Danfoss mixing module FH-MJA Installation guide

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The FH-MJA mixing module is designed for con-

nection to the boiler loop of low temperature

heating systems, e.g. underﬂoor and wall heating

systems.

FH-MJA is a low-noise, compact mixing module,

designed for installation in the manifold cabinet.

For multi-family houses the feed temperature can

be selected individually for each apartment.

1. High eﬃciency circulator pump

2. Floor heating loop feed side

3. Floor heating loop return side

4. Control valve with mechanical actuator (20-55 °C)

5. Presetting knob for control valve

6. Bypass valve (keep closed)

7. Integrated check valve

8. Boiler loop feed side

9. Boiler loop return side

10. Ball valve boiler loop feed side

11. Ball valve boiler loop return side

12. Control knob pump

13. Automatic air vent

14. Safety temperature thermostat

15. Bleeding valve

16. Filling valve

Application

Instruction

Installation and operation manual

for mixing module FH-MJA

Danfoss HES VI.UL.R1.02 © Danfoss 06/2009 1

Function

Floor heating loop

The pump (1) circulates the water through •

the ﬂoor heating feed connection and the

ﬂoor heating loops to the ﬂoor heating return

connection.

Mixing

When the control valve (4) opens, boiler loop •

feed water (8) is mixed to the ﬂoor heating

loop feed side and the same amount of water is

returned from the ﬂoor heating return side (3)

to the boiler loop return side (9).

The control valve adjusts the quantity of water •

coming from the boiler loop to control the

desired ﬂoor heating feed temperature.

Control and safety device

The mixing unit has both integrated, a feed •

temperature control (setting range 20-55 °C)

and a safety temperature device (20-90 °C). In

the unlikely case of an overtemperature situ-

ation, the safety temperature device switches

the pump oﬀ.

Please consider, that the setting of the safety •

device must be minimum 8° higher, than the

setting of the wished feed temperature.

The wished feed temperature is set by the •

mechanical feed thermostat, which setting

range is 1-9 (= 20-55 °C).

Thermostat display Feed temperature

1 20 °C

2 26 °C

3 30 °C

4 34 °C

5 38 °C

6 42 °C

7 46 °C

8 50 °C

9 55 °C

Control

18 16

17

8 10 14 2

5 4 7

1

12

6

15

9 11 3

13

Instruction Installation and operation manual for mixing module FH-MJA

2 VI.UL.R1.02 © Danfoss 06/2009 Danfoss HES

Wiring diagram

Feed safety temperature

thermostat (20-90 °C)

Presetting knob for control valve 5

With this knob you can adjust the resistance •

value of the FH-MJA control valve.

This controls the maximum amount of water •

which enters the FH-MJA from the boiler loop

with the control valve fully open.

Use this knob to adapt the mixing unit to the •

heating system and to optimize the control

characteristics.

It is especially important to adjust the presetting •

knob correctly if several Floortec stations are

attached to one boiler loop. This ensures that

all stations will get a suﬃcient amount of water

from the boiler loop.

Setting:

Use the diagram below for setting the presetting •

knob correctly. It shows the diﬀerential pressure

vs. ﬂow rate for the boiler side of the mixing

unit including control valve.

First, determine the amount of boiler water •

needed during peak heat demand. Using the

amount of water and the diﬀerential pressure

available during peak heat demand, you ﬁnd

the appropriate setting of the knob in the

diagram.

Close the presetting knob completely (turn •

right until full stop). Open counter clockwise the

number of turns shown in the diagram.

kPa

300

100

10

1

0,03 0,1

1 3 m

3

/h

0,75 1 1,5 2 3 4

Bypass for step-down control

If the bypass valve (6) is opened, a small quantity •

of boiler feed water will run constantly through

the mixing module. The unit is shipped with the

bypass valve closed. We recommend to keep

this valve closed.

Fill and drain valves

If you ﬁll the system from the ﬁll valve (12), the •

check valve (7) will close. In this way, the water

will ﬂow through the ﬂoor heating loops and

not through the mixing module. Excess water

drains through the drain valve of the manifold’s

return.

