CGi Manual

Part Number 550-142-302/0520
CGi
SERIES 4 — GAS-FIRED WATER BOILER — Boiler Manual
47
10b
Service & maintenance – annual start-up (cont.)
❏ Check/test . . .
Gas piping
1. Sniff near floor and around boiler area for any indication
of a gas leak.
2.
Test gas piping using bubble test, per Section 5 of this
manual, if there is any indication of a leak.
Cold fill and operating pressures
1. While the system is cold, note the pressure reading on
the boiler pressure/temperature gauge. Verify that cold fill
pressure is correct.
2.
Watch the pressure as the boiler and system heat up to
ensure pressure rise is normal. Too high a rise would indicate
a waterlogged or undersized expansion tank.
Air vents and air elimination
1. Inspect automatic air vents (if used). Also inspect air separa-
tors to ensure they are operational.
2. The cap must be unscrewed one turn to allow air to escape.
3. See
Figure 34. If the air vent is leaking, remove cap A and
briefly push valve B and then release to clean the valve seat.
4. Replace cap
A by twisting all the way onto valve B and then
unscrewing one turn.
Figure 34 Automatic air vent, typical
Limit controls and cutoffs
1. Inspect and test the boiler limit control. Verify operation by
turning control set point below boiler temperature. Boiler
should cycle off. Return dial to original setting.
2. Inspect and test additional limit controls or low water cutoffs
installed on system.
Expansion tank
1. Expansion tanks provide space for water to move in an out
as the heating system water expands due to temperature
increase or contracts as the water cools. Tanks may be open,
closed or diaphragm or bladder type. See Section
4 of this
manual for suggested best location of expansion tanks and
air eliminators.
Open-type — located above highest radiator or
baseboard unit, usually in the attic or closet. Has a
gauge glass and overflow pipe to a drain.
Closed-type — welded gas tight and located above
boiler. Tank is partially filled with water, leaving an
air cushion for expansion.
• Make sure this type of tank is fitted with a
tank
fitting
, such as the B & G Tank-Trol or Taco Ta c o -
Tro l. This fitting reduces gravity circulation of
air-saturated tank water back to the system and
prevents the air from bubbling up through the
water as it returns from the system.
•
Do not use automatic air vents in systems
with closed-type tanks.
The air will escape
from the system instead of returning to the tank.
Eventually, the tank will waterlog and no longer
control pressurization. The boiler relief valve will
weep frequently.
Diaphragm- or bladder-type — welded gas tight
with a rubber membrane to separate the tank pres-
surizing air and the water. May be located at any point
in the system, but most often found near the boiler.
• Systems with this type of expansion tank require
at least one
automatic air vent, preferably lo-
cated on top of an air eliminator, as shown in
examples in manual Section
4.
2. If relief valve has tended to weep frequently, the
expansion tank may be waterlogged or undersized.
Closed-type tank — tank is most likely waterlogged.
Install a tank fitting if not already installed. Then
check fill level per fitting manufacturer’s instruc-
tions. If fill level is correct, check tank size against
manufacturer’s instructions. Replace with a larger
tank if necessary.
Diaphragm- or bladder-type — first, check tank
size to be sure it is large enough for the system. If
size is too small, add additional tank(s) as necessary
to provide sufficient expansion. If tank size is large
enough, remove tank from system and check charge
pressure (usually 12 psig for residential applications).
If tank won’t hold pressure, membrane has been
damaged. Replace tank.