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Brian HVAC Guy
Brian HVAC Guy, HVAC Technician
Category: HVAC
Satisfied Customers: 800
Experience:  I have been an HVAC/R mechanic/technician for 30+ years.
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I have a commercial building with an Rheem RTU model number

Customer Question

I have a commercial building with an Rheem RTU model number RKNL-A060JK13E. It runs for a while and then shuts off. A technician came out and cleaned the filter and coils. The problem persists however. When I push the reset button the unit begins to operate for an hour or two and then shuts off. I have instructed the tenant to keep the thermostat at 77 degrees or no lower than 20 degrees below the outside air temp. I haven't noticed evidence of freezing up but I'm not sure I'm getting there in time to actually see it.
Submitted: 5 months ago.
Category: HVAC
Expert:  Brian HVAC Guy replied 5 months ago.

Hi Bob, I'm Brian and I'm here to help!

Can you please bear with me for a moment while I retrieve the documentation for your unit. I'll be back very shortly.

Thanks,

Brian

Expert:  Brian HVAC Guy replied 5 months ago.

Bob, do you happen to have the serial number for your unit? I want to be sure I am looking at the exact service manual to give you correct info.

Thanks,

Brian

Expert:  Brian HVAC Guy replied 5 months ago.

It's not that big of an issue if you don't have the serial number. The fact that you are pushing the reset button pretty much tells me what I need to know. If you are pushing the little red button that pokes through the unit casing by the compressor section, that is the high refrigerant pressure switch and means that your unit is cutting out on high refrigerant pressure.

Considering the tech cleaned the coils, the most likely cause for this is still a plugged condenser coil (air side, not refrigerant side). That particular model has a condenser coil that is two rows deep and the rows of tubes are actually in two slabs that are separate from each other but tied together at the ends. On one end they are tied together by the tube sheet where the coils are connected to the unit's liquid and hot gas lines. At the other end of the coil the two slabs are tied together either by clips, zip ties or screws. There are two separate tube sheets and they can be separated without removing the refrigerant. What happens with these type of coils (we call them "split face condenser coils"), is the space between the two coils gets plugged with debris. Many times it's fine particulate from tree blooms, especially if you live in an area with Cottonwood trees! This is a very common problem and surprisingly few techs know that the coils can be carefully "split" to clean the inside faces of them. The top has to be either removed or propped up a few inches in the front, then the coil retainers have to be removed on the side opposite where the liquid and hot gas lines attach. The coils can then be carefully separated from each other as much as necessary to clean the inside faces of them. After cleaning, everything can be reassembled and you're good-to-go!

Let me know if you have further questions on this subject. Otherwise, please remember to rate before leaving (3 stars or higher please!). Bonuses are always appreciated! Thanks for allowing me to help and thanks for using Just Answer!

Thank you,
Brian

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