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Jiangxi Hewei New Energy Technology Co., Ltd.

Why can't the home multi-connection be fully opened?

Jiangxi Hewei New Energy Technology Co., Ltd. Posted on: 2019/4/4 17:29:47

Why can't the home multi-connection be fully opened?


Any brand of multi-connection allows over-matching. Over-matching refers to that the combined capacity of multiple internal units of the same multiple-line system exceeds the rated capacity of multiple outdoor units. Dividing the cooling capacity of the indoor unit by the cooling capacity of the outdoor unit multiplied by 100% is the proportion. For example: the total cooling capacity of the indoor unit is 17KW, the cooling capacity of the outdoor unit is 14KW, and the over-provisioning rate is about 121%. That is, the internal machine has a large cooling capacity and the external machine has a small cooling capacity. In popular terms, it is a small horse-drawn cart. Some manufacturers allow more over-matching, while others allow less over-matching. Daikin ’s allowable over-matching is 120%, Midea ’s allowable over-matching is 130%, and Gree ’s allowable over-matching range is 135%. What about it? There are several reasons:


Generally, the simultaneous use rate of the internal unit in villas and other places is almost zero. In order to save costs, reduce engineering costs and save energy, the external unit that matches the area used is selected to be one smaller, that is, the total capacity of the internal unit is rated higher than the external unit. Great ability. Or in the same place, the air conditioners in most rooms need to be operated at the same time, and the corresponding external machines just meet the use of these rooms. For a few other rooms, such as utility rooms, cloakrooms, etc., they are rarely used or occasionally used. The multiple connections of this system can be equipped with a few more internal machines to achieve the purpose of cost savings. The above is the origin of multi-connection over-provisioning. From the above situation, all the internal units of the over-configuration multi-connection system will not be turned on at the same time.


For an over-equipped normal multi-connected system, all the internal units are fully open. According to the law of conservation of energy, the energy allocated to each internal unit must be reduced, so it cannot meet the normal use of each room under the rated operating conditions. The premise of distribution is that all the internal units of the system will not be fully open. After understanding the mechanism of over-provisioning, you must carefully understand the user's needs when designing. You can appropriately over-provision for places that are not fully open, but the external machine capacity must meet the needs of the normally open room capacity, and the over-provisioning ratio cannot exceed 130. % (Due to oil return defrosting and other reasons, the internal and external unit capacity ratio cannot be lower than 50%). For all systems with the internal unit fully open in the same multi-line system, it must not be over-designed to avoid affecting the normal use of users.


I. Cost savings


Family use of central air conditioning rarely turns on fully. You can think of a scenario where a family of four, two adults and two children, a four-bedroom and two-living house, have six internal units installed, and one internal unit for each of the living room and dining room. Each of the three bedrooms has an internal unit, and there is also an internal unit in the study. Four people are at home on Sunday. This may be the time when the air conditioner is used the most. The living room, study, and dining room are turned on during the day. The three bedrooms are turned off. The dining room and study are closed and three bedrooms are turned on. At night, there are people watching TV in the living room. The air conditioner is on. One child is doing homework in the study. The air conditioner is on. Another child is playing with toys in the bedroom. The air conditioner is also on. When playing with a mobile phone, the air conditioner is turned on, the dining room and a kid's bedroom are turned off, and at night, three bedrooms are turned on, and up to four internal units can be turned on at most. If you configure the external unit according to the cooling capacity of the internal unit, does the compressor often run at low load? According to the cooling capacity of the internal machine to match the external machine, the user has to spend a lot of money, which is an unnecessary waste. Therefore, allowing over-provisioning is a good way to reduce user costs.


Second, reduce project cost


When you make a budget, you will consider reducing costs, increasing profit margins, the internal cooling capacity is large, and the external cooling capacity is small. This situation is a good choice. You can directly lower your offer price and give you competition. Bring advantages. If you make a budget according to 1: 1, your price will be higher than your competitors, and it will be difficult to receive sales orders. This over-allocation scheme is to reduce the total cost.


Third, save energy


When the sum of the cooling capacity of the internal unit is greater than that of the external unit, when some internal units are turned on, the compressor of the external unit will run in the energy-saving section. In fact, the most energy-saving section of the multi-frequency inverter is the compressor running at 25% —85 %between.


The air conditioner can be over-provisioned, but it cannot be over-used. It can be over-provisioned by 130%. However, it can only be turned on to within 100%. After over-provisioning, it is not used without any problems. It will cause some problems.


1. The air conditioner cannot reach the required cooling effect;


At the beginning of the design, you may have designed the cooling capacity according to 200W / m2. After over-provisioning, according to the law of conservation of energy, the actual cooling capacity allocated to the internal function will be greatly reduced, which is less than 150W / m2. The cooling effect is all worse. The temperature of the internal tube detected is too high, and the temperature of the inlet pipe is above 15 degrees Celsius, which causes the temperature of the air outlet to be too high. The direct feeling of the user is that the cooling effect is poor.


2. The compressor life is shortened;


After over-provisioning, over-opening for a long time is harmful to the compressor, and it does not save energy. After over-opening, the compressor of the host is always running at full load. When the inverter compressor is used at a fixed frequency, the service life of the compressor will be shorten.


3. The outdoor unit is very noisy.


If the over-connected multi-line system over-opens the internal machine, it will overload the compressor, which means that the load of the compressor increases, the operating current increases, and the noise of the external machine increases, which may affect the use of the owner. Experience, or bother neighbors.


When is it okay to open super? That is, when the outdoor ambient temperature is turned on at 30 degrees Celsius, the cooling can be super opened, because the air conditioning is turned on at that time, and the cooling capacity generated by the host exceeds the nameplate! Why do manufacturers strictly control over-provisioning? The super configuration is within the allowable range, that is, the user will fully open the internal unit when he is not aware of it, which will not cause damage to the compressor. At most, the cooling effect will be a little worse. If the compressor is killed, it will cause irreversible damage to the compressor.


So it comes with risks, so choose carefully


Commercial environment, office environment is not recommended to over-provision, unless there is a meeting room and idle warehouses do not need to turn on air-conditioning, air-conditioning use frequency is not high, you can over-provision 110%.


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