Combi Boiler

A combi boiler (wall-mount / floor-standing) is widely used to provide independent heating for residential and office units. The following provides the specifications, brands, models, analysis, capacity estimation tips, and the best purchase price of all combi boilers for wholesale purchase with warranty.

Combi Boiler Review, Selection, and Pricing

The central combi boiler is the kind of device that can simultaneously supply hot water for consumption and heating water for each of the apartment units instead of the central engine room. The floor or wall-mounted combi boilers can be easily installed in a cabinet place. In addition to higher efficiency, combi boilers have lower fuel consumption than those big boilers in the engine room.

Also, the use of a combi boiler, in addition to eliminating extensive piping in the building, makes each unit independent in terms of providing heating and hot water consumption. In general, combi boilers are divided into two types: wall-mounted and floor-standing in terms of placement and installation.

At the beginning of this article, we suggest calculating the approximate capacity of the combi boiler (both wall or floor standing) required for apartment units, multiplying the square footage of the unit by the number 150, and for office units, multiplying the square footage of the unit by the number 100, and for houses and buildings outside the city, multiply the square footage by 200 to get the capacity of the boiler (either gas or diesel). For more information, you can contact the experts of DamaTajhiz HVAC.

The supply of all types of authentic brands of central combi boilers with a guarantee of product authenticity and a delivery time of 2 to 4 hours (in Tehran), along with free installation and the most appropriate prices, has been done by the DamaTajhiz HVAC Group since 2013 as a valid and official member of the Union of Heating Equipment and Ventilation Equipment Sellers.

Combi Boiler Capacity Determination

The capacity of the combi boiler means the effective heating power of the device, which is calculated in units of kilowatts (kW) or kilowatts per hour. This capacity indicates the heat a combi boiler can produce in one hour.


The capacity values of the combi boilers can be different and depend on the heating needs of the desired place.


The measurement of the capacity of the wall-mounted combi boiler in the form of kilowatts is usually done in ranges such as 24kW, 28kW, 30kW, and 35kW, and based on kilocalories, it is usually 28, 25, 20, 35 kilocalories per hour, and based on the heating requirement of the relevant unit, you can choose a wall mounted central heating or a suitable floor standing one.


There are two common methods to calculate the capacity of the combi boiler: the approximate method and the exact method.

The approximate method of calculating the capacity of the combi boiler

To calculate the approximate capacity of the combi boiler (wall or floor-standing) needed for apartment units, multiply the square footage of the unit by 150; for office units, multiply the square footage of the unit by 100; and for villas and buildings outside the city, multiply the square footage of the villa by 200 to get the capacity of the wall or floor-standing combi boiler (gas or diesel) required for the relevant space.

The exact method of calculating the capacity of the combi boiler

In this method, various parameters are considered, such as:

• weather conditions
• geographic location
• place area
• number of residents
• building materials
• number and dimensions of windows and doors
• heat transfer coefficients
• the amount of cold air entering the building and the air change rate
  
  

These are carefully calculated to determine the exact heating load of the particular unit. Facility engineers and professional consultants usually do the exact calculation of the capacity of the combi boiler.

The formula for calculating the capacity of the combi boiler

QT=[(U1*A1+U2*A2+U3*A3+…)∗ΔT+(V*0.0749*0.24* ΔT)]*4

• QT: Heating load of each unit in kilocalories per hour
• U1 to Un: Heat transfer coefficient of each surface between the inside and outside of the building in terms of BTU/ft2.hr. °F, which should be determined based on the material of each wall, using engineering reference tables.
• A: The area of each peripheral surface of the corresponding unit that transfers heat to the outside of the building. This area (in square feet) includes walls, windows, doors, and ceilings.
• ΔT: The temperature difference between the inside and outside of each unit under normal conditions, which is in °F.
• V: Total amount of air infiltrating through door or window seams (CFH) in ft3/hr
• Constant factor 0.0749: Air density in conventional conditions in the English system of units
• Constant coefficient of 0.24: Specific heat capacity of ambient air in conventional conditions in English units

In the above formula, by calculating the values of all the parameters, you can get accurate results to determine the capacity of the combi boiler required for each building unit. Note that the exact values of U and area A for each surrounding surface must be considered based on specific details in each building and heat transfer coefficient tables.

