Mini 3 18 to 39kW - CMS

Hoval Mini-3 heating 

and combination boilers 

for oil or gas firing from 

18 to 39 kW

Don’t just rely on your woolies to keep you warm this 

Winter. Allow Hoval to bring some comfort into your life. 

Whatever your heating and hot water requirements, Hoval 

can satisfy your needs. For your large domestic heating 

and hot water demand, there is the 

Hoval Mini-3.

Suitable for small commercial and large domestic installations. 

The Mini-3 and Mini-3H boilers provide the quality 

and reliability associated with larger installations. 

The Hoval pressure jet program 

The Mini-3 and Mini-3H boilers are the entry boiler for the 

Hoval pressure jet program. The smaller version of the 

Uno-3 boilers, the Mini-3 and Mini-3H offers an output 

range from 18kW through to 39kW. 

Available also as a combination boiler the Mini-3H can 

be supplied to provide domestic hot water (DHW) up to 

300 litres storage. 

Bizonal Technique 

The design of the Mini-3 and Mini-3H incorporates the 

“Bizonal Technique” which increases efficiency and 

life expectancy. The lower operating temperatures 

associated with high efficiency boilers present a 

higher risk of corrosion. The Mini-3 and Mini-3H 

boilers have been designed with this in mind. Areas 

within the boiler, where combustion gases are close 

to the dew point are protected by the Bizonal Technique. 

This directs flow of the low temperature return 

water away from these areas. This is accomplished 

by a series of strategically positioned baffle plates 

which restrict the natural flow of water through the 

boiler and encourages the water to flow through the 

boiler in a way that prohibits corrossion.

The Hoval Mini-3 and Mini-3H boiler can be fired using either 

oil or gas. With top or rear water and flue connections there 

is a solution to meet your installation requirements. 

Dry back type flue box 

permits lower operating 

temperatures 

3rd pass through the 

Thermolytic heat 

exchanger with regulators 

2nd pass through baffle 

plate 

1st pass into combustion 

chamber 

Mini-3H (rear flue) Mini-3 (top flue) 

Where required TopTronic 

controllers can be fitted. 

Burner acoustic cover 

Double hinge door with 

swivel arrangement for 

ease of servicing (even 

with low NOx burners with 

longer blast tubes). 

Burners suitable for natural 

gas, oil and LPG firing. 

Mini-3 & Mini-3H heating only boilers 

The Mini-3 boiler with vertical flue outlet and Mini-3H boiler with horiziontal flue outlet 

couples high efficiency with low NOx emissions, and as such satisfies current demands 

for economy and environmental protection. These dual goals are achieved with 

the special design which incorporates the unique Hoval thermolytic heat exchanger. 

Mini-3 boilers are available as heating only units or with a calorifier as a combination unit, 

with ratings between 16 - 39 kW and DHW up to 670 litres per hour. 

Construction 

Heating only and combination boilers are constructed of high quality steel plate, with 

80mm thick insulation around the boiler body and 50mm thick around the flue gas collector 

and over the boiler door. 

All models are encased within red and orange steel panels, matching the Hoval range of 

boilers and calorifiers. 

Low temperature operation 

The Mini-3 boiler has a dry backed flue gas collector so that the boiler can safely 

operate with boiler flow temperatures as low as 38 o C, and return temperatures of 

30 o C without the risk of condensation within the boiler. 

Three pass design 

With the Mini-3 boiler the combustion gases fire to the back of the combustion chamber 

and then upwards through the second pass where it reverses through a baffle towards 

the front of the boiler. The hot gases then flow through the thermolytic heat 

exchanger which is the third pass before leaving the heat exchanger through the flue 

box at the back. 

Thermolytic heat exchanger 

The unique thermolytic design of the third pass makes fine tuning of the flue gas 

temperature possible. 

In general, a 20K reduction in flue gas temperature will give a 1.5% gross efficiency 

increase.

Double-hinged door for reduced plantroom space and easy maintenance 

Instead of a normally hinged door, the Mini-3 has a proven double hinged door allowing 

problem-free extraction and swivelling out of long burner heads, typically associated 

with low NOx burners. 

Opening and swivelling out is also no longer hindered by adjacent walls or other burners 

in a multi-boiler system. (See space requirments below). 

