MHS Boilers Monomax 80, Monomax 90, Monomax 70, Monomax 100, Monomax 250 Series Manual

PRESSURISED STEEL BOILER

GAS, LIGHT OIL AND DUAL FUEL

SERIES:

INSTRUCTIONS FOR INSTALLATION AND USE

MONOMAX

N/NS

NC/NCS

DUOMAX

N/NS

PN/PNS

i

MHS

LB1957 • 23/03/2009

page. 2

MONOMAX N / NS - NC / NCS
DUOMAX N / NS - PN / PNS

MHS

Index:

Monomax N/NS - NC/NCS technical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 4,5

Monomax N/NS - NC/NCS overall dimensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 6

Duomax N/NS technical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 7

Duomax N/NS overall dimensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 8

Duomax PN/PNS technical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 9,10

Duomax PN/PNS overall dimensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 11

General specifications and Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 12

Control panels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 13

Fitting the bolier insulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 14

Fitting the casing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 15,16,17,18,19

Fitting the burner . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 20

Water treatment and Cleaning the boiler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 21

Prevention of Condensation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 22,23

Electrical connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 24

page. 3

MONOMAX N / NS - NC / NCS

DUOMAX N / NS - PN / PNS

MHS

Simply Powerful

Manufactured to exceptional build quality standards, the Monomax range of boilers includes 26
models with outputs from 70 to 3500kW, and utilising the same robust boiler shells; the Duomax
(stacked twin versions) are available in a range of 10 models from 140 to 700kW; with the Duomax
P (twin parallel versions) offered in 19 models sizes with outputs from 140 to 2600kW.

Constructed using thick gauge steel plate and stainless
steel flue tube turbulators, these reverse flame steel shell
and tube boilers combine reliability with efficiency to
return a long and trouble free working life. Available with
gas, oil or dual fuel forced draught burners mounted to
the handable hinged combustion chamber door, the
Monomax & Duomax boilers are the perfect choice when
selecting steel shell and tube boiler plant. The
comprehensive control panel is complete with all
necessary burner wiring harnesses and is suitable for
on/off, high/low and modulating burner types.

Standard features

Conformity with standards

Meeting the essential requirements of EN303 in respect
to overpressure within the combustion chamber, surface
temperature, and combustion chamber dimensions,
distance between flue tubes and selection of material,
welding methods and temperature control, each
Monomax and Duomax Boiler is CE marked.

Space saving

For installations where floor area is limited, then the
Duomax with a stacked twin boiler arrangement offers
the solution or where plant room depth is restricted, the
Duomax P twin parallel version accords high output from
minimum boiler length dimensions. The direction of ope­ning of the combustion chamber door is reversible to suit
site conditions.

High standards of build quality

Welding to the highest standards of workmanship and
fully adjustable door hinge mechanisms ensure reliability
and accuracy in door sealing.The smart and robust outer
casing finishes off the assembled unit with pleasing clean
lines.

Low thermal losses

Equipped with a ceramic lining to the combustion cham­ber door of generous thickness, plus an insulating
jacket of 80mm depth of foil backed high density glass
wool; the Monomax & Duomax Boilers have low
operational heat loss which enhances the efficiency of
the plant and reduces boiler room temperatures.

Comprehensive control panel

Each boiler is equipped with a top mounted control pod
which includes all of the necessary control and instrumen­tation expected for boilers of this type plus the inclusion of
a burner wiring harness in flexible conduit which makes
burner connection a matter of simplicity
and to a highly professional standard.

Option of boilers for site assembly.
Where access to the boiler plant room is restricted and
where the installer has the necessary welding skills;
Monomax Boiler models in the output range 100 to
1300kW can be supplied in kit form for on-site assembly.

Outputs up to 7MW

To special order and POA, "Trimax" 3 pass steel shell
and tube boilers with outputs at 3500, 6000 and
7000kW are available - contact MHS sales dept for
details.

Warranty

The factory assembled boiler body carries a 5 year
guarantee; all other components carry a 12 month
guarantee. Burners not less than 12 months but certain
burners may have longer warranties.
All guarantees are against manufacturing or material
defects only.