Note: The heat required to provide hot water in floor-standing and wall-mounted combi boilers is not calculated separately for heating systems and consuming water. When the hot water tap is opened, the combi boilers cut off the heating system of the unit and allocate their heating power to the hot water through the flow switch and the automatic brass tap using their second heat exchanger until the hot water tap remains open, and then again provide heating for the relevant unit heating system.

Choosing the right place to install the wall-mounted / floor-standing combi boiler

Choosing the right installation location for the wall or floor combi boiler can have a great impact on their performance and efficiency. Each of these devices meets different needs according to the model and capacity. For the proper and optimal installation of the combi boiler, you must pay attention to the following:

The wall-mounted combi boiler is suitable for small houses and apartments of 60 to 180 square meters that have less space. Because this system takes up little space and in some cases gives a beautiful look to your environment. For example, residential units, office rooms, shops, or cafes with a maximum area of ​​180 square meters, which require proper and regular environmental heating, use this type of system.

Installing a wall combi boiler helps to beautify the environment, internal or external walls. These systems are usually installed secretly in the kitchen cabinets and are hidden from the normal view of people, which helps to beautify the space. Of course, it is necessary for the floor and ceiling of the wall cabinet where the combi boiler is installed to be completely open so that the proper airflow is available for complete combustion.

Floor combi boiler For large houses and villas of more than 200 square meters that need uniform heating in all their spaces, the ground combi boiler is a good option. Ground boilers, which are naturally installed on the ground, have more heating power, a hot water storage source, and a stronger circulator pump compared to their wall types, and based on the capacity and according to the information contained in the technical specification tables, even for substructures up to 400 square meters or More are also used!

Types of Combi Boilers

The wall-mounted and floor-standing combi boilers have different types that are designed based on the different sizes and capacities. To choose the right combi boiler, you must first determine the desired capacity and dimensions. On the website of DamaTajhiz HVAC, the technical information of dozens of models of wall and floor-standing combi boilers from reputed brands and with their main guarantee has been provided for you to enjoy the good feeling of optimal and smart shopping.

Types of Combi Boilers in Terms of Fuel Consumption

combi boilers are divided into four types according to the fuel type:

• Gas burner combi boiler (noiseless wall and floor-standing)
• Diesel burner combi boiler (floor-standing with the ability to be installed in the engine room or a warehouse outside the unit)
• Dual-burner combi boiler (floor-standing with the ability to be installed in the engine room or a warehouse outside the unit)
• Electric combi boiler (noiseless wall and floor-standing)
  
  

Note: Diesel and dual-burner combi boilers are mostly installed in the engine rooms of houses and private buildings that have front and/or backyards.

Types of Combi Boilers in Terms of Heat Exchanger Numbers

combi boilers, in terms of the number of heat exchangers, are divided into two categories:

Single heat exchanger combi boiler

The structure of the heat exchanger in these boilers is such that the heating system water pipe and the consumption water pipe are separated. Still, they are exposed to the flame of the burner at the same time, and the water inside them is heated simultaneously.

This results in quick hot water production and less depreciation of the combi boiler due to the inactivity of the pump in the summer season. It goes without saying that the amount of sedimentation in single-exchanger boilers is more than in double-exchanger ones, and the output water may have temperature fluctuations.

Double heat exchanger combi boiler

In double-exchanger combi boilers, one heat exchanger is installed to provide hot water for the heating system, and one heat exchanger (of plate type) is installed to provide healthy consumable hot water.