The opening direction of the double hinged door can be easily reversed on the boilers. 

Regular boiler cleaning will contribute towards the lowest possible energy consumption. 

The Mini-3 double-hinged door enables the boiler to be opened for cleaning without the 

need for the burner to be dismantled. 

A further advantage of the double-hinged door is that, in contrast to traditionally hinged 

doors, it makes uniformly even contact on all sides, thereby achieving absolute gas 

tightness. It is therefore not necessary to adjust the hinges to give a gas tight seal. 

Space requirements 

The boiler should be sited on a flat, level and fireproof floor / base. A plinth is not 

necessary as the boiler sits on a channel base. 

Wherever possible space should be left around the boiler to enable all parts to be examined 

and the cubicle casings to be fitted or removed easily. 

Back clearance is required for the system connections, flue connections and access to 

the cleaning door. 

Front clearance is required to swivel the boiler door, including burner, by 90 o , (standard to 

the right, optional to left). 

Space requirements to right when right hinged 80mm (plus burner length). 

Space requirement at front where possible should allow for extraction of retarders etc. 

(nominally 500mm from boiler door). 

Controls 

The standard control panel incorporates: 

n flow thermometer 

n temperature control thermostat 

n on/off switch 

n high temperature limit thermostat 

with manual reset 

n excess temperature indicator 

(The panel can be top or side mounted depending on the boiler model selected) For 

combination boilers additional temperature control and temperature indication is included. 

Each control panel is equipped for two stage burner operation for matching 

seasonal load requirements on low fire rating option. TopTronic controller(s), volt free 

contacts and an hours run meter can be supplied as optional items. If TopTronic controller(s) 

are required the control panel, as shown, is utilised. 

TopTronic control 

The TopTronic control system brings 

together Hoval’s considerable experience in the field of heating & hot water control, 

together with a high performance micro-processor controls package. The result is a 

simple user-friendly operating platform that controls individual heating and hot water 

systems and optimises energy conservation. 

Databus connections 

Optional TopTronic controllers can be fitted directly into the boiler control panel (as shown) 

enabling control of up to two variable temperature, one constant temperature and one 

calorifier primary circuits. These are linked together by databus connections. Please 

refer to our separate TopTronic leaflet for further information. 

Electrical supply 

230V 50 Hz single phase mains supply should be connected to the boiler control panel via 

a fused isolator. 

Delivery and assembly 

The Mini-3 & Mini-3H heating only boilers are supplied fully assembled and cased. Delivered 

shrink wrapped on a pallet for ease of handling on site. Control panels & burners are 

supplied separate for fitting by the installer. 

The Mini-3H combination units are supplied with boiler, burner, calorifier, pump & pipework 

and control panel separate for site assembly.

The Hoval Mini-3H boiler / calorifier combination is a compact 

solution for your heating and hot water requirements. 

Dry back type flue box 

permits lower operating 

temperatures 

3rd pass through the 

Thermolytic heat 

exchanger with regulators 

2nd pass through baffle 

plate 

1st pass into combustion 

chamber 

Enamelled calorifier shell 

Calorifier primary coil 

Mini-3H combination boiler 

The Mini-3 can be supplied as a combination boiler with an integral temperature controlled calorifier. 

This is available as either a 150, 200, or 300 litre unit. 

The enamel lined steel calorifiers are fitted with a built-in primary heating coil, providing rapid recovery of DHW, and insulated with 

50mm polyurethane plastic foam within a steel Hoval red casing. 

Optional electric immersion heater 

A 3kW electrical immersion heater is available as an optional extra. 

Where required TopTronic 

controllers can be fitted. 

Burner acoustic cover 

Double hinge door with 

swivel arrangement for 

ease of servicing, even 

with low NOx burners with 

longer blast tubes. 

Burners suitable for natural 

gas, oil and LPG firing. 

Magnesium sacrificial anode 

Calorifier immersion sensor 

Calorifier insulation 

Note: This version is offered in the UK as 

a special. The standard combination unit 

has the calorifier on top of boiler. Please 

see dimensional details. 

Mg anode protection 

The DHW side of the calorifier is protected from corrosion by a Magnesium (Mg) sacrificial anode which is supplied on all combination 

units.

