Bell & Gossett HFT Expansion Tanks for Hydronic Heating Systems User Manual

Page 4

SERVICE INSTRUCTIONS

1. Check the expansion tank periodically for signs of

external leakage or corrosion. If any is found, the tank

must be replaced.

2. If a HVAC system is shut down for long periods or

emptied for any reason, it is necessary to follow the

following procedure:

a. Fill system.

b. Vent air from system (see system venting and

purging).

c. Bring system up to maximum operating temperature.

Before filling and starting the operation of a HVAC

system, a properly applied and sized pressure relief valve

must be installed and in good operating order.

During filling and start-up after servicing, the system

pressure should be closely monitored to ensure the

pressure does not exceed the pressure relief valve rating.

Consult the applicable pressure relief valve

manufacturer’s instructions as necessary.

3. If the system pressure is too high:

a. Check gauge calibration.

b. Check to see if expansion tank has lost its air charge.

NOTE: To check the expansion tank air pressure with a

tire gauge, either:

1. Disconnect the expansion tank from the system or,

2. Draw off system water until boiler pressure reads zero

or isolate the expansion tank from the system in domestic

water systems, and bleed pressure from the system. All
drains must be kept open during servicing of the

expansion tank. (Expansion tank must be empty of

expanded system water.)

3. Then check tank pressure with tire gauge.

c. Check for faulty fill valve operation. First, close manual

shutoff located before the fill-valve; then, draw system

pressure down to pre-set pressure open shut-off valve

and observe system for pressure build-up several hours

later. If pressure build up beyond set pressure is found,

replace fill valve following the manufacturer’s instruction.

d. Check for service water entering system from any other

source such as a defective tankless heater or indirect fired

water storage tank. Use same procedure as above after

shutting off possible water source. Replace defective

device if found following manufacturer’s instruction.

4. If pressure relief valve drips water:

a. First, check system pressure. If too high, follow

steps 3.a., b., c., and d. above.

b. If pressure relief valve continues to drip water,

even at reduced pressure, flush relief valve by quickly

raising lever several times. If drip continues, replace relief

valve following manufacturer’s instruction.

c. If multiple expansion tanks are installed in the system,

check pressure of each for possible air leaks. Be sure air

valve caps are on tight. Multiple tanks should be in the
same location.

WARNING: Improper use of air charging

valve during venting of air pressure from

tank will create a hazardous condition due

to the escape of high velocity gas and/or

liquid. Depress the center valve core stem, as with a tire

valve to slowly vent off gas pressure. Do not remove

the valve core until pressure in expansion tank has

reached zero. Failure to follow these instructions could

result in serious personal injury or death and property

damage.

WARNING: Signs of leakage or corrosion are

indications the tank may have failed.

Periodically check the expansion tank for

signs of external leakage or corrosion. If

found, the tank must be replaced. Failure to follow

these instructions may result in serious personal injury

or death and property damage.

WARNING: System fluid under pressure

and/or at high temperatures can be very

hazardous. Before servicing, reduce system

pressure to zero or isolate the vessel from

the system. Allow system to cool below 100

F and

above 35

F. Failure to follow this instruction may result

in serious personal injury and /or property damage.

Xylem Inc.

8200 N. Austin Avenue

Morton Grove, Illinois 60053

Phone: (847) 966-3700

Fax: (847) 965-8379

www.xyleminc.com/brands/bellgossett