Setting up Nibe VVm320 air water heat pump

[LouiseSJPP]

I have had a Nibe ASHP installed, F2040 and VVM320 indoor module. The manual for setting it up goes through how to do each step, but gives no overview.
There are three different ways of setting internal temperature; by setting an internal level (or an internal temperature of a thermostat is fitted, by setting a heating, based on an external temperature sensor or by making an offset to the heating curve.
Knowing how critical minimising flow line temperature is to COP, i'm surprised the manual doesn't cover optimisation. Getting the heat curve and offset right over time I can see, but where does the internal temperature setting come in? Does it influence flow line temperature or does it simply control pump speed in the central heating circuit?
If the former, I would need to balance internal temperature setting and heating curve somehow, no idea how. if the latter,I would set the internal temperature (ie CH flow rate) to max, set the heating curve to a minimum level to heat the house,I believe.Can anyone shed any light?

 

[Brambles]

The below is on the assumption that you are not using the Open Therm interface unit:

The easiest way to setup the 2040 is through the SMO 20 ( I think that is the part reference number) control module.

If your aim is to maximise the COP you really need an external temperature sensor mounted on a North facing wall. The sensor should not be able to see the sun.

Thereafter, optimise the unit by adjusting between the offset curves - it will take several attempts over an autumn or spring period. It is best to optimise as you go from the cooler part of the year to the warmer or vice versa.

I think you are misreading the instructions, the external sensor determines the flow conditions from the curve. In fixed temperature mode the curves are not used.
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Apologies, the above assumes that you are not going to use the unit for cooling in the summer. I would not recommend using an external temperature sensor if you are - achieving consistent operation for heat and cool mode with an external sensor is very tedious - you really need a relay to deactivate it ( the external sensor) in the summer.

With respect to optimising COP you will probably find that configuring the unit to operate in Fixed Condensing mode will help.

 

[a62vw]

The below is on the assumption that you are not using the Open Therm interface unit:

The easiest way to setup the 2040 is through the SMO 20 ( I think that is the part reference number) control module.

If your aim is to maximise the COP you really need an external temperature sensor mounted on a North facing wall. The sensor should not be able to see the sun.

Thereafter, optimise the unit by adjusting between the offset curves - it will take several attempts over an autumn or spring period. It is best to optimise as you go from the cooler part of the year to the warmer or vice versa.

I think you are misreading the instructions, the external sensor determines the flow conditions from the curve. In fixed temperature mode the curves are not used.
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Apologies, the above assumes that you are not going to use the unit for cooling in the summer. I would not recommend using an external temperature sensor if you are - achieving consistent operation for heat and cool mode with an external sensor is very tedious - you really need a relay to deactivate it ( the external sensor) in the summer.

With respect to optimising COP you will probably find that configuring the unit to operate in Fixed Condensing mode will help.

What is the Opentherm Interface unit you mentioned? I cannot find any reference to NIBE using Opentherm communications.

Thanks.

 

[LouiseSJPP]

I've lived with the Nibe for a month now. I'm far from happy with it or the installers. The installers strongly discourage owners from fiddling with the control and they leave it set to run 24/24. I don't like a house hot at night, I can't sleep, so I invoke the schedule to try to turn it down overnight. It doesn't respond, not to any noticeable degree, and as the installer doesn't support the use of the schedule, they won't take my complaint about it.

They also invoked the room stat which is fine but it means there's no feedback if the heating curve is too high. With a max flowline temperature of 65° set (at -7°C) it seems to me that this beast has the possibility of running at a very low COP, and I won't find out until I've had a year's energy bills.

 

[Brambles]

Through a Raspberry Pi interface. It is occasionally used when combining an ASHP with a secondary thermal source ( often a log burner with backboiler).

A standalone Nimbe F2040 controlled through an SMO20 is very straightforward to set up - to optimise it (maximise COP) is a little more challenging and in reality will be dependent upon the overall design of your installation and its suitability to operate in Fixed Condensing mode.
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Louise

65 degrees C flow at -7 degrees C is very high, even for a high temperature heat pump. In Oxfordshire, I set 45 degrees C flow at 2 degrees C - on 24/7 - for correctly configured systems that delivers a very warm home.

