Multifamily Program Gas Water Heaters: Sealed Combustion Crossover Products
Abstract
The purpose of this paper is to document the benefits of using crossover gas water heating products that
combine the benefits of instantaneous and storage units for use in the Investor Owned Utilities
Multifamily Upgrade Program (MUP), California Multi-Family New Homes (CMFNH) or the California Tax
Credit Allocation Committee (CTCAC) program. This paper uses the HTP RGH-75F Condensing Sealed
Combustion 20 gal water heater to demonstrate the benefits of the crossover configuration which yields
substantial performance improvement and energy savings. Acceptance of these units into the multifamily
programs will encourage the use of ultra-low NOx certified tank type water heating units with significantly
improved efficiency, reduced energy cost, reduced greenhouse gas emissions, reduced utility space
requirements, and the elimination of combustion appliance safety testing for water heating.
At this time there are no sealed combustion water heaters available to California multifamily housing
builders with an energy factor (EF) rating. The acceptance of these 20 gallons units, with an energy factor
rating of .83, where 40 or 50 gallon units are typically required will allow the specification of higher
performing modulating condensing sealed combustion units for use in multifamily housing projects for
domestic hot water, including hot water and space heating combinations. These units provide a higher
First Hour Rating, lower energy use, reduced devoted space requirements and the safety of sealed
combustion.
This paper demonstrates the project energy savings available with crossover units using two completed
multifamily projects as examples. The savings are calculated under the projected scenario where the RGH75F is approved for the MUP program and specified for use on these projects rather than the actual lower
efficiency units installed. The enhanced performance of these units would benefit residents, multi-family
housing operators and project developers through better indoor air quality, lower capital and operating
expenses, and reduced construction testing requirements.
Description of need
The renovation of multifamily projects presents the opportunity to reduce energy cost, reduce
greenhouse gas emissions and enhance life safety. However, the currently approved units for supplying
hot water for occupant use and space heating all have an Energy Factor (EF) less than .71 for the capacities
of 75kbtu or less. A standard tank type unit specified for the MUP is limited to an EF equal to 0.71 or less.
Instantaneous water heaters have higher Energy Factors but are typically not viable for these projects as
they require supply lines greater than existing .5” diameter gas lines. Replacing the lines is typically
impractical and cost prohibitive for these applications. Additionally, some areas of California have very
hard water where instantaneous gas water heaters are not recommended.
Furthermore, the use of water heater units that are not sealed combustion run the risk of leaking
combustion gases into the living spaces. Costly and time consuming combustion appliance safety testing
is required for these units to ensure life safety. The use of sealed combustion units provides a cost
effective alternative that resolves this issue.
8/10/2016
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Description of opportunity
The need to reduce energy costs and to eliminate installations requiring combustion appliance safety
testing can be addressed by allowing the use of crossover units similar to the RGH-75 residential water
heaters for program certification in place of the required 40 gal or 50 gal standard units. The use of these
units will allow the specification of better performing and substantially more efficient sealed combustion
water heating units than what is currently available in the market. These units have the added benefit of
significantly reduced space requirements with dimensions of 21” diameter and 47” height. The
specification of crossover units will hasten the realization of the many benefits including cost reduction,
greenhouse gas reduction and occupant safety.
Crossover Sealed Combustion Units Comparison to Currently Available Storage Units
The specification of this product type provides substantial energy savings in comparison to the base case
unit, in addition to the other non-energy benefits discussed above. This table provides a summary of the
energy savings percentage realized by specifying the RGH75 in place of the code base case unit in two
example projects.
RGH-75 Estimated Energy Savings
Over Code Basecase Unit (EF=.60)
City and
Climate Zone
Retrofit
New Construction
(DHW and Hydronic
(DHW only)
Heating)
San Francisco CZ 3
36%
24%
San Diego CZ 7
37%
26%
Escondido CZ 10
37%
25%
Sacramento CZ 12
36%
24%
Palm Springs CZ 15
39%
27%
First Hour Ratings
The RGH75 crossover units combine the benefits of instantaneous and storage water heater designs
without sacrificing performance. These units utilize .5” inch diameter gas supply lines and provide
superior First Hour Ratings. The table below provides a comparison to standard storage units base on the
AHRI Certification results1.
