• DWHR Basics and History (Gary Proskiw, Proskiw Engineering Ltd.)

• Installation Considerations and Procedures(Gio Robson , prairieHOUSE Performance Inc.)

• Manitoba Hydro Programs (Allison LundManitoba Hydro)

Drainwater Heat Recovery Systems (DWHR)

• What are they?

• What are their benefits?

• Have they ever been used in Manitoba?

• How do they work?

• How are they installed?

• Why should you care?

DWHR Basics and History

• DWHR Systems are simple water-to-water heat exchangers which recover aportion of the energy in a home’s wastewater and use it to preheatthe incoming cold water – thereby reducing the Domestic Hot WaterHeating (DHW) load.

What Are They?

• About 90% to 95% of all new homes in Manitobause electric hot water tanks.

• Average annual DHW energy use : 3400 kWh/yr, which costs the homeowner about $250 /yr.

• This represents about 15% to 25% of the home’stotal energy use).

Some Basic Facts About DHW Heating In Manitoba

• Higher insulation levels, improved airtightness,high performance windows, better heatingsystems, HRV’s, etc. have all reduced the spaceheating load of our houses.

• But little has been done to reduce the DWH load.

Some Basic Facts About DHW Heating In Manitoba (con’t)

• Reduced energy consumption

• Reduced energy costs

• Longer showers – even with electric tanks!

• Reduced environmental impact

• Extends the life of the water heating elementsor burner

• Faster tank recovery

• Improved output capacity for instantaneous water heaters

Benefits of DWHR Systems

A Little Bit of History

• Over the years, many people have experimented with DWHR systems.

• In 1978, Electrohome developed a heat pump-based DWHR system – which never went into production.

A good example of abad example!

A Little Bit of History (con’t)

• Most early attempts to develop a workable DWHR unit incorporatedsome form of thermal storage.

• But storage is problematic:(leaks, smells, maintenance, needfor segregated plumbing lines,lost floor space and the $$$$$).

• Today, no one uses thermal storagefor residential DWHR systems.

A Little Bit of History (con’t)

• The first, known, commercially available residential DWHR system – known as the GFX – was introduced in 1997.

• In 1998, 18 GFX units were installed in a variety of new and existing houses under a Manitoba Hydro-sponsored research program. They were monitored for a total of 26.5 house-years.

The 1998 Manitoba Hydro Study.....What Was Learned

• The DWHR systems reduced the hot water load by an average of 16%, although significant variations occurred among houses.

• However, during showers the recovery efficiency increased to between 30% (high flow rate) and 54% (low flow rate)

• No water leaks were reported with any of the systems (or have been reported since).

• No smells or other problems were reported.

The 1998 Manitoba Hydro Study.....What Was Learned (con’t)

• Homeowner satisfaction was very high. Many felt that their supply of hot water had increased, in some cases substantially.

• More showers, or showers of greater duration, could take place without a significant reduction in water temperature.

• Further, when the supply of hot water was approaching depletion, the temperature drop-off was slower and much less pronounced.

The 1998 Manitoba Hydro Study.....What Was Learned (con’t)

Ideal residential DWHR applications:• Big families• Expensive fuel source• High DHW consumption• Poor water heating efficiency• Need for two DWH tanks

The 1998 Manitoba Hydro Study.....What Was Learned (con’t)

0

1000

2000

3000

4000

5000

6000

7000

0 2 4 6

DH

W U

se (

kW

h/y

r)

Number of People

So, How Do DWHR Systems Work?

• All commercial DWHR systems designed for houses utilize the Coanda effect, which is the tendency of a fluid jet to be attracted to a nearby surface. The principle was named after Romanian aerodynamics pioneer Henri Coanda

• Wastewater flowing down the pipe tends to cling to the walls of the inner pipe – not to the interior of the pipe.

• This greatly enhances heat transfer!

Batch vs. Simultaneous Flows

• Batch flows: the drainwater and fresh water flows DO NOT occur at the same time (baths, washing machines, automatic dishwashers). BAD

• Simultaneous flows: drainwater and fresh water flow DO occur at the same time (showers and some manual washing). GOOD

• To capture energy from batch flows, thermal storage is needed (which is a problem).

• In most houses, roughly 1/3 of the DHW load is simultaneous flows and 2/3 batch flows.

DWHR units use a “double-wall heat exchanger” to separate the waste and fresh water streams.

Contamination would require:1. Failure of the inner pipe and2. Failure of the outer tubing and3. Failure of the mains water

pressure and4. No one noticing.

But, what about cross-contamination?

Basic DWHR Installation

Some DWHR Tidbits:

• Over 200 different DWHR models are listedin the data base maintained by Natural Resources Canada.

• Three Canadian manufacturers:(Power Pipe, Watercycles Energy Recovery Inc. and EcoInnovationTechnologies Inc.)

Some DWHR Tidbits (con’t):

• The longer the unit, the more heat isrecovered.

• Lengths range from 24” to 120” (0.6 m to3.1 m). Available diameters: 2”, 3” and 4” (51, 76 and 102 mm).

• Annual energy savings range from1100 to 2650 kWh/yr (worth $80 to $200 per year).

EQUAL FLOW UNEQUAL FLOW COLD SIDE ONLY UNEQUAL FLOW HOT SIDE ONLY

Installation Configurations

Section 9.36Energy Efficiency

• In 2014, the Part 9 Sub-Committee on Energy & Water Efficiency of the Manitoba Building Standards Boardcompleted its review of the recently published“Section 9.36 Energy Efficiency” of the NBC.

• This included the recommendation that DWHR systems bemandatory for all new construction in Manitoba except forhouses with crawl space or slab-on-grade construction.