Getting your HVAC system ready for cooler weather
Tips and advice from a BC Hydro expert
Despite record breaking temperatures this summer, with B.C. enduring the 3 hottest days ever in Canadian history, it's never too early to start getting your HVAC system ready for the cooler weather that's on its way.
As fall approaches, we spoke to Bojan Andjelkovic, Specialist Engineer at BC Hydro to get tips on managing your HVAC system. "Whether you're in a factory, a warehouse, or an office, the best place to start is by looking to reduce your loads and losses first," says Andjelkovic. "So before you do anything else, look around the building envelope to identify any air leakage from doors and windows. And if you have air curtains – for example, in a warehouse – check that they're all functioning properly."
Once you're happy that your building envelope is under control, it's time to take a closer look at your HVAC system. We've organized Andjelkovic's advice into four categories: preparation, occupancy, maintenance and common errors.
1. Preparation: Check everything is working efficiently
Ideally, you should schedule a heating system tune-up with an HVAC specialist in early fall. Identifying any issues as soon as possible means you can fix them before the cold weather arrives. If you have gas boilers, they should be serviced once a year, while heat pumps need servicing in the fall for heating, and again in the spring for cooling.
Here are some areas to check:
- Check your ductwork for leakage. Seal up any gaps and fix any insulation issues. Damaged ductwork and connections are easy to overlook but can lead to up to 20% heat loss.
- Check your ductwork damper operation to make sure that all dampers can open and close as required.
- Check your HVAC filters and replace them as necessary or as recommended by the manufacturer. Clogged or dirty filters will make your fans work harder and will use more energy.
- Clean your air handling unit and your rooftop unit heating coils.
- If you have a heat pump or heat recovery chiller, you'll need to get an engineer to check and clean the evaporator/condenser coils. Dirty coils can cause a pressure drop, affecting your heat exchange and your fan speed. Your heat pump service contractor should also check for refrigeration leaks and compressor oil levels.
- Check all your heating and ventilation control sequences and calibrate your thermostats, air flow, humidity, and CO2 sensors.
- Check all your fan motor belts for cracks, fraying, and other signs of wear and replace as necessary.
Hydronic (hot water) heating systems
- Do your motorized hot water control valves open and close completely? If they're stuck (which is quite common) you'll be heating more water than you need – and using more energy.
- Check the hot water chemical treatment level in hydronic heating loops to ensure proper water circulation and to prevent your pipes from clogging. You should also make sure any hot water strainers are clean.
- Check the glycol level in your hydronic pre-heaters to prevent any freezing on very cold days.
- Make sure your hot water balancing valves are working and remove any air stuck in the pipes.
2. Occupancy: Keep everyone safe and warm
It may have been a while since your workplace has been at full capacity. As occupancy numbers increase, check to ensure your system is able to keep everyone safe and warm.
- More people mean more airborne particles. So you'll need to confirm that your system can deliver at least the required minimum amounts of outdoor air for ventilation. You'll need a filter combination that can achieve a rating of at least MERV 13 or higher for recirculated air. Check if your existing fans can handle the additional static pressure to maintain this airflow and calibrate your ventilation ductwork if necessary.
- Along with your visible pandemic strategies – such as social distancing and mask requirements – there are lots of invisible HVAC strategies you can be implementing too. These include improving your filtration and adding air cleaning technologies such as UVC lamps. And if you have a mixed air system that mixes outdoor air with return air, then you should increase ventilation.
- Run daily pre- and post-occupancy flushes with outdoor air. This removes any contaminants before people arrive and again after they leave. Your pre-occupancy flush should happen two hours before people arrive for the day. In accordance with ASHRAE guidance, all flushes should be long enough for the building to achieve three air changes of outdoor air.
- If your building occupancy fluctuates a lot, consider introducing energy efficient demand-controlled heating and ventilation using CO2 sensors to detect occupancy levels and variable speed drive (VSD) fans to deliver an appropriate amount of air.
3. Maintenance: Optimize performance through the winter
With your system serviced and an occupancy plan in place, you'll need to stay on top of things during the winter by ensuring that you:
- Regularly run diagnostics to find faults outside your confirmed air flow range and your control setpoints.
- Set up alarm notifications for all operating parameters that exceed your recommended values.
4. Common errors: Other ways to avoid big HVAC bills
"My team helps lots of customers make simple changes that can save them a lot of money," says Andjelkovic. Here are the mistakes that he sees on a regular basis:
- Excessive heating set point temperatures: When you're overheating a large space, the costs add up fast. For instance, a warehouse doesn't need to be 20°C.
- Simultaneous heating and cooling issues: This is often a consequence of heating set point temperatures being too high. After a while, cooling systems kick in to counterbalance the excessive heat and suddenly, you're paying to heat and cool the same space.
- Ventilation running as normal during unoccupied periods: Your HVAC system should be running at a lower set back temperature during unoccupied periods. Your set back temperatures should be at least 4°C lower than your set point. Ventilation should be turned off during the unoccupied periods (nights and weekends) If you're running at your set point and constant ventilation 24 hours a day, you're using twice as much energy as you need to – and putting excessive strain on your system.
- Hydronic hot water temperature: Every hydronic heating system should have a hot water temperature reset using an outside air temperature sensor. This means that on warmer days, you'll be heating water to a lower temperature, but still achieving your desired indoor temperature.
- Oversized heating equipment: Oversized heating equipment will cycle more frequently, reducing its lifespan – and increasing your energy usage. Many systems are designed for a worst-case scenario. But there are few genuinely cold days in many parts of B.C., so if you do have an oversized system, it's worth considering replacing it with something more realistic.
- Only one boiler: While it may seem counter intuitive, it does take more energy (and time) for one big boiler to heat the same amount of water as two or more smaller boilers. Multiple small boilers will help your system warm up faster and more efficiently.
- Constant Primary boiler water loop flow: Your primary boiler needs a constant water flow so it can easily maintain the water temperature and run at maximum efficiency.
- Wasted heat in high ceiling spaces: We all know hot air rises. So in high ceiling spaces like warehouses, heat gets trapped up in the ceiling zone and the HVAC system has to work very hard to keep the lower occupied zone warm. The most efficient solution is to fit axial fans that constantly push that warm stratified air back down to occupied zone where the thermostats are located.
- Perimeter heating zones: Buildings with vents that blow air up against windows will lose a lot of heat and create drafts. And vents that blow down will create drafts, too. For maximum efficiency and comfort for occupants, vents should be blowing draft-free air across a space and be located close to where people are working.
- Thermostat location: Thermostats can't do their job efficiently if they're located in an area that misrepresents the ambient temperature in a space. Avoid locating them next to windows, on exterior walls, in direct sunlight or areas with high heat gain from equipment.
"When it comes to maximizing your HVAC efficiency, there are so many factors to consider," says Andjelkovic. But many of them require only a small amount of effort or are simply operational changes. Together, they can add up to some very significant savings, and most likely, a more pleasant working environment."
Need advice on how to handle your HVAC system?
To get started, contact your Key Account Manager or Regional Energy Manager, or call 604 522 4713 in the Lower Mainland or 1 866 522 4713 elsewhere in B.C. Or, if you want to find an HVAC service contractor, try the BC Hydro Alliance of Energy Professionals.