AHRI Certified First Hour Rating
Crossover
20 gal
Natural Gas
AHRI certified
products:
40 & 50 gal
Natural Gas
HTP RGH-75
104.5 gallons
AO Smith
70-92 gallons
RHEEM
59-93 gallons
Whirlpool
67-70 gallons
Bradford White
55-112 gallons
1
Air-Conditioning, Heating, and Refrigeration Institute (AHRI) Directory of Certified Product Performance;
https://www.ahridirectory.org/ahridirectory/pages/home.aspx ; August 2, 2016
8/10/2016
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Presentation of model results
The opportunities represented by the inclusion of high efficiency sealed combustion water heater units
have been quantified using two actual completed projects and their associated energy models. The
projects are described below. The savings are presented for five typically encountered climate zones.
Example 1 – Retrofit Project: combined domestic hot water (DHW) and Hydronic Heating
 Multifamily project: 6 buildings, 68 units (2, 3 and 4 bedrooms) water heaters providing domestic
hot water and hydronic space heating with hot water fan coils.
o 72,593 sq.ft. of conditioned floor area
o Two, three and four bedroom apartments
o One 50 gallon water heater per apartment
 Water heater used: AO Smith-50 gal with Energy Factor = .62
 Funding Program: CTCAC; Target savings 10%
 RGH75 high efficiency sealed combustion alternative measure
o Energy Factor = .83
o Project energy savings = 11.3%
Project energy savings = 22% over unit specified for this example project (CZ3 results)
City and
Climate Zone
San Francisco
CZ 3
San Diego
CZ 7
Escondido
CZ 10
Sacramento
CZ 12
Palm Springs
CZ 15
Project Percent
Improvement
Model
EF
TDV2
Project
Therms/year
(used)
Basecase
0.60
0.0%
25,109
AO Smith Low Efficiency
0.62
1.0%
24,605
AO Smith Cyclone
0.72
6.9%
21,730
RGH75
0.83
12.3%
19,093
Basecase
0.60
0.0%
16,894
AO Smith Low Efficiency
0.62
1.0%
16,394
AO Smith Cyclone
0.72
5.4%
14,192
RGH75
0.83
8.8%
12,530
Basecase
0.60
0.0%
19,267
AO Smith Low Efficiency
0.62
0.7%
18,768
AO Smith Cyclone
0.72
4.2%
16,366
RGH75
0.83
7.1%
14,406
BaseCase
0.60
0.0%
29,027
AO Smith Low Efficiency
0.62
0.7%
28,525
AO Smith Cyclone
0.72
4.9%
25,318
RGH75
0.83
9.2%
22,187
BaseCase
0.60
0.0%
15,365
AO Smith Low Efficiency
0.62
0.4%
14,869
AO Smith Cyclone
0.72
2.2%
12,764
RGH75
0.83
3.4%
11,282
2
Note: TDV =Time Dependent Valuation of Energy
RGH 75 Percent
Project Therms
Saved
24%
22%
12%
NA
26%
24%
12%
NA
25%
23%
12%
NA
24%
22%
12%
NA
27%
24%
12%
NA
2
TDV: Time Dependent Valuation of Energy for Developing Building Efficiency Standards, E3/CA Energy
Commission, Feb. 2011
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Example 2 – New Project: DHW only
 Multifamily project: Four stories, 60 units
o 42,531 sqft of conditioned floor area
o One, two and four bedroom apartments
o One 50 gallon water heater per apartment
 Water heater used: AO Smith-50 gal with Energy Factor = .62
 Funding Program: CTCAC; Target savings 30%
 RGH high efficiency sealed combustion alternative measure
o Energy Factor = .83
o Project energy savings 6.5% (CZ 3)
Project energy savings = 29% over unit specified for this example project (CZ3 results)
City and
Climate Zone
Model
Code Standard
San Francisco AO Smith Low Efficiency
CZ 3
AO Smith Cyclone
RGH75
Code Standard
San Diego
AO Smith Low Efficiency
CZ 7
AO Smith Cyclone
