• Air Source Heat Pump Sizing

    I’m a huge advocate for air source heat pumps and electrification but I’ve seen a lot of questions and miss-information online on sizing an air source heat pump for your house.

    Rules of thumb are often innaccurate

    Part of the issue is that most, if not all, HVAC companies use simple rules of thumb to size air source heat pumps that can be very inaccurate. Typically the only detail they want from you to size your air source heat pump is the area (square footage) of your house but that does not take into account the level of insulation, type and quantity of windows, form/shape of your house, and air tightness. These lookup tables for air source heat pump sizing can be very wrong.

    Energy Audit Recommended

    Here in Canada one of the best ways to determine how large of an air source heat pump (or furnace!) you need, is to get an energy audit done. During the energy audit the energy advisor will document all of the items above (level of insulation, type and quantity of windows, & form/shape of your house) and also perform a blower door test to determine how air-tight your home is. Based on this information they use a program called HOT2000 created by Natural Resources Canada to calculate the design heating & cooling loads for your house. This design heating load is way more accurate than the rule of thumb area based lookups and I would recommend that anyone thinking of replacing their furnace with an air source heat pump pay the $300-600 to get one of these energy audits done.

    Where I live in Hamilton a great company to get an energy audit done is Green Venture.

    Design Heating Load

    Once you have the energy audit complete, you can find the Design Heating Load in the “Homeowner Information Sheet” under Mechanical Systems > Space Heating > Design heating load. Below is the one from my report:

    Air Source Heat Pump Capacity Varies by Outdoor Temperature

    Capacity of a 4 ton Gree Flexx at different outdoor temperatures

    Another confusing aspect is that the capacity of an air source heat pump varies with the outdoor temperature, and they all lose capacity as it gets colder outdoors. So to properly size an air source heat pump you need to know how cold it gets in your area, and it is recommended to use the design temperature for your location. The design temperature is based on historical records and is the temperature that 99% of the time the outdoor temperature is higher than that amount.

    In Ontario you can look up the design temperature for your location in the tables in MMAH Supplementary Standard SB-1 or the ASHRAE Climatic Design Conditions.

    For example, where I live in Hamilton, Ontario the design temperature is -19C / -2.2F (SB-1 2014) or -17.6C / 0.32F (ASHRAE 2021) which means for 99% of the 8,760 hours (24 hours x 365 days) in the average year it is warmer than -19C / -2.2F in the case of the SB-1 and -17.6C / 0.32F in the case of ASHRAE. To be safe I would use whatever temperature is lowest.

    Looking back at my design heating load above, if I was sizing a heat pump for my house I would need to get a system that could produce 17.74 kW at the 99% design temperature of -19C / -2.2F.

    Backup: Electric vs Gas Furnace

    A thing to note when comparing electric resistance to a furnace is that electric resistance can be run concurrently to your air source heat pump so it adds to the capacity of the air source heat pump, but gas furnaces run instead of the air source heat pump so they need to be sized for 100% of the design heat load.

    The 99% design temperature is irrelevant when picking a gas furnace or electric heat as they are not affected by the outdoor temperature, but it is very important in picking an air source heat pump as they lose capacity in colder weather, as noted above.

    kW vs Tons vs BTU/hr

    What can be very confusing is that there are three different units used for the heating capacity of heating systems. Gas furnaces are typically sized by BTU/hr, heat pumps are sized in Tons, and electric backup in kW and it can be very confusing. It is really helpful to convert the design heating load into both BTU/hr and Tons to help understand what is needed to heat your home.

    And again, the capacity of an air source heat pump is based on a set outdoor temperature which is typically 8C / 47F and all air source heat pumps lose capacity as it gets colder outside.

    How to size your system

    So the first thing we should do is to convert the design heating load from kW into both BTU/hr and Tons so that we can easier compare this to what is available.

