DRASH Unit AC issue

[Daltondbl]

Maybe this is in the right location but anyway.

I have a 2008 DRASH unit, generator works perfectly but my issue lies with AC unit itself. Specifically getting the AC compressor to start and pump. If the soft starter starts the compressor, you can hear it run but it will not pump the refrigerant (verified by gauges).

However, I can manually press the contactor in on the soft starter with a screw driver and the compressor will start and pump.

anyone had this issue? I’m leaning towards a bad soft starter but not sure if something else would be tripping the thermal overload on the compressor. The soft starter itself is not tripping or throwing a fault code. Picture is of the soft starter I’m dealing with. Timers seem to be working as they should as it does delay when the call for cooling is on before it tries to start.

 

[Guyfang]

I think there is a schematic on one of the doors. What gives the contactor the impulse to close the contactor?

 

[Daltondbl]

I think there is a schematic on one of the doors. What gives the contactor the impulse to close the contactor?

I have the schematic for it, the 24v runs through all the pressure switches and given all you those safeties are closed, the 24v goes to a relay and then into the contactor. The starter pulls in like it’s supposed to and stays pulled in but the compressor is tripping out on something. Unless I just hold the contactor in, it runs fine. I’ve even tried doing the 100% initial torque and 0sec ramp time to simulate just mashing the contactor in and it won’t start it and pump. The compressor runs but won’t pump. Never heard of that but there is a sticker on the compressor that says it will do that if tripped on thermal overload. System is not overcharged either

 

[Guyfang]

And you have tried to jump all the pressure switch? I would jump the whole pressure/safety circuit and see if it kicks in. If it kicks in, then you at least know where to start. One switch at a time.

 

[Daltondbl]

And you have tried to jump all the pressure switch? I would jump the whole pressure/safety circuit and see if it kicks in. If it kicks in, then you at least know where to start. One switch at a time.

Yes, on these, in order for the soft starter to actually engage with the 24v. The 24v has to flow through all of the safeties in order for it to pull in and I have traced where the 24v comes out of the last switch and I have 24v which then runs into a timer and a relay which then tells the soft starter to pull in and start the compressor.

However the soft starter pulls in like it should but the compressor unloads and wont pump. Only unloads when the soft starter starts the compressor. Manually started by just pushing the contactor in at the soft starter with a screwdriver, compressor starts, pump and cools like it should, condenser fan follows in correctly etc. it’s just getting the soft starter to start the compressor. I just don’t know if there’s something else I’m missing that’s causing the compressor to unload. I don’t know is somethings up with the lower half of the soft starter and somethings not closing or what’s up with it.

 

[Guyfang]

Is the contactor getting any voltage at X1/X2, (The coil on the contactor?)

 

[Daltondbl]

Is the contactor getting any voltage at X1/X2, (The coil on the contactor?)

Contractor has 24v to it and once the 24v has run through all the safeties and switches it completes the circuit and closes the soft starter.

I’ve been told that timers are an issue on these as well. And that it could be something between the hot gas valve and the “cool” switch causing the compressor to unload. So it may not be the soft starter, not sure yet.

I keep the switch on “vent” when I hold down the contactor manually as I don’t want it trying to pull in while I’m holding it. So right now I’m looking into the timers and relays in between that valve and the switch

 

[LuckeyD]

Good Day. I'm Dave. This is gonna sound funny, any way to find out what model your working with? I'll bet I have the info your looking for but everyone called a gen trailer with an ECU on it a DRASH and there are about 30 different models and they do not all have the same things in them. I have seen the motor starter in the PICs on about 12 different ECU units from different manufacturers. Before I open my mouth and mention something about a bypass valve and several open in different stages it would be great to know what model. Compressors are almost all vain type and some are variable vain type. So far you seem to have a motor starter with pitted or bad contacts. Try removal, clean or burnish the contacts and try again. I probably have factory settings if you did not write them down.

 

[Daltondbl]

Good Day. I'm Dave. This is gonna sound funny, any way to find out what model your working with? I'll bet I have the info your looking for but everyone called a gen trailer with an ECU on it a DRASH and there are about 30 different models and they do not all have the same things in them. I have seen the motor starter in the PICs on about 12 different ECU units from different manufacturers. Before I open my mouth and mention something about a bypass valve and several open in different stages it would be great to know what model. Compressors are almost all vain type and some are variable vain type. So far you seem to have a motor starter with pitted or bad contacts. Try removal, clean or burnish the contacts and try again. I probably have factory settings if you did not write them down.

This is it. 35KW generator, 8 ton AC.
I think these were set at 16% initial torque at 10 second ramp time (if that’s right). Once the refrigerant equalizes the soft starter will start it and the compressor will pump but the compressor will overload after about 5 seconds of running and stop pumping. When checking power through the soft starter, correct voltage on all legs is coming out of the top when it’s pulled in. It’s a 2008 Powersystems international. Model on the plate is 2003850. I have sprayed the starter with contact cleaner. Can those be taken apart and reassembled easily for cleaning ?

