Setting up Nibe VVm320 air water heat pump

[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!