TRICOOL / Television Van AC

[davidk]

Hi!

I am currently servicing some old Tricool QR-25 AC units (25000BTU) on top of an television OB van.
Basically these are on the roof of the truck and cools the installations and the people operating inside. My problem is these units operate with very high head pressures, always above 22 bars, even when outside air temperature is below 30degC (or 86F) which is very high for R22.
After few days of working, the HP protection set at 28 bar trips.
They have mechanical TXV's and manual valves in series with it. Since these are very old, I don't know how may stuck their fingers in them.

Previously I have had the same problem with some very similar Noske Kaesser units on other vans; these units are working poorly even today.
Do you think the condensers aged so their capacity reduced too much? Of course I washed thoroughly the coils, the fan motors are working good and running capacitors are new.
I need to make these work or, better, to install other new units but I can't find something like this.
15242

[Brian_UK]

You say the fan motors are good but how are the fan blades?

Dirt buildup can seriously reduce the airflow.

[r.bartlett]

reclaim and recharge..once you know the charge is correct then trouble shoot

[cadwaladr]

Yes i would reclaim the charge ,condensor may have issues blow it out with compressed air and chemically clean it

[cadwaladr]

Also does it have a suction regulator?

[charlie patt]

These units had issues there was a modification on high ambient units we looked after some on the massive electrical excavators in the quarries in cheddar at a high head pressure there was a unloader to be fitted that unloaded and reduced head pressure I believe it dumped it back in the suction line and supplied in the kit was a mini c p r it was a bit tight to fit

[davidk]

As I said, condensers are clean. I washed condensers at both units and I'm sure the fans are working properly.
Brian, thanks for the tip about the fan blades; I'll take a look tomorrow.
I tried to lower the head pressure by undercharging but without reasonable effect. I don't have any suction regulator; only TXV. I'm thinking to lower the evaporator fan speed to decrease the load.
In my picture I removed the top cover, but of course the cover is always in place while running.

Since this is an old truck, it was upgraded several times and probably the heat load increased. These two units can still chill inside, though, if both are working and not tripping.
Charlie, thanks for your tip, but didn't quite understood; can you tell me more?