Help, My FDECU-5 is bi-polar

Help, My FDECU-5 heat pump is bipolar

I bought a FDECU-5 (field deployable environmental control unit) which is a 3 or 5 ton heat pump recently from GL for $120 all in. I have been looking for something to heat and cool the room above my attached garage which is about 25' square. I left it unfinished when I built my house so that I could get in quicker and finish it later. My big mistake was not running 240v up there although I could probably just put in a window unit. I did look into a split system but just the equipment is 2-3K. I saw a FDECU-4 at Ft Bragg last year that looked perfect and almost unused but I fell out of the bidding at $600. This other unit came up at Portsmouth, VA along with another. Upon inspection, this unit had the flex tubes inside but a Sharpie note about failing to power up. The other unit did not have the flex ducts. I thought I could figure out the problem or $120 would not be too bad if no go. If I can make it work, I can heat and cool both the garage and the room above.

When I got it home, the attached plug fit right into the outlet on my 804a 15 kw generator. The internal fan ran fine but I do not remember if I tried the heat pump (made the compressor kick in) at that time. The next time I tried it, it would start for half a second and then kick out the breaker on the gen with a short light illuminated. On another day, everything would work fine except that in full cold, the output air would get hotter instead of cooler. Lmtv772 had a thread about a month ago about his FDECU-5s and we PMed several times. He also sent me a PDF of TM-9-4120-411-140012 which had Table 4-3 filled in unlike the TM that Hard Head had posted on another thread about FDECUs. I had a feeling that the reversing valve was stuck since it would heat instead of cool when in full cold mode. Further reading of the TM showed me how to get in the manual override mode (para 4.9.4) and turn on things one at a time. The reversing valve indeed cycles and it would put out air so cold my hand would hurt. With both heater units on, my gen would start to grunt and stabilize at around 125% output. In full cold, it stays around 50%. I think I saw that each aux heating unit pulls around 5.2 kw in the TM.

To fight the kick out the breaker and show a short on the gen panel problem, I have run a direct 10 ga ground wire to my house ground. It seemed to solve that problem until just the other day when it has again started to kick off after about 1/2 sec run. Also recently, going into manual override mode, the comp relay (I think) would cycle on off until I deselected the comp DIP switch which was a new problem. Today, as it has for the last several days, it does the 1/2 sec thing and shows a short on the gen panel which it had quit doing for the middle two weeks. It has also started to kick out as soon as any DIP switch other than #8 (the one putting the unit in manual override) is selected. It is strange how the problems shift around depending on how the unit feels that day

My thoughts are there are some relay problems causing the generator breaker to kick out and possibly a thermistor temp sensor causing the output to get hotter in full cold. I found in the TM how to test the thermistors but got sidetracked when earlier problems seemed to come back. Can someone please help me to understand Table 4-3 and how to interpret the binary fault codes.

Robert

I ran the FDECU-5 some more today and it decided to actually almost work correctly! I tried during the week and it was doing the usual start for .5" and then kick out the 804a gen breaker. Today I thought it was going to do that again when it kicked off after running for three minutes until the comp lockout timer was satisfied (the FDECU) but the gen breaker stayed in so I tried it again after pressing the comp timer bypass button and it worked. Turning the temp knob to full cold did the usual of making the output air hot so I still suspect one of the thermistors for that problem.

I went to mx override mode and everything works as advertised. With the reversing valve selected while the inside and outside fan and comp are running, it again makes air so cold your hand hurts and I ran it that way for 45 min. I then deselected the RV and turned on heat bank 1 and 2 and it ran fine for an hour. The pictures show what that looks like on the panel and how my 804a gen handles the load. The exhaust is totally clean. I did finally get the percent current gauge to work. I had been exercising the AM-VM switch to try to clean the contacts. I was doing that today and saw the needle move. It looks like that gauge only works in the L1,2, or 3 position on the AMPS circle which is the inside one. I did not notice that in the TM when I scanned it.