Function

1. Circulator

2. Feed for ﬂoor heating circuit

3. Return for ﬂoor heating circuit

4. Control valve

5. Presetting knob for control valve

6. Adjustable bypass valve

7. Check valve for ﬁlling of ﬂoor

heating loops

8. Boiler feed connection

9. Boiler return connection

10. Ball valve of boiler feed connection

11. Ball valve of boiler return

connection

12. Fill valve

13. Drain valve

14. Sensor for ﬂoor heating feed

temperature

15. Sensor for ﬂoor heating return

temperature

16. Sensor for safety temperature

17. Sensor for boiler feed

temperature

18. Space for calorimeter dip tube

Grommet Mounting bracket

[large hole spacing]

Spacer 20 mm

Spacer 22 mm

Spacer 5 mm

Grommet

Instruction Installation and operation manual for mixing module FH-MJA

Danfoss HES VI.UL.R1.02 © Danfoss 06/2009 3

Presetting knob for control valve

The control valve is equipped with a presetting •

knob 5, with which the maximum amount of

water from the boiler loop can be reduced.

The unit is shipped with the presetting knob

completely open.

Bypass for step-down control

If the bypass valve 6 is opened, a small quantity •

of boiler feed water will run constantly through

the mixing module. This is necessary for a

step-down control, which derives its outside

temperature information from the boiler feed

temperature. The unit is shipped with the by-

pass valve opened 1/2 turn.

Fill and drain valves

If you ﬁll the system from the ﬁll valve 12, the •

check valve 7 will close. In this way, the water

will ﬂow through the ﬂoor heating loops and

not through the mixing module. Excess water

drains through the drain valve 13.

Sensor positions integrated in the base module

Floor heating feed temperature 14.•

Floor heating return temperature 15.•

Safety temperature 16.•

Boiler feed temperature 17.•

Dip tube for calorimeter sensor 18.•

Installation options

The FH-MJA station can be installed in two dif-

ferent ways. The mounting hardware required for

both ways is included with the station.

Parallel installation:• the ﬂoor heating pipes

are guided parallel to the wall. At the place

were the pipes leave the ﬂoor, they have to be

fastened to ensure that they come straight up

into the manifold.

Angled installation:• in this case the FH-MJA

unit is installed at an angle of approximately

eight degrees, so that the ﬂoor heating pipes

are guided to the wall at that angle and enter

the ﬂoor directly at the wall.

The part of the grommets facing the wall has to have its thickest part facing downward.

On delivery, the FH-MJA is attached to a wooden

base. Re-use the hardware for mounting of the

mixing module.

The picture below shows the parallel installation

with the mounting hardware attached accord-

ingly.

Use the 20 mm spacer at the upper mounting •

eyelet.

Use the 22 mm and the 5 mm spacer at the •

lower mounting eyelet.

Turn the rubber grommets in such a way that •

they are parallel to the wall.

Fix the manifold by attaching the side of the •

mounting bracket with the large hole spacing

to the manifold.

Parallel installation

Grommet Mounting bracket

[large hole spacing]

Spacer 20 mm

Spacer 22 mm

Spacer 5 mm

Grommet

Instruction Installation and operation manual for mixing module FH-MJA

4 VI.UL.R1.02 © Danfoss 06/2009 Danfoss HES

Start-up

Preconditions

The system boiler loop must be ﬁlled properly.•

The ﬂoor heating system must be ﬁlled properly.•

A suitable control for the mixing module must •

be in place.

The bypass valve must be closed.•

The presetting knob must be set correctly for •

the system.

The heating loops must be open.•

The connection to the boiler loop (ball valves 10 •

and 11) must be open.

Start-up

Switch on the pump by turning the pump’s •

control knob to step 7.

The ﬁrst heating up of a ﬂoor heating system •

can take a long time since the ﬂoor can absorb

a lot of heat. Additionally, in new constructions,

the high humidity in the slab can delay the heat

up process.