RGH75
Code Standard
Escondido
AO Smith Low Efficiency
CZ 10
AO Smith Cyclone
RGH75
Code Standard
Sacramento AO Smith Low Efficiency
CZ 12
AO Smith Cyclone
RGH75
Code Standard
Palm Springs AO Smith Low Efficiency
CZ 15
AO Smith Cyclone
RGH75
8/10/2016
EF
0.62
0.72
0.83
0.62
0.72
0.83
0.62
0.72
0.83
0.62
0.72
0.83
0.62
0.72
0.83
Project Percent
Improvement Project Therms/
TDV
year (used)
0.0%
2.3%
6.2%
8.8%
0.0%
2.4%
6.5%
9.2%
0.0%
2.0%
5.4%
7.6%
0.0%
1.9%
5.2%
7.3%
0.0%
2.0%
3.8%
5.5%
10,513
9,550
7,872
6,759
10,127
9,159
7,505
6,421
10,037
9,066
7,417
6,340
10,358
9,391
7,723
6,622
9,279
9,066
6,666
5,647
RGH 75 Percent
Project Therms
Saved
36%
29%
14%
NA
37%
30%
14%
NA
37%
30%
15%
NA
36%
29%
14%
NA
39%
38%
15%
NA
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Conclusion
There are considerable costs and energy savings available to California multifamily projects if new
crossover water heating products which combine the benefits of instantaneous and storage strategies are
allowed to be specified for the multifamily housing market. The allowance of these units in the multifamily
programs by accepting the 20 gal units where the programs specify 40 or 50 gallon units will benefit
residents, multi-family housing operators and project developers through better indoor air quality, lower
capital and operating expenses, and reduced construction testing requirements.
The enhanced performance of these units would benefit residents, multi-family housing operators and
project developers through better indoor air quality, lower capital and operating expenses, and reduced
construction testing requirements.
Appendices
Appendix A: Energy Model Details
Appendix B: RGH 75 Product Specifications
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Appendix A: Energy Model Details
Following pages
Example 1:
Energy Model Details
Multiple buildings-Existing building built in 1972
6 buildings, 68 units (2, 3 and 4 bedrooms)
72,593 sqft of conditioned floor area
Domestic hot water and hydronic space heating with hot water fan coils
Target Compliance margin:
10%
Modeling software:
EnergyPro 5.1.9.12
Envelope:
R-6 walls wood framed 16”OC
R-11 wood framed roof 16”OC
Slab on grade floors
Double metal tinted windows U= .79, SHGC=.59
Hollow metal exterior door
Mechanical:
Hydronic space heating provided by domestic hot water with forced air
cooling, 10 SEER, 9.2 EER
Existing Ducts located in conditioned space
Example 2:
Single building Multi-Family- New construction
1 building, four stories, 60 units (1, 2 and 4 bedrooms)
Domestic hot water only (no hydronic space heating)
Target Compliance margin:
30%
Modeling software:
EnergyPro 5.1.9.12
Envelope:
R-15 walls 2x4 wood framed 16” OC
R-38 Cathedral roof wood framed 16”OC
Cool roof with Aged solar=.68, Thermal Emmitance= .84
Uninsulated raised slab floor
NRFR tested windows U value=.34, SHGC .31
Mechanical:
Ducted split heat pumps, HSPF=10, SEER=15, EER=12
Ducts located in conditioned space
Appendix B: RGH-75 Product Specifications
Following pages
TM
Residential Water Heater
RGH-75F & RGH-100F
Advanced Heating
& Hot Water Systems
Fighting the
High Cost of
Water Heating!
Fully Condensing
Achieves up to
95% Efficiency
Half the Storage &
Twice the Btuh Result
in a Recovery Rate
that is 4 Times Faster
than Traditional
Storage Units!
