【 Weak current College 】 household air-source heat pump water flow control technology

0 overview
Household air-source heat pump unit is top grade apartments and Villa users widely recognized a domestic central air conditioning, it is air cooled condenser, compressor and water refrigerant heat exchangers, etc. Water refrigerant heat exchangers is the refrigerant and water heat, resulting in a chilled water or hot water, then pump the frozen water or hot water supply air blower plate Tube, then through the fan-coil within the fan coil of frozen water or hot water for cold or heat blowing into the room, meeting room cooling or heating requirements. The system of energy transfer by the refrigerant into the water (refrigerant), followed by water energy transfer to the indoor air. Relative to the variable refrigerant system its pipeline system in a small leak or water flow exists allocated slightly uneven, shall not affect the unit runs, but for variable refrigerant flow unit is different, when the system in a refrigerant leak exists, refrigerant distribution, pipe plug, oil pipeline problems such as poor, and the entire system will be paralyzed.

Because household air-source heat pump unit is a large central air conditioning system miniaturization, but completely in accordance with the design of a large central air conditioning installation method is not suitable, whereas consideration must be given to the use of the target group are a home user, it is not possible to have the specialist to manage, so in the chiller design process must carry out the maintenance-free and low-maintenance design guidelines. The current residential central air conditioning sales and installation of mostly previously sales conditioner transferred, since the residential central air conditioning installation and conditioner and a completely different-sized central air-conditioning, many installation ' lack of experience, combined with the factory itself is also not installed too much experience cannot be installed on the sale of units good training, chillers installed often appear many problems, the most serious is the heat exchanger by frost, the unit will be scrapped, and the risk of being claimed. For water heat exchanger freezing of the main reason for this is through the heat exchanger water does not meet the requirements for reliable work unit minimum flow. Ensure that the heat exchanger is a suitable water chillers and reliable work necessary to ensure that no appropriate water flow may cause chiller evaporator ice (serious potential Frost), condensing pressure is high, the compressor cylinder "bite". In the event of the failure, the brand's quality reputation will be very large. As a result of household water chiller water flow control and protection is very important, appropriate water testing methods and testing parts can guarantee the unit only in system water is greater than the minimum allowable work under water, to a large extent can avoid air-conditioning host fails.

1 household heat pump units connected to the pipe design
1.1 household heat pump units within the main principle of material selection

Household heat pump units within the main design's main goal is to follow the maintenance-free and low-maintenance design, select the appropriate pipe material, if the use of rust, scale and corrosion of the water pipes, the user needs for maintenance each year while the other takes a small fee, and the variable refrigerant flow system for copper tube is not required that amount. From the main road system running reliability, a suitable water pipeline material will not be generated because the construction of a water filter caused by improper or heat exchanger clogged and also will not produce pipes rust, corrosion and scale effect unit life. Although good plumbing materials increase installation cost, but greatly reduce air-conditioning unit of repair and maintenance costs, in the life of the integrated costs will be significantly reduced.

1.2 household heat pump outer tube material selection principle

Household heat pump units, water pipe design should follow the maintenance-free and low-maintenance design, select the appropriate pipe material, otherwise the unit in the selection of appropriate although pipe material, but the unit still use easy rust out, scaling and corrosion of the water pipeline system and cannot implement maintenance-free and less maintenance. I think manufacturers in household heat pump products installation instruction on addressing water pipeline material clearly stipulated, which does not allow the use of material, what materials recommended by the manufacturer's technicians to dealers and installers full training to completely avoid water pipeline material impact caused by the water system. Thereby reduce pipeline blockage caused by water flow declined freezing heat exchanger.