Hoval Mini-3 and Mini-3H 

Technical Data 

Mini-3 & Mini-3H 

Model (18) (25) (32) (36) (39) 

• Nominal thermal output kW 18 25 32 36 39 

• Thermal output range kW 16-18 20-25 26-32 33-36 33-39 

• Maximum burner capacity kW 19.5 27.1 34.6 38.8 42 

• Maximum operating temperature 1 °C 90 90 90 90 90 

• Minimum operating temperature °C 482 /383 482 /383 482 /383 482 /383 482 /383 

• Minimum return temperature °C 382 /303 382 /303 382 /303 382 /303 382 /303 

• Minimum flue gas temperature at outlet °C 110/130 110/130 110/130 110/130 110/130 

• Temperature limit (STB) °C 110 110 110 110 110 

• Max operating pressure / test pressure bar 3 /4,5 3 /4,5 3 /4,5 3 /4,5 3 /4,5 

• Regulators for 160°C flue gas temperature 1xR5/290 2xR5+ 3xR5+ 3xR5+ 3xR5+ 

1xR3/290 2xR2/290 2xR2/290 2xR2/290 

• Boiler efficiency at 80//60°C % 92 92.2 92.5 93 92.7 

• Standard efficiency 75//60°C (to EN 303) % 94,3 95 95,1 95,2 95,3 

• Standing losses qB ((70°C) Watt 240 260 260 270 270 

• Combustion chamber resistance 

160 °C flue gas temperature,12,5 %CO2 ,500 m ü.M 

(Tolerance +/-20 %) mbar 0,03 0,05 0,12 0,16 0,20 

• Flue gas mass flow 12,5 %CO2 (oil) kg/h 30,6 42,5 54,4 61,2 66,3 

• Primary resistance 5 z—Value 6,5 4,3 4,3 4,2 4,2 

• Primary resistance ( t = 10K) mbar 15,58 19,74 32,57 40,26 47,25 

• Primary resistance ( t = 20K) mbar 3,89 4,93 8,14 10,06 11,81 

• Hydraulic mass flow ( t = 10K) m 3 /h 1,55 2,15 2,75 3,10 3,35 

• Hydraulic mass flow ( t = 20K) m 3 /h 0,77 1,08 1,38 1,55 1,68 

• Boiler water content Litres 76 71 71 85 85 

• Gas volume m³ 0,050 0,058 0,058 0,068 0,068 

• Insulation thickness around boiler shell m m 80 80 80 80 80 

• Dry Weight (including casing) kg 145 170 170 180 180 

• Noise level with acoustic shroud 4 

– Heating noise dB(A) 62 63 64 64 68 

– Chimney noise (at flue outlet) dB(A) 79 80 81 81 83 

• Combustion chamber i/dia x Length m m ø312x520 ø312x520 ø312x520 ø312x630 ø312x630 

• Combustion chamber volume m³ 0,039 0,039 0,039 0,048 0,048 

•Mini-3 Width m m 600 600 600 600 600 

Length (without burner and shroud) m m 1098 1098 1098 1208 1208 

Height m m 1006 1006 1006 1006 1006 

•Mini-3H Width m m 600 600 600 600 600 

Length (without burner and shroud) m m 1072 1072 1072 1182 1182 

Height m m 976 976 976 976 976 

1 Limited to 90ºC by control stat 

2 Values are valid at minimum flue gas temperature of 110ºC 

3 Values are valid at a minimum flue gas temperature of 130ºC 

4 Detail are based on a Hoval oil fired burner and may vary depending on make and model 

resistance in mbar = Volume flow (m 

2004. 

Hoval Ltd, Northgate, Newark, Nottinghamshire. NG24 1JN. England. Tel (01636) 672711. Fax (01636) 673532. website: www.hoval.co.uk March 3 /h) 2 

x Z


Technical Data 

Mini-3H boiler / calorifier combinations 

Calorifier Model 150 200 300 

Volume litres 150 200 300 

Maximum pressure / Test Pressure bar 10 /15 10 /15 10 /15 

Maximum operating pressure °C 75 75 75 

Insulation mm 50 50 50 

Coefficient of Thermal Conductivity Watt/mK 0,025 0,025 0,025 

Weight kg 98 118 194 

Width m m 600 600 740 

Length m m 991 1261 1435 

Height m m 640 640 732 

Fixed Primary coil, heating surface m2 0.75 1.0 2.1 

Primary water content litres 4.2 6.8 15 

Primary resistance (1) z-Value 12 14.2 15 

Primary load kW 21.8 27.6 39 

Max operating pressure / test pressure bar 10 /15 10 /15 10 /15 

Max operating temperature °C 80 80 80 

1 Primary resistance (mbar) = (Primary flow rate (m 3 /h)) 2 x z 

DHW performance EWE calorifiers with Mini-3H boilers. 