RGH100 Specifications
w w w.htproducts.com
®
SCAQMD Rule 1146.2
TM
Thermal Efficiency (NG)
Installation
Gas Input Rate
LLC
96%
Indoor / Floo
100,000 Btuh
Crossover
We are excited to introduce the new high efficiency
Crossover models – RGH-75F and RGH-100F. This
revolutionary product was designed to be the most
highly efficient affordable residential tank type
product in the industry.
The
TM
incorporates the best of both
worlds in one unit with its tank and
tankless components. The result is
one appliance that exceeds all of
your hot water needs
High Performance
The Crossover Residential Floor model combines
the flow capacity of a 50 gallon tank type water
heater with the continuous flow feature found in
tankless water heaters. It has dual activation by
flow or thermostat sensing which guarantees hot
water delivery even with low flow fixtures. It’s
built in fire tube heat exchanger is surrounded by
a stainless steel tank that holds a full 20 gallons
of up to 167 degree hot water and then mixes
the delivered temperature down through a ASSE
1017 mixing valve and can thus fill a 40 gallon
tub at the same rate as a traditional 50 gallon tank
type water heater. The RGH 75 and 100 can also
produce more first hour delivery than conventional
50 gallon water heaters. These two new models
will change the way people view residential water
heating and it is only available through HTP and
our agent partners.
Fantastic Features
Extra thick insulation combined
with small water volume storage
result in very low standby loss
High altitude compliant – certified
up to 10,000 ft. above sea level
All stainless steel tank
construction with integrated fire
tube heat exchanger design
Endless hot water - advanced
temperature control - compatible
with recirculation systems
Preset for natural gas
ships with a liquid propane
conversion kit
Eco-friendly and low
NOx combustion system
Air handler application:
Combination heating & DHW
leave almost no carbon footprint
Includes an ASSE 1017 domestic rated thermostatic valve (prepiped) increasing 1st draw capacity & temperature control
Compare the RGH with the Competition
Crossover
Features
199 Btuh (Non
.70 EF
.95 EF
.82 EF
NO
NO
Varies by
Model
Varies by
Model
100,000
40,000
40,000
199,000
199,000
107
130
88
90
NO
NO
YES
YES
YES
YES
NO
NO
YES
YES
YES
YES
NO
NO
Optional TwoTemperature Delivery
Capability (with kit)
YES
YES
NO
NO
NO
NO
Annual Operating
Energy Cost (NG)
$196
N/A - TE
Classification
$272
$233
$172
$199
Tank
Stainless
Steel
Stainless
Steel
Stainless
Steel /
Copper
Copper
Heat
Exchanger
Stainless
Steel
Stainless
Steel
Annual HX Anti-Scale
Maintenance Required
NO
NO
NO
Venting
PVC
PVC
Vent Length
2" at 50'
Efficiency
Ultra Lo NOx
Complaint
First Hour Rating
@ 90°F Rise
30 Gal. Dump
Performance
Capabilities
Zero Flow Activation
Materials
Installation
Display
Dimensions
Tankless
199K
Btuh
Btuh
Savings
Tank Type
50 Gal.
50 Gal.
Atmospheric Power Vent
RGH-75
RGH-100
.83 EF
.88UEF
95% TE
.60 EF
YES
YES
75,000
Glass Lined Glass Lined
Carbon
Carbon
Steel
Steel
Stainless
Steel /
Copper
Copper
NO
YES
YES
B-Vent
PVC
PVC
2" at 50'
3" at 50'
3" at 100'
2" at 50'
Stainless Steel
Category III
3" at 50'
YES
YES
NO
NO
NO
NO
Anti-Draft Direct
Vent Capable
YES
YES
NO
NO
YES
YES
Field Convertible
YES
YES
NO
NO
Varies
Varies
Anti-Scald Mixer
(ASSE 1017)
YES
YES
NO
NO
NO
NO
Digital with
Error Codes
YES
YES
NO
NO
Varies by
Model
Varies by
Model
Height
38.6"
38.6"
57"
50 3/4"
23 5/8"
20 1/2"
Width
21"
21"
22"
24"
17 3/4"
13 3/4"
Depth
21"
21"
22"
24"
11 1/4"
10 1/2"
Space Saving Low
Profile Vent Capability
Diameter
Weight
21"
110 l bs.
