Bell & Gossett HFT User Manual

HFT Expansion Tanks for

Hydronic Heating Systems

INSTALLER: PLEASE LEAVE THIS MANUAL FOR THE OWNER’S USE.

INSTRUCTION MANUAL

V1000002B

WARNING: California proposition 65
warning! This product contains chemicals
known to the state of California to cause
cancer and birth defects or other reproduc­tive harm.

Safety Instruction

This safety alert symbol will be used in this
manual to draw attention to safety related

instructions. When used, the safety alert
symbol means ATTENTION! BECOME ALERT! YOUR
SAFETY IS INVOLVED! FAILURE TO FOLLOW THE
INSTRUCTIONS MAY RESULT IN A SAFETY HAZARD.

WARNING: Explosion or Rupture Hazard.

A relief valve must be installed to prevent

pressure in excess of local code requirement

or maximum working pressure

designated in the Product Manual, whichever is less.
Do not expose Product to freezing temperatures or
temperatures in excess of 240°F. Do not adjust the
pre-charge or re-charge this Product except for any
adjustments at the time of the initial installation,
especially if Product is corroded, damaged or with
diminished integrity. Adjustments to pre-charge must
be done at ambient temperature only. Failure to
properly size the Product or follow these instructions
may result in excessive strain on the system and may
lead to Product failure, serious or fatal personal injury,
leakage, and/or property damage.

WARNING: Read carefully the product
installation, operating and maintenance
instructions. Failure to follow the instruc-

tions and warnings in the manual may result
in serious or fatal injury and/or property damage, and
will void the product warranty. This product must be
installed by a qualified professional. Follow all
applicable local and state codes and regulations, in the
absence of such codes, follow the current editions of
the National Plumbing Code and National Electric
Code, as applicable.

DESCRIPTION

When water is heated, it expands. Provision must be
made for this expansion in a closed hot water heating
system. The Bell & Gossett Series HFT pre-charged
diaphragm tank stores the expanded hot water and
returns air-free water to the system when the
temperature drops.

OPERATIONAL LIMITS

Maximum Operating Pressure: 100 PSI.
Maximum Operating Temperature: 240ºF.

WARNING: This product, like most products

under pressure, may over time corrode,

weaken and burst or explode, causing

serious or fatal personal injury, leaking or
flooding and/or property damage. To minimize risk, a

licensed professional must install and periodically
inspect and service the Product. A drip pan connected
to an adequate drain must be installed if leaking or
flooding could cause property damage. Do not locate in
an area where leaking could cause property damage.

INSTALLATION INSTRUCTIONS

A. PRE-INSTALLATION

1. Visually inspect expansion tank and check for damage
prior to installation.

WARNING: If the expansion tank is
damaged, it must be replaced. Failure to
follow this instruction may result in serious
personal injury or death and property
damage.

4. If an HFT tank is used with a volume smaller than
required to accommodate expanded water from a cold
start to maximum operating temperature, some
preliminary expanded water must be drawn from system
to bring operating pressure down to normal level. Drain
water from boiler until pressure reads at maximum range
(25 PSIG).

Generally, a smaller tank will cause a higher system
pressure than desired when system reaches operating
temperatures. This condition is normally referred to as a
Summer/Winter installation (boiler is always at
temperature). Tank should be tagged to denote this.

2. Bell & Gossett Series HFT diaphragm tanks are factory
pre-charged to 12 PSI. Adjust pre-charge to equal system
fill pressure.

3. Replace and tighten cap on air fitting.

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.

B. INSTALLATION

The Bell & Gossett Series HFT pre-charged diaphragm
tank may be installed into a tee or any other suitable
tapping anywhere in the hot water heating system.

WARNING: A residential tank must be

installed vertically or horizontally. Do not

install on a dead end pipe or in an overhead

joist space.

An ideal HFT tank installation is to screw it into the
bottom of a Bell & Gossett air separator (IAS, EAS or
EASB-JR) located on the supply line. This combination
offers both control of expanded water and continuous
automatic air removal from the system.

After installing Bell & Gossett HFT tanks on the system:

1. Fill system.

2. Vent air from system.

3. Bring system up to maximum operating temperature.

WARNING: This expansion tank, as all
expansion tanks, will eventually leak. Do not
install without adequate drainage provisions
where water flow will cause damage.

WARNING: RUPTURE OR EXPLOSION
HAZARD Like most pressurized tanks, this
tank can over time corrode, weaken, and

burst or explode. Failure to follow this
instruction may result in serious personal injury or death
and property damage.

WARNING: CHLORINE & AGGRESSIVE

WATER HAZARD The water quality can

significantly influence the life of your

product. You should test for corrosive

elements, acidity, total solids, and other relevant
contaminants, including chlorine and treat your water
appropriately to insure satisfactory performance and
prevent premature failure. Failure to follow this
instruction may result in serious personal injury or
death and property damage.

SYSTEM VENTING AND PURGING

After initial venting and purging of air from the system,
more air will be released from the water as it is heated.
Therefore, it is recommended that a Bell & Gossett air
separator be installed on the main.

If the system has multiple loops or zones, the supply
water for all loops and zones must pass through the air
separator for complete and continuous air removal. In
case the piping arrangement does not permit the
installation of a single air separator on the main, air
separators should be installed on each loop or zone. In
this event, only one expansion tank is required for the

system.

Shut Off Valve

C.W. Fill

B&G Relief
Valve

B&G Pressure
Reducing Valve

Flow

Air Separator

Figure 2

B&G Booster

Diaphragm Type Expansion
Tank “HFT”

B&G Flow
Control Valve

To System

Boiler

Return

OPERATING INSTRUCTIONS

1. The expansion tank is typically installed in the bottom
of an air separator. Its sealed-in air pre-charge prevents
water from entering the tank until the system pressure
exceeds the pre-charge pressure

2. As the water temperature rises, expanded water enters
the expansion tank’s water reservoir. The pre-charge air
chamber absorbs the pressure increase, keeping system
pressures below the relief valve setting.

3. As water temperature decreases the pressure in the
air chamber forces water back into the system until the
expansion tank is empty.

The selection, application, installation and servicing of
this product should be performed by a qualified
professional within all applicable safety and code
requirements.

Optional Side
Outlet Boiler
Connection

Air

Cushion

Air

Cushion

Air

Cushion

Air

Cushion

Air

Cushion

Models HFT-15

thru HFT-90

Air

Cushion

Models HFT-30V

thru HFT-160V

SERVICE INSTRUCTIONS

1. Check the expansion tank periodically for signs of
external leakage or corrosion. If any is found, the tank
must be replaced.

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.

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.

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.

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.

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 100o F and
above 35o F. Failure to follow this instruction may result
in serious personal injury and /or property damage.

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.

Xylem Inc.

8200 N. Austin Avenue
Morton Grove, Illinois 60053
Phone: [phone]
Fax: [phone]
www.xyleminc.com/brands/bellgossett

Bell & Gossett is a trademark of Xylem Inc. or one of its subsidiaries.
© 2012 Xylem Inc. V1000002B May 2012

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.