Review:
STANDARD PROTOCOL FOR
MEASUREMENT OF FAN AND COOLING
SAVINGS FROM COMMERCIAL-SECTOR
PACKAGED ROOFTOP HVAC UNITS
Regional Technical Forum
February 14, 2012
RTU Savings/MWa – NPCC 6th Power Plan
RTUs in 6th Power Plan…
45.00%
Primary HVAC System Type - REGIONWT07 - n= 1.3 billion SF (nearly
half the stock) - Only cases with some primary or secondary Package
HVAC equipment
#1 TARGET
40.00%
35.00%
30.00%
25.00%
20.00%
15.00%
10.00%
5.00%
0.00%
#2 Target
NW Commercial Building Stock
Assessment(CBSA) RTU counts-6th Power Plan
Average of Count
Package RTU
Units
1.9
4.3
8.8
16.1
19.7
Average of Pack
HVAC Tons
4.7
5.5
9.0
27.5
14.1
6. >500,000
5.5
5.2
4%
175
Grand Total
8.9
7.0
100%
174023
AREABIN
1. <5,000
2. 5,000-20,000
3. 20,000-50,000
4. 50,000-100,000
5. 100,000-500,000
52% floor area <50kSf
64% of buildings <6 tons
79% of buildings <10 tons
Faction of PNW Building Fraction
Floor Area
Count with RTU RTU Count
10%
89877
70%
118,000.00
23%
57593
61%
151,000.00
19%
15616
54%
74,000.00
15%
5816
35%
33,000.00
28%
4946
30%
30,000.00
5%
100.00
406,100.00
Population
PNW RTUs an aging fleet…
Age category
Under 5 tons
44%
5 to 10 tons
36%
Over 10 tons
20%
0 to 4 17%
30,000
24,000
14,000
5 to10 32%
56,000
46,000
26,000
10 to 19 35%
62,000
50,000
28,000
20+ years 16%
28,000
23,000
13,000
51% = 204,000 of the units have been on the roof for over a decade!
RTU Protocol Issues Raised

Measure exclusions: which measure are excluded even though
not tested?

Pre and Post upgrade scheduling: can we do Pre in August and
Post in May?

Multiple annual site review to better understand confidence
interval

Cost to implement the protocol needs closer review: cost
estimate based on mature program and lessons learned

Calculator is for a single unit; sampling protocol is for program
evaluation purposes, not unit savings calculations

All protocols and calculators will need ongoing RTF support
(2013 work plan/budget)
RTU Protocol Confidence Limits
Limited Sites
Confidence Limit, % of
Annual Energy
Hi & Lo Confidence Limits as % of Annual Estimate
25%
20%
15%
10%
5%
0%
-5%
-10%
-15%
-20%
-25%
05/02/10
05/22/10
06/11/10
07/01/10
07/21/10
08/10/10
08/30/10
Beginning of 28 Day Metering Interval
lo-4
hi-4
lo-2
hi-2
• Confidence limits are normalized relative to annual energy
• Confidence limits highest for metering periods starting in late June to
mid-July
• Confidence limits of +- 5% are achieved with metering periods starting
in late May and early August
09/19/10
Assessment of 90% Confidence Intervals (West)
Assessment of 90% Confidence Intervals (East)
Nominal 90% Confidence Intervals (East)
(Actual coverage rate around 50%)
40%
30%
20%
10%
0%
-10%
-20%
-30%
-40%
RTU0300
RTU0304
RTU0305
RTU0306
RTU0353
RTU1004
RTU1005
RTU1006
RTU1017
Nominal 90% Confidence Intervals (West)
(Actual coverage rate around 50%)
Nominal 90% Confidence Intervals (West)
40%
30%
RTU0032
20%
RTU0034
10%
RTU0036
0%
RTU1001
-10%
-20%
-30%
-40%
RTU M&V Field Protocol
•
•
•
•
Purpose
Definition of Key Terms
Required Knowledge and Skills of Practitioner
Required Data Logger Commissioning
o
o
o
•
•
•
•
One Time Site Measurements and Descriptions
Data Logger Measurements
TMY3 Weather Data
Savings Estimation Steps
Estimate of Typical Measurement Cost
Relationship to Other Protocols and Guidelines
Sampling Procedure for Program Evaluation
Purpose

Establishes a method by which annual
electrical cooling and fan energy use and
savings (kWh) can be estimated for a
commercial packaged rooftop unit (RTU)
optimized for performance including in-field
data collection requirements/methods,
annualized use/savings calculation method
Definition of Key Terms

Baseline

Pre

Post

Commissioning:
– data logger/storage/comm equipment
– RTU post-upgrade

Upgrade Measures
Required Knowledge
and Skills of Practitioner

Appropriate electrical and related safety
procedures

Knowing the protocol and calculator

Equipment inspection: control points,
schedules, cooling stages

Logging equipment selection and use

Measurement equipment commissioning

Ability to interpret results
Required Data Logger Commissioning






Communications & data storage
True power sampling with current
transducers @ 3-minute interval
If site temperature measurement is used,
verify temperatures with 2nd instrument
If supply air temperature is used, place away
from supply air plenum walls
Full data set should be tested immediately
Onboard data storage up to 70 days @ 3-min
interval
Key Measurement Considerations

Outdoor air temperature on site or nearby NOAA
weather station

Supply air temperature optional: for diagnostics, not
calculator

Timing of measurement: 4 wks pre/4 wks post
pre: 3rd wk May-June; post: 1st wk August-Sept

Timing of retrofit: July
Savings Estimation

Automated calculator with true power/temperature data
only
Sequence of Calculations:

Compute the Normalized Annual Consumption (NAC) for
pre/post data

Energy Savings Calculation Sequence

Electric Load Shape Calculation Sequence

Demand Savings Calculation Sequence
Estimate of Costs

Mature case with lessons learned

Expedited approach using NOAA weather for
2 RTUs in same panel = $1250 or $635/RTU

Comprehensive approach site weather, 3
RTUs single roof = $2,450 or $817/RTU
Annualized Energy Use / Savings
Calculator
Next Steps

February 16, 9am-12pm RTUG follow up
meeting to Feb 14 RTF review

RTF members invited to participate

Planning to make final protocol
recommendation at March RTF meeting