21"
110 lbs.
Glass Lined Glass Lined
Carbon
Carbon
Steel
Steel
Condensing)
22"
165 lbs.
24"
198 lbs.
N/A
63 lbs.
N/A
51 l bs.
RGH-75F & RGH-100F
Produce More
Hot Water than a
Standard Tank with
40%
Less Space Required
than a Standard Tank
A Closer Look Inside
Super Durable All
Stainless Steel Fire Tube
Heat Exchanger
RGH-75
4
Less S
Than a
a
7
Mo
Than a
+
++ ===
+
=
WaterWater
Water
Water
HeaterHeater
Heater
Heater
Tank Tank
Tank
Tank
Tankless
Tankless
Tankless
Tankless
Water
Water
Water
Water
HeaterHeater
Heater
Heater
GALLONS PER HOUR @ 90ºF
RGH-75F & RGH-100F
Model
Efficiency
Ke
H
Ho
But
7
RGH-75F
50G Tank
RGH-100F
RGH-75F
RGH-100F
EF .83 (Energy Factor) | UEF .88 (Uniform Energy Factor)
TE 95% (Thermal Efficiency)
Installation
Indoor / Floor Standing
Vent Run
3” PVC or Polypropylene
Up to 100ft, 6 Elbows Max (3” pipe) [3ft Deduction Per 45º Elbow] [5ft Deduction Per 90 º Elbow]
2” PVC or Polypropylene
Up to 50ft, 6 Elbows Max (2” pipe) [5ft Deduction Per 45º Elbow] [8ft Deduction Per 90 º Elbow]
Condensate Discharge
2GPH
Condensate pH Level
4 pH
Gas Type
Preset for NG / LP Conversion Kit Included
Unit Connections
Gas
1/2” or 3/4” Female NPT (3/4” by 1/2” Bushing Adapter Included)
Water
Electricity
3/4” Male NPT
Dedicated 120VAC, 60Hz w/3 Pronged 5 1/2 ft. Power Cord
Condensate
Gas Input Rate
Hourly
Gas Supply Pressure
NG / LP
1/2” Male NPT Connection
Max: 75,000 Btuh – Min: 37,500 Btuh
Max: 100,000 Btuh – Min: 50,000 Btuh
3.5” WC to 14” WC / 3.5” WC to 14” WC
Ignition System
Spark Ignition, No Pilot
Burner System
Gas Valve System
Air Ratio Negative Pressure
First Hour Output @ 77°F / 90°F
125 Gallons / 107 Gallons
Reserve Tank
160 Gallons / 130 Gallons
20 Gallons
Tank Material
Stainless Steel
Temperature Sensing
Inner Tank and Hot Outlet Discharge Pipe Sensors
Domestic Temperature Control
Domestic Temperature Settings Range
Thermostatic Mixing Valve - ASSE 1017 Rated
120°F Factory Preset / Adjust Knob 70°F to 145°F
Tank Storage Temperature Settings
Normal 127°F / Hotter 147°F / High Output 165°F
Unit Dimensions (D x H)
21” x 47”
Unit Weight
110 lbs
Safety Devices
T&P Valve, Vent Blockage APS, Flame Rod, Fan RPM Check, Eco Burner Plate (305º F), Eco Water Limit (194º F)
Optional Accessories
3” or 2” Horizontal Terminal, Concentric Venting Kit, Condensate Neutralizer Kit
FRONT VIEW
SIDE VIEW
TOP VIEW
2 7 2 D u c h a i n e B l v d , N e w B e d f o r d , M A 0 2 7 4 5 • M K T L I T-XX - 0 6 / 2 0 1 6 © H T P
In accordance with our company policy of ongoing product improvement, HTP Inc. reserves the right to make changes without prior notice. • All weights are approximate.
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