    KW to Tons or BTU/hr1.000.2843453,412.142
    Tons to KW or BTU/hr3.521.00000012,000.000
    BTU/hr to KW or Tons2.930.83333310,000.000
    Conversion rates for kW into Tons or BTU/hr

    For my example design heating load of 17.74 kW this gives:

    Example Design Heating Load17.745.0460,531
    Example design heating load in kW, Tons, and BTU/hr

    Option 1: No backup, heat pump only

    If you wanted to heat my house exclusively with a heat pump and avoid any type of backup, I would need to find one that could output a minimum of 5.04 tons / 17.74 kW / 60,531 BTU/hr at your locations 99% design temperature of -19C. If you can find (and afford!) a heat pump that large then you wouldn’t need any backup heat at all.

    I did look on the NEEP Air Source Heat Pump list and there is a single heat pump on the list that can meet this criteria, a 6 ton VRF Gree Ultra Heat that appears to typically be used for small commercial buildings. There are likely more heat pumps available on the commercial market but pushing beyond 4 tons is getting beyond the capacity of typical residential systems.

    In Hamilton, if your design heating load is less than or equal to 10 kW / 2.84 Tons / 34,534 BTU/hr you likely can find several residential heat pumps available that could take on 100% of your design heating load at the design temperature.

    Option 2: Electric backup

    For electric backup I’m going to start by assuming a 10 kW electric heat unit as that is a common size and it’s easy to adapt this process to smaller or larger electric heaters.

    So based on this assumed 10 kW electric backup, then you can deduct 10 kW from the design heating load, which in my example would give me 7.74 kW (17.74 kW less 10kW). As electric heat elements can run concurrently to the air source heat pump you only need to cover the difference between your design heating load and the output of your electric heat.

    Example Design Heating Load17.745.0460,531
    10 kW Electric Heat102.8434,121
    Minimum Heat Pump capacity at Design Temp7.742.2026,410
    Design heat load less 10kW electric heat

    So assuming a 10kW electric heat backup, I would need to get at minimum a heat pump that can output 2.2 tons of heat at my locations design temperature.

    Option 3: Gas furnace backup

    If I wanted to go with a gas furnace backup I would need a gas furnace rated for 100% of my design heating load as a gas furnace cannot be run at the same time as a an air source heat pump. But because your gas furnace is sized for 100% of your design heating load there is no minimum size of heat pump required because your gas furnace can provide 100% backup.

    Example Design Heating Load17.745.0460,531
    Gas Furnace Backup17.745.0460,531
    Minimum Heat Pump capacity at Design Temp000
    Design heat load less gas furnace backup

    In this option I would recommend actually using the square foot / area based rule of thumb to figure out the recommended size of Air Conditioner and using that as the minimum size of air source heat pump to buy. For example if based on the area of my house it is recommended that I have a 2 ton air conditioner, I would use that as the minimum size of an air source heat pump in a gas furnace backup scenario. The maximum size of heat pump recommended would be one that could produce 100% of your design heat load at your design temperature, just like in option 1 above.

    What type of backup should I use?

    So while I’m hoping the above helps you understand the minimum size of heat pump required for the various backup scenarios it doesn’t really help you pick what size of heat pump to go with as each option has its advantages and disadvantages.

    No Backup, Heat Pump Only> Lowest electrical usage
    > No greenhouse gas emissions
    > Can help avoid electrical panel upgrade
    > Allows you to get off gas
    > Highest cost to install due to very large heat pump required
    > Even with a variable speed heat pump the unit might not be able to ramp down low enough to avoid short cycling in sholder seasons
    > Requires very large ductwork that might not exist in older homes
    > The heat pump may be oversized for the cooling season
    Electric Backup> Lowest cost to install
    > No greenhouse gas emissions
    > Allows you to get off of gas
    > Electric heat backup pulls a lot of electricity and this typically requires at least a 200 amp service to your home
    > Electric backup is typically more expensive to operate than gas backup
    Gas Furnace Backup> 100% backup
    > Depending on the cost of gas & electricity this can be the cheapest to operate
    > Requires you to keep a gas service to your house year round even if you only need gas for 1-2 months
    > Great for single speed or small heat pumps
    Advantages & Disadvantages of backup options

