American Water Heater ATO-305-N, GTS-305-PI, GTS-305-NE, GTS-705-NI, ATI-705-P User Manual
...
Tankless Water Heater
System Design Manual
Plumbing schematics for single
and multiple tankless water
heaters in use with domestic
systems, recirculation, and
storage tanks.
PRINTED 0708 186965-000
Table of Contents
Certifications..................................................................................3
Water Quality and Scale ................................................................4
Pump Sizing for Circulation..........................................................5
Tank Water Heaters in a Circulation Loop
Additional Guidelines
Pump Sizing for Storage Tank Applications
Pressure Loss Curves
Domestic Hot Water - Standard Installation
1 Water Heater
2 Water Heaters (WH3 Water Heaters (WH4 Water Heaters (WH5 Water Heaters (WH6 Water Heaters (WH-
Domestic Hot Water with Optional Freeze Protection
on Outdoor Models
1 Water Heater
2 Water Heaters (WH-23 Water Heaters (WH-36 Water Heaters (WH-6-
Domestic Hot Water with Circulation Systems
1 Water Heater - Preferred (WH1 Water Heater - Optional (WH-1-R)
2 Water Heaters - Preferred (WH-2-RGE)
2 Water Heaters - Optional (WH3 Water Heaters - Preferred (WH-3-RGE)
6 Water Heaters - Preferred (WH-6-RGE)
Domestic Hot Water with Backup Storage Tanks
1 Water Heater
1 Water Heater with Circulation (WH2 Water Heaters (WH-22 Water Heater with Circulation (WH3 Water Heaters (WH-33 Water Heater with Circulation (WH6 Water Heaters (WH-66 Water Heater with Circulation (WH-
Maintenance Procedure
Scale Flush
(WH-1)....................................................................9
(WH-1-D)..............................................................15
(WH-1-B)..............................................................25
Procedure (M-1-F
....................................................................6
2)................................................................10
3)................................................................11
4)................................................................12
5)................................................................13
6)................................................................14
..................................................................8
D)............................................................16
D)............................................................17
D)............................................................18
1-RGE).......................................19
..............................................20
2-R)............................................22
1-B-R)................................. 26
B) ............................................................27
2-B-R)................................. 28
B) ............................................................29
3-B-R)................................. 30
B) ............................................................31
6-B-R)................................. 32
) .....................................................33
...................................6
...............................7
.....................................21
.....................................23
.....................................24
2
Approvals
ATI-305-N GTS-305-NI GT-305-NI
ATI-305-P GTS-305-PI GT-305-PI
ATO-305-N GTS-305-NE GT-305-NE
ATO-305-P GTS-305-PE GT-305-PE
ATI-505-N GTS-505-NI GT-505-NI
ATI-505-P GTS-505-PI GT-505-PI
ATO-505-N GTS-505-NE GT-505-NE
ATO-505-P GTS-505-PE GT-505-PE
ATI-705-N GTS-705-NI GT-705-NI
ATI-705-P GTS-705-PI GT-705-PI
ATO-705-N GTS-705-NE GT-705-NE
ATO-705-P GTS-705-PE GT-705-PE
ATI-705A-N GTS-705-NIA AGT-705-NI
ATI-705A-P GTS-705-PIA AGT-705-PI
ATO-705A-N GTS-705-NEA AGT-705-NE
ATO-705A-P GTS-705-PEA AGT-705-PE
The models listed in this manual have received the following certifications except where noted:
Certified to applicable U.S.
standards for appliances using
gas or other petroleum fuel.
EFFICIENCY
HEATING
CERTIFIED
Energy efficiency certified by
Gas Appliance Manufacturers
Association (GAMA),
www.gamanet.org
Certified to applicable Canadian
standards for appliances using
Met the California Energy
Commission (CEC) standards
gas or other petroleum fuel.
U
P
C
Certified by the Uniform
Plumbing Code (UPC)
Certified by National Sanitation
Foundation (NSF), www.nsf.org
(indoor models must use the
Approved by the Commonwealth
of Massachusetts
Received New York City’s
Material and Equipment
Acceptance (MEA)
NSF approved top guard)
3
Water Quality and Scale
A complete water analysis and an understanding of system requirements are needed to protect the
tankless water heaters and water heating systems from scale. Water analysis shows whether
water is hard or soft. Hard water, unless treated, will cause scaling or liming of the heat exchanger.
The rate of scaling increases with temperature and usage because calcium carbonate and other
scaling compounds lose solubility (fallout of solution) at higher temperatures. For example, for every
20°F over 140°F, the rate of scale increases by a factor of 2 (See figure below). Reference target
water quality levels found in the operation / installation manual and consider water treatment if these
levels are exceeded. *
LIME DEPO SITED, lb/yr
210
180
150
120
90
60
30
BASED ON 10 grains/gal HARDNESS
*
180°F
170°F
160°F
150°F
140°F
0
300
0
900
1500
2100
2700
3300
120°F
3900
WATER USA G E , g al/day
*Source 2003 ASHRAE Handbook HVAC Applications
4
Pump Sizing for Circulation
1. Use the chart below or one appropriate for your conditions to determine the heat loss in the length of
the hot water supply and return piping. For example, 100 ft of 1-1/2 in bare copper tubing results in a
heat loss of 5300 Btu/h.
Approximate Heat Loss from Piping at 140 ºF Inlet, 70 ºF Ambient *
Nominal Size, in. Bare Copper Tubing,
Btu/h-ft
2/1-2
* Source: 2003 ASHRAE Handbook HVAC Applications
2. Determine the acceptable temperature drop at the last fixture in the loop. For example, if the supply
temperature from the water heater is 120 ºF (49 ºC) and an acceptable temperature at the last fixture
is 100 ºF (38 ºC) then the acceptable temperature drop is 20 ºF (7 ºC).
3. Calculate the required pump flow rate using the following formula:
FLOW RATE (gpm) = HEAT LOSS (BTU / h)
500 X ACCEPTABLE TEMPERATURE DROP (ºF )
1/2 in. Glass Fiber Insulated
Copper Tubing, Btu/h-ft
7.71 03 4/3
3.02 83 1
4.32 54 4/1-1
4.52 35 2/1-1
6.92 66 2
8.33 08
5.93 49 3
4.84 021 4
4. Based on the above calculations select a pump for the type of circulation system you will be utilizing:
A). Preferred Method (reference drawing WH-1-RGE) - Reference pump manufacturers flow vs.
pressure specifications to select a pump that can provide the flow rate calculated above
while overcoming the pressure loss through:
• Tank water heater (reference manufacturer’s information)
• All building supply and return plumbing in the circulation loop (reference
local plumbling codes, standards, or practices)
B). Optional Method (WH-1-R) - Reference pump manufacturers flow vs. pressure specifications
to select a pump that can provide 3 gpm of flow or the flow rate calculated above, whichever
is greater, while overcoming the pressure loss through:
• Tankless water heater (reference flow
being used)
• Optional storage tank (reference manufacturer’s information)
• All building supply and return plumbing in the circulation loop (reference
local plumbling codes, standards, or practices)
NOTE: Only use pumps of brass or stainless steel construction. Do not use pumps of iron
construction as they will oxidize and clog the inlet filter on the appliance.
vs. pressure curve of the model
5
Tank Water Heaters in a Circulation Loop
The following applies when using a tank water heater (gas or electric) to provide heat for a circulation
loop. Drawing WH-1-RGE is an example.
The heat output of the tank must be equal to or greater than the calculated circulation loop heat loss.
(Reference page 6, Step 1 on calculating heat loss).
Electric Tank Water Heater
Since the input and output are the same for an electric tank water heater, this can be expressed as:
Electric Tank Input (Kw) >
3413
(1 Kilowatt = 3,413 BTU)
Gas Tank Water Heater
When using a gas style water heater, the efficiency of the tank must be taken into account.
Available Btu output = (Btu input of tank) x (efficiency) >
Example:
30,000 Btu input gas tank
0.62 Efficiency
30,000 x .62 = 18,600 available Btu output
Circulation loop heat loss (Btu/h)
Circulation loop heat loss (Btu/h)
Additional Guidelines
Tankless water heaters not recovering a storage tank: In applications involving a commercial
dishwasher, a hot water circulation loop feeding the dishwasher is required.
Tankless water heater recovering a storage tank: In applications involving a commercial dishwasher, a
hot water circulation loop feeding the dishwasher may be required depending on the distance between
the dishwasher and the storage tank. Refer to local codes when determining the need for circulation
loops to dishwashers.
6
Pump Sizing for Storage Tank Application
The following applies when using tankless water heaters to recover a storage tank.
Drawing WH-1-B is an example.
Tankless water heaters have a pressure loss which must be considered in the system design.
Reference the pressure loss curve for the heater model being used to determine the pump size for the
desired recovery rate.
For recommended pump sizes use the table below. Additional pressure losses in plumbing between the
Heater(s) and the storage tank must also be taken into consideration.
The specified pump size is to provide maximum recovery of the storage tank. A smaller pump size may
be used, but could result in longer recovery time of the tank. Please contact the Tech Services department
with any questions on pump sizing.
NOTE: Only use pumps of brass or stainl ess steel construction. Do not use pumps of iron
construction as they will oxidize and clog
Pump Flow Requirements
Number of
Tankless
705/505
Water Heaters
the inlet filter on the appliance.
305
1 6 gpm @ 30' head 5 gpm @ 25' head
2 12 gpm @ 30' head 10 gpm @ 25' head
3 18 gpm @ 30' head 15 gpm @ 25' head
4 24 gpm @ 30' head 20 gpm @ 25' head
5 30 gpm @ 30' head 25 gpm @ 25' head
6 36 gpm @ 30' head 30 gpm @ 25' head
7 42 gpm @ 30' head 35 gpm @ 25' head
8 48 gpm @ 30' head 40 gpm @ 25' head
9 54 gpm @ 30' head 45 gpm @ 25' head
10 60 gpm @ 30' head 50 gpm @ 25' head
11 66 gpm @ 30' head 55 gpm @ 25' head
12 72 gpm @ 30' head 60 gpm @ 25' head
13 78 gpm @ 30' head 65 gpm @ 25' head
14 84 gpm @ 30' head 70 gpm @ 25' head
15 90 gpm @ 30' head 75 gpm @ 25' head
7
Pressure Loss Curves
Pressure Loss (ft head)
705
505
305i
60.0
50.0
40.0
30.0
20.0
10.0
0.0
305e
45.0
40.0
35.0
30.0
25.0
20.0
15.0
10.0
5.0
0.0
Water Flow (gpm)
01234567891011
Pressure Loss (psi)
8
Pressure Regulator
Circulating Pump
Solenoid Valve
Boiler Drain Valv e
S
Key
QTY
Tankless
Equi pment List
1
Tankless
Water Heaters
Tankless
3/4" Ball Valve
3/4" U nion
e
in
ly
L
p
ly
p
p
u
p
S
u
s
S
a
r
G
e
t
a
W
d
l
o
C
"
4
/
3
Pressure Relief Valve
Check Valve
Water Heater
1 Tankless Water Heater
Preferred Piping Installation
Domestic Hot Water - Standard Installation
3/4" Hot Water Su pply Line
WH-1
Drawing Number:
as a replacement for professional engineering project drawings. This
drawing is not intended to describe a complete system. It is up to the
This is not an engineering drawing; it is intended only as a guide and not
contractor or engineer to determine the necessary components and
configuration of the particular system to be installed. The drawing does
not imply compliance with local building code requirements. It is the
responsibility of the engineer or contractor to ensure that the installation is
in accordance with all local building codes. Confer with local building
officials before installation.
June 11, 2007
Drawing Date:
9
Pressure Regulator
Circulating Pump
Solenoid Valve
Boiler Drain Valv e
S
Key
Tankless
Equipment List QTY
Tankless 2
Water Heaters
Tankless
Water Heater
Tankless
Water Heater
Electronic Connection *
electronic connection details.
* Refer to Tankless Accessories
and Model Applicability for
Sub 1
Primary
Gas Supply
Cold Water Supply Line
2 Tankless Water Heaters
Preferred Piping Installation
Domestic Hot Water - Standard Installation
3/4" Ball Valve
3/4" U nion
Pressure Relief Valve
Check Valve
10
Hot Water Supply Line
Drawing Number:
as a replacement for professional engineering project drawings. This
drawing is not intended to describe a complete system. It is up to the
This is not an engineering drawing; it is intended only as a guide and not
WH-2
contractor or engineer to determine the necessary components and
configuration of the particular system to be installed. The drawing does
not imply compliance with local building code requirements. It is the
responsibility of the engineer or contractor to ensure that the installation is
in accordance with all local building codes. Confer with local building
officials before installation.
February 27, 2008
Drawing Date:
Gas Supply
Pressure Regulator
Circulating Pump
Solenoid Valve
Boiler Drain Valv e
S
Key
Tankless
Equipment List QTY
Tankless 3
Water Heaters
Tankless
Water Heater
Tankless
Water Heater
Electronic Connection *
electronic connection details.
* Refer to Tankless Accessories
and Model Applicability for
Sub 1 Sub 2Primary
Cold Water Supply Line
3 Tankless Water Heaters
Preferred Piping Installation
3/4" Ball Valve
3/4" U nion
Check Valve
Pressure Relief Valve
Tankless
Water Heater
11
Domestic Hot Water - Standard Installation
Hot Water Supply Line
Drawing Number:
as a replacement for professional engineering project drawings. This
drawing is not intended to describe a complete system. It is up to the
This is not an engineering drawing; it is intended only as a guide and not
WH-3
contractor or engineer to determine the necessary components and
configuration of the particular system to be installed. The drawing does
not imply compliance with local building code requirements. It is the
responsibility of the engineer or contractor to ensure that the installation is
in accordance with all local building codes. Confer with local building
officials before installation.
February 27, 2008
Drawing Date:
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