Makes no difference with capillary or EEV controlled units with most splits. Cooling mode requires the expansion to occur at the outdoor unit first before entering the indoor unit. There are no expansion valves at the indoor units unless your dealing with VRV/VRF systems or specialised large commercial units.
The reason for this is that the refrigerant can be pushed greater distances with a smaller displacement compressor at the trade off with fixed maximum pipe run lengths depending on unit model size. By creating a pressure drop at the outdoor unit,you have a greater potential to push refrigerant further where as normal subcooled liquid lines run at equal high side pressure and need greater pumping effect.
This is why the liquid line leaving the outdoor unit is not a true liquid line in cooling mode. It is realistically an expanded liquid line and part of the low side evaporator circuit as soon as it leaves the outdoor unit. This is why it needs to be insulated, otherwise it might flash the gas and yes take it from me that latent pipe pair coil rubbish is not good enough.
Keep these pipes out of direct sunlight, but as you go longer in pipe run you will lose the specified unit capacity due to pressure drop. There is NOTHING you can do about that.
The good news is that in heating , the liquid line is a true liquid line and it suffers much lesser losses in capacity for distance.
Now if your going to run a domestic type split the full distance of installation lengh. Ask yourself this very important question,
"should I upsize?"
The standard capacity distance is based on 7.5 metre piping run, with cooling mode. The bigger the capacity the unit is the greater the losses on cooling mode over a longer piping distance. Check the engineering data for this info from your manufacturer of brand air-conditioner
The BRC1E61 controllers Energy Saving features
Many know I used to work for Daikin , I really like the way the Japanese think about how to improve constantly
When the BRC1E61 controller came out, they also incorporated some features which quite frankly negate the use of a centralised controller for small scale installations.
Up to that point , a centralised contoller was needed to reset temperatures or fix temperature limits. Now it is embedded into single one on one systems.
Here is what is really great about this new controller
It has an energy saving feature which allows the user to do the following...
1 - Temperature Limits.. .. for both heating and cooling the controler can fix the range of selectable temperatures.
2 - Temperature Auto-Reset. Here you can select a preferred standard setpoint for heating and cooling, which will automaticaly reset to the preset temperature after a time period has expired. This way people can adjust setpoints but it will always reset to the preferred standard setting.
Now that is a really great idea...
This eliminates the need for higher host control for basic requirements with typical settings.
Note.. If centralised control is fitted later , it will overide the internal settings. But thats the way it should be.
Testing the Testo
Well, the age of the digital service technician is well underway with new era, gauges , vacustat's and WIFI!!!!!!!
Enter the Testo WiFi temperature and pressure test equipment which can be fitted to a system and then data delivered to an application (downloaded) which converts to real-time system service information.
Trend mapping , logging, monitoring , recording of system data which was once only available to high end recording tools.
Yet your saturation,superheat,subcooling and vapour temperatures are only a transducer away.
I prefer a tablet over a smart-phone but then , the new phones are getting bigger all the time.
Clamp on or screw on , then your away.
Say goodbye to the bourdon tube gauge , a relic of once past which now lies with the tradie of old. Yet I will always subscribe to analogue measures as being somewhat accurate in their own right.
The Greek philosopher "Herclitus" said "The only constant is change"
And as I always say , the industry is changing , so lets change with it.
The flexibility of technology see's no limits.
Carel's EEV driver systems have a lot going for them, Here below the EVD series with something very different.
We have fitted two Carel E2V electronic linear pulse valves which operate a common base load in a complimentary arrangement.
The unit here is between 1800 to 2000 W refrigeration capacity with a 6K evaporator design working at -4 saturated evaporation temperature based on a 2.c room temperature. You can have one larger EEV serving the load but in this case we have used two smaller EEV units to give us a combined total capacity. This feature is known as "complimentary" mode where they open and close together in a parallel arrangement driven by the common driver signal , no need for a second input at the controller. You cant do this with all EEV arrangements but it does work and it works very well. We set them into a Y-junction with equidistant lines (both the same size) into a larger diameter feed pipe to the indoor coil. We did this to test it out and see how it all works.
