DRAIN WATER HEAT RECOVERY IN A NUTSHELL

102 D-E-FLesson

D- How DWHR worksE- Difference in designsF- Selecting the right size

How it works

The Process: Heat the incoming cold water with the heat energy from waste water. The Result: Less energy required to heat water and 3x more shower timeLife expectancy: Thicker coil walls, larger coil diameter = longer life. 50+ years

DifferenceDesigns

in

All DWHR units should be safety and performance certified to CSA B55.2 and CSA B55.1

Factors that determines a good DWHR design1) Length versus efficiency – you should aim between 36 and 48 inches with a rating of 1%

efficiency per inch. Example: 42 inches = 42% efficient

2) Pressure drop – Anything below 4 psi rating is good.

3) Number of braze joints – The more joints, the more potential problems with leakage. Avoiding brazed or soldered coil joints in design selection. A single ¾” coil design with no interruptions in cold water flow should be your first choice for a long trouble free unit.

4) Diameter and thickness of the coil walls – Thicker walls means longer service life, larger diameter walls means less chance of blockage and reduction of performance over time.

What size?

Factor 1 – What is the inside diameter of your drain pipe 3 or 4 inches.Note: 99% of the time you will have a 3 inch diameter pipe.

Factor 2 – Do you have any height restrictions? Call the manufacturer for help.

Factor 3 – Coil joint is ¾” if preheating to the hot water tank.

Factor 4 – What do you want as a payback period and return on investment. – use DHWR course 101 and try the online calculators to help.

Remember – Unless comparing models from the same manufacturer, longer is not necessary better. Always compare length versus kW ratings. Example: Manufacturer A has a 58 inch long unit that has a lower kW rating than manufacturers B’s 40 inch unit. Length = deception