Put your mind at rest

At MHS Boilers we provide a
life time maintenance and ser­vice solution for your heating
system - enabling you to
rest safe in the knowledge
that we’ll take care of it.
Go to our website
www.mhsboilers.com and
download or request a copy
of our Maintenance and
Service Solutions brochure.

page. 4

MONOMAX N / NS - NC / NCS
DUOMAX N / NS - PN / PNS

MHS

page. 5

MONOMAX N / NS - NC / NCS

DUOMAX N / NS - PN / PNS

MHS

page. 6

MONOMAX N / NS - NC / NCS
DUOMAX N / NS - PN / PNS

MHS

N1 - Flow connection
N2 - Return connection
N3 - Ancillary Tapping
N4 - Drain connection
N5 - Safety Valve Tappings
Poket “P” for thermostats not shown

N1 - Flow connection
N2 - Return connection
N3 - Ancillary Tapping
N4 - Drain connection
N5 - Safety Valve Tappings
N6 - Poket for T/Stats etc

Monomax Models 70 to 1300

Dimensions - Monomax

Monomax Models 1400 to 3500

H

C

N1

P

N8

ø c

D

N4

A
A1

P

H

ø c

D

N4

N1

N8

N5

N6

N6

N3

N2N3N5

B
B1

C

L

N2

M

M

QL

E

Q

E

A

A1

B
B1

page. 7

MONOMAX N / NS - NC / NCS

DUOMAX N / NS - PN / PNS

MHS

page. 8

MONOMAX N / NS - NC / NCS
DUOMAX N / NS - PN / PNS

MHS

N1 - Flow connection
N2 - Return connection
N4 - Drain connection
N6 - Instrument Pokets

Dimensions - Duomax

H

C1

C

N1/N2

ø c

N4

N1/N2

D1

ø c

D

N4

B2 Q

N6

G

N6

N2

N2

F

EE

N1

N1

A

A1

B

B1

page. 9

MONOMAX N / NS - NC / NCS

DUOMAX N / NS - PN / PNS

MHS

page. 10

MONOMAX N / NS - NC / NCS
DUOMAX N / NS - PN / PNS

MHS

page. 11

MONOMAX N / NS - NC / NCS

DUOMAX N / NS - PN / PNS

MHS

N1 - Flow connection
N2 - Return connection
N3 - Tapping for Gauges etc
N4 - Drain connection
N5 - Safety Valve Tappings
N6 - Instrument Pokets

Dimensions - Duomax P

C

N5

N6

N3

L

N2

B

B1

N1

P

H

65

A

A1

ø c

D

N4

M

Q

E

page. 12

MONOMAX N / NS - NC / NCS
DUOMAX N / NS - PN / PNS

MHS

Monomax boiler units are formed by matching a gas, gas
oil or gas/gas oil mix burner, depending on requirements,
with a high quality, high performance steel boiler. To obtain
maximum performance from the unit, the burner is
specifically designed and calibrated to match the
boiler.The quality of the burner-boiler combination in
Monomax units has been designed in minimum detail,
especially those concerning the decrease of polluting
gases, silent running and reliability.

Monomax units are available in the following versions:

- 2 stage

- gas modulating

- gas/gas oil mix

- fuel oil

Boiler Body

The body of the boiler is manufactured in thick, high quality
steel, with pressurised combustion chamber and flame
reverse, large flue gas flues which guarantee long periods
of autonomous operation and are easy to clean, equipped
with a highly efficient stainless steel baffles to increase
heat exchange; The back base also has an
anticondensation effect.
The door opening direction can be simply adjusted by
reversing its clamping elements.

Casing

The casing is packed separately from the boiler body and
is constructed of painted panels.

Insulation

Particular attention has been paid to the insulation of the
Monomax boiler body. It is composed of a thick layer of
fibreglass which completely covers the body reducing loss
of heat to a minimum and contributing towards a high level
of boiler performance.

Control Panel

The control panel of Monomax boiler has been designed
to solve all the installer’s problems relevant to electrical
connections and correct unit operation.
In fact, it is equipped with components and instruments
geared towards facilitating control and regulation of the
boiler. When the preset flue temperature limit is reached, a
warning light indicates that the combustion chamber and
flue pipes of the boiler require cleaning.

Installation

Warning: this boiler is designed to heat water to a
temperature below boiling point at atmospheric pressure; it
must be connected to a heating system and/or domestic
water production and distribution system which is within
the limits of its performance and capacity.
Any other use of this unit must be considered incorrect
and, therefore, dangerous.
The heating unit must be installed by professionally
qualified technicians, in compliance with the safety
regulations and local building regulations in force at the
time.
Warning: when installing and assembling the various parts
of the boiler, check that the earth wire is correctly
connected.
Incorrect installation can cause damage to people and
objects for which the manufacturer is not responsible.

