Does anyone have sizing guidelines to provide a builder? Is it something we could develop? 

There are many factors to consider that can have differing priorities:

- climate

- backup heat electricity or gas and its price

- cut-off (switchover) temperature

- cooling load

- GHG emission reductions v.s. energy savings v.s. operating cost

- duct sizing / cost

- capital cost

- optimizing GJ rating in HOT2000

Some ideas - 

1.25 x cooling load was one guideline in the past but that is very old

Just size it to meet the cooling load and let the backup provide the coldest weather heating. Could make sense in Ottawa

Lately I have been using -12 C in Ottawa as the cutoff temperature since it is reasonable in practice and contractors agree

I think CACEA could come up with a general set of principles

And a HOT2000 recommended modelling practice 

Would make sense if EAs were equally informed and on the same page wrt advising on this topic.

I always use calculated unless I know the size of the equipment going in. Also I thought we are to use the restricted temperature that the equipment manufacturer specifies. ie. the lowest temperature it can operate during heating mode.

Thanks Jack,

This could be useful. Do you also have the "ASHP Sizing and Selection Tool" mentioned for download in the pdf?

Hi everyone, 

The heat pump tool has been released Friday. Feel free to share as it is now published. Here is a link to the tool:

https://www.nrcan.gc.ca/maps-tools-and-publications/tools/modelling-tools/toolkit-for-air-source-heat-pump-sizing-and-selection/23558

Enjoy!

JZ

Angela Bustmante wrote:

EAs should always encourage builders to work directly with their HVAC designers to determine the heatloss/heatgain and duct design including equipment sizing such as an ASHP.  Hot2000 is only a guide.