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Model RA-28
Four-Chamber Tankless Electric
Water Heater
The Model RA-28 four-chamber tankless electric water heater
is designed for potable whole house, residential, applications
and commercial applications, such as specialty restaurants,
convenience stores, hotels and pet grooming shops. The
Model RA-28 is ideal as a back-up to solar and/or geothermal
passive heat recovery systems. A minimum of 200 AMP whole
house electrical service is recommended.
Model RA-28
Features
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Exterior
An endless supply of hot water
Heats water only when you need it
Very small & compact
Lightweight
Microprocessor controlled
Power sharing technology
Continuous venting
No moving parts
No restriction to flow
Self-diagnostics
Redundant safety devices
Heating chamber made of performance polymer
nylon material
Specifications
Interior
A tankless electric water heater shall be installed where indicated on the plans. The water heater shall provide an endless
supply of hot water on an as need basis. The water heater
shall be compact, lightweight, microprocessor controlled and
contain power sharing technology. A minimum of 200 AMP
whole house electrical service shall be provided. The tankless
electric water heater shall be a Watts Regulator Company
Model RA-28.
Approvals
UL, CSA, BOCA, SBCCI
"RA" designed models are for potable water heating applications only and are not warrantied for use in
space heating applications.
Watts product specifications in U.S. customary units and metric are approximate and are provided for reference only. For precise measurements, please contact Watts Technical Service. Watts reserves the right to change or modify product design, construction, specifications, or
materials without prior notice and without incurring any obligation to make such changes and modifications on Watts products previously or
subsequently sold.
Dimensions - Weight
Installation
Water Fittings
Inlet: 3/4" (20mm)
HOT*
Outlet: 3/4" (20mm)
Shut-Off
COLD
Mounting Holes
240 volt (AC)
BREAKERS
4 pairs of #10 cu
AWG w/ ground
A – 141/4" (362mm)
B – 161/8" (410mm)
or
30 A
WATTS
RA-28
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240 volt (AC)
BREAKERS
60 A
30 A
60 A
30 A
2 pairs
of
#10 cu
AWG w/ground
30 A
*T&P Relief Valve
Not Required
B
*Maximum system flow will depend on design & model selection
FLOW RATES, TEMPERATURE RISE & HEAT RATINGS
Model
Heat Output
Rating (BTU)
Max. GPM
for Temp. Rise
42° –120°
Max. GPM for
for Temp. Rise
50° –120°
Max. GPM for
for Temp. Rise
55° –120°
Max. GPM for
for Temp. Rise
60° –120°
Max. GPM for
for Temp. Rise
65° –120°
RA-28
95,560
2.5*
2.8
3.0
3.2
3.4
GPM = Gallons per minute (Flow Rate) Note: Increasing the temp. output from 120°F will reduce the max. GPM at the higher temp. but will not change the total GPM of tempered water (hot & cold mix)
*Note: This represents the maximum flow rate (gpm) to obtain 120°F water when the incoming water temperature is 42°F. ( a max "delta rise" at 2.5 gpm of 78°F)
MODEL SPECIFICATIONS
Model
Weight
RA-28
lbs
kg
23
10.4
Height
inches
mm
Width
inches
mm
Depth
inches
mm
153/4
153/4
61/4
159
400
400
Plumbing Fittings
inches
mm
3 4
/
20
Heating Elements
(Watts X No.)
Energy Factor
7000 x 4
0.99+
ELECTRICAL RATINGS **
Model
Maximum
Power Rating
(kw)
Voltage
Rating
(VAC)
Maximum
Current Rating
(AMPS)
Number of
Circuits Required
(two wire)
Number of Circuit
Breakers Required
(Double Pole)
Circuit
Breaker Size
(AMPS)
RA-28
28
240
116
4*
4*
30
**Optional wiring: Two, 2-wire, double-pol, 6 amp circuits (jumpers must be installed on control board for this option - check with manufacturer.)
Capacity
WATTS 240 VAC RATED, 240 VAC SERVICE
WATTS 240 VAC RATED, 208 VAC SERVICE
KW vs GPM For Various Inlet Temperatures To Deliver 120°F
3.5
3
Flow Rate (GPM)
Flow Rate (GPM)
KW vs GPM For Various Inlet Temperatures To Deliver 120°F
4.5
4
3.5
3
2.5
2
1.5
1
0.5
0
2.5
2
1.5
1
0.5
9
11
14
18
Power (KW)
22
28
0
6.75
8.25
10.5
13.5
Power (KW)
16.5
21
Key
44 F INLET
56 F INLET
72 F INLET
WATTS 208 VAC RATED, 208 VAC SERVICE
Flow Rate (GPM)
4
3.5
KW vs GPM For Various Inlet Temperatures To Deliver 120°F
3
2.5
2
1.5
1
0.5
0
5
7
10
14
Power (KW)
18
24
USA: 815 Chestnut St., No. Andover, MA 01845-6098; www.wattsreg.com
Canada: 5435 North Service Rd., Burlington, ONT. L7L 5H7; www.wattscda.com
ES-WHW-RA-28 0330
© Watts Regulator Company, 2003
Printed in U.S.A.