1nolaguy Posted July 9, 2023 Share Posted July 9, 2023 Last year I changed out both non-working Penguin II A/C-HP with RecPro A/C-HP (Haughton 3800). The new RecPro have a simpler internal thermostat system controlled by a thermister attached to the evaporator coil of each unit. The two units share common ducting that run from the front to the back of the coach. When both units are on I noticed an issue with one or both cutting out or short cycling. When I switched the unit from A/C to the fan would come on and the ceiling mounted thermostat would show a temperature drop of 2-4 deg and then a gradual warm up at which point I can switch back to A/C and it works fine. If I just run one A/C it does not be an issue. I suspect that when running two units the air in the ducts coming from both units may be causing a early drop in temperature below the setting of the thermostat. Any suggestions or similar experiences? Link to comment Share on other sites More sharing options...
timaz996 Posted July 9, 2023 Share Posted July 9, 2023 Do you have any ducts that might be blowing at your thermostats. When both are running, you obviously will have a lot more air coming out of your air duct. Link to comment Share on other sites More sharing options...
1nolaguy Posted July 9, 2023 Author Share Posted July 9, 2023 I try to make sure the duct registers are pointed away from the ceiling unit but as many as there are it is not a sure thing. Link to comment Share on other sites More sharing options...
Jerry G Posted July 9, 2023 Share Posted July 9, 2023 I put in the same units, 15k each. I put a cardboard baffle in the ducts so one does the bedroom and the other the living room and that pretty much eliminated that issue for us. We can go to bed with ac on in bedroom, and have the livingroom programmed to come on heat at 3am, so it's warm when we get up. Link to comment Share on other sites More sharing options...
1nolaguy Posted July 9, 2023 Author Share Posted July 9, 2023 Great Idea! Where and how did you install the cardboard baffle? Link to comment Share on other sites More sharing options...
Tom Cherry Posted July 9, 2023 Share Posted July 9, 2023 Typically….so be careful. One side of the motor home will (may) have a duct, by design, that runs full length so the front and the rear commingle. The other side, usually on the Shower side are blocked and there are two separate ducts. Finding the mid side on the full length run is easy. Turn off one AC. TURN the other ON - HIGH. Now start working your way back from the furthest duct on that side. You will feel faint air past the hall on the other side. Repeat on the other side in case you have two full ducts. Find a register in the middle (hall or bathroom) and pull down the register. Then fabricate a blocker baffle on the “front zone” side and slow down or block it. You will have to experiment and be creative….that should fix the issue. The other fix….do your blocking In the last register up front….whichever is easiest. Repeat if two full length ducts. Link to comment Share on other sites More sharing options...
MyronTruex Posted July 9, 2023 Share Posted July 9, 2023 On my ducts, think of a railroad track going down the middle of the RV, however on mine one of the tracks does not go all the way back. Just the one closest to the drivers side. The last duct in the living room is where I dropped in a block. I have taken it out since because the additional cooling coming from the bedroom during the hot days helps a lot. The main issues with mine short cycling has always been the location of the remote thermostats. On the front AC it would not cycle off during the day with the RV drivers side in the sun. The thermostat sensor is not in a good place and the bedroom one had too much cold air on it all the time. With the bedroom one I just modified it slightly and make sure no vent blows directly on it and also leave the ceiling fan running 24/7. The living room issue was solved by installing a new sensor. Nothing fancy. Its pickup nose is actually just protruding out fomr one side of the inside shroud. Right at the ceiling level. It works excellent there. Link to comment Share on other sites More sharing options...
Tom Cherry Posted July 9, 2023 Share Posted July 9, 2023 10 hours ago, 1nolaguy said: Last year I changed out both non-working Penguin II A/C-HP with RecPro A/C-HP (Haughton 3800). The new RecPro have a simpler internal thermostat system controlled by a thermister attached to the evaporator coil of each unit. The two units share common ducting that run from the front to the back of the coach. When both units are on I noticed an issue with one or both cutting out or short cycling. When I switched the unit from A/C to the fan would come on and the ceiling mounted thermostat would show a temperature drop of 2-4 deg and then a gradual warm up at which point I can switch back to A/C and it works fine. If I just run one A/C it does not be an issue. I suspect that when running two units the air in the ducts coming from both units may be causing a early drop in temperature below the setting of the thermostat. Any suggestions or similar experiences? BTW….Please comment on how you kept, assuming you did, the old thermostat(s) for heating. Did you have the 4 or 5 button Multiplex system or a more conventional analog thermostat. Pictures of the thermostat and explanation of what you had to do would be great. THANKS. 1 Link to comment Share on other sites More sharing options...
Gary 05 AMB DST Posted July 9, 2023 Share Posted July 9, 2023 I bought a new temperature sensor, disconnected the original one and installed the new sensor and placed it near the return air vent on the ceiling. Gary 05 AMB DST Link to comment Share on other sites More sharing options...
1nolaguy Posted July 9, 2023 Author Share Posted July 9, 2023 Thanks Gary. Can you post a pic or link for the replacement temp sensor? 2 hours ago, Tom Cherry said: BTW….Please comment on how you kept, assuming you did, the old thermostat(s) for heating. Did you have the 4 or 5 button Multiplex system or a more conventional analog thermostat. Pictures of the thermostat and explanation of what you had to do would be great. THANKS. Tom, I will need to take some photos when back at the RV, which is stored in an adjoining state. I have a 5 button multiplex controller (that is not longer working) mounted on the bedroom wall common with the powder room. It is in a larger panel that also houses electrical monitoring systems and several switched. The controller or "brains" for each original A/C was zip tied in the plenum between the roof system and the ceiling grill. This will make more sense once I have pics to attach. Link to comment Share on other sites More sharing options...
Gary 05 AMB DST Posted July 10, 2023 Share Posted July 10, 2023 (edited) Loel, I don't remember the name of the supply house, they were bought out, in Elkhart. A Dometic supplier will probably have a listing. I did this a good 10-12 years ago. It's just the temperature sensor that you already have with wire and plug. I just unplugged the plug and left the sensor under the front tv, coiled the new wire and hung the sensor near the A/C grill. Gary 05 AMB DST Edited July 10, 2023 by Gary 05 AMB DST more info Link to comment Share on other sites More sharing options...
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