1.3 household heat pump water filter selection and installation

Household heat pump unit of tube diameter is generally quite small (not more than DN65), pipeline between the pipe thread connection, if the use of reinforced plastic and other materials whose connection to melt or glued. Select water filter is filtering water pipe in the installation when the impurities and long-running pipeline corrosion, dirt and other impurities, the peeled off and avoid impurities into the heat exchanger, if impurity once inside the heat exchanger against very large, will likely heat exchanger partially blocked. If the unit heat exchanger using brazing or heat exchanger tube heat exchanger will be very difficult to remove, because both of these heat exchangers are not mechanical cleaning can only try the way through the recoil. If you are unable to effectively clear the heat exchanger of impurities will result in the Shui side heat exchanger local water flow down, at which time the refrigerant side refrigerant flow base maintained, might lead the water temperature has dropped below the freezing point of water even, because the water side of traffic jam down cause adjacent of refrigerant side appears incomplete evaporation, back to the trachea or even freeze Frost, easily densener. If the heat exchanger local jam light degree of a system's entire water flow without too much change, current protection switch has no effect. And antifreeze protection sensor (inserted into the heat exchanger for internal testing water temperature) are not detected by the lowest temperature, anti-freezing protection and cannot work, terrible thing happened-the heat exchanger Frost until the entire refrigeration system for scrap. In order to prevent as galvanized pipe construction using sealing belt, ropes and other impurities clogging heat exchanger except during construction construction specifications, manufacturers of chillers design process can prevent this from happening.

Water filter is heat pump water system in the most critical one of two parts. Select the appropriate water filters can effectively prevent water pipe construction process of impurities into the heat exchanger. Proper water filter mesh size and the form is very critical, AnnLoading time reserved by-pass unit fles valve, after the installation is complete before commissioning bypass module unit heat exchangers for water pipes cleaning. At this point in the inlet water filter it is best to use the 100 mesh stainless steel stamping filter, to the end of a water filter mesh size should be larger than 100 mesh (temporary use, open the debugging after bypass valve). If the system has an alternate pump when open main standby pump, the pipes of the maximum flow rate, open 24 hours after cleaning filter. This can be almost all large particle impurities accumulate in water filter, and then replace the water filter to 60 end up debugging. Also convenient for the user's own filter, it is recommended that you install the filter, consider future kick ball cleaning of heat exchanger to heat pump inlet and outlet outside of a three-way ball valve can be installed on. Diagram as follows:

2 household heat pump water detection method
2.1 household heat pump water flow detection

Residential heat pump unit on water detection in currently there are two simple and practical, cost-effective form of detection, target-type flow switches, a pressure differential and flow switches, the following comparison of the two test methods of installing and using properties.

2.2 target-type flow switch installation and use

Target-type flow switch is installed on the target movie, water pipe in pipe flow in water impact target flow sheet of bending deformation, thereby driving the micro switch output control signal to module unit controller advised flow can start unit.

Because household heat pump unit of tube diameter is smaller and to target-type flow switch installation to a certain degree of difficulty. Typically target flow plate installation has three conditions: first, it is not an action, the second is stuck in the tube upside not reply, the third is normal. Installation is very good and the pipe diameter and Installer experience very relevant, pipe diameter larger target-type flow switch once installation accuracy is higher, for household air-conditioning installers install residential heat pump unit target-type flow switch when an installation is not as high as 70 per cent success rate.

Typically target stream tablets not action because the target stream movie installed depth, need to swing or replace the target stream. Many installation workers encounter this situation if you cannot quickly resolve often shorted flow switch or adjust adjusting screw making a module unit loses water protection.

If you are stuck in the pipe not reply often target stream movie is too wide for the sake of the first action is to be stuck in the upper part of the pipe (the situation in small diameter pipes in cold for more), this is to install the provider cannot be found, flow switch also lost its role. If the installation space not enough even if you can work, as the pipes rusty or scaling and so the actual use of smaller diameter, is also possible to make the water flow switch card within the pipe cannot be effective action.