DHW performance Weight Standing losses 

litres/10mins (1) litres/hour (2) Mini-3 with EWE qB (70 °C) 

Mini-3 /EWE Type 60 °C 60 °C k g Watt 

(18) / 150 90 240 238 331 

(18) / 200 120 309 259 352 

(25) / 150 90 290 253 343 

(25) / 200 120 340 274 364 

(32) / 150 90 290 273 379 

(32) / 200 120 360 294 400 

(36) / 200 120 360 304 419 

(36) / 300 180 619 380 432 

(39) / 200 120 360 304 419 

(39) / 300 180 670 380 432 

DHW Performance in 10 Min (calorifier is pre-heated to 60ºC) 

1 

2 

DHW continuous performance per Hour 

Hoval Ltd, Northgate, Newark, Nottinghamshire. NG24 1JN. England. Tel (01636) 672711. Fax (01636) 673532. website: www.hoval.co.uk March 2004.


Dimensional details 

Mini-3H heating only boiler with rear flue outlet 

960 

199.5 

C 

Burner 

Acoustic 

Shroud 

15 

1 Heating Flow R1" 

2 Heating Return R1" 

3 Safety Valve / Vent R1" 

4 Hydraulic Drain R1" 

5 Flue Outlet 

6 Explosion / Cleaning Door 

7 Control Panel 

8 Electrical socket for burner 

9 Electrical cable entry 

Boiler Model A B L C 

Mini-3H (18) 813 757 1012.5 350 

Mini-3H (25) 813 757 1012.5 350 




L 

A 60 

B 

Hoval Ltd, Northgate, Newark, Nottinghamshire. NG24 1JN. England. Tel (01636) 672711. Fax (01636) 673532. website: www.hoval.co.uk March 2004. 

129 

31 

739 

5 

810 

20 - 30 Levelling Feet 

715 

242 

600 

473 

8 

167 

190 

300 

125 

1 

30 

3 

150 

4 x M8 

500 

600 

220 

400 

4 

1 

7 

2 2 

6 

330 

9 

5 

100



Mini-3 heating only boiler with top flue outlet 

990 

600 

199.5 

9 1 2 

Boiler Model A B C D E 

Mini-3 (18) 655 899 1098.5 757 350 

Mini-3 (25) 655 899 1098.5 757 350 




E 

Burner 

Acoustic 

Shroud 

15 

9 

1 

C 

28 

3 

2 

B 

73 

D 

A 

10 

415 

5 

129 

105 

1 Heating Flow R1" 

2 Heating Return R1"” 

3 Safety Valve / Vent R1" 

4 Hydraulic Drain R1" 

5 Flue Outlet 

6 Explosion / Cleaning Door 

7 Control Panel 

8 Electrical socket for burner 

9 Electrical cable entry (either side) 

10 Cable channel (either side) 

Hoval Ltd, Northgate, Newark, Nottinghamshire. NG24 1JN. England. Tel (01636) 672711. Fax (01636) 673532. website: www.hoval.co.uk March 2004. 

6 

125 

150 

5 

56 

20 - 30 Levelling Feet 840 

100 125 

300 

54 

8 

300 

125 

4 

150 

4 x M8 

166 

30 

500 

7 

360



Mini-3H combination unit with rear flue outlet 

715 

473 

1 Heating Flow R 1" 

2 Heating Return R 1" 

3 Safety valve / Vent R 1" 

4 Hydraulic Drain R 1" 

5 Flue outlet, 129 mm O / dia, 

3 mm thk. 