General Specification

page. 13

MONOMAX N / NS - NC / NCS

DUOMAX N / NS - PN / PNS

MHS

Control Panels

1-

On/Off switch

2 - Burner

switch

3 - Heating pump

switch

4-

High and low flame thermostat

5-

Boiler thermostat

6-

Lock out burner lamp

7-

Manual reset safety thermostat

8 -

Thermometer

9 - Minimum thermostat (already adjust to 50°C)

To gain access to the controls, push and release on P and rotate
transparency panel towards you.

To close the transparency panel, rotate in vertical position and
push and release it on P.

ELECTRIC PANEL FOR MONOMAX in the version 2
FLAME or MODULATING settings

MONOMAX control panels

1-

On/Off switch

2 - Burner

switch boiler

A

3 - Burner

switch boiler

B

4-

Boiler A thermostat

5-

Boiler B thermostat

6-

Lock out burner A lamp

7-

Lock out burner B lamp

8 - Heating pump

switch boiler A

9 - Heating pump

switch boiler

B

10 -

Manual reset safety thermostat boiler

A

11 -

Manual reset safety thermostat boiler

B

12 -

Thermometer boiler

A

13 -

Thermometer boiler

B

14 -

Minimum thermostat (already adjust to 50°C)

Duomax 2 or 4 flames

DUOMAX control panels

12 4 5

6

78

3

9

12634 5

A B

7

8

9

A

B

A

B

A

B

11 12 13

10

14

A

B

AB

A

B

50

40 60
30 70
20 80

10 90

°C

A B

40 60
30 70
20 80

10 90

°C

50

page. 14

MONOMAX N / NS - NC / NCS
DUOMAX N / NS - PN / PNS

MHS

Fitting the boiler insulation

1 2

A

B

3

B

C

A

B

C

4

B B

C C

A

page. 15

MONOMAX N / NS - NC / NCS

DUOMAX N / NS - PN / PNS

MHS

Fitting the casing Monomax N - NS - NC - NCS (up to 420 model)

- Wrap the glass wool around the boiler body leaving the
bulb well (P) on the top side exposed.

- Loosen screw (V) and rotate towards you the frontal part
of the electric control panel (see fig.11-2) and remove
the half cut plastic plate K

- Pass the burner connection plug through the slot on the
lower side of boiler front plate and insert the
thermometer and thermostats bulbs in the slot K and in
the wells P.

- Fit the panels (1S) and (1D)

inserting the upper fold into
the square tube and the lower fold to the boiler side
frame.

-

Fit the upper panel

(3S)

on the boiler

-

Fit the panel

(3D)

ensuring that the capillaries are

inserted in the slot provided in the panel

(3D).

- Fit the electric control panel on panels (3S) and (3D)
using screw (V1) (see fig. 11-3).

- Connect electric control panel to mains supply following the
wiring diagram included in the control panel.

- Re-place the front part of the control board and tighten

the screw V.

Fig. 11-1

P Bulb well for:

Regulation boiler thermostat
Security thermostat
Minimum thermostat (Circulator consent thermostat)
Thermometer

Fig. 11-2

V1

V1

V1

V1

V

V

K

page. 16

MONOMAX N / NS - NC / NCS
DUOMAX N / NS - PN / PNS

MHS

- Wrap the glass wool around the boiler body leaving the
bulb well (P) on the top side exposed.

- Loosen screw (V) and rotate towards you the frontal part
of the electric control panel (see fig.11-2) and remove
the half cut plastic plate K

- Pass the burner connection plug through the slot on the
lower side of boiler front plate and insert the
thermometer and thermostats bulbs in the slot K and in
the wells P (see fig. 11-4).

-

Fit the panels (1S)

inserting the upper fold into the
square tube and the lower fold to the boiler side frame;
repeat this operation to fit the (2S) panel

- Fit the upper panel

(3S)

on the boiler

- Fit the panel(1D), (2D) and

(3D)

ensuring that the
capillaries are inserted in the slot provided in the panel
(3D).

- Fit the electric control panel on panels (3S) and (3D)
using screw (V1) (see fig. 11-5).

