Carrier system

[martin102]

Has anyone come across a Carrier 38 ocacc3-903 condensing unit. One of our apprentices were sent to carry out a routine maintenance on this system and reported a strange airflow arrangement through the condenser coil. In stead of the usual fan pulling air through the coil he reported the fan blowing air through the condenser coil(Not the most efficient way to distribute air through a coil) Now imagine the condensing unit being install with the coil 120mm from a wall and you can imagine the recirculating problems. Having never seen one of these units before and not being able to find any information on them was wondering if anyone can tell me if this is how they are designed or if my apprentice is smoking too much fuuny stuff.

[narkom]

I guess you should check phase sequence and change it.

[paul_h]

It's normal for carrier. Most of the smaller old units are blow through.
I always scratched my head at why, but that's the way they are.

[Makanic]

yep thats how they are
scratched my head too, the first time i saw it..

[Brian_UK]

Check the Carrier literature section, can't find an OCACC3 though..

http://eto.carrier.com/lit.asp

[martin102]

I guess you should check phase sequence and change it.

Its a three phase unit but a single phase fan. Apparently there is a rotation arrow on the fan motor (clockwise) and it is going the right way.

[rude]

Ive come across the same sort of unit and they seem to work fine.

[martin102]

Sorted the problem, Carrier do a kit to change airflow direction from a blow through coil to a pull through coil. Fitted the kit(New motor and blade) and the head pressure dropped like a stone and is in fact now showing signs of an undercharge. 3 kgs of r-22 later and she is working like a dream. The customer says the system has never worked properly from first installation in 1996 and that the installers kept releasing gas to reduce head pressure.

[paul_h]

I thought of changing the direction of a couple of them before (ones that don't work to well in very high ambients), but I decided not to.
The reason why is because condensers are designed to blow air from the exit of the coil (liquid side) first, then over the entry (discharge side). Ie the warmest pipes get the airflow after the cooler pipes.
If you reverse the fan flow, wouldn't the 80+C part of the condenser be warming up the end loops of the coil?

Anyway, that's the the reason why I never bothered doing it. Interesting that you've done it and it works.
Now I know there's a kit I might do it if I come across a system that has never worked properly since install.
But there's plenty of blow through carriers out there that seem to work OK with the blow through design though, just like all the window rattlers seem to cope OK.