6 Explosion / cleaning door 

7 Control panel type 150-200 

7a Control panel type 300, on 

either left or right hand side 

8 Electrial socket for burner 

9 Primary flow R 1" 

10 Primary return R 1" 

c 

a 

8 

u 

e 

d 

b 

15 

Front view (all models) 

14 14 

210 

13 

235 

10 

1 

11 

3 

12 

22 

1 

9 

21 

2 5 2 

6 

400 

20 

4 

167 

Rear view Mini-3H with 150 / 200 litre calorifier 

o 

7 

p q 

r s 

h2 

t 

11 DHW cold feed 150-200 =R 1", 

300 = R 1 ½" 

12 DHW flow 150-200 = R 1", 

300 = R 1 ½" 

13 DHW circulation150-200 = R ¾", 

300 = R 1" 

14 Cable channel 150-200 

15 Boiler door hinge right hand as 

standard, left on request 

16 Base channels 

17 Adjustable feet 

18 Burner 

19 Accoustic shroud 

n 

20 Primary return pipework with 

pump and non-return valve (150,200) 

21 Primary flow pipework (150,200) 

22 Automatic air vent 

23 Calorifier temperature sensor 

24 Sacrificial Anode 

25 3kW Immersion heater (optional) 

26 Primary flow pipework with 

pump and non-return valve (300) 

27 Primary return pipework (300) 

2004. 

March 

Mini-3H Boiler / Calorifier Combinations 

Boiler Cal’r l l 2 b h h 2 a c ød øe f g i k m n o p q r s t u 

18-32 150 1163 – 600 1648 1481 330 810 125 150 813 757 350 991 – 640 600 739 951 1176 1231 1311 – 

18-32 200 – 1401 600 1648 1481 330 810 125 150 813 757 350 – 1261 640 600 739 951 1176 1231 1311 – 

36-39 200 – 1401 600 1648 1481 330 810 125 150 923 867 450 – 1261 640 600 739 951 1176 1231 1311 – 

36-39 300 – 1635 600 1542 1650 330 810 125 150 923 867 450 – 1395 640 600 739 – – – – 710 

Hoval Ltd, Northgate, Newark, Nottinghamshire. NG24 1JN. England. Tel (01636) 672711. Fax (01636) 673532. website: www.hoval.co.uk 

m 

g 

f 

k 

7a 

l 

l2 

206 710 

7a 

16 

17 

175 

2 

100 

1 

5 

9 

10 

11 

3 

6 

4 

12 

225 

1 

2 

210 

440 

i 

7 

24 

23 

25 

h 

19 

18 

Rear view Mini-3H with 300 litre calorifier 

13 

7a 

27 

Side view 

(all models) 

22 

971 

26 

1395 

h

Other associated products 

MultiJet 

The MultiJet is a compact floor standing, oil-fired condensing 

boiler. Three models are available with outputs ranging between 

14 and 26kW. A unique design of heat exchanger allows the 

MultiJet to reach efficiencies as high as 104% net and can be 

as much as 40% more efficicient than your existing boiler. The 

MultiJet is suitable for oils with a sulphur content up to 0.2% 

by weight. 

Uno-3 

The Uno-3 boiler couples high efficiency with low NOx emissions. 

These dual goals are achieved with the special 3-pass 

design which incorporates the unique Hoval thermolytic heat 

exchanger. Available as heating only units or with a calorifier 

as a combination unit, with ratings between 50 -280 kW and 

DHW up to 1110 litres per hour. A modular heatpack version is 

also available up to 180 kW output. 

TopTronic 

The TopTronic control system brings together Hoval’s considerable 

experience in the field of heating and hot water control, 

together with a high performance microprocessor controls 

package. The result is a simple user-friendly operating platform 

that controls individual heating and hot water systems and 

optimises energy conservation. 

PressVal Mini 

The PressVal Mini is a compact wall mounted pressurisation 

unit which provides automatic make up and pressure for 

smaller sealed systems using expansion vessels up to 300 

litres. Single and duplicate pump models are available complete 

with system high and low pressure switches and a 

common volt free contact. A separate system filling loop is 

supplied with all models. 

Hoval Ltd 

Northgate 

Newark 

Notts 

NG24 1JN 

Tel: (01636) 672711 

Fax: (01636) 673532 

e-mail: boilersales@hoval.co.uk 

Web Site: www.hoval.co.uk 

Hoval follows a policy of continued improvement and reserves the right to change specifications without notice. Conservation of energy - protection of the environment 

March 2004

Mini 3 18 to 39kW - CMS

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