# stuck piston HVAC



## DOUG1111 (Apr 13, 2015)

What is stuck piston mean???? :wink: I got a report said stuck piston or piston not there- I trust the supply house to size piston # .082 --- R22--3.5 -12 SEER condenser with new 4.0 AH 14 SEER that I put the new piston in .082 --- New AH is for R22 or R410A came with .072 piston installed. Low side pressure is high just one of the issues. Delta T inside 13 split. 41% RH inside


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## supers05 (May 23, 2015)

They don't stick..... But what are your pressures /sh? Why did you change the orifice size? It matches the evaporator, not the condenser. You have to actually evaporate all the liquid that passes through the orifice. 

Cheers!


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## COLDIRON (Mar 15, 2009)

Deleted


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## yuri (Nov 29, 2008)

It would not work at all w/o a piston which actually is called a orifice or metering device. Not like a piston in a car as it does not move.

You can have a stuck thermostatic expansion valve/ TX valve if that is used instead of a orifice. Whoever gave you that info does not know what they are talking about.


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## