10
Part Number 550-110-772/0816
OSB
Series 2
Oil-Fired Steam Boilers –
Boiler Manual
5 Connect tankless heater piping, if used
Boiler
model
number
Heater
number
Intermittent
draw ratings
(GPM)
(
Note 2
)
Inlet and
outlet
tapping sizes
OSB-3
35-S-29
3.25
3/4”
OSB-4
35-S-29
3.50
3/4”
OSB-5
35-S-29
3.75
3/4”
OSB-6
35-S-29
4.00
3/4”
Notes:
1. To avoid supplying steam to system during summer tankless
operation, raise water level to one inch above normal water line.
2. Gallons of water per minute heated from 40°F to 140°F with
200°F boiler water temperature. Tested in accordance with
I=W=H Testing and Rating Standard for Indirect Tankless Water
Heaters Tested with Boilers.
Figure 10 Piping connections to tankless heater,
typical
Hot water can scald!
• Consumer Product Safety Commission and some
states recommend domestic hot water temperature
of 130 °F or less.
• When installing an automatic mixing valve,
selection and installation must comply with
valve manufacturer’s recommendations and
instructions.
• Water heated to a temperature suitable for clothes
washing, dish washing and other sanitizing needs
will scald and cause injury.
• Children and elderly, infirm or physically handicapped
persons are more likely to be injured by hot water.
Never leave them unattended in or near a bathtub,
shower or sink. Never allow small children to use a
hot water faucet or draw their own bath. If anyone
using hot water in the building fits this description,
or if state laws or local codes require certain water
temperatures at hot water faucets, take special
precautions:
• Install automatic mixing valve set according to those
standards.
• Use lowest practical temperature setting.
• Check water temperature immediately after first
heating cycle and after any adjustment.
Studies have indicated that dangerous bacteria can
form in potable water distribution systems if certain
minimum water temperatures are not maintained.
Contact local health department for more information.
Table 7
Tankless heater ratings
These single wall heat exchangers comply with
National Standard Plumbing Code provided that:
• Boiler water (including additives) is practically
nontoxic, having toxicity rating or class of 1, as listed
in Clinical Toxicology of Commercial Products.
• Boiler water pressure is limited to maximum 30 psig
by approved water relief valve.
Pipe tankless heater
1. Size piping no smaller than tankless heater inlet and outlet.
2. Following controls (furnished by others) must be installed:
a. Automatic mixing valve. See Figure 10. (Read
DANGER
statement at left.)
b. Flow regulating valve (see Figure 10). Size according to
intermittent draw of tankless heater. See Table 7. Follow
valve manufacturer’s instructions to install.
3. Additional anti-scald devices may be installed at each hot
water faucet, bath and shower outlet.
4. In hard water areas, soften cold domestic supply water to
heaters to prevent lime buildup.
Tankless heater ratings are based on 200°F boiler
water temperature. To get rated output, set tankless
heater control to 200°F. Control can be adjusted to
meet system hot water requirements.
