Is this normal behaviour - cycling ??

[mk1_man]

Hi, I have just started off in the exciting world of heat pumps.  I have recently completed my diy install of a Vaillant 7kW unit and 250l Vaillant cylinder.  Its a very simple setup with single zone covering underfloor on ground and first floors although there is only one active circuit upstairs as we don;t like bedrooms warm. I am monitoring on OEM which gives fantastic feedback so thoroughly recommend anyone doing this on their setup be it not a cheap option.  Heating has been on for a few days now  and I am getting strange on off periods throughout the day, is this normal?  Curve was set to 0.4 but I have dropped to 0.35 as house was almost too warm.  Pump has been running at around 3.3kW output and around 590W input, flow temp steady around 30degrees.

 

[crispy_wafer]

15 minutes ago, mk1_man said:

I am monitoring on OEM

Whats this please vaillant built tools or 3rd party like heatpumpmonitor.org?

[sharpener]

I would say that looks normal for mild weather. The HP accumulates error degree-minutes i.e. how much the integral of temp differs from the setpoint and switches the HP on when the total reaches a trigger value (by default AIUI -100 or maybe -60) and switches it off when it reaches 0 again. You can change the trigger value somewhere deep inside the installer settings but default is OK for many ppl. This accounts for the cycling. Up to 3 cycles/hr is reckoned OK and you have a lot less than that.

 

Also depends on control strategy. If you have the SensoComfort controller it has 3 possible modes for "room temp mod": off, active and extended. Active uses the sensor in the controller to tweak the flow temp according to actual room temp so if yr controller is sensibly sited in living room you can probably use that. Extended turns the whole system off when the sensor is up to temp which is prob OK for you but no good for multizone systems.

 

Arotherm FB page is good for this stuff also. Worth following for useful hints on setup though a bit repetitive.

 

@JohnMo will no doubt be along soon to add to this, IIRC he has commented on the energy integral approach in the past so I imagine Ecodan use it too.

 

 

16 minutes ago, crispy_wafer said:

Whats this please vaillant built tools or 3rd party like heatpumpmonitor.org?

 

Open Energy Monitor, has separate power, flow and temp sensors.

 

 

Edited September 13 by sharpener

[crispy_wafer]

5 minutes ago, sharpener said:

 

Open Energy Monitor, has separate power, flow and temp sensors.

Yes, thanks, that's on my radar for my install too.

[PhilT]

It's that power spiking which is interesting. The Ecodan never does that in auto mode, just a smooth ramp up, however it does spike considerably in WC mode. Great COP though

Edited September 13 by PhilT

[mk1_man]

Thanks all for the feedback, its a fascinating journey, wife thinks I have gone mad though.  All the Vaillants appear to have this weird initial spike before it settles down.  The open energy monitor is great, my advice would be have a look on Ebay for the heat meter element itself as there are some great buys.  I managed to get a brand new Superstatic 440 with 11/4" connections so no impact on flow rate for £100 instead of £650, chuffed to bits.

 

Edited September 13 by mk1_man

[PhilT]

Which heating mode are you using?

Normal, Eco, Balance
 Sensocomfort
 Inactive, Active, Expanded
 

[mk1_man]

DHW : Eco mode,  space heating is set to Inactive

[ProDave]

26 minutes ago, mk1_man said:

DHW : Eco mode,  space heating is set to Inactive

So that is ONLY heating DHW in your original plot, not space heating?

 

If that is so you must be using a lot of hot water or it is losing heat from the tank and regularly topping up?

[mk1_man]

No, those were all space heating. I have a sensor on the diverter valve that tells oem when I am doing dhw so it then plots it with a blue background and keeps a separate tally of COP etc which is cool.  That way dhw which is always lower cop doesn't distill the space heating cop.  I have my water set for 50 degrees. I have an additional sensor in oem that tracks my cylinder temp - the black line :

 

 

 

Overall it looks like this. Its nice to see the two separate cop figures also :

 

Edited September 13 by mk1_man

[PhilT]

1 hour ago, ProDave said:

So that is ONLY heating DHW in your original plot, not space heating?

 

If that is so you must be using a lot of hot water or it is losing heat from the tank and regularly topping up?

That previous post should have said Sensocomfort mode is set to "Incative", which is pure WC mode heating with no roomstat temp influence. "Active" means flow temp is influenced by room temp of any assigned roomstat. "Expanded" is the full monty, outside and room temp influenced flow temp using that wizzo Vaillant Sensocomfort roomstat controller, which suggests that it might work like the Ecodan "Auto" mode, which is highly desirable, as it does many important things over and above pure WC mode; suppresses start up power spikes, flattens out then, if necessary, reduces flow temp as room temp is approached, compensates for solar gain and defrost, and never allows compressor cycling, and works the heat pump at it's optimum efficiency level

Edited September 13 by PhilT

[mk1_man]

Apologies, yes my Sensocomfort is set to Inactive.  I will do some reading up on the Expanded mode and see if it brings any benefit.   Thanks

[IGP]

Have you checked your firmware?

 

https://energy-stats.uk/vaillant-arotherm-firmware-351-06-07-problems-energy-integral/amp/

[mk1_man]

Thanks, that's a really interesting article.  I have just checked and I look as though I have the latest firmware 351.09.02   at least the article answers my question about how do you update the firmware, I just assumed you could do it as long as it was hooked up to the Internet !

 

As for the on off behavior I suspect I was running it a little warmer than the house needed, yesterday it did get a bit warm even though it was showing 10 degrees outside, this morning I changed it from 0.40 to 0.35 curve and the system has been off all day after the initial 04:00 - 08:00 period. It has only just fired up again at 18:00

 

Crikes, we never paid this amount of attention to the old gas boilers !

[Richard S]

On 13/09/2024 at 14:52, mk1_man said:

Apologies, yes my Sensocomfort is set to Inactive.  I will do some reading up on the Expanded mode and see if it brings any benefit.   Thanks

Hi, did you ever play about with the Active and Expanded modes. I have a very similar performance graph to yours in a highly insulated new build with a 5kw Vailllant pump. I am running in inactive mode and would be interested in your thoughts on changing to Active. I have turned the heat curve down to 0.1 and the house is still nice and warm.