Hi everyone, I’m Kevin Zhang, a Building Control Specialist that started in August. I will be working on improving Building Automation Systems (BAS) to make UHN buildings’ Heating, Ventilating and Air Conditioning (HVAC) systems more reliable and efficient. Below is an example of how a little change to the BAS makes the system easier to control and saves energy.

Toronto General Hospital (TGH) is comprised of multiple buildings constructed in different years, so TGH’s outside lighting is controlled differently by each building. Currently the Eaton building and part of Norman Urquhart use a schedule; RFE uses a time clock; Gerrard wing is controlled by a local photocell switch; and the Peter Munk building uses another time clock.

All of these methods have their own limitations and disadvantages:

1. Schedule:

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The Eaton outdoor lighting schedule

A schedule sets fixed turn on/off times in each day of the week. Since sunrise time and sunset time are continuously changing in the year, in order to save energy, operators need to adjust the schedule every week or two, depending on how precise they want it to be. Anyway, it’s a nuisance job. Another disadvantage is in very cloudy or snow days, the lights won’t be turned on even if the sky is already very dark. In practice, for safety, operators usually leave the lights on little bit longer after sunrise and earlier before sunset, but this wastes energy on brighter days.

2. Time Clock (Astronomic Timer):

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RFE outdoor lighting time clock

A Time Clock is like a self-adjusting schedule with consideration of ever-changing sunrise and sunset times. That sounds good, but it still cannot accommodate the dark conditions on very cloudy days. Besides, it must be adjusted locally if operators want to change settings.

3. Local Photocell Switch:

A typical photocell

It is the smartest way to turn on/off the lights as it depends on the lightness of daylight. But it is usually installed in the lighting fixture and it’s hard to adjust and maintain. We have some failed photocell switches in Norman Urquhart building which are 40 feet high and it’s very expensive to change them.

The Solution?

The solution we came up with is to install a light level sensor and connect it to the BAS.

The light sensor we are going to install

The sensor can be installed anywhere it will be exposed to daylight, so we found a location where only minimum wiring is needed (and it’s not 40 feet in the air!). Once the sensor is connected to BAS, it will perform as a central control source. A small controller will be installed to control Gerrard wing outside lighting and short distance wires will connect it to BAS. We have a similar task with RFE. An Outside Lighting graphic will illustrate the control logic, parameter, and lighting status for each building. Once it is setup, outside lighting of Eaton building, RFE, Gerrard wing and part of Norman Urquhart will be automatically controlled by daylight level in unison without any need of human intervention.

What if the sensor fails? No problem. A backup schedule will take over and it will be business as usual. Operators also have ability to override the command and adjust the light level set point.

Bring this idea home

If you think this is a good idea, you can do your own automatic lighting control at home. The holiday season is here, and with that comes a lot of outdoor festive lighting.

Lisa Vanlint, my colleague in our energy team, spent only $10 (discount price) to control her holiday lights. The device is a light switch and timer combination.

Light switch and timer combination

All you need to do is turn the dial to your desired lighting hours. Once the daylight is dark enough, the device turns the switch on and keeps it on for your specified hours, then turns it off. You can reuse it year after year. Isn’t it a good and simple action we can take to save energy and do our part to protect our environment?


Lisa’s warm and energy efficient LED holiday lights controlled by light switch

Finally, I wish you all happy holidays!