- Connect electric control panel to mains supply following the
wiring diagram included in the control panel.

- Re-place the front part of the control board and tighten
the screw V.

P Bulb well for:

Regulation boiler thermostat
Security thermostat
Minimum thermostat (Pump consent
thermostat)
Thermometer

Fig. 11-1

Fig. 11-2

Fitting the casing Monomax N - NS - NC - NCS (from 510 to 1300 models)

For Modulating version,
remove the original pocket
and insert the probe pocket.

V1

V1

V

V1

V1

V

K

page. 17

MONOMAX N / NS - NC / NCS

DUOMAX N / NS - PN / PNS

MHS

Fig. 11-4

Fig. 11-3

The assembly described hereafter concerns the control
panel installation placed on the left side of the boiler.
In case of installation on the right side, follow the indica­tions assembling the parts on the opposite side.

- loosen the screw V and turn forward the control panel

front part 3 (fig. 11-3)

- remove the half cut plastic plate K1

- insert the bulbs of the thermometer and of the thermo-

stats inside the half cut plastic plate K1 pocket

- insert all the bulbs of the thermometer and the thermo-

stats inside the rear pocket of the rod and ensure they
slide inside the tube of the support 2 until they emerge
(fig. 11-3).

- Lift the panel R, fit the control panel on the support 2

using screws V1 supplied and replace panel R.

- Remove the half cut plastic plate K, insert the cable
wiring terminal block C inside the hole and secure it to
the control panel using the cable holder supplied.

- Remove the plate 4, fit the support 2 to the boiler as indi­cated in fig. 11-3, paying attention to slide the bulb inside
the hole of the boiler towards the plate 5, remove the
plate 5 and insert the bulbs inside the pocket P .Once
these operations have been carried out re-fit the plates 4
and 5.

- Using the screws supplied, fit the bases of the supports
D and E to support cable C approx. in the positions indi­cated in fig. 11-4 in according to the indicated values
(see fig. 11-5), slide the cable and secure it with the
upper support.

- place the burner cables around the base of the front plate

- carry out the electrical connections following the wiring
diagram enclosed in the control board

- Re-place the front part of the control panel and tighten
the screw V.

frontal wiewrear wiew

Fig. 11-5

supports D

support E

Fitting Electrical Panel Monomax N - NS - NC - NCS

(from 1400 to 3500 models)

4

R

5

2

P

V

3

D

C

C

V

V1

K1

V1

K

C

ø 3,5mm

ø 3,5mm

25mm

D

D/E

15mm

25mm

E

page. 18

MONOMAX N / NS - NC / NCS
DUOMAX N / NS - PN / PNS

MHS

Fig. 11.1-1

5

Fig. 11.1-2

- Wrap the glass wool around the boiler body leaving the

bulb well (P) on the top side exposed.

- Loosen screw (V) and rotate towards you the frontal part

of the electric control panel (see fig.11.1-2) and remove
the half cut plastic plate K

- Fit the electric control panel to the top panel using screw

(V1).

- Pass the burner connection plug through the slot on the

lower side of boiler front plate and insert the
thermometer and thermostats bulbs in the slot on panel
(5) and in the wells P1 and P2.

- Connect electric control panel to mains supply following the

wiring diagram included in the control panel.

- Re-place the front part of the control panel and tighten

the screw V.

-

Fit the panels (1, 2, 3, 4)

inserting the upper fold into the

square tube and the lower fold to the boiler side frame;

- Fit the panel

(5)

P1 - Bulb well for 1stboiler:

Regulation boiler thermostat
Security thermostat
Minimum thermostat (Circulator consent
thermostat)
Thermometer

P2 - Bulb well for 2ndboiler:

Regulation boiler thermostat
Security thermostat
Minimum thermostat (Circulator consent
thermostat)
Thermometer

Fitting the casing Duomax N - NS

V1

V1

V1

V1

V

V

K

page. 19

MONOMAX N / NS - NC / NCS

DUOMAX N / NS - PN / PNS

MHS

Fig. 11.2-2

Fig. 11.2-4

Fig. 11.2-3

Fig. 11.2-3

P Bulb well for:

Regulation boiler thermostat
Security thermostat
Minimum thermostat (Circulator consent
thermostat)
Thermometer

- Wrap the glass wool around the boiler body leaving the
bulb well (P) on the top side exposed.

- Fixing in the right position the boiler body (65mm
between the boilers, see pag. 7)

- Loosen screw (V) and rotate towards you the frontal part
of the electric control panel (see fig.11.2-3) and remove
the half cut plastic plate K

- Insert all cables in the slot K and in the slot on plate W.

- Fit the electric control panel on panels W using screws
(V1).

- Pass the burner connection plug through the slot on the
lower side of boiler front plate and insert the
thermometer and thermostats bulbs in the slot on panel
(5) and in the wells P

- Fit the panels (1S) and (1D)

inserting the upper fold into
the square tube and the lower fold to the boilers side
frame.

-

Fit the upper panel

(3S)

on the boilers

-

Fit the panel

(3D)

ensuring that the capillaries are

inserted in the slot provided in the panel

.

- Fit the plate W on boilers using screw (V3)

- Connect electric control panel to mains supply following the
wiring diagram included in the control panel.

- Re-place the front part of the control board and tighten
the screw V.

Fitting the casing Duomax PN - PNS

V1

V1

V

V1

V1

V3

= =

V3 V3

V3

V3

W

V

W

K

W

page. 20

MONOMAX N / NS - NC / NCS
DUOMAX N / NS - PN / PNS

MHS

In order to fit the burner correctly, follow the below instruc­tions:

1 - tighten the stud bolts provided with the boiler onto the

boiler door;

2 - fit the burner gasket with the burner, and then the bur-

ner;

3 - fix the burner with the flanged nuts. The slots in the bur-

ner flange allow it to be fitted and removed by simply
loosening the nuts, without having to remove them
completely;

4 - connect the burner to the power supply, fitting the plugs

into their corresponding sockets.

When fitting the burner make sure that there is a perfect
seal between the burner attachment flange and the boiler.
The wiring diagram of the heating unit, according to the
type of fuel and type of operation of the appliance, is atta­ched.
Fuel must be supplied to the burner in compliance with the
instructions contained in the instruction manual provided
with the burner.

1 - Burner
2 - Door
3 - Insulate material
4 - Gasket

The dimensions below are for burners fitted on Monomax
NC ed NCS models:

Monomax NC - NCS Lenght L Diameter D hole

models blast tube (mm) burner (mm)

100÷1300 270 ÷ 400 280

1400, 1600,

400 ÷ 550 300

1800, 2000

2400, 3000,

530 ÷ 600 330

3500

Fitting the Burner

page. 21

MONOMAX N / NS - NC / NCS

DUOMAX N / NS - PN / PNS

MHS

Limestone deposits strongly impair the efficiency of heat
exchange between combustion gases and the system
water, causing a decrease in the performance of the
appliance (see graph); it also causes an increase in the
temperature of the metal walls of the boiler body, thus redu­cing its life span.
Another phenomenon linked to the quality of the water is
the corrosion of metal surfaces due to iron passing into the
solution. The presence of dissolved gases such as oxygen
and carbon dioxide greatly influences this phenomenon.
Softened and demineralised water are more aggressive to
iron and therefore these must be conditioned with substan­ces which inhibit corrosive processes.
It is therefore advisable to perform periodic chemical analy­sis on the degree of hardness of the water, the pH (this
must be between 7 and 8) and the iron content (which must
be < 1ppm).

Clean as follows:

- switch off the heating unit and disconnect the power
supply:

- loosen the fastening handles of the hatch and open it;

- extract the baffles from the flue pipes (see figure);

- clean the flue pipes using a metal brush and remove
residue;

- clean the combustion chamber with a metal brush;

- replace the baffles and close the hatch;

- close everything up once more;

- reconnect the power supply.

The boiler body must be cleaned regularly in order to gua­rantee constant efficient operation of the appliance, as soot
deposits lower its performance, as can be seen from the
graph at the foot of the page; the frequency of this opera­tion depends on the type of fuel and combustion quality. For
this purpose, it is extremely useful to check the temperatu­re of flue gas as a progressive increase in this value
through time is linked to the amount of soot in the boiler
body and flue pipe. It must also be borne in mind that if cor­rosive residue (which mainly derives from combustion of
liquid fuels) is left in the boiler for long periods this can lead
to serious damage of the appliance.

Cleaning the boiler

Water treatment

30

20

% of fuel not used

10

0 5 10 15 20

thickness of limestone [mm]

Decrease of boiler performance as a function

91

90

89

88

η Boiler

87

86

85

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

of the amount of soot

amount of soot [mm]

page. 22

MONOMAX N / NS - NC / NCS
DUOMAX N / NS - PN / PNS

MHS

Prevention of Condensation

Condensation within steel boilers is very harmful and precautions must be taken within the system design to prevent
condensation from occurring within the flueways. The boiler should work at a return temperature in excess of 60°C. In order
that the boiler should reach this temperature as quickly as possible, it is imperative that an anti-condensation system is
installed. This is achieved by installing a bypass between flow and return pipes as shown below.

System Water

Monomax and Duomax boilers must always be installed on closed systems, whether they are of open vented or sealed and
pressurised type.
All systems should be thoroughly cleaned prior to the installation of the boiler and the system water must be treated with a
good quality corrosion inhibitor to prevent the deposition of scale or sludge in the boiler waterways. The system water must
be of a sufficient quality to maintain the following requirements:

• pH between 7 and 8

• hardness between 8 and 12 grammes of calcium carbonate per 100 litres of water.

Clearances

Front Clearance

Equal to approximately the length of the boiler base should be allowed for tube cleaning or tube repairs. Shorter clearances
are possible subject to cleaning methods and plantroom layout.

Side Clearance

Boilers may be arranged in “close to” battery formation but a minimum of 450mm should be allowed where possible.

Rear Clearance

Sufficient space should be allowed for connection of the flue system and for rear inspection and maintenance.

Burner Clearance

Consideration must be given to the clearance required by the burner, particularly when the boiler door is open at 90°, and
this point must be considered when positioning boilers if it is desirable to retain the burner affixed to an open door. The
matched burner, as a general guide, will project from the front of the boiler by approximately 30% of the boiler length.

Boiler Base

Monomax and Duomax boilers should be installed on a level fireproof plinth with a minimum height of 100mm. The plinth
must be capable of supporting the weight of the boiler/s when they are filled with water. The front of the plinth can be level
with, but not extend beyond, the front of the boiler casing. Depending on the make of burner selected, dual fuel applications
may require a higher plinth. Details will be provided on request.

1 - Boiler
2 - Burner
3 - Min Temp Thermostat (TR)
4 - Anti-Condensation Pump
5 - Non-Return Valve
6 - Boiler/System Pump

Install an anti-condensation pump as shown in the
diagram on the left. The pump (4) should be
controlled by the minimum temperature thermostat
(TR) (3) which should be set at not less than 60ºC.
The minimum flow rate for the anti-condensation
pump is detailed in the Technical Data Tables under
the heading “Shunt Recirculation Flow Rate”

Failure to observe this important installation and
operational requirement will render the warranty
on the boiler null & void.

page. 23

MONOMAX N / NS - NC / NCS

DUOMAX N / NS - PN / PNS

MHS

Installation Requirements

Installation requirements

Monomax and Duomax boilers must be installed in accordance (as appropriate) with the requirements of the Building
Regulations, Health and Safety Executive Regulation PM5, IEE Regulations, Gas Safety (Installation and Use) Regulations,
National Water Byelaws, Clean Air Act Memorandum on Chimney Heights and Insurance company requirements.

Codes of practice

Furthermore, in accordance with BS6644, for boiler/s with an input greater than 70kW net, an automatic pressurization unit
must be installed to automatically replenish any lost system water.
For information on the comprehensive range of pressurization units available from MHS boilers, please visit our website,

www.mhsboilers.com

• Control Valve, on the Mains Cold Water pipework.

• Strainer.

• Verifiable Backflow Device with Reduced Pressure Zone
(RPZ Valve) Incorporating a 'Type BA' air gap.

• Tundish

• Control Valve, on the Heating System pipework.

BS 6880 Code of practice for low temperature hot water
heating systems of output greater than 45kW. Parts 1, 2 & 3:

1988.

CP342 Part 2: 1974 Code of practice for centralised hot water
supply.

BS5410 Part 2: 1978 Code of practice for oil firing
installations of output capacity of 44kW and above for space
heating, hot water and steam supply purposes.

BS6644 Specification for installation of gas-fired hot water

boilers of rated inputs between 70kW net and 1.8 MW net.

IGE/UP/2 Gas installation pipework, boosters and
compressors on industrial and commercial premises.

IGE/UP/10 Part 1 Installation of gas appliances in industrial
and commercial premises

CIBSE Guide Reference sections B7, B11 and B13

LPG When boilers are fired with LPG it is recommended that

gas leakage detection equipment is installed at low level
near the boiler or boilers.

Filling the System

The Initial filling of a sealed heating system, and subsequent refilling, must be by a method that has been approved by the
Water Regulation Advisory Scheme (WRAS) for the type of heating system, i.e.: Non Domestic (other than in-house) Fluid
Category 4 (C-4). For Category4 systems, the approved method of filling must comprise of the following components in the
arrangement shown;

page. 24

MONOMAX N / NS - NC / NCS
DUOMAX N / NS - PN / PNS

MHS

20.1 ELECTRICAL BLUEPRINT BASE CONTROL PANEL

FOR MONOMAX N, NS, NC AND NCS . . . . . . . . . . . . pag. 25

20.1.1 ELECTRICAL CONNECTION BLUEPRINT TO BASE

CONTROL PANNEL FOR MONOMAX BOILER NC

AND NCS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . pag. 25

20.1.2 ELECTRIC AL CONNECTION BLUEPRINT TO BASE CONTROL

PANEL FOR MONOMAX N AND NS BOILER WITH

SINGLE-PHASE BURNER

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . pag. 26

20.1.3 ELECTRIC AL CONNNECTION BLUEPRINT TO BASE CONTROL

PANEL FOR MONOMAX N AND NS BOILER WITH

THREE-PHASE BURNER

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . pag. 26

20.2 ELECTRIC AL BLUEPRINT BASE CONTROL PANEL

FOR DUOMAX N, NS, P AND PNS

. . . . . . . . . . . . . . . . . . . . . pag. 27

20.2.1 ELECTRIC AL CONNECTION BLUEPRINT CONTROL

PANEL FOR DUOMAX N, NS, PN AND PNS BOILER,

BASE MODEL OR WITH ELECTRONIC MANAGEMENT

OF HI-LOW FLAME,WITH SINGLE-PHASE BURNER

. . . pag. 28

Electrical connections

page. 25

MONOMAX N / NS - NC / NCS

DUOMAX N / NS - PN / PNS

MHS

Without burner : rif. CEM04101N

With single-phase burner : rif. CEM04102N

With three-phase burner : rif. CEM04103N

FU fuse
HLB block bulb
HLF operation bulb
HL2 second flame bulb
SAC recirculation switch
SAL line switch
STL working thermostat

SAB burner switch
STR recirculation thermostat
STS security thermostat
STAB high-low flame thermostat
J1 jumper for boiler safey and external controls
J2 jumper for burner external control

J1 J2

181076981211 13 14

C

N

L

5

Q

PE

NL

~ 50÷60Hz

220÷240V

213 1716154192021

(PORTATA MAX.
CONTATTI 1A)

PANNELLO DI COMANDO

alimen
elettric
brucia

linea te

segna

segna
funzio
brucia

conse
alta -

thermostatic line

Maximum elec­trical rate con­nections 1A

block signal

burner’s working signal

high-low flame thermostat

Electrical power for the burner

C Boiler’s circulator

Q Main switch

CONTROL BOARD

rif. CEM04101N

20.1 Electrical Blueprint base control panel for Monomax N,NS,NC and NCS

20.1.1 Electrical connection Blueprint to base control panel for Monomax Boiler
NC and NCS

J1 J2

SAL

FU

6,3 A max

STAB

STL

T

18

T

P

P

21

HLF

HL2

HLB

NL

213 17161541920

STR

T

SAC

1076981211 13 145

STS

SAB

T

P

P

page. 26

MONOMAX N / NS - NC / NCS
DUOMAX N / NS - PN / PNS

MHS

rif. CEM04102N

rif. CEM04103N

C Boiler’s circulator

Q Main switch

C Boiler’s circulator

CONTROL BOARD

CONTROL BOARD

Maximum elec­trical rate con­nections 1A

Maximum elec­trical rate con­nections 1A

WARNING: THE 4 POLES TERMI­NAL BOARD (W4) IS CONNECTED
ONLY IF THE BOILER IS COUPLED
WITH A TWO-STAGE BURNER

20.1.2 Electrical connection Blueprint to base control panel for Monomax N and NS

Boiler with single-phase burner

20.1.3 Electrical connection Blueprint to base control panel for Monomax N and NS

Boiler with three-phase burner

ATTENZIONE:
LA MORSETTIERA A 4 POLI (W4) VA
COLLEGATA SOLO SE ALLA CALDAIA
VIENE ABBINATO UN BRUCIATORE BI-
STADIO (ALTA-BASSA FIAMMA)

