1. HPWH Findings from Northern Climate Field Study
ACEEE Hot Water Forum – Nashville
February 23, 2015
Hugh Henderson sponsored by:
CDH Energy Corp NYSERDA
Cazenovia, NY

2. Do HPWHs Make Sense in Northeast?
Many rural homes do not have natural gas
Fuel oil / wood widely used for space heating
Electric water heaters are common
Most homes have basements
HPWH pulls heat from the basement/ground … not the “home”
Dehumidifiers are widely used
Efficiency can be reasonable
Loads are high, capture waste heat
Efficiency can approach COP of 2?

3. Field Test Site Remodeled Farm House 2 to 5 occupants
wet stone basement
new plumbing
oil boiler w/ indirect tank
use DH in summer
2 to 5 occupants

4. Instrumentation 15-minute data (1 sec scans)
Integrates ΔT and flow every second to get Q
Power and element status
Space conditions (T & RH)
Dehumidifier status
Pre-HPWH data collection (Nov-2012 to April 2013)

5. HPWH GE GeoSpring™ HPWH purchased February 2013 Model: GEH50DEEDSR
50 gallon
2.4 EF
Set to “Hybrid” Mode

6. Daily Efficiency vs. HW Load
EF= @ 64 gal/day
AVG= @ 49 gal/day
Large draws hurt efficiency

7. Daily Power vs. HW Load

8. What Drives Resistance Element Operation?

9. Large Draws Drive Resist. Elements
2 cycles of element operation
1 cycle of element operation
few minutes of unexplained operation

10. Basement Space Conditions
HPWH Installed

11. Basement Space Daily Conditions
HPWH lowered temperatures by 2-4F

12. Basement Humidity vs. Outdoor Humidity
Winter
Summer

13. Impact on Dehumidifier Performance

14. How Does HPWH affect DH Runtime?

15. Statistically Analyze Impact
Multi-linear Regression Model
Coefficient a2 indicates impact
a2 =  “each hour of HPWH decreases
DH runtime by 0.2 hrs”
T-ratio = 2.5  “different from zero at 90% CI”
DH = a0 + a1×WO + a2×HP
where: DH - Dehumidifier Runtime (minutes/day)
HP - HPWH Runtime (minutes/day)
WO - Outdoor Humidity Ratio (lb/lb)

16. Annual Dehumidifier Savings

17. Summary Overall COP is 1.4 @ 49 gal/day HPWH impacts space conditions
basement is colder (50-65F)
resistance elements respond to large draws (e.g., 20 gal)
better controls could reduce element operation
HPWH impacts space conditions
operation lowered space temps by 2-4F
HPWH reduces Dehumidifer (DH) operation
Every 5 hours of HPWH operation reduces DH runtime by one hour
Saves an additional 84 kWh per year (10%)