Caution! Operation without the integrated control •

can result in overheating of the underﬂoor heating

system.

The picture below shows the angled installation

with the mounting hardware attached accordingly.

Use the 20 mm and the 22 mm spacer at the •

upper mounting eyelet.

Use the 5 mm spacer at the lower mounting •

eyelet.

Turn the rubber grommets in such a way that •

they are parallel to the wall.

Fix the manifold by attaching the side of the •

mounting bracket with the small hole spacing

to the manifold.

Angled installation

Attach the manifold (see previous chapter).•

Install the station directly on the wall or in a suf-•

ﬁciently large cabinet.

Use the two eyelets of the base module for •

installation.

Use the spacers, the grommets and the washers.•

In addition, attach the manifolds before mount-•

ing the module in a cabinet.

If you purchased the base

module without manifold

Avoid any metal contact between the base •

module and the wall.

Avoid any metal contact between the manifold •

and the wall.

Use rubber grommets at all mounting points on •

both sides to avoid metal contact between the

mounting screws and base module or manifold

(the rubber grommets and washers for the

mounting eyelets of the FH-MJA are supplied

with the station).

Important advice for

avoiding noise problems

Technical data

Floor Heating loop Boiler loop

Maximum pressure 6 bar 6 bar

Maximum temperature 55 °C (70 °C thermostat available) 105 °C

Connections 1” male thread ¾” female thread

Circulator see diagram -

kPa

40

30

20

10

0

0,5 1,0 1,5 2,0 2,5 m

3

/h

7

6

5

4

3

2

1

Instruction Installation and operation manual for mixing module FH-MJA

The pump curve shows the hy-

draulic performance available at

the manifold connections.

Use the control knob (12) of the

pump to set its speed:

pos. 1 = min. performance.•

pos. 7 = max. performance.•

end pos. anti-clockwise = pump •

switched oﬀ.

Pump curve

Pump setting

Add the maximum operation point (mop) value

of the system into the diagram on the top. The

mop is a resulkt of the max. pressure loss, which

usually is caused by the one longest loop of the

ufh system and the max. required total ﬂow for

all loops.

Then set the pump to the value, which is verti-

cally closest to the mop.

Example:

An ufh-system requires a total ﬂow (when all loops

are open) of let’s say 1000 l per hour. With reference

to the pressure loss, the worst loop (usually the long-

est one) creates a pressure loss of let’s say 10 kPa (=

1.0 mWS = 100 mbar).

If you add this value to the diagram on the top the

nearest curve in vertical direction is curve no. 3. So

please set pump to setting 3.

Troubleshooting

Pump is not running

Possibly the safety temperature device has •

tripped and shut oﬀ the pump.

If not, the pump may be clogged by dirt. •

Remove the circulator to inspect it.

Heating performance is insuﬃcient

The presetting knob is turned in too far.•

The bypass valve is opened too far.•

The system is just being put into service, in •

which case it may take longer to heat the ﬂoor

for the ﬁrst time. As long as the ﬂoor heating

return temperature is still cold, the feed tem-

perature also cannot increase independently

since most of the feed water comes from the

ﬂoor heating return and only a small portion is

boiler water!

LED indication

of the pump

Theres a green LED in the centre of the pump’s

control knob showing the operating state:

LED on: Pump is switched on and operating •

properly.

LED oﬀ: Wrong wiring or missing voltage.•

Flashing LED:

1 short, 1 long: Incoming voltage below 200 V •

or pump switched oﬀ by control konob being

set anti-clockwise to end position.

3 short, 1 long: Processor temperature of pump •

is too hot. Please check allowed max. tempera-

ture of the pumped medium.

5 short, 1 long: Rotor blocked due to dirt. •

System and pump need to be cleaned.

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230 V ~

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Instruction Installation and operation manual for mixing module FH-MJA

Wiring with

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1 2 3 4 5 6 7 8 9 10

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230 V ~

L

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Instruction Installation and operation manual for mixing module FH-MJA

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Instruction Installation and operation manual for mixing module FH-MJA

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