Honeywell C7195A Product Handbook

PRODUCT HANDBOOK

C7195A

WATER FLOW SENSOR

EN2R-- 9029 0101R2--NE

APPLICATION

The sensor is primarily designed to measure the Domestic
Hot Water (DHW) flow rate in domestic appliances as follows:

 Combi boiler

 Instanteneous Water Heater (IHW)

 Other systems such as applications where the

instanteneous DHW is produced from district heat
input.

Contents

General Page

Description 2........................................

Typical applications 3................................

Technical

Specifications 4.....................................

Electrical specifications 5.............................

Performance 6......................................

General considerations 7.............................

Dimensional drawing 8...............................

Various

Standards and approvals 9............................

Ordering information 10..............................

Associated products 11...............................

Subject to change without notice. Printed in the Netherlands.

EN2R-- 9029 0101R2--NE

2

DESCRIPTION

The C7195A is a mechanical water flow sensor (fig. 2.).
A turbine rotates with water flow. The turbine supports a
magnet which rotates in front of a Hall effect sensor.

This Hall effect sensor picks up the field of the magnet giving
a pulsed output.The output is directly proportional to the water
flow through the sensor.

This frequency output is easily processed by an electronic
controller which can then modulate the burner load (for
feed--forward loop) or simply open heat demand when the
flow reaches its defined minimum rate (electronic flow switch).

The sensor body is constructed from pressure and
temperature resistant plastic, with easy connections to
traditional pipes used in domestic appliances.

Feed forward control loop concept

See fig. 1.

Electronic
Controller

Flow rate input
for modulation

Cold water

Modulating control

Heat
supply

Temperature feed back
Option: Compensation
of tolerances and
hysteresis

_C

T7335

C7195A

Domestic
hot water

Fig. 1. Feed forward control loop concept

Fig. 2. Open view C7195

EN2R-- 9029 0101R2--NE

3

TYPICAL APPLICATIONS

The C7195A sensor is designed to measure the Domestic Hot
Water (DHW) flow rate in appliances as follows:

 Combi boiler (instanteneous or with small buffer)
 Instanteneous Water Heater (IWH), gas or electric

powered.

 Other systems where DHW is produced instantaneously

Modulation input
and/or electronic
flow switch

Modulating
control

Electronic
controller

Cold water

Temperature
feed back

Domestic hot
water

_C

_C

Fig. 3. Instanteneous combi boiler with feed forward or

feed back control loop

Temperature
feed back

Modulating
control

Modulation input
and/or electronic
flow switch

Electronic
controller

Cold water

Domestic
hot water

_C

Fig. 4. Instanteneous water heater with feed forward or

feed back control loop

For the above mentioned appliances, the sensor can be used in two specific ways:

1

Feed forward control loop

This is an advanced electronic control concept which
improves the DHW temperature control thanks to fast
reaction to flow rate changes. Indeed, before the
temperature sensor sees a change in hot side, the
electronic board can react promptly following the flow
measurement. A temperature sensor can be used
anyway as an option to compensate the tolerances and
hysteresis of the complete system.

2

Feedback control loop

This is the traditional electronic control, reacting to the
DHW temperature sensor output. A flow detector is
needed to detect when the DHW is tapped.
The C7195 water flow sensor can be used as an
electronic flow switch with the following advantages
over ON/OFF switches:

 Flexibility:

Electronically (auto)adjustable ON--point, for
instance depending on DHW temperature setting
point (to avoid ON/OFF recycling)

 Safety:

Can not be blocked in ON position (the turbine can
only turn with flow).

EN2R-- 9029 0101R2--NE

4

SPECIFICATIONS

Model

C7195A water flow sensor

Ambient temperature

--20 ... + 85 _C

Dimensions

See fig. 11.

Fluid

Water for sanitary use

Permissible fluid temperatur

0 ... 80 _C

Minimum operating flow rate

1.5 liter/minute or lower

Maximum operating flow rate

30 liter/minute

Mounting position

 The shaft of the rotor shall be horizontal ¦ 5_. See fig. 5.
 Provided the shaft of the rotor is horizontal, most

positions are acceptable, but the position as indicated in
fig. 6. is not recommended because water will remain in
the sensor when the installation is drained (frost risk).

All positions

Shaft axis

Shaft axis

5_

5_

5_

5_

Fig. 5. Mounting positions

Fig. 6. Not recommended mounting position

Measuring range

2.1 ... 30 liter/min

Nominal output frequency

f = Q x 7.0 (Q = flow rate in l/min; f = pulse signal in Hz) with
> 60 mm straight pipe on both sides.

Accuracy

¦ 10% of measurement over the measuring range.

Withstand pressure

When a water pressure of 17.5 bar is applied, no external
leakage shall be measured and no body damage shall occur.

Water connections

PF

1

/2” minimum 8 mm (4.4 threads)

Recommended tightening torque of inlet/outlet connections

2.5 ... 3.5 Nm

Pressure drop

0.15 bar or less at 10 l/min flow rate.
(Outlet pressure is at atmospheric pressure)

Endurance

Indicated value will shift < 5% under following conditions:

10000 hr at 10 l/min and 20 _C
7000 hr at 4 l/min and 45 _C

or

100,000 cycles ON/OFF at 10 l/min and 45 _C