Question about Ruud UAKA042 Air Conditioner

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High side low side pressures don not respond to freon levels

I have a new 2stage Ruud heat pump. It runs well in cooling mode but makes a rumbling noise in heat mode. The rummbling noise is in sync with vibrations felt in the suction line. The freon pressures suggest a little low in freon. The addition or removal of several pounds of 410A have no effect on the highside or low side pressures. Current draw of the compressor is 6.5 amps on stage 1 heating and 10 amps on stage two heating. I would not have looked at it if it were not for the noisy operating when heating. What is going on here? Why does it not respond to freon additions with pressure changes or current draw? I have added as much as 6 pounds in this 3 ton unit.

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Chances are you have a TXV already installed. Thats why simply adding refridgerant is not effecting the pressures.

All you are doing by adding refridgerant is overcharging the unit, and possibly forcing the compressor to try to pump liquid instead of vapor. Not god for the compressor.

If the vibration noise is your only problem, I would try emilinating the vibration.
Find where the lineset is touching other parts of the house and install vibration dampening opads there. If the airahndler is mounted to the structure of the house, install vibration reduxction pads there too. If it is suspended from the floor joists you may have to change that mounitng method.

You can suspend the drain overflow pan and then set the unit in that on dampening pads, or set it on blocks from the floor/crawlspace.

Check your data sticker to find out how many pounds of refridgerant the unit takes.

By now, you are probably way overcharged.

Posted on Dec 24, 2008

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Have you tried to add a txv to the indoor coil? It sounds like there is restriction... Obviously if it's also a new indoor unit it allready has a txv, and if thats the case sorry, just wanted to make sure..

Posted on Dec 11, 2008

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Posted on Jan 02, 2017

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WELL this could be a couple of problems the reversing valve could be stuck either from not enough pressure which would be a leal and low on freon or the unit is off on low pressure switch/high pressure switch from either being low on freon or something restricting it and caused unit to shut down, ive been a servicer for many years and if it gets below 30 degrees outside i would recommend running the e-heat anyway it does cost more money minute for minute. but you will find it will heat alot faster in those colder nights than the heat pump therefore cost is about the same.
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BOTH High and low readings should be checked to have a better idea of what is going on with an AC system but based on the limited information… the compressor is not engaged or is not pumping. Below are some things I would check;

1. Check the high and low gauge readings with the AC on & set on MAX/Recirculate, middle vents with the engine at 2,000 RPM’s, blower speed on high.

2. Check the vent temperatures with a thermometer from the middle vents, far right & far left vents?

3. What is the outside temperature at the time the readings were taken?
4. Check to see if the condenser fan blowing strong?

5. Notice if compressor clutch is cylcling excessively.
Could be overcharged, not enough air going across condenser fins, compressor not pumping sufficiently… BOTH gauge readings are really needed to get a better idea.
Below are normal car AC pressure readings with 134A.

Normal readings on high and low side with AC OFF (static pressure) – Depends on outside temperature, but normally is between 80-105 PSI

Normal low side reading with AC on high speed and MAX & engine at 800-1000 RPM’s – Ranges from 25-35 PSI

Normal high side reading ranges from 200-350 PSI

Don’t assume that if adding little Freon is good that adding a lot is better! Overcharging just a little can decrease the performance of the system and possibly damage the compressor

Thank you for using fixya and good luck, keep me posted. Be glad to help you get your A/C running again soon.

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I take it that this is a heat pump. Check your coils and your filter, make sure they are clean. It could be a dirty eveperater coild or dirty filter. It could also be a freon issue (to much freon). Heat pumps are touchy when it comes to Freon pressure. When in cooling mode, it's not that cretical but when in the heat mode, it has to be real close or you will have problems. Normally, the pressure switch is set off due to one of two reasons.
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  2. To much Freon pressure.
Good luck!

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