As many of you are aware, the National Weather Service has issued and extreme cold warning as Chicagoland area is forecasted to experience severe cold temperatures over the weekend with lows occurring well below zero with the forecasted lows Friday morning reaching -10F to -15F. The forecast predicts temperatures that will test the limits of the heating capabilities of your equipment and are below typical design conditions. In advance of this and other extremely cold weather events, it is important to make sure your building is prepared.
We recommend taking the following steps to ready your building for the extreme cold, especially if changes have been made to heating or ventilation system operating since last winter. This is especially the case for new equipment experiencing extreme weather for the first time:
- Turn off all non-critical exhaust systems (i.e. residential kitchen and toilet exhaust)
- Temporarily reduce ventilation only where possible
- DO NOT turn off 100% Makeup Air Units (MAUs). Below items should be considered for mixed air AHUs as well
- If 100% MAUs shut down unexpectedly and cannot be restored, we advise shut down of the associated toilet and kitchen exhaust systems
- Consider increasing the increasing discharge air temperature setpoints for boosted heating and pressurization
- Test 100% MAUs freeze stats in preparation of the cold weather to assess their operation and resulting sequence of operation. The freeze stat can me ‘tripped’ using an inverted can of keyboard cleaner (canned air) or another means. Typical sequence of operation for a freeze stat ‘trip’:
- Outside air dampers close
- Fans turn off
- Heating valves and coil pumps operate at 100%
- The particular freeze stat operation may vary depending on the specific design of your 100% MAU
- Override thermostat unoccupied and overnight setbacks to occupied. In residential applications, advise your tenants to do the same
- Although increasing the thermostat temperature leading into the cold weather to “preheat” the spaces is advisable, consider adjusting thermostat setpoints to minimum heating (i.e. 68F -70F) during the coldest weather to ease stress on central equipment
- Avoid scheduled shutdowns of systems
- Avoid turning heating related equipment off
- Verify all coil pumps are operational
- DO NOT shut coil pumps off or other coil freeze protection systems
- Maintain continuous operation of all heating related pumps
- Minimize infiltration
- Keep doors, windows and other openings sealed
- Add temporary heat where infiltration can’t be controlled
- Maximize pressurization if possible
- Keep blinds and shades closed on windows at night and those not receiving direct sunlight during the day
- Perform a system check of all heating critical equipment
- Verify operation of redundant heating equipment by switching the lead operating equipment prior to the cold weather
- Perform any outstanding maintenance items that may be preventing heating equipment from operating prior to the severe cold weather
- Provide preventative checks on critical system as well as electrical components which may be critical to heating operation
- Remove snow and ice from air intakes to ensure proper airflow for outdoor air-based heat pump systems
- Remove snow and ice from and around air-source heat systems such as VRF or heat pump chillers. This is especially critical this year where there has been significant snow accumulation
- Verify the location of isolation valves, verify their operation and understand when to use them
- During an emergency situation where a pipe, coil or other system has frozen, the reliability, and proper use of isolation valves is critical
- Isolate the leak to as local an area as possible
- Take care not to close the wrong valve (essentially stopping the flow of water)
- Water at rest is much more likely to freeze. Therefore, do not risk further freezing of the system by closing the wrong valve, should isolation be required
- Exercise all heating equipment isolation valves prior to the cold weather event
- Verify isolation valves are in the correct position and seasonal switch over procedures were implemented correctly
For more information or to address specific concerns or questions, please contact us at info@elaraeng.com.