    Note: It is a common misconception that if the power grid goes down you are better off with a gas furnace, but all gas furnaces require electricity to run so if the grid goes down so will your gas furnace. That being said, it doesn’t take a very large generator to power a gas furnace so if you are concerned about the grid going down and you are planning on buying a generator you will need a much smaller generator if you have a gas furnace backup.

    Recommended sizing

    What is typically recommened is to get a heat pump that can output 80-90% of your design heating load and do the rest with backup. The outdoor temperature varies a lot and for the vast majority of the heating season your heat pump will be able to provide 100% of your heating needs and the backup will only be required on those few days or weeks when it gets really cold.

    So again using my example of 17.74 kW design heating load, at 80% of that would give the following heat capacity:

    Example Design Heating Load17.745.0460,531
    80% of the design heating load14.194.0448,425
    Remaining heat load3.55112,106
    80% of design heat load

    80% of my example heat load is almost exactly 4 tons which works out nicely as heat pumps are typically sold in 2, 3, and 4 ton sizes.

    Warning: while this seems to be saying if I get a 4 ton heat pump I will only need 3.55 kW of electric heat, remember that we need to look at the capacity of the specific air source heat pump we are considering at our location’s design temperature. As stated several times, all air source heat pumps lose capacity in the cold so you need to calculate the output of your air source heat pump at your location’s design temperature.

    Note: If you get a gas furnace or you get an electric backup that is sized at 100% of your design heating load then you don’t have to worry about what size of heat pump you have as worst case your backup gas furnace or electric heat can take on 100% of the load.

    Minimum Electric Backup Sizing

    To correctly determine the minimum size of electric backup required, you need to pick specific make and model of air source heat pump and look up the details on how much heat it produces at your locations design temperature.

    For this example I’m going to use the Gree Flexx 4 ton ducted air source heat pump and the NEEP Heat Pump List. This is a great air source heat pump that is very cost effective and while it is rated to work down to -30C / -20F it loses a substantial amount of capacity at lower outdoor temperatures so it is helpful to use it as an example.

    Gree Flexx 4 ton central ducted heat pump

    What we are looking for is the max heat output at our design temperature. As stated above, the design temperature for Hamilton, Ontario is -19C / -2.2F which falls between the last two rows of this chart, but I’m going to use the last row as a worst case scenario.

    Warning: What is very confusing about the above table is that there is a kW number in the max column but that is the input kW not the output kW and we need to ignore that number for load calculations. The input kW is telling you how much electricity the heat pump uses at that outdoor temperature, not how much heat it can putput.

    Example Design Heating Load17.745.0460,531
    Output of 4 Ton Gree Flex at -22F / -30C6.891.9523,500
    Remaining heat load10.853.0537,031
    Actual output of 4 Ton Gree Flexx at -30C / -22F

    So even though this particular heat pump is technically a “4 ton” unit, at -30C / -22F it puts out less than 2 tons of heat at -30C / -22F so if your design temperature for your location was that cold you would need just over 10 kW of electric backup.

    What did I go with?

    As I was shopping around and getting quotes I was very impressed with the low temp performance of the Fujitsu XLTH heat pumps and so that is what I went with. As a comparison to the Gree Flexx unit above, here are the performance charactics of my “4” ton Fujitsu central ducted heat pump.

    What really blew me away about this Fujitsu unit is that while it is called a “4 ton” air source heat pump it actually produces 4.25 tons / 51,000 BTU/hr / 14.95 kW of heat all the way down to -15C / 5F, and at the bottom end of its operating range it is still producing 81% of its 4 ton rated capacity all the way down to -26C / -15F, which is very impressive. In addition to this impressive heat output across its operating range it also is very efficient with a COP of 2.34 at -15C / 5F and 1.82 at – 26C / -15F.

