Quote:
Originally Posted by billybek
There could be several issues at play here.
If it is a TX (thermostatic expansion) valve system and the liquid line (the small one exiting the condenser) has a sight glass and you can see bubbles in it all the time, it is probably low on refrigerant.
Trane employed a layered condensing coil on a lot of their roof top units. If you live somewhere that there is a lot of pollen/poplar fluff/seed blowing around, the coil can look clean from the outside and inside, but split it apart and there could be a blanket layer in between blocking air flow. This should cause unit cycling on high pressure and will not keep up with the load.
Possible that you have too high a load (too much air flow or too high of indoor air temp or both) and that would cause a TX valve to go wide open. This would result in bubbles in the liquid line sight glass.
I worked for Trane for many years and started with there roof top equipment and have seen many quirks right at start up with some units. We sold a ton (forgive the pun) of these units so finding a few quirks is not unusual.
A good mechanic should be able to find what is going on pretty quickly.
Don't let them run away from a problem that isn't yours.
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thanks for the input bill. it does have a TX valve. but here is another kicker. the evap is waay too small for the condensing unit, plus, the unit (carrier?) came fully charged.
some more details.
we have a small chiller unit that cools the whole tower. (i work for the FAA and this is for our control tower). when the military had the building, they had 2 air handlers for the chiller that were used to cool the tower cab itself. when the chiller broke (this was back in the 90's), we did not have a backup unit to cool the cab, so we, the FAA, put 2 condensor units (5 ton ) on the roof and converted one of the chiller air handlers over for the condensor units. the air handler had 2 seperate coils so TRANE used each coil for each condensor unit. IE, the coils were not changed plus, they may be too small. whatever they are, we could only run one condensor unit at a time or they would both freeze up because we were trying to put 10 tons of cooling into a 5 ton air handler. anyhow, trane never got the one unit to work from the time it was put in. BTW, the water pump broke on the chiller last week so the chiler was OTS for several days. trane screwed us on that deal too. but thats another story. (we keep going back to trane because they are better than the others we have to choose from, plus the chiller is a trane).
now that we have done this, the chiller can not cool the cab because it is too small, so we have to use one of the condensor units to cool in the summer. problem is, we dont have a backup other than the chiller.
i was not responsibe for the HVAC back then and was not really involved in this addition.
what would the indications be if the low side of the comp had a small blockage or something was wrong with the comp?
the site glass did show it was low and i put in a good bit of r22, but never saw any change in pressures or the site glass. but why would it freeze from the comp back to the service port.