Heating and Cooling

Introduction to the System

90 George uses a 4-pipe system which offers pronounced advantages over the 2-pipe systems used in most buildings.  A 4-pipe system can supply and return hot and cold water from central boilers and chillers to every unit in the building, all year round.  A 2-pipe system can supply and return only heating or cooling water to the building at any given time.

The 4-pipe system shows its advantages particularly in the shoulder seasons, when a cool spring or fall night can often be followed by a very warm day.  The environmental controls of a building with a 2-pipe system cannot accommodate the wide temperature variances that typically occur in the shoulder seasons, particularly in Ottawa where temperature variations over short periods of time are commonly more extreme than in other cities like Toronto and Vancouver.  You will either be too cold at night, or too hot during the day, because you cannot obtain heat and cooling at any time you require it.

A 4-pipe system requires twice as much environmental-related plumbing and significantly more control equipment, making it more complex and expensive.  This makes such systems rare, and consequently, few people have experience with operating them.  There are some fundamental differences, and these instructions will provide some simple recommendations for ensuring you get the most out of the very advanced, and very distinctive environmental systems installed at 90 George.

Setting the Temperature Controls

The defining advantage of this system is that heating and cooling is available through the shoulder seasons.  One consequence of this, is that the two are available simultaneously.  It is possible to set your thermostats in such a way that both the heat and AC will compete with each other.  Should this occur, not only is energy squandered, but you will not obtain the temperature in your unit that you intended.

To ensure such a conflict does not develop, you must set a comfortable temperature range using the thermostats in your unit, and this range must have a span of a minimum of 3 degrees Celsius, or more as needed.  You do this by setting a ceiling for the temperature, above which you do not wish it to rise, as well as a floor below which you do not wish it to drop.

This is done first at the AC thermostat control in your hallway.  Here, you will set the ceiling for your temperature range.  You can differentiate the cooling controller from the heater thermostats by the fact that it has two additional controls on it, both mechanical switches.  For normal operation, the top switch should be set to snowflake.  The other positions for this switch make cooling unavailable.

The second operation is to set a floor for your comfortable temperature range.  The temperature will not drop below this value.  You do this at each of the other thermostats in your unit; these control the heaters of the individual room in which they are located.  This allows you to set different minimum temperatures in different rooms to conserve energy.  For example you could set a lower minimum temperature in a 2nd unoccupied guest bedroom, which would reduce the heating expenditure in that space.  These thermostats can be differentiated in that they have no switches, only 3 buttons: up, down, and a screen illumination button.  As indicated before, you must maintain a range of 3 degrees or the heat and cooling units can conflict with each other.

A typical configuration in summer may be to set the thermostats for the heaters at 20 degrees Celsius and for the AC unit at 23 degrees Celsius.

NOTE:  The heating system has a built-in redundancy feature that allows it to supply heat in the event of a POWER FAILURE.  This means that, regardless of the season, all heating thermostats will automatically reset themselves to 25C.  After any POWER FAILURE, please reset all your thermostats to the appropriate temperature setting.

Air Exchanger

There is a further aspect to the system that is important to bear in mind.  There is a switch in the closet that controls every unit’s air exchanger.  Larger units may have more than one air exchanger. This switch is set to remain in the on position. The function of the air exchanger is to provide cooling to the unit, as well as to provide air flow.

Settings During Absences

Should you be away and wish to reduce the energy consumption for your unit during this time, you should not disable the system. Instead, you should set a very wide temperature range.  For example, in winter, set the heaters to come on at 21 degrees Celsius, and the AC at 28 degrees.

Summary of Thermostat Controls

Air Exchanger/Air Conditioner Control Thermostat:


This unit is located in the hallway of every unit.  There is only one, and it can be differentiated from the thermostats that control the heaters by the fact that it has two mechanical switches in addition to a button pad.  The thermostats controlling the heaters lack these mechanical switches.


Button Pad:


  1. Up Arrow:  Adjusts the temperature range’s maximum temperature higher.
  2. Down Arrow:  Adjusts the temperature range’s maximum temperature lower.
  3. Hand w/Pointed Finger:  Illuminates the screen for checking the current temperature at night.


Top Switch (Activates & Deactivates Available Systems):


  1. Top Position  (Candle): Deactivates the AC system.
  2. Middle Position (Solid Dot):  Deactivates the AC system.
  3. Bottom Position (Snowflake):  AC is available.  This is the position required for normal operation of the system.


Bottom Switch: (Controls Air Exchanger):


  1. Fan:  Forced air is provided continuously.  This setting will use more electricity.
  2. Auto:  Forced air is provided regularly, and as required.  This setting will conserve electricity, but may be less effective at cooling the unit on very warm days.


Heater Thermostats:


These units are located in every room that has a heater.  They can be differentiated from the thermostat that controls the AC/Air Exchanger, according to the absence of mechanical switches –these units only possess a single button pad, with 3 buttons.


Button Pad:


  1. Up Arrow:   Adjusts the temperature range’s minimum temperature higher.
  2. Down Arrow:  Adjusts the temperature range’s minimum temperature lower.
  3. Hand w/ Pointed Finger:  Illuminates the screen for checking the current temperature at night.