In addition when water mixed with air, the water of air shocks caused by target stream tablets, target flow velocity tablets instantly reset to unit error flow information (to prevent this error usually unit controller delayed processing flow information). At the same target-type flow switch target flow in normal use is prolonged water pressure, easy bending deformation, especially installation of fatigue damage in the vertical pipe and flow velocities exceed 3m/s and above their life will significantly shorten the correct installation of the General target-type flow switch's life for one year, this is the basic and medium-sized chillers are replaced each year target-type flow switch.

2.3 differential pressure flow switch installation and use

Differential pressure flow switch is based on the resistance of the HVAC equipment and flow curve design. We know that the HVAC equipment, heat exchangers, water filters, water pumps and valves, and other devices has its resistance and flow characteristic curve, by testing it at both ends of the poor and out of the water and the device preset values, you can precisely control flow.

Pressure-and target-type flow switch than it is a precise flow control, it has precise flow control value. It is directly installed on the machine, avoiding the user is not properly installed. If the installation of the unit from the pressure differential switch connect two copper tube-heat exchangers and export, import and export of measuring the differential pressure, which is reflected in the flow. But the user does not need to be installed on-site and wiring, which avoids the target-type flow switch installation not accurate result set failed.

Differential pressure flow switch with flow control and accurate, the system is no longer the extra resistance, also on the pipe diameter is not required and no flow disturbance interference, and other characteristics, you can replace any form of target-type flow switch as HVAC water system of flow control, relative to the target-type flow switch it to avoid pump cavitation induced false flow (actual velocity is very big, but the water mixed with air and the actual flow rate is not significant), and therefore can be widely used brazed plate heat exchangers, a tube heat exchanger and shell and tube heat exchanger modular air-source heat pump water flow control and also some antifreeze protection features.

3 differential pressure flow switch in the application in the residential units
3.1 water protection

For household machines using brazing or heat exchanger tube heat exchanger the pressure differential and flow curve may vary, but in factories through the test uses a fixed set-point pressure differential switch, ensure that the configuration of the pressure differential switch protection flow value is appropriate. Recommend disconnecting the flow is greater than the rated flow of 50 per cent reduction in flow rate proposal is less than 80% of the rated flow.

3.2 exposed pipe installation design issues

After the factory configured with the appropriate action and reset the value of pressure differential flow switch can be used as a check out of the water chiller system design and installation are correct, an important basis. Because a chiller regardless of what your installation, through the heat exchanger water does not reach the pressure differential switch reset flow (factory configuration data when testing, pressure differential switch type unchanged its reset flow also unchanged) the pressure differential switch will not be closed when the scene situation encountered not closed will be set out in the Shui system problems, did not achieve the reduction of traffic. Usually the system pipe resistance is too big, some valve does not open, the pump did not put the air, the filter is not blocking and pipelineExclude air situation that prompts the installer to check for and resolve, with guidance on one at a time. Because the installer is usually no meter, it is not possible to install pipe flow testing, if the target type flow switch is difficult to judge the pipes where the problem is, as a result of unsure pipe flow.

3.3 for filter clogging caused the water to flow protection value of pressure differential flow switch can be very effective protection. If you installed units at the end of the fan coil using 2-way valve, that is, the error using vwv, gradually closed 2-way valve, once you are opening two way valve's flow is less than the pressure differential switch's flow, pressure differential switch in 3 seconds, accurate output disconnect signal.

4 closing
After residential heat pump on the use of feedback, the pressure differential switch can effectively determine the chiller field installation of water pipes, completely avoid end error using 2-way valve causing heat exchanger by frost, can also be protected because the water filter blockage caused by the water flow down the heat exchanger of frost, water pipeline pressure differential switch did not target flow switch fatigue failure risks, especially in the water pipes have a small amount of air pressure differential switch work very stable, not appear similar to the floating target flow switches, after years of using feedback did not find the pressure differential switch itself has failed, and the target stream switch generally one year would not be reliable, its reliability is much better than target-type flow switch. This differential pressure flow switch is household heat pump unit of optimal choice.