 

[LuckeyD]

Cool! THIS IS NOT A DRASH. This is a PSI system and the issued 6 different models, and it was a combined effort done for the defunct Base X system the ARMY did away with about 10 years ago. I had to try to support this with what I am sending you. Some old guy named Dave reversed engineered and color coated the schematics so We could support the thing. Files attached. Just take it slow and after a few headaches these systems do well, but have to be looked after better than regular army junk.
STEP 1: IMPORTANT: find a fire resistant plate and place it under the trailer where the exhaust points to the ground. They had fires at FT.Hood so please protect yourself. Flex tube on that puppy bent to point up somehow will save you from calling the fire department. If you also got the tent with it please follow the operations manual exactly.
Step 2: Your text sounds like the compressor has a plug in the system, or it is receiving incorrect power. Please recheck that connection where the power enters the ECU at a power block/ terminal board. Fans are 3 phase so if they run backwards some one cabled it wrong and that also causes the soft starts to do funny things. Pitted or slightly smoked contacts also cause what you are having. Finally you also may have a faulty soft start as one part is a sensing section and if it is going out it causes funny stuff as well. Lets hope all it has is lack of use and repairs are inexpensive. Repaired one over the phone with a medic as I asked him to check for lose connections which are common with these. Some repair stations put in valves so they can replace the compressors. Please follow both suction back to the compressor, and the high side for and refrigerant blockages which may be a safety or bypass valve. This guy has a lot of R22 (407C) in it. I would have to read the books again to say and the military unit that had this may have put something else in there too. The not real bright sometimes. Hope not. It says on the ECU door how much of what that is supposed to be in that system as some units tried to change to 408C from the R22 OEM and they never changed the TEV adjustment. Compressors did what yours is doing and some just gave up the ghost. We usually did a pump down after testing what was in there and reused what we could if pressures were running funny. Check your safeties, any bypass valves, and then put in the proper amount. Don't be surprised if it has too much in the system as most I was called on were overcharged. There is a heater and a safety on that compressor. Please check those. Some units took away that safety. You have what we started out with. Take your time and you should have no issues, but some things are hidden. Settings should be in what I have attached. Good Luck, but above all be safe. Guy and I settled on individual effort when it came to some of these type systems. Give it a go and let us know how it all goes.

 

[Daltondbl]

Cool! THIS IS NOT A DRASH. This is a PSI system and the issued 6 different models, and it was a combined effort done for the defunct Base X system the ARMY did away with about 10 years ago. I had to try to support this with what I am sending you. Some old guy named Dave reversed engineered and color coated the schematics so We could support the thing. Files attached. Just take it slow and after a few headaches these systems do well, but have to be looked after better than regular army junk.
STEP 1: IMPORTANT: find a fire resistant plate and place it under the trailer where the exhaust points to the ground. They had fires at FT.Hood so please protect yourself. Flex tube on that puppy bent to point up somehow will save you from calling the fire department. If you also got the tent with it please follow the operations manual exactly.
Step 2: Your text sounds like the compressor has a plug in the system, or it is receiving incorrect power. Please recheck that connection where the power enters the ECU at a power block/ terminal board. Fans are 3 phase so if they run backwards some one cabled it wrong and that also causes the soft starts to do funny things. Pitted or slightly smoked contacts also cause what you are having. Finally you also may have a faulty soft start as one part is a sensing section and if it is going out it causes funny stuff as well. Lets hope all it has is lack of use and repairs are inexpensive. Repaired one over the phone with a medic as I asked him to check for lose connections which are common with these. Some repair stations put in valves so they can replace the compressors. Please follow both suction back to the compressor, and the high side for and refrigerant blockages which may be a safety or bypass valve. This guy has a lot of R22 (407C) in it. I would have to read the books again to say and the military unit that had this may have put something else in there too. The not real bright sometimes. Hope not. It says on the ECU door how much of what that is supposed to be in that system as some units tried to change to 408C from the R22 OEM and they never changed the TEV adjustment. Compressors did what yours is doing and some just gave up the ghost. We usually did a pump down after testing what was in there and reused what we could if pressures were running funny. Check your safeties, any bypass valves, and then put in the proper amount. Don't be surprised if it has too much in the system as most I was called on were overcharged. There is a heater and a safety on that compressor. Please check those. Some units took away that safety. You have what we started out with. Take your time and you should have no issues, but some things are hidden. Settings should be in what I have attached. Good Luck, but above all be safe. Guy and I settled on individual effort when it came to some of these type systems. Give it a go and let us know how it all goes.

Thank you! This thing has been a booger with a few things. But I’ve got it all sorted except for this. I talked to someone that said timers were a big issue on them and the “cool” switch runs through timers and relays to open and close the hot gas valve and maybe that was closing and making the compressor unload. I believe the power to it is good as I can manually press the contactor in on the soft starter and it will run, pump etc with the EcU control set to “vent”. The soft starter will also start the compressor fine as long as the refrigerant pressures are close to equal and it doesn’t have a big load on it (however once the high side builds pressure it unloads anyway)

my plan right now is to replace all 6 timers with new and if no change, swap around a couple of known good relays into the load shed section in the generator. If no luck there, I’m going to replace the compressor soft starter with a standard 3 phase contactor and see if any change. Trying to rule out some of the easier fixes. Phase is correct as fans turn correctly and the compressor pumps correctly when running.

also when the contactor is manually pushed in on the soft starter. System will run, compressor will pump and cool until I release it.

Thanks for the downloads, I have the schematic but the color coding is very nice !