    In comparison the 4 Ton Gree Flexx heat pump mentioned above can only produce 3.25 Tons / 39,000 BTU/hr / 11.43 kw at -15C / 5F and drops to 1.95 tons / 23,500 BTU/Hr / 6.89 kW at -30C / -20F. Also the Gree Flexx is less efficient with a COP of 1.8 and 1.23 respectively. The main advantage of the Gree Flexx is it is less expensive and can operate at lower outdoor temperatures. If the design temperature for your location was close to -26C / -15F and you wanted the Fujitsu you likely would need to get a backup heat source sized at 100% of your design heat load for when it got so cold out that the Fujitsu couldn’t operate, but if you had the Gree Flexx you could still count on its heat output all the way down to -30C / -26F

    In terms of backup I went with a 10kW electric heat element so if we calculate my heat output at -15C / 5F we get the numbers below:

    Output of “4 Ton” Fujitsu XLTH at -15 C / 5 F14.954.2551,000
    10 kW electric heat10.002.8434,121
    Total system output at -15 C / 5 F24.957.0985,121
    Example Design Heating Load17.745.0460,531
    Surplus heating capacity at -15 C / 5 F7.212.0524,590
    My system at -15 C / 5 F

    And again for -26C / -15F we get the numbers below:

    Output of “4 Ton” Fujitsu XLTH at -26C / -15F11.433.2539,000
    10 kW electric heat10.002.8434,121
    Total system output at -26C / -15F21.436.0973,121
    Example Design Heating Load17.745.0460,531
    Surplus heating capacity at -26C / -15F3.691.0512590
    My system at -26C / -15F

    So as you can see for temperatures all the way down to -26C / -15F my system has more than enough capacity to heat my home.

  • How to transcribe Bell Mobility Voicemail (AMR) using VLC and Word Online

    If you are a Bell Mobility customer and you get messages like this whenever someone leaves you a voicemail, here is how to get a transcription.

    This is not an automatic process and you have to manually do it for each voicemail received, but it can be helpful when you need to forward the voicemail to someone else or collaborate on a response.

    To do this you will need VLC and access to the online version of Microsoft Word.

    Step 1 – Get the file on your computer

    If you are an android user, the easiest way is to use messages.google.com which will allow you to send and receive text messages (and attachments) from your computer.

    Step 2 – Convert AMR to MP3 using VLC

    Open VLC and click File > Convert / Save

    Then click add and find your file

    Then click Convert / Save

    Make sure that the profile is set to Audio – MP3 and click browse to pick where you want the output file to be saved, and then click start.

    For voicemail files this typically only takes a second or two to convert so it might seem like it didn’t do anything, but check the destination folder to see if it worked.

    Note: this will work to convert any file VLC can open to MP3, including videos.

    Step 3 – Use Word Online to transcribe the MP3

    Open Microsoft Word Online in your web browser: https://www.office.com/launch/word

    Click Blank document under Create new

    Click the drop down under Dictate and then pick “Transcribe”

    In the Transcribe sidebar click Upload audio and find the MP3 file you created in step 2.

    This can take a few minutes, but when it is done you can add it to the document. For voicemails I typically pick “Just text”

    Note: if you use this for files with multiple people speaking, the transcription engine will try to label each person Speaker 1, 2, etc. and you can edit their names by hovering over a section of the transcript and clicking the pencil icon.

  • Electricity Cost of Electric Vented Dryer

    I live in Ontario and my electricity is billed on a time of use plan.

    Time of Use Table from https://www.oeb.ca/consumer-information-and-protection/electricity-rates

    I had assumed that one of my biggest electricity users was my vented electric dryer as it has a 240V/30AMP service, and my sub-metering system showed high spikes whenever it ran.