Again, this unit presents moving targets depending on what day it is. I was at a GL facility this week and saw they had several FDECU-5s in line to sell soon. They are pretty rough but perhaps I can get one or two for spare parts, one looked like a forklift has pierced one of the sides. I would probably try to switch out the electrical rack to see if that would solve the problems. None had the flex ducts inside but the cords and connectors alone are worth $100. Again, if anyone has suggestions on possible fixes or how to diagnose, please let me know. Robert

After reading other threads about problems with generators, I bought a can of DeOxit and douched the daylights out of S6 and then cycled it about 100 times on both my 804a and 804b generators. It seemed to show improvement on both. Before, the short light would come on 90% of the time the compressor tried to start. Saturday a week ago, my geothermal unit in the attic (3/4 ton) decided to pack it up. I had noticed that the pump for the ground loops was getting noisy like a leak was present and was adding water. Now that unit kicks out after trying to start. The other unit under the house (1.5 ton) was replaced 18 months ago when the original died (only 5 years but enough to be out of warranty) but never hooked up yet to the air handler. Well, I have yet another leak in my ground loops which gets me to at least 5 repairs. I have five loops of 750’ each and three were in operation at the time with leaks in two (now three!) and it is not easy digging down 5’ and finding the leak.

Meanwhile, back at the ranch, I needed some A/C so I decided to try a FDECU to see if it would work. As noted in previous posts, I had been considering using one to cool my garage and the room above it. Looking under my house, I saw a way to use the supply and return ducts for the lower geothermal unit with the FDECU. I connected my 804b to a new never put in service unit I bought at Ft Bragg that had worked fine in the past. It would quit and I would restart it and it would quit again. I switched out to a used unit and it has run fine. It was already bolted to another new, never put into service unit (which had the 134a removed prior to sale, don’t get me started) so I left it since it is easier to move. My 804a needs a new Magnetic pickup and I haven’t had a chance to look up the NSN yet so I can’t confirm if it worked on that unit as well as the b model. So mark me down as another satisfied DeOxit user. One interesting thing I noticed was that S6 on the 804a goes all the way around while the 804b stops and you have to go the other way.

If the mag pickup fits the hole, it should work.

My new magnetic pickup (MPU) arrived the other day. Today, it’s only 91 degrees with an overcast so I installed it. The Ohms only measured 398 when the book said 800-900. The initial Vac was like 0.3 so I cranked it in and finally got 2.8. I believe Guyfang mentioned that closer to 3 was better than 2 Vac. The previous MPU had gotten ground off on the end somehow all of a sudden, perhaps it got loose. It starts fine now.

I wanted to see if the DeOxit worked on the 804a as well as the 804b so I moved it over and hooked it up. I was disappointed when it did the same thing as before, when the compressor came on it would show a short light. I hit S6 hard with the DeOxit and cycled the switch for a while. It felt grabby as the material worked into the switch. Fired it up again and same result—short light when the compressor tries to come on. I plugged back into the 804b (the camouflaged one) and it also didn’t want to start the compressor except it would just kick off the FDECU-5 without a short light. I’m thinking this is bad, since it had been working fine for a week and ~50 hours until I shut it down to experiment. I sprayed the pins and sleeves on the power plug and it is back to working as it should. Would a little WD40 into S6 help it not feel grabby without negating the benefits of the DeOxit on the 804a?

The first two pictures show the 804b with the FDECU in the cooling mode. If it was in the heating mode with the heat strips on, it would pull around another 11 kW. Someone said they could run a FDECU-5 in the cooling mode on a 003a and I tended to not believe him but I may give it a try again, the noise will be double though. The other pictures are of the 804a. I will keep spraying and exercising S6.

Robert

Fdecu will not run on a 10k anything. It needs at least the 15k. The newer 5ton ac units will start and run on my 803a. Trying to start a fdecu in ac mode results in a short circuit fault every time with the 10k.

There is not a big difference between short circuit and overload. That's why both functions are in K8.

Thanks Guyfang, I will try to clean all of the terminals I can to see if that improves performance. The 804a has always been more sensitive than the 804b in that area.

Robert