brianpgriset
Well-known member
Recently my Mr Cool Universal 3 ton ducted split system started throwing an E3 code - low pressure protection. What was odd was the unit would throw the code immediately, even before the compressor started running. To me that suggested a large sudden leak or a bad pressure switch. Zero issues prior to this since I did the install 5 years ago. With some help from Mr Cool I confirmed the pressure switch was working fine. I called out a local HVAC tech, they hooked up gauges and confirmed no pressure. They then connected a nitrogen bottle and pressured the system to 200psi and quickly found the leak. Unbeknownst to me this system contains a fusible plug, which appears to have relieved. The small lead plug in the middle was missing and gas was coming out the port. I suspect this plug is for the same purpose as other fusible plugs I am familiar with - to relieve gas pressure in the event of a fire. Not for over pressure protection. In addition the unit has a high pressure cutoff switch which has never triggered and the unit has never had refrigerant added, only the factory charge, again with five years of perfect operation.
When I showed this to the Mr Cool support they said they have seen this on a few units in the Deep South where it gets very hot. They are going to send a new plug under warranty, but that isn’t the issue so much as the 10lbs of R410a that was released.
Per the Mr Cool tech support the fix is straight forward. Replace the plug (it’s threaded). Pressure test with N2 and confirm no leak at the replaced plug. Evacuate the system and recharge with the correct weight of R410a (9.85lbs).
My questions and concerns:
- my original plan was to replace the plug myself and call a local HVAC contractor to pressure test and evacuate/charge the system. I’ve called two local vendors and both want ~$1000 to do this which is frustratingly high, considering 410a looks like it costs $10-$12 per pound. I would like to get the vac pump and gauges and do it myself, along with taking the EPA608 certification (seemed pretty easy and I almost passed on a practice test with zero prep). Would this be a reasonable path?
I’m also a bit concerned the system has been “open” to the atmosphere for awhile now (About 10 days, albeit through the very smal fusible plug port). Won’t moisture contaminate the system? My concern is if I hire someone they will do a quick evacuation of th system and not really take the time to draw a deep vacuum and make sure all the moisture is removed. Thats part of my motivation to do it myself, but I’m also worried I might mess something else up.
Input welcome. Oh and depending on the threads of the fusible plug, I might just get rid of it and put a regular plug its place. I do not want to be doing this again in 5 more years.
When I showed this to the Mr Cool support they said they have seen this on a few units in the Deep South where it gets very hot. They are going to send a new plug under warranty, but that isn’t the issue so much as the 10lbs of R410a that was released.
Per the Mr Cool tech support the fix is straight forward. Replace the plug (it’s threaded). Pressure test with N2 and confirm no leak at the replaced plug. Evacuate the system and recharge with the correct weight of R410a (9.85lbs).
My questions and concerns:
- my original plan was to replace the plug myself and call a local HVAC contractor to pressure test and evacuate/charge the system. I’ve called two local vendors and both want ~$1000 to do this which is frustratingly high, considering 410a looks like it costs $10-$12 per pound. I would like to get the vac pump and gauges and do it myself, along with taking the EPA608 certification (seemed pretty easy and I almost passed on a practice test with zero prep). Would this be a reasonable path?
I’m also a bit concerned the system has been “open” to the atmosphere for awhile now (About 10 days, albeit through the very smal fusible plug port). Won’t moisture contaminate the system? My concern is if I hire someone they will do a quick evacuation of th system and not really take the time to draw a deep vacuum and make sure all the moisture is removed. Thats part of my motivation to do it myself, but I’m also worried I might mess something else up.
Input welcome. Oh and depending on the threads of the fusible plug, I might just get rid of it and put a regular plug its place. I do not want to be doing this again in 5 more years.