W4

B4 T2S3 T1 N L1

W7

B5T8 T7 T6

~ 50÷60Hz

220÷240V

L

N

PE

Q

(PORTATA MAX.
CONTATTI 1A)

J1 J2

NL

213 1716154192021

PANNELLO DI COMANDO

C

5

181076981211 13 14

C CIRCOLATORE DI CALDAIA

Q INTERRUTTORE GENERALE

N

L1

W3

W4

B5T8 T7 T6

B4 T2S3 T1 N L1

W7

(PORTATA MAX.
CONTATTI 1A)

J1 J2

PANNELLO DI COMANDO

C

5NL213 1716154192021

181076981211 13 14

C CIRCOLATORE DI CALDAIA

page. 27

MONOMAX N / NS - NC / NCS

DUOMAX N / NS - PN / PNS

MHS

With single-phase burner : rif. CEM04104N

With three-phase burner : rif. CEM04105N

FU Fuse

KA rele

HLB block bulb

HLF operation bulb

HL2 second flame bulb

SAC recirculation switch

SAL line switch

STL working thermostat

SABR burner switch

STR recirculation switch

STS security thermostat

STAB high-low flame switch

J1-J3 security and eventual external command bridge

J2-J4 bridge for external commands of the burner

20.2 Electrical Blueprint base control panel for Duomax N,NS,P and PNS

HL2-b

HLB-b HLF-b

P

T

STAB-b

J4J3

543

STS-b

STR-b

T

P

T

STL-b

P

P

T

SABR-b

SAC-b

FU-b

6,3A max

HL2-a

HLF-a

HLB-a

T

STR-a

STS-a

P

STL-a

P

T

P

T

SABR-a

SAC-a

P

T

STAB-a

J2J1

761298 1011 13141516 61511987101312 14 16 17 1817 18LN

435 N2L2 2112L1 N1

FU-a

6,3A max

SAL

KA

page. 28

MONOMAX N / NS - NC / NCS
DUOMAX N / NS - PN / PNS

MHS

rif. CEM04113N

Ca A boiler’s circulator
Cb B boiler’s circulator
Q Main switch

BOILER A

BOILER B

CONTROL BOARD

Maximum
electrical rate
connections
1A

Maximum elec­trical rate con­nections 1A

rif. CEM04104N

20.2.1 Electrical connection Blueprint control panel for Duomax N,NS,P and PNS
boiler, base model or with electronic management of hi-low flame, with
single-phase burner

WARNING:THE 4 POLES TER­MINAL BOARD (W4) IS CON­NECTED ONLY IF THE BOILER
IS HIGH-LOW VERSION.

50-60Hz

~

220-240V

W4-aW7-a

Q

L

N

PE

435 N2L2 2112L1 N1

LN

761298101113141516 6 1511987101312 14 16 17 1817 18

C-a

(PORTATA MAX.

CONTATTI 1A)

J2J1

T8 B5T7 T6

PANNELLO DI COMANDO

C-a CIRCOLATORE CALDAIA A
C-b CIRCOLATORE CALDAIA B

Q INTERRUTTORE GENERALE

ATTENZIONE:
LE MORSETTIERE A 4 POLI (W4-a e W4-
b) VANNO COLLEGATE SOLO SE ALLE
CALDAIE VIENE ABBINATO UN BRU-
CIATORE BISTADIO (ALTA-BASSA
FIAMMA)

(PORTATA MAX.

CONTATTI 1A)

C-b

543

CALDAIA BCALDAIA A

T8 B5T7 T6

J4J3

W7-bW4-b

B4 S3 T2 T1 N L1B4 S3 T2 T1 N L1

page. 29

MONOMAX N / NS - NC / NCS

DUOMAX N / NS - PN / PNS

MHS

MHS Boilers Ltd

3 Juniper West, Fenton Way, Southfields Business Park, Basildon, Essex, SS15 6SJ - tel. [phone] - fax [phone]

B MHS reserves the right to make any adjustments, without prior notice, which it considers necessary or useful to its products,
without affecting their main features.

MHS