ASHRAE Journal - July 2019 - 41

2019 ASHRAE TECHNOLOGY AWARD CASE STUDIES

Heating system conversion from steam to hot
water. The three main boilers were converted from
steam to hot water, and the control for the three burners was also modernized. A new hot water network
(Photo 3) was built to replace the steam network. The
primary hot water heating loop was created by reusing the supply steam pipes and installing new properly
sized return pipes, complete with two new redundant
variable ﬂow pumps of 60 hp (45 kW). All existing
steam to hot water exchangers were replaced by injection valves.
Heat recovery. Two new 200 ton (703 kW) heat recovery chillers were installed to take advantage of Quebec's
clean and inexpensive hydroelectricity rates. The heat
pumps supply a low-temperature heating network with
130°F (54°C) water that heats ﬁve pools including the
Olympic diving, swimming and synchronized swimming
pools, and provides air heating in the sports center. This
network also preheats the various domestic hot water
heating loads. In addition, a new ﬂue gas heat recovery
system was installed on the stack of the primary boiler
(Photo 4), boosting the boiler's efﬁciency to 89%.
The heating and cooling loads at the Olympic Park are
highly variable, depending on the events taking place
in the venues. This presented one of the primary design
challenges, requiring detailed analysis from the designbuild ﬁrm, along with input from the operating staff.
The new heat pumps were carefully sized to provide
the entire summer heating load (allowing the boilers to
shut down, eliminating natural gas consumption from
mid-May to mid-October) and the entire winter cooling
load (allowing the main chiller plant and cooling towers
to shut down in the winter). See Figure 1.

PHOTO 4 The existing boilers were converted from steam to hot water and downrated to decrease
the level of supervision required in the plant.

25
Heating and Cooling Load (Btu/h) (in Millions)

PHOTO 3 The steam to hot water exchanging station was converted into a hot water distribution
hub with new control valves and pumps.

20
Heating Load
15
10

Cooling Load
Maximum Power of Heat Pumps

5
Heat Recovery Load

0
Oct

Dec

Feb

Apr

Jun

Aug

Oct

FIGURE 1 Olympic Park's new heat pumps are perfectly sized to assume the full summer
heating load and the full winter cooling load.

The major steam to hot water conversion of the heating
network was an exceptional engineering feat, requiring
both a deep understanding of the building loads and
precise project coordination. It was imperative for the
Olympic Park to remain fully operational throughout
project implementation, without interruptions to events
or inconveniences for long-term tenants. The order in
which the measures were implemented was very strategic. The two new heat pumps were installed and operational by spring 2017, before beginning the steam to hot
water conversion. Since the two new heat pumps could
assume the summer heating load, the natural gas supply was completely shut down in May 2017 to convert the
network and boilers to hot water over the following 18
weeks before the heating season began. During the conversion, the Olympic Park relied exclusively on the heat
pumps and electric water heaters to meet their summer
heating and domestic hot water needs.
J U LY 2 0 19

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ASHRAE Journal - July 2019

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