    Chart from IotaWatt Graph+ of the Dryer running

    I looked back over the past few days whenever the dryer ran and made a table of the kWh for the last 7 loads.

    Excel table of kWh used per load

    And based on that average, calculated the cost to dry a load of laundry at each of the three time of use rates

    Excel table of electricity cost to dry a load of laundry

    I was a bit surprised how cheap this was. Under 40 cents to dry a load of laundry at the highest time of use rates. It is double the cost to dry at on peak vs. off peak but it is only 20 cents more a load.

    Looking back over January it looks like we dried 14 loads of laundry, so if we did all of them off peak we would have saved $2.80/month which is $33.60 a year.

    So, drying laundry with an electric vented dryer, which is really the most energy intensive way to dry laundry is surprisingly cheap and while you can save some money by shifting your drying to off-peak times it really doesn’t amount to much.

    Also this calls into question the business case for a heat pump dryer as even if they used no energy to dry clothes, it would only save us around $60/year which likely doesn’t justify the additional cost of a heat pump dryer.

  • How to decrypt secured PDF files

    Here is how to unlock / decrypt (SECURED) PDF files on windows. This uses the excellent qpdf application.

    QPDF is a command-line tool and C++ library that performs content-preserving transformations on PDF files. “


    Note: This doesn’t work on PDFs that require a password to open. Just the (SECURED) ones that let you view them but stop you from printing/copying text/extracting pages/assembling them.

    Setup: Get qpdf

    Download the latest version of qpdf from this website: https://github.com/qpdf/qpdf/releases

    There are a bunch of different versions but the one you should try first and will likely work for 99% of people is the one ending with msvc64.

    qpdf releases at time of writing

    The exe file is an installer and requires admin permissions and the zip file is a “portable” version that can be run without admin permissions once you extract it.

    How to use qpdf

    What I like to do is copy the target pdf file into bin folder in the qpdf application folder. The default location for the installer is:

    C:\Program Files\qpdf 11.2.0\bin

    Now you need to open a terminal / command line and navigate to the directory. I find the easiest way is to go there in windows explorer and right click in the files pane and choose “open in terminal”

    Windows 11 File Explorer: open in terminal

    Now you just need to execute the following command, replacing inputfile.pdf and outputfile.pdf as required. Windows command line does do command line autocomplete so you can type the first letter of the file name and hit tab to cycle through all of the file names that start with that letter.

    qpdf.exe -decrypt inputfile.pdf outputfile.pdf

    If the command works there won’t be any feedback on the command line, but “outputfile.pdf” will be created.

  • How to get a cheap conference call number using voip.ms

    So, with this crazy COVID-19 pandemic it might be useful to have a conference call number to facilitate physical distancing.

    This is a how to set up a conference call number using the very cost effective voip.ms service.

    If you set this up using a local number it will cost you less than 1 cent per minute per caller. For example a call with 8 people dialing in that lasted 2 hours your cost will be under $5.

    Step 1: Create an account at voip.ms

    Please use my referral link: https://voip.ms/en/invite/MjYwOTA2

    If you use the referral link we both get $10 in credits.

    Here is the non-referral link: https://voip.ms/login?redirect=/m/index.php

    Step 2: Add funds to your account

    Under Finances click add funds to do this.


    • You need to add a minimum of $15 to your account to proceed. If you used the referral link above you will get an additional $10 of account credit to work with.

    Step 3: Order (set up) a DID (phone number)

    Under DID Numbers click Order DID(s)

    Once your DID is set up, write down the number.


    • The cheapest option is a local number in your area, but you can also pick a toll-free number if you want at a slightly higher cost.
    • Note: You need to pick a per minute plan to use the audio conferencing feature.

    Cost examples:

    • A local number in Ontario Canada costs $0.85/month and $0.009/minute (that’s 9/10th of a cent) under the per minute plan.
    • A toll free number costs $1.25/month and $0.027/minute (that’s 2.7 cents) under the per minute plan.

