The PCB is the brains of the whole system. It has a lot of functions and many pieces that must work together. While the majority of known issues are settings in the Controller, and the next significant category is sensor install issues, the need to replace the whole PBC is unlikely. If there is a significant surge, short, or component fault on the Printed Circuit Board "PCB", and it needs to be swapped out, this is the procedure to save a lot of time. There are a few stages that will make it go smoother than an unplanned attack. Sap the whole unit including the aluminum heat sink as one assembly - do not try to remove the heat sink or reuse the old one, it is difficult to remove and has heat transfer issues if not bonded properly. The combination new part you have to swap is also what you expect to remove in whole.
- Prepare by taking some pictures of the PCB wiring for reference when it comes time to put the wires back in all the right places.
- Use something like an egg-tray to organize the screws as you take them out. Start groups and save in sequential order, to avoid mixing them up, guessing what goes where, or losing them.
- Mark some wires or locations with tape, clips, or a marker as needed.
- Bring a wide variety of Phillips screw drivers that are in great shape.
- Bring a foot stool to put your arms and eyes above the opening
Secrets To Removal.
The PCB is secured by 14 fasteners from the back side, and it is way to difficult to remove the 8 Phillips head screws plus 6 nylon spacers operating blind. I recommend flipping the electrical box forward and down so the back can be worked on. How you do this is to remove 3 screws that hold the box in place, there are L-brackets on the left and right sides plus a screw in the middle-bottom of the opening. The one on the right is challenging, you need a good screwdriver, small hands, and some luck to blind-feel the removal. Once the 3 mounting screws are removed, the electrical box can be tilted forward 90-degrees so the back is visible.
(Alternatively, the SP3.1 has removable sides that could work. The motivation to make the sides removable was trying to swap the first PCB is a tight room.)
Above is the view from the inside of the electrical box opening - after the PCB and heat sink were removed. It helps to know how many fasteners you have to remove to avoid doing brute-force damage when some are still attached. The 14 is the combined total of 8 metric M4, plus 6 nylon spacers. Use an egg carton or plastic organizer to group the screws.
The 6 nylon spacers shown above circled in white, are best cut off from the back. Use a box-knife or thin blade to get under the round cap and slice the plastic. We have not found a way to save them, it is a matter of cutting them out. We plan to locate the supplier and stock some to be applied during the reinstall. A soldering iron tool with a blade or trowel bit works great, slices the off like butter even from the front. Consider wearing a glove to prevent scraping your knuckles when the nylon part is cut.
The 8 Phillips screws can demand a crisp new bit to avoid stripping that one difficult one that just will not budge. A Z-shaped Phillips worked well a few times around the fan and when more leverage was needed to get the first turn. Plan to have a variety of Phillips screwdrivers, you will struggle if you have just one and it is worn.
If the PCB with Heat Sink does not want to pull out, you have missed a fastener. Do not force it out with a pry bar or hammer, look for what is holding it in to complete the removal.
If you are wondering about the 5 screws you can see from the front of the PCB, they should be ignored. Leave them alone. They serve to press 3 small plates against the heat sink and are all gunked up with thermal paste. These 5 have nothing to do with holding the unit to the electrical box, they only mate the PCB to the Aluminum fins. Touching them can wreck the bond and cause heat damage. For clarity, leave the PCB and Heat Sink attached as one unit, do not try to separate the PCB because it has thermal transfer consequences that will result in having to buy another set.
Above is an SP2.3 PCB for a 10 kW (36000 BTU) size. It was removed to upgrade the Controller and Electric Heating logic on the first handful of 2015 models in BC. There have been zero PCB board swaps for 2016-2017 SP3x models.
SP3.1 New Sensors
There are some additional sensors on the recent model that need to be included for the matching Controller to function correctly.
- The only 6-pin plug at socket CN32 had:
- a) the top two pins/wires are for the Compressor discharge temp 25K sensor. The wire goes out the left box opening and to the top of the compressor.
- b) the middle two pins are not used on older models, but are required for new SP3.1 Touch Screens, it is for a panel defrost 10K sensor. If it is missing you will get an E05 message on the screen
- c) the bottom two pins/wires are for the Ambient Air 10K sensor in all models. If it is not connected an E06 message shows.
The other change is the addition of d) a 10K sensor at socket CN37 for suction temperature with Electronic Expansion Valve models of SP3. If it is missing, you get an E19 message. Both b) and d) can be plugged in while operating to remove the Exx message with instant clearing. Also both are not needed in upgraded models, the sensors can be left bundled and not installed anywhere. If they were needed then both were factory installed, only upgrades need to satisfy the requirement for a closed 10K circuit in the Controller logic.