Hybrid heat pump systems

By Michael Ridler 

If you were at Eden Energy’s recent hydronic heat pump seminar in Guelph this past September, you would have had an opportunity to see the latest in hydronic heat pump technology. The biggest takeaway from that training seminar was that there is a need for heat pumps in this industry and, most importantly, a hybrid approach. Many intelligent people in the industry right now are focused on heat pumps and see it as an all or nothing approach. I see it as an opportunity to adopt the best of both worlds while still delivering energy savings and a positive impact to the environment.

With the increase in popularity of heat pumps, the dialogue has focused on replacing furnaces and boilers with electric heat pumps. The reality is that the future of electrification in Canada and the United States will rely on a hybrid approach where we use both electricity and gas and, most importantly, exactly as written. Electricity first and backed up by fossil fuels or another source of energy. Even our national and local utilities are getting in on the game of helping to build an approach that will ensure early adoption of heat pumps without disrupting our economy or adding undue burden on Canadians who need to upgrade.

Why upgrade?

According to Natural Resources Canada (NRCan), there are around 700,000 heat pumps installed in Canada; compare that to over five million fuel furnaces. Of those five million furnaces and/or boilers, how many have actually reached the end of life? If you thought inflation was bad now, imagine if we outright banned gas furnaces today and made everyone buy a heat pump without an actual plan. Having seen many rounds of incentives in Canada, incentives can cause three things when poorly executed. They can cause an unnatural spike in the replacement business, drive up equipment and installation costs, and cause a period of deflation afterwards as contractors do five years of business in one year.

Worse yet, most homeowners have no clue what a heat pump is or how to go about buying one from a reputable installer. This can lead to shoddy installs and premature failure. It takes moderate skill to install a heat pump, but it takes a professional to install it in such a way that it is actually working effectively.

Perpetual myths

In a survey by BC Hydro, they found that over 30 per cent of Canadians don’t understand how a heat pump works and would be less inclined to upgrade to a heat pump versus a traditional fossil fuel furnace.

With five million gas heating appliances installed in Canada, we are not going to just rip them out and throw them away. A more viable approach is a hybrid system where the heat pump is the principal source of heating/cooling, and the fuel appliance is the backup for the times when we are hit by Canada’s iconic stubborn cold weather a few weeks out of the year.

In my own home, I have a Gradient SyncFurnace installed, which is a Canadian made product which replaces a traditional furnace and water heater with an engineered furnace that offers the benefits of a tankless and a furnace with a single appliance, vent, and gas run. The real beauty in this product is that it is installed just like a furnace, allowing for traditional HVAC contractors to do the work with ease and very little learning curve.

Personal case study

I am in the process of installing an air-to-water heat pump in my home because my air conditioner has finally run its course. The unit will sit outside where my A/C used to live, and the only difference is the heat pump will not only condition my home in the summer, but it will be my principal heat source in the wintertime.

My five ton fully modulating vapor injected air-to-water heat pump is sized to carry the heating load during the more moderate winter months. The remainder of the heating during the few very cold days are made up by my Gradient SyncFurnace.

The hybrid approach means we are not throwing away heating equipment that may still have 15 years of life left in it. In a pilot project east of Ottawa, research engineer Jeremy Sager for NRCan noted the merits of this proven system, “During one particularly cold day, there were 7.58 kilograms of CO2 emissions reduced while the heat pump ran from 12 a.m. to 6 p.m,” explains Sager.

Currently, the Achilles heel to a heat pump hybrid system that uses traditional fossil fuels is a lack of off the shelf controls that can properly control the system. Fortunately, there are some highly invested players on the utility side and in manufacturing working quickly to develop such controls. The controls, believe it or not, are not the hardest part. Ensuring the heat pump is the first stage in the heating operation is just as equally difficult.

Important nuances

The controls should be smart enough to know the time of day, the outdoor temperature and also how to drop out the various equipment stages, heat pump or fossil fuel based on the noted conditions. The heat pump must always be the first stage on. This also means the heat pump coil must be in the equipment return and not the supply. If this happens, we know from the work of Sager that we can save up to 7.58 kilograms of CO2 emissions in a six-hour window.

Additionally, extra care has to be put into the installation of traditional thermostat controls to avoid sabotaging your control strategy. Specifically, thermostats with adjustable cycle rates and offsets between stages. The key point here is if you bought a $20,000 heat pump system, don’t run it with a $10 control or you will quickly add $500 to $1,000 a month in operating costs due to negligence.

In my own home, I am piloting an air-to-water heat pump. The Gradient SyncFurnace that currently resides in my home is a tried-and-true technology, but what we are testing is the integration of a heat pump and the heat pump control operations. Gradient Thermal has manufactured a coil stand which sits under the unit and allows the heat pump to be my first stage.

Why air-to-water?

A few of you at this point could be wondering why I chose an air-to-water for a forced air application. This is for two reasons. I own a pool and my pool heater is reaching the end of its life. The second reason is because I am moving away from forced air in my home.

This fall, I will be fixing a large portion of my home that doesn’t heat or cool properly due to duct issues by installing Jaga Briza units. These convectors also produce high amounts of usable heat with low water temperatures.

In the city where I live, the outside design temperature is 2C and I have sized my equipment to maximize the usage of the heat pump. At 2C, my air-to-water heat pump gives me a COP of 2.8 versus my Gradient SyncFurnace of 95 per cent. With my control strategy, the heat pump is on first and, when it is not able to keep up during March Madness cold, my Gradient SyncFurnace will come on to supplement my heat pump maximizing my system performance while delivering comfort.