Home Forums General Discussion Heating Assessment Tool Reply To: Heating Assessment Tool

Adam Reid

Thanks Richard and Ian for your feedback,
Some interesting points there.

I totally agree with Richard’s point that 18 ℃ is not a comfortable living room temp by any stretch of the imagination. But I would like to share a couple of personal examples of why I feel the calculations don’t necessarily fit with my practical experience. Bear in mind when reading that I am the sort of nerd who is constantly checking my indoor /outdoor temperature to see how things are tracking so I have a pretty good handle on how my heating is performing.

1) In my own home my 7.5kW log burner can heat the living area to 25 C plus even in the coldest weather and I have to let it burn down after 3-4 hours use as it becomes uncomfortably warm. I consider the burner to be excessive. Yet if I wanted to rent my house out, I would have to install additional heating to meet the 8.6kW required by the tool.

2) At my rental property (where we lived until 18 months ago) we have a 6kW heat pump which we are happy with. It is a small 2-bedroom house with both bedrooms opening off the living room. We always left the bedroom doors open (more than doubling the area) and were able to heat the whole area to 21 ℃ quite comfortably in most conditions. On frosty mornings the heat pump did struggle, and the indoor temp might drop as low as 16-17℃. As these conditions only ever lasted for a couple of hours it was more of an inconvenience than a hardship. According to the tool we require 4.9kW of heating for the living room alone, discounting the bedrooms. I know the H2 output of the existing heat pump is 3.95kW so only around 80% of the requirement. I don’t know what the output at -4℃ is but I think it is safe to assume that it will be less than 3.4kW so will require replacement of the heat pump as it would need more than the maximum 1.5kW of top up heating.

I know the heating standard is something people in our group have advocated for over many years and it is fantastic to see this being implemented. It would be a great shame if an aspect such as incorrect sizing was to provide ready ammunition for those who oppose the legislation. I think if the tool is not right, we risk alienating the good landlords who already have good quality heating installed by forcing them to replace existing heating or install inefficient and unnecessary top up heating

I think Ian’s suggestion that the government publishes a list of the outputs at various temperatures is an excellent idea. I know from experience that heat pump manufacturers are not always eager to share this data. Having a published list would make this much easier for assessors trying to determine if an existing appliance meets the criteria.

One point I think it is important to make is that oversizing of heat pumps is not always a good thing. Oversized heat pumps tend to switch off and on more frequently, run less efficiently and consequently use more electricity than a unit which has been sized correctly. They can behave more like an old fixed speed unit rather than an inverter and the frequent on off cycling tends to wear the units out more quickly My main concerns about this are…

a) Some grossly oversized heat pumps were installed in Christchurch as part of the heating replacement scheme following the earthquakes. I have seen more than one instance where people have found their oversized heat pumps performing poorly, too expensive to run and simply don’t use them. This would be the worst possible outcome for vulnerable tenants.

b) Each heat pump manufacturer has specific guidelines for sizing their heat pumps which they train their installers to use. Will heat pump manufacturers honour the warranty on a worn-out compressor if they deem the unit was not correctly sized in accordance with their specifications?