Before you start to configure a schedule, I would leave the system on 24/7 - but at a much lower level - If your outside temp rarely drops below -3 degrees C 45/2 is a good starting point.

A 65 /-7 setting is for areas where the external temperature dips below -12 degrees C
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Even a 16kw Nimbe F2040 will struggle to get a flow above 55 to 60 degrees C. in any operating environment.

I would question your installer as to why / how he/she believes that the pump can achieve that flow temperature.

 

[LouiseSJPP]

In France we find it is very hard to query a professional: they tend to close ranks rather than engage in discussion. I really need a way of getting some professional advice about the way this system has been set up and the problems it may cause. Is there any way of asking Nibe for advice, direct?

 

[Brambles]

Louise,

You really need to find a good ASHP installer you trust to set up and optimise your system. Nibe (in the UK and I guess France too) operate on a service contract basis. For an ASHP that is around £360 to £400 per annum to service and maintain the system - however, the costs of setting up or bringing a system up to standard before they will offer a service plan are normally in addition to that cost.

Sorry that is probably not what you want to hear.

However, be mindful that if your system is indeed set up to try and deliver 65 degrees C, your electricity bill ( if you were in the UK ) would be in the region of £12 to £17/ day at an overnight ambient of 1 degree C.

 

[LouiseSJPP]

Brambles, thank you for this. Not entirely good news, I agree....

My plan is to log the system for a while: outdoor and indoor temperatures as reported by the Nibe, flow and return temperatures at the buffer tank and pump speed. This is going to show problems with the set-up but won't address any COP issues arising from the high operating temperatures.

Have you any ideas how to get some log data on the COP?

With a month's logging, I can then legitimately start a support enquiry which might lead to a complaint.

The installer has the annual maintenance contract. Changing that at the moment would be messy.

 

[Brambles]

Louise,

With respect to COP, with an ASHP running with an inverter, you really need an ultrasonic energy (heat) measurement meter fitting to the flow as close as possible to the pump. That will give you net output on an hourly / weekly / monthly et al. For gross input measure the electrical power consumption into the unit. Thereafter (over time) you will get reasonably accurate COP calculation. The cost of the equipment to install is around £300.

Measuring flow temperature does not give you anywhere near a credible COP with an inverter driven ASHP. That method is ok with fixed speed pumps on continuous running heating a swimming pool or a large UFH system.

In an earlier post, I think you cited a flow temperature of 65 degrees C - if that is true it needs to be reduced to an absolute max of 58 degrees C - beyond the issue of it delivering a very low COP you are at risk of damaging to coverings et al to your UFH - unless it has been set up with adequate provision to blend the flow down to around 45 degrees C.

I suspect that 65 degrees would also be outside the operating envelope for any Nibe warranty you may have.

 

[LouiseSJPP]

I don't like to ask basic questions of a pro forum, please excuse me: do heat pumps run 24/7/365 even when heat load is low? By 'run' I mean maintain a minimum flow temperature in the primary circuit?

 

[Brambles]

Generally in a domestic situation no, but it depends on how the installation has been designed and configured.

Continuous operation on a variable speed pump would normally be associated with a very large unconstrained underfloor heating system or a swimming pool.

For a decently designed domestic system, near continuous running would only be expected as the ambient temperature moves towards zero and below.

However, with a high temperature ASH pump set at a high flow temperature, the perception will be that the pump is running 24/7.

From what I have read above, I would be surprised if there are any technical issues with the ASH pump - I suspect that the installation has not been commissioned and balanced.

If you were around when the system was commissioned - it would take a day plus to properly commission and then two or three further visits to balance and properly optimise the instalation. Once done, it will run unimpeded for years.

 

[LouiseSJPP]

Many thanks for all the advice. I'll continue to log and then demand a service call to resolve issues. At that point I'll find out of I am dealing with heating engineers or cowboys!