Funny enough the EEV's can also be set up to work as an opposing arrangement where one will open and the other will close in unison equal steps. (of course im not sure where I would use that)
Now , The controller has it all and more, It even has built in wiring schematics in the interface display on how to wire the components such as the EEV, transducer and NTC probe and where. great if you forgot your installation manual. :D
I want to show you just how accurate these are, we are maintaining 5K with no load but getting from 75 to 80% relative humidity as per the expected refrigeration evaporator differences using a much lower TD than an air-conditioner. I have fitted a humidity meter in the cabinet.
No need for an EPR ,(on conventional coolroom design) the coil is saturated constantly,providing maximum efficiency ,no pressure drop from hunting through a conventional thermostatic expansion valve when the superheat and load is low. In that case the evaporator temperature difference widens temporarily lowering the relative humidity and drying out your high water content food products. We also fitted a speed controller to govern a high ambient 46.c condenser. This unit also Carel can work local or feedback to host PCo2 through network control.
You can see just how easy these are to use. Controls ready engineered to work local or by network. Another good feature is that a local digital input (switch) can be fitted to drive the EEV's closed which could be used as a pump down arrangement similar to a solenoid valve. We have one fitted to our electrical box.
A variety of downloads will be now featured on this site..... no opt in required....
Estimating added winding superheat in hermetic compressors.
Hermetic compressors A good idea but hungry on refrigerant vapour to cool the electricals.
Now many have heard me go on about the pressure enthalpy charts. They can be used very loosely to predict winding superheat on the refrigerant , and this is no means accurate but as a guide.
The theoretical discharge port temperature is derived from adiabatic compression lines but it predicts this from given vapour entering temperatures to the compressor. What we don't see is the extra energy added to the already superheated vapour by the electrical motor in the atmosphere of the dome prior to inlet for compression.
You can sort if predict it , but its best done with a system balanced and with ideal evaporator design superheats. Using the difference between the vapour entering temperature , referenced back to the actual real discharge pipe temperature we can estimate the added K to the gas by the motor. Now this is not to be taken as literal , yet it is a guide to future problems.
If you understand the charts , you might get the idea , where we estimate the vapour entering temperature prior to compression by the given discharge pipe temperature as close to the compressor as possible. If you know the real vapour entering temp to the compressor. then it becomes a sort of take one from the other. I have shown an example of a AC unit system on R22 with around an estimated 15K of winding superheat added to the refrigerant after entering the compressor pulling down to 4.c S.E.T. at 40.c condensing temp and a vapour entering temperature of 15.c
Hermetics have bigger condensers due to this added heat, And why i always say that using a hermetic compressor for a freezer system is not the best option. Keeping hermetics well tuned and with low vapour entering temperatures by lower superheat really helps.
Check out my new YouTube video on semi-hermetic protection modules.
This is the Lodam SEB1 (signal evaluation basic) used on Bitzer semi-hermetic compressor. Here we have created a simulation rig to show how it detects motor overheating. The compressor uses embedded PTC thermistors in the stator. With up to 9 in series , anyone can create an overload condition using a series looped total resistance signature R1+R2+R3 etc until the trigger resistance (equivalent temperature) is reached.
The simulation unit uses a 10K ohm variable resistor to represent an overheating compressor.
These devices are so very important, and save many compressors.
Yes the vid is a bit shaky, hand filmed , low budget on the mobile.
Check out my YouTube video on simple made DC motor
Exactly 20 turns of laminated wiring to make the rotor. The pole ends are etched at 180 degrees to provide the short circuit for alternating commutation and reverse current flow. Using a permanent magnet and power supply from 6Vdc battery, see how magnetic field reversal affects the direction.
Note that brushless DC motors do not use commutation and effectively arrest any sparks/ozone generation.
This video was made by Dennis Kenworthy for WWDD
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