    Step 4: Setup the audio conference

    Under DID Numbers click Audio Conferencing

    Click add a conference


    • Each Conference is like a room, anyone who is allowed into this conference is in the same “room”.
    • So if you are setting this up for multiple people to use at the same time you need enough conferences for everyone.
    • To control access you can assign participants on the participant tab. This list shows all of the participants for all conferences. If you have multiple conferences (aka rooms) then you need to review the settings for each one so that each participant is linked to the correct room. I would suggest keeping this simple and having a single participant linked to each room so that there is a 1 to 1 relationship between rooms and pin numbers.

    Step 5: Link your DID to the audio conferencing

    Click DID numbers > Manage DID(s)

    In the DID numbers table click the edit DID icon in the actions column for the DID you want to link to the conference.

    In the routing pick audio conferencing and pick the conference you created earlier

    Click the “click here to apply changes” at the bottom of the email.


    • You can also change a few other features here also. I would recommend turning on the caller ID lookup, it does cost $0.008 (8/10th of a cent) per lookup, but without you won’t know who is dialing in.

    Step 6: Test it

    You can now call the DID number and it will ask you for your pin that you set up in step 4.

    I would test that different people can call in using the PINs you established and that they end up in the correct “room” (conference).

    Optional: Check on how much it’s being used / costing you

    If you want to see how much this is being used, you can run a “Call Detail Report” under the CDR and Reports tab.

    Note, I don’t think there is any way to differentiate the usage by conference (rooms) or participants, so all calls to a DID will be charged to that DID and you can’t find out which room they used. If you need to separate costs for different people/groups you need to sign up for another DID.

  • R-Values do not reflect reality


    So this is really interesting. This company constructed two identical boxes, one with Glutex wood fiber insulation rated at R-5.7 and one with XPS foam insulation rated at R-10 and monitored the internal temperatures over a month. And if you are still reading you’ll probably guess what happened, the Glutex wood fiber insulation performed better, even though it is almost half the r-value of the XPS foam!

    Part of the issue is how the r-value is determined:

    Standard tests for R-value use a steady-state temperature (ASTM 2018), but our enclosures exist in a world of highly variable temperatures. Furthermore, R-value tests typically only include conductive heat transfer, missing any influence of radiant heat transfer, and are conducted under unrealistic conditions, such as 50 degrees F at the interior with 100 degrees F at the exterior (Bailes 2013).

    This scenario actually happens almost all the time. Someone notices a difference in how things perform (in this case insulation) and comes up with a way to measure the difference (the r-value). This method of measuring the difference is almost always optimized to be cost effective to test which means it usually is quick to do and/or is based upon a limited number of variables. (i.e. testing at a steady state temperature, ignoring radiant heat) Based upon this new way of measuring the difference, companies come up with new products that are optimized for profit based upon that measurement (i.e. highest r-value/inch) and given enough time, these products take over the marketplace, even though they do very poorly outside of the test conditions.

    Another great example of this is Polyisocyanurate insulation which has the amazing feature of being less effective at resisting temperature the colder it gets!

  • Why time management is ruining our Lives


    Here is a great article on the other side of time management. I’m a huge fan of the productivity movement but it’s good to read something like this once in a while to provide some context to what we are deciding to do when we focus on productivity as our top priority.

  • Think about what you could do

    Thinking about what you should do narrows the options down, instead try to think about what you could do in this situation to widen the potential options and come up with better solutions.


  • A year of progress

    A year ago (2018-01-11)
    Last week (2019-01-09)

    It’s pretty amazing what can get done in a year! We went from a dirt path to a two storey space.

  • Self Control Psychology Myth

    Interesting article on self control.

    The paper stumbled on a paradox: The people who were the best at self-control — the ones who most readily agreed to survey questions like “I am good at resisting temptations” — reported fewer temptations throughout the study period.