By Roy Collver
In the last issue of Plumbing and HVAC magazine, Bruce Nagy wrote an article concerning the latest industry trends which were posed as a survey to our readers. The top two responses to the question, “What will grow in the next five years,” was hydronics and air-source heat pumps (ASHP).
I am sure most respondents were thinking air-to-air heat pumps would be replacing gas and oil furnaces, but air-to-water heat pumps are going to become a bigger part of the hydronic business. As an installing or service contractor, it is pertinent to understand how this technology works, how to install and service them, and how to design a hydronic system around them.
Some of the barriers that might be stopping companies from fully divulging into the hydronics industry might be due to a lack of proper licensing to perform the basic electrical installations and upgrades, basic refrigeration installations and service, and lastly, advanced electrical troubleshooting for low-voltage controls up to high-voltage equipment.
Not enough of a spark
Substituting an ASHP for a boiler will seldom be a plug-and-play procedure, although it is starting to get easier with some of the newer equipment being offered. The advent of lower temperature “warm water” hydronics with the adoption of condensing boiler technology and supply water temperature mixing has made the substitution easier in many cases. Yet there can still be major issues with equipment short-cycling due to the variable loading of some hydronic systems. Most compressive refrigeration equipment does play well with deep load reduction, requiring system design tweaks to allow equipment to have reasonable run-times.
Adding a buffer tank is the standard solution in most designs, but clever control technology to synchronize zone operation can be successful as well as careful mechanical layout to ensure minimum loads are always maintained.
In retrofit situations, a designer should first ask if there is enough electricity at the building service panel. This might turn out to be the biggest impediment to making an easy conversion from fossil-fuel burning equipment to electric heat pumps.
Although ASHP units are becoming more efficient, even smaller ones add a significant electrical load, and it doesn’t end at the heat pump. If de-carbonizing our residential building stock is the goal, owners will need to consider adding the loads of electric ranges and heat pump water heaters to replace fossil-fuel fired equipment. When you take the long view into account by adding an electric car charger or two, future-proofing the average home is going to start looking like a minimum 150-to-200-amp service. If the house already has a central air conditioning unit, don’t forget that the heat pump can also do the cooling with chilled water. This will allow you to possibly use the existing AC breaker.
If your hydronics company lacks the expertise in-house to do some of this work, find out who does it now and see if you can partner-up. Trade qualifications tend to vary by province or even by municipality, so local jurisdiction requirements need to be studied.
Where hydronics has been done strictly by the plumbing and pipe trades, more training is likely required. Refrigeration and HVAC trades often have a technical edge in the electrical, refrigeration and control aspects of heat pump installations, but don’t sell your plumbing and gas expertise short.
The exclusively-HVAC people may need your skills as much as you need theirs. If your shop already has the necessary skills diversity, then full steam ahead! You are about to get really busy. Multi-trade companies are able to provide their staff with ongoing, in-house, on-the-job training, which helps to cross pollinate the skills between trades. This really benefits companies who are active in service-work, allowing standby personnel to be able to respond to every call rather than needing multiple employees on-call for different types of equipment.
Now some good news! One clever work-around for traditional hydronic installers who lack expertise in refrigeration comes from a number of manufacturers who have stepped up to offer air-to-water heat pumps that contain all of the refrigeration equipment as a sealed package entirely in the outdoor unit. Much like putting in a residential refrigerator or window air conditioner, installers of these ASHP units don’t need to mess with the sealed refrigerant equipment and can simply place the outdoor unit and run the power to it.
The supply and return piping (hydronic not refrigerant) is then run into the house and connected to the hydronic equipment, typically to a buffer tank that then takes the place of the boiler in the hydronic piping design. Of course, it is not quite that simple. The ASHP manufacturer should have a variety of recommended piping and control schematics to help make everything work.
Air-to-water heat pumps follow a true system approach and offers a fully integrated design with hardware software and controls. It can be quite expensive, but your customer gets what they paid for — out of the box ease of installation that works with the flip of a switch.
Manufacturers are entering the market at a furious pace from Europe and Asia, but there are some notable Canadian designed and manufactured units that have proven to be robust in our cold climate and are well supported in our market.
Readers should talk to suppliers and search the internet for units that have local support for inventory, parts, and technical information. Check out industry organizations like the Heating Refrigeration, and Air Conditioning Institute of Canada (HRAI), the Canadian Institute of Plumbing and Heating (CIPH), and the Thermal Environmental Comfort Association (TECA), to see what information and training might be available. For emerging technology, there is a tremendous amount of information available from manufacturers to help give you a boost up onto the saddle.
Not a total deal breaker
There is so much more that could be covered in this topic, but I will wrap it up by de-bunking some misinformation about ASHP and cold weather operation. Yes, ASHP performance drops off as outdoor temperatures drop. No, that is not a deal breaker in our cold Canadian winters. It all comes down to proper design and providing the necessary back-up heat when required.
How much supplemental heat is needed? How often and for how long depends on the location and so, climate data for your area will need to be examined. Talk to your ASHP supplies and do the math. The attached graphics are based on work by NRCan and my own research and shows how little extra heat will be needed in the average winter.