The water pipe of the heating system is directly exposed to the burner flame, but the plate heat exchanger provides the consumable hot water through heat exchange with the hot water of the heating system. Due to the existence of a plate heat exchanger in the double exchanger combi boiler, hot water comes out with a uniform temperature, and the amount of sediment in these boilers is much less than in the single exchanger ones.

These categories are determined based on the number of heat exchangers in each central combi boiler, and each type of combi boiler may have differences based on other features and characteristics.

Factors to Keep in Mind When Buying a Gas-Burning Combi Boiler

It is important to keep these points in mind so you will not experience a malfunction or low function in your device:

• The surface of the building or the size of the residential unit
• The amount of hot water required is based on the number of bathrooms in each unit
• How to implement the chimney of the building (vertical to the roof or with a horizontal path)
• Supply of fresh air or oxygen required for the combustion of fuel used in the combi boiler (for units smaller than 65 square meters)
• The minimum area that can be approved for installing a combi boiler in an apartment unit is 64 square meters. Otherwise, it is mandatory to install the combi boiler outside.
  
  

Combi Boiler Technical Tips & Points

The following tips will grant you the acknowledgment of these devices, which in some cases is very necessary:

Combi Boilers with Built-In Fans

In the conditions where the installation of the combi boiler is in an open space such as a balcony or patio, or a part of the chimney path runs horizontally (more than 30 cm), the fan combi boiler is used, the ventilation fan in the section The exhaust combi boiler transports combustion gases outside the building.

For this reason, the fan combi boiler is usually equipped with a special double-walled chimney, whose inner wall has a diameter of 6 cm. With this method, the combustion gases of the combi boiler are discharged to the outside environment through this chimney, whose outer diameter is 10 cm.

Note: If your combi boiler is going to be placed in an open environment such as a balcony, patio, or backyard, you should definitely use a boiler with a built-in fan, as well as an anti-freeze system. The anti-freezing system works only if the combi boiler is connected to the electricity and if the device has started its operation at a low temperature.

Double Heat-Exchanger Combi Boilers

The combi boiler with two heat exchangers (one for the heating system of radiators and one exchanger for supplying hot water consumption); due to having two heat exchangers, the flow of hot water is continuous, which reduces deposits in the exchanger.

A double heat exchanger combi boiler is used where either the incoming water is hard (salts) or the apartment floor is more than 120 meters.

Frost Resistant Combi Boilers

Some models of combi boilers are equipped with a protection system against freezing, which must be turned on for its activation. In addition, the following terms are required:

• Connecting to electricity
• A minimum pressure of one atmosphere to the water inside
• Gas connection (the advantage of these combi boilers is that they can be installed both indoors and outdoors)
  
  

Combi Boilers for Multiple Units (Shared Combi Boiler)

A combi boiler for two office units that do not consume much hot water can be used if the heating power of the combi boiler is proportional to the size of the mentioned units and some technical measures are followed.

However regarding residential units, due to the limitation of hot water supply in combi boilers and the possibility of using hot water in two residential units at the same time, installing a combi boiler for two residential units (even if they have a small area) is not appropriate.

Combi Boiler Matching Devices

Today, in many buildings, the heating supply system of the units consists of "a combi boiler with a radiator", "a combi boiler with a ducted split AC", or "a combi boiler with a ceiling-mounted fan coil", which in order to provide hot air in the cold season of the year, the hot water combi boiler must have the power to flow through the fan coil or the split AC.

In this case, considering the limited pressure of the circulator pump of the combi boilers (6ft), it is necessary to calculate the diameter of the pipes, the distance of the boiler from the AC or the fan coil, as well as the piping installation in the ducts, must be done exactly according to the piping table of closed systems and under supervision of the experts.

Note: To calculate the approximate capacity of the required combi boiler, we multiply the square footage of the residential unit by 150 (kilocalories) and the square footage of office units by 100 (kilocalories) (because office units do not consume much hot water) and you can contact the experts of Damatajhiz HVAC Group for more info.

