Boiler Retra-4M Combi 150 kW
Loading and burning of fuel can occur in three ways:
Manual download mode:
Fuel is loaded through the top hatch onto the grate (upper combustion chamber), where it is burned. This mode is designed for any coarse-grained fuel (wood, briquettes, lump coal, straw, etc.). Primary air is supplied through a diffuser by a fan mounted underneath on the rear wall of the boiler; secondary air for burning pyrolysis gases is supplied through nozzles on the side and top walls of the firebox by a fan mounted on the top wall. The combustion process and the central heating pump are controlled by a control panel, and ash removal is manual.
Operating mode with a flare burner: 
A flare burner is installed in the lower boiler hatch, where fuel is mechanically fed from the hopper. Fuel combustion occurs in the lower chamber. This automatic loading mode is designed for burning pellets (including agricultural pellets). The pellet burner's flame is aimed at the rear wall of the boiler's lining. A multifunctional control unit controls automatic ignition, combustion, and burner cleaning. The mechanized fuel feed, hopper, and automation are supplied with the flare burner.
Operating mode with retort burner: 
The boiler's side hatch is removed and a retort burner is installed in its place. Fuel is fed from the hopper via the burner's auger, and combustion occurs in the lower chamber. This automatic loading mode is designed for burning pellets and fine coal. The combustion process is controlled by a control unit. The fuel feed hopper is protected by a BVTS fire suppression system with a thermostatic valve.
Purpose
The boilers are designed for operation in central water heating systems with forced (closed pressure heating system) or natural (open heating system) circulation of the coolant for warm and hot water supply of residential buildings, summer cottages, industrial and warehouse premises, retail facilities, social and administrative buildings.
The boilers are designed for operation in systems with an operating pressure of no more than 0.2 MPa (0.6 MPa on request) and a water temperature at the boiler outlet of no more than +95 °C.
Advantages of the Retra-4M Combi boilers: 
- Three operating modes.
- Brand reliability.
- Two combustion chambers.
- Modern automation.
- 5 years warranty.
- Permanent service.
- The boiler design allows burning different types of fuel (pellets, coal, wood, briquettes, sawdust, wood waste).
- High versatility: possibility of using different types of burners or manual operation mode.
- The wall thickness of the heat exchanger is 5 mm (up to 100 kW), 6 mm (150 kW), which ensures a long service life.
The design of the Retra-4M Combi boiler with a capacity of 25-150 kW
The steel heat exchanger (1) consists of three main parts: the lower combustion chamber (15) is located at the bottom, for use with the burner, and the upper combustion chamber (16) is located at the top, for manual operation. Behind them are straight baffles (21), which form the heat exchanger's convection channels. Both chambers are separated by a grate (9). The straight baffles and the heat exchanger walls are cooled by water, forming the so-called "water jacket."
When operating the boiler in manual mode, combustion occurs in the upper combustion chamber on the grate. A primary air diffuser (5) is located beneath the grate, which, together with the fan (8), forms the primary air supply system. Secondary air enters the combustion chamber from the fan (7) through the supply manifolds and nozzles (10). The lower combustion chamber also serves as an ash collection chamber, housing an ash drawer (6).
On the front side of the boiler there are hatches with doors: for loading fuel (2), stoking (3), and a lower hatch (4) for removing ash.
The boiler kit includes a control panel with temperature sensors immersed in a sleeve (11). The boiler is connected to the water supply via a feed pipe (12), located on the top wall of the boiler, and a return pipe (13), located on the rear wall of the boiler. Also located on the rear wall of the boiler is a drain pipe with a ball valve and a safety valve that is activated when the pressure exceeds the permissible value. A pressure gauge with a valve (14) is located on the top wall of the boiler.
When operating with a flare (17) or retort (19) burner, the primary air diffuser (5) is removed and the primary air manifold plug (18) is installed. The rear wall of the lower combustion chamber (15) is protected from the burner flame by a lining (21).
Types of boilers:
- F – with lined hatches;
- B – with water-cooled hatches;
- P – the front side of the boiler is vertical (straight);
- K – the front side of the boiler is inclined (at an angle).
Upon special request, the boiler heat exchanger can be made reinforced - operating pressure up to 0.6 MPa.
The principle of operation of the boiler
Water from the heating system enters the boiler through the return pipe (13), spreads throughout the internal cavities of the heat exchanger, and absorbs heat from the burning fuel through its metal walls (via contact and radiation in the furnace) and from the combustion gases (via convection in other parts of the heat exchanger). Heated water enters the heating system through the supply pipe (12).
When operating the boiler with a flare or retort burner, the primary air diffuser and cast-iron grate are removed, and the boiler's primary and secondary air fans are not used (only the burner-mounted fan operates). A plug is installed in place of the primary air diffuser. Ash removal from the boiler is manual using an ash pan. For automatic operation, the boiler is equipped with a hopper (for a flare burner, an adapter for the hopper and a flexible auger are additionally supplied). After the boiler is lit, combustion is controlled automatically. All you need to do is refill the hopper with fuel.
Delivery set of "Retra-4M Combi"
Item No. | Name | Units | Manual operation mode | Operating mode with a retort burner | Flare mode of operation burner |
1 | Boiler Retra-4M Combi | pcs. | 1 | 1 | 1 |
2 | Fan with damper | pcs. | 2 | 2 | 2 |
3 | Remote control | pcs. | 1 | 1 | 1 |
4 | Pressure gauge DM 05-MP-ZU | pcs. | 1 | 1 | 1 |
5 | Tap for pressure gauge | pcs. | 1 | 1 | 1 |
6 | Safety valve | pcs. | 1 | 1 | 1 |
7 | Ball valve 1/2" | pcs. | 2 | 2 | 2 |
8 | Pancerpol PPSM TRIO burner cap | pcs. | 1 | 1 | 1 |
9 | Pellet burner Pancerpol PPSM TRIO | pcs. | - | 1 | - |
10 | Fire extinguishing system with thermostatic valve BVTS | pcs. | - | 1 | - |
11 | Feeding bunker | pcs. | - | 1 | 1 |
12 | OXI* Torch Burner | pcs. | - | - | 1 |
13 | Flexible feed auger with fire-resistant PU sleeve | pcs. | - | - | 1 |
14 | Transition from bunker to flexible auger | pcs. | - | - | 1 |
15 | Fastening | K-kt | 1 | 1 | 1 |
16 | Operating documentation | K-kt | 1 | 1 | 1 |
Overall and connection dimensions of the Retra-4M Combi boilers with a capacity of 25-150 kW
Boiler passport Retra-4M Combi 25-150 kW
Passport of the RETRA-1NEW(P) remote control (Appendix G)
Technical characteristics of the Retra-4M Combi boilers with a capacity of 25-150 kW
