"York" Ducted Split - Pressures ok in cool, trips on HP in heat
Wondering has anyone had this problem:
York ducted split, runs fine in cool mode, pressures and current draw spot on.
Runs for about 4 min on heating and trips on HP.
Evap airflow is OK
Unit is not overcharged.
Unit uses two orifice refrigerant controls, 1 at condenser, 1 at evaporator.
Suspected that rubbish in evap orifice that blocked the orifice in heat mode - nothing.
This one is doing my head in, or maybe it's time to get out of the game.
i venture to say the refrigerant is overcharged or air flow is NOT ok or both
We really need change now
Catman - system is not overcharged and airflow across evap is perfect
If not a mismatched system I would have to agree with catman. Can you post actual data used to determine charge and airflow
yea either overcharge or undersize coil inside..
Questions regarding similar situations show up on this forum about once a week. Take the advice received so far.
Originally Posted by petem
OK, to answer your questions.
Firstly, I have disconnected duct work off flow side and removed filters. The return duct work is fully visible and not collapsed. There is about 900 l/s air flow. Superheat on cooling is 8.5 degrees C at air on of 23 degrees C The unit is about 8 years old and has been functioning correctly till now. I still believe that there may be something floating around in the distributor prior to the orifice (acurator) that when in heat mode is restricting flow through the orifice. I pumped the system down yesterday, removed orifice and blew high pressure nitrogen through the suction line, which in reverse mode is the discharge line. Evacuated system and dropped charge - same problem.
Liquid refrigerant could be what is carrying debris to the face of the orifice, where as nitrogen will not lift the debris in order to restrict the orifice. What are your thoughts?
The problem I have is that 2 or 3 people have looked at this unit prior to me and no one has changed anything, just one fridgy increased charge, which I have bought back to correct charge.
The units are definitely not mismatched, checked through old York manuals.
900 l/s = 1890 cfm...5 ton system? 8.5˚ C = 47˚ F. It would take unusual conditions for that value to be a "good" number...It's high.
Originally Posted by petem
And restrictions don't generally create high head pressures unless the system is overcharged. A restriction would also be accompanied by a decreasing suction pressure. Was that the case with your situation?
If you would provide all the numbers: suction and head pressures, superheat and subcooling (in both operating modes) and ID / OD temps, it would be easier to evaluate the situation. There may well be a restriction somewhere, but it alone, isn't what's causing the high head pressure.
Hey saturate, thanks for the reply,
Firstly, you cant take readings on heat when unit runs for 4 min and then trips on HP.
The readings I have given are when it runs on cooling.
The manufacturers charge is just over 12 lb. I have charged it with 4 kG 350g, this is not overcharged, it equates to roughly 9 lb. These types of units are very close to being a critical charge unit because of the 2 acurators, almost the same as a capillary unit. If the subcooled liquid from the evaporator in heating mode is not returning to to the condenser then you will build high head pressure and trip the HP cut out. Remember, the hot gas is entering the evaporator through the suction line, going through evaporator, then distributor then orifice then to condenser orifice, distributor and through condenser back to compressor suction.
Hope this is not screwing with your heads like it is with mine at the moment.
I know the penny will drop shortly, just don't know why it hasn't yet.
Probably worrying about the excess time that I will have to try and bill the customer for such a small unit.
Hey guys, listen up!
We have achieved an end result.
Thanks for all of your help, but there is a lesson in the learning here.
NEVER, EVER listen to people, they are full of ****.
8 hours today and we have a unit that is fixed and working as it should, even though it is York rubbish.
My theory was half right, but rglasgow was partially right when he said mismatched, but not mismatched units.After pumping unit down and using high volume high pressure air determined that the restriction/blockage was not in evaporator, so next point of call is the condenser.
Pulled the orifice out of the condenser and guess what.......size 65 orifice. A couple of phone calls later to find old York specs, should be an 85 orifice. Hey, this problem has been here since day 1, but how come only now the unit was tripping on HP? Well, remember I changed the reversing valve at it was leaking. I also found out today that someone changed a burnt out compressor about 18 months to 2 years ago and the system is about 8 years old.All starts to make sense. Original installer dropped part of the original charge to get the unit to run, but how inefficient, and no cooling to compressor through suction line temperature and hence a compressor burn out. Well, no orifices available, so we drill out the 65 to about 80 thou. Evacuate, drop charge and hey presto, all works but trips on HP after about 30 min. Start up again and observe pressures. Had to drop about 750 grams out of unit and it works like a dream. Works a treat on heat, as a piece of York **** does, but not as good on cool, but that is the York design.
So after 3 days we have a result, but I feel for the customer. It's going to cost him dearly, but was never his fault or problem, and remember I was starting to be frowned upon because I couldn't fix it, but have now. This leads to the old problem, TOO many cowboys in our industry.