The Difference Between Wall and Floor Combi Boilers

These 3 differences are considered the most important ones and probably all that you need to know:

Location & Installation: The main differences between wall-mounted and floor-standing combi boilers should be the different types of space and installation methods they require.

Heat Production: Floor-standing ones are usually more powerful. Therefore, it is obvious that for places that require more heat production, a floor-standing combi boiler is a far better option, especially for apartments and large houses.

Water Storage: Ground combi boilers have a coiled tank or water storage tank, and this difference is very important when there is a water cut or water pressure fluctuations.

Combi Boiler Performance in Different Seasons

As you know, in the cold seasons of the year, in addition to providing hot water, the combi boiler must also provide water for radiators and heating circuits. In the summer season, however, the only task of the combi boiler is to supply hot water for consumption.

In other words, whenever there is a need for hot water in summer, the combi boiler burner is turned on automatically when the faucet valve is triggered. As the water consumption is stopped and the device is turned off, the electronic board is all on that task.

Installation Location for Wall-mounted Gas Burning combi boiler

These 7 tips will help you install your boiler in the most efficient way possible:

1. The installation site of the combi boiler should not be above the gas stove and other heat-generating devices.
   
   
2. The minimum distance from the floor to the bottom of the combi boiler is 120 cm.
   
   
3. The distance between the device and the opposite wall should be at least 1 meter.
   
   
4. The minimum distance from the adjacent wall or cabinet should be 15 cm on each side.
   
   
5. The vertical distance from the adjustment cap of the combi boiler chimney to the chimney valve should be at least 50 cm.
   
   
6. The chimney of the combi boiler should never be installed directly to the chimney vent inside the wall, but it should be placed at least 30 cm below the chimney vent. It is better to install the device as low as possible to the chimney valve. Increasing the distance between the combi boiler and the chimney valve increases the suction and improves the exit of combustion gases; however, if your device has a built-in fan, you can easily install it in a place where a part of the chimney runs horizontally.
   
   
7. If you want to install the combi boiler inside the cabinet, note that the combi boiler device needs enough oxygen for combustion, so the bottom of the cabinet must be open. The cabinet door must be shuttered so that the device can receive the oxygen it needs from the environment.
   
   

Buying Combi Boilers

Today, combi boilers are very popular among people from all around the world due to the independence of water consumption these devices offer.

To choose and buy the most suitable combi boiler from various models in bulk, you must first determine the capacity and type of the combi boiler. On the website of DamaTajhiz HVAC, technical information on dozens of combi boilers from reputed brands, along with the main guarantee, has been provided for you to enjoy the good feeling of optimal and smart shopping.

The Price of Combi Boilers

The prices of combi boilers vary based on the capacity, model, and brand available in the market; it should be noted that the prices presented on the DamaTajhiz HVAC website are all up-to-date, with a generous discount being applied to them. Therefore, the best price for all wall-mounted and floor-standing combi boilers is guaranteed.

Also note that in the specialized HVAC group of Damatajhiz, all the combi boilers are only sold in bulk. Therefore, if you want to wholesale any of these products, contact us.

The price list of the best-selling wall and floor-standing combi boilers

Please note that some models have asking prices, and prices may change. For more detailed information and more updated prices, you can contact the sales experts of Damatajhiz HVAC Group.

Dear Users:

As you may be aware, throughout the colder months of the year, the combi boiler should also supply radiator water and heating circuits in addition to hot water.

The combi boiler should only supply hot water during the summer. In other words, whenever hot water is required, the combi boiler's burner is automatically activated by opening the hot water valve. When the water consumption is reduced, and the hot water tap is turned off, the burner is turned off, which is controlled by the Electronics board.

If you need more questions to decide on the purchase of wall-mounted and floor-standing combi boilers after you read the above, you can contact the Sale of DamaTajhiz HVAC Group and ask your questions.

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