So... when you say, the coil is clear of ice and the room is down to temperature, is the other evaporator also free of ice?
One EPR for each evap right?
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So... when you say, the coil is clear of ice and the room is down to temperature, is the other evaporator also free of ice?
One EPR for each evap right?
That's correct mikeref, the other evap is also free of ice.
There's just one EEPR for both evaps.
I was looking for an edge on this problem. One EPR.. One leg of distributor feeds on each evap and does so enough to fool the expansion valve element into throttling back.
Pressure in evap should have been high enough to prevent that amount of ice (in your pic) from happening.
Flow through expansion valves?
**** up by "Mad" not EEV but TEV. SORRY.
Yep, just as you described it, everything is working properly...:eek:
O.K, had a thought about how this effect might have come about. (Ice buildup on part of coils).
EPR was regulating the pressure on the two evaporators. The pressure was low enough to allow a restricted flow through both TX valves, however, since the room thermostat was calling for cooling, and the valves could only deliver a fraction of their ability, the result is the loss of average or normal defrost cycles when the room was to reach it's set point.
With only your forced defrost cycles, the room never achieved temperature, and the refrigerant took the path of least resistance for the available "on cycle" time.
Now, the EPR allows more vapour flow and the evaporators can do their job and cycle at the thermostat setting, masking an unbalanced refrigeration flow through distributor.
Reach set point on a coldroom, and evidence disappears with the defrost cycle.;)
Ok, I like that explanation. So if there's no vapor flow restrictions in the future there shouldn't be ice formation problems.
There's still the distribution problem, wich has no other repercussions if the room temperature is at desired and superheat is ok, right?
Hi George, I ran your info through the spolan distrib select pogram and everything is pretty much on the button. One thing that influences the orifice size is the entering liquid temp. [ my earlier question ]
For a +2'C room, sst -8'C and correct 35 psi delta P there should be zero ice build up on distrib tails.
Suggest that the orifice has been left out and feed from TXV direct, so tails are at evap pressure and giving erratic feed pattons. Your pics show ice from body of valve right to evap., thick ice for 3/16 " tails.
The prgm also had 100% plus rating, which could mean the TX is undersized for application, creating same symptons as no orifice and what you have.
The liquid temp at TXV and condensing temp/ pressure would allow me to check further. TXV 's are effectively variable flow control devises, that respond differently at different delta pressures
Is there some sort of subcooler that actually reduces liquid temperature below the evap temperature on this thing? Economized screw?
That is a pretty descriptive frost pattern on the suction header in one of those photos...Appears like three tubes are getting all the liquid. In the meantime the frost is all the way back to the outlet stub on the TXV...
Somebody mentioned orifice plate...I've seen TXV's this way just a few times. One TXV was receiving Min 15 deg upstream liquid and trying to maintain a 9-deg room on a 0-deg EPR setting. TXV head was much colder than the suction and all the charge was lying right on top of the diaphragm. No Feed.
Other one had no orifice plate in the distributor but that did not cause funny distribution....just a lot of frost on the cap tubes.
Third one had a collection of tubes crushed due to ice bridging at the pan; that never cleared during the defrost. Didn't pass much gas during the defrost either.
This unit have a hot gas header? Does it use hot gas in its pan?
Hello Ster, sorry for delay. There is no Hot Gas on this system, and neither there is subcooling/economizer.