiring centre, is to see if you have a sensor in S1. It could be using either of these.

I think you can also confirm if this sensor is/isn’t connected in the sensoConfort menus’s.

16

Are there any thermostat radator values?
If so are they all on max?

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17

Definitely disconnected fully. Don’t have a VR71 wiring centre just the sensocomfort and the controller. I definitely did a reset of the controller after i disconnected it.

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18

Spoke to Vaillant renewables tech support. Very helpful and it seems the plot thickens. Going through the settings and explaining my issues he had me bring on the heat pump, check flow rates on the live monitor on thecheat pump interface. All good there. While there we looked at what the interface target flow temperature was and it was very different to what the sensocomfort was targetting. Example, sensocomfort targetting 34 degrees C, heatpump interface module targetting 50 degrees C. However, both sensocomfort and interface module were measuring the same flow temperature. The Vaillant guy was stumped and I’m waiting to hear back as he was going to do a deep dive in the literature to investigate. Seems like the interface module is overriding the sensocomfort, anyway I will update. Also investing in the myVaillant gateway.

19

This is exactly what it does when VF1 is connected, but yours isn’t connected. Really weird! Out of interest, did they mention VF1 at all?

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I told him VF1 wasn’t connected, and i had no error on my sensocomfort, which he was surprised at. Anyway i can but wait. Might no more once i get the gateway installed.

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