Hobart IB140 ML-110899 User Manual

– 6 –

WARNING:   PROVIDE A SCREEN OR BARRIER TO PREVENT PERSONAL INJURY IN AREAS
WHERE INADVERTENT PERSONNEL CONTACT WITH THE HOT VENT PIPE CAN OCCUR.

Models IB57 and IB140 are Category IV (positive flue
pressure, excessive condensate, and flue gas
temperature at the heater outlet approximately 330

°

F).

Models IB235 and IB290 are Category III (positive flue
pressure, not excessive condensate, and flue gas
temperature at the heater outlet approximately
530

°

F). The vent outlet on the booster heater is  3

inches in diameter.  Models IB57 and IB140 require
3 inch minimum vent pipe throughout.  Models IB235
and IB290 require 4 inch minimum vent pipe; the 3
inch adjustable vent pipe elbow and the 3 inch to 4
inch vent pipe adapter (provided on IB235 and IB290)
are to be installed at the vent outlet of the booster
heater (Fig. 1). On all models, 

1

/

4

 inch per foot minimum

incline must be maintained.

Vent piping must be one of the types mentioned in this manual and must be properly installed according
to the vent pipe manufacturer's instructions.  Each vent joint must be properly sealed and secured so
it stays in place.

Per the National Fuel Gas Code, ANSI Z223.1, the heater must be vented in one of three ways:

1. Into the exhaust system (Fig. 2).  The vent pipe must not penetrate the filter.  When the heater is

vented into the exhaust system, an electrical interlock must be provided (by others) to allow the flow
of gas to the booster heater burner ONLY when the exhaust system is functioning.  Refer to APS1
and APS2 on the wiring diagram in the control box accessed by removing the left side panel (also
refer to pages 12 and 13).

2. Through the sidewall, or the ceiling (Fig. 3).  Type B-1 vent pipe (4 inch minimum diameter for IB57

and IB140, 5 inch minimum diameter for IB235 and IB290) may be used when venting vertically,
provided a one inch minimum clearance to combustible construction is maintained and the
termination above the roof uses a listed wind cap.

3. Freely vented into the room or space where it is installed (Fig. 4), provided that:

a. A mechanical exhaust system is present in the kitchen,

b. The flue outlet of the booster water heater is at least 36 inches vertically and 6 inches

horizontally distant from any surface other than the booster / or dishwasher, and

c. Any or all gas fired equipment is installed so the total BTU input rating of the unvented gas

appliance(s) divided by the total cubic feet of the room area (including any areas adjacent that
cannot be closed off) does not exceed 20 BTU per hour per cubic foot.

Water In

Water Out

Gas

Vent

Temperature and 
Pressure Relief Valve

PL-53440

3 to 4 Inch
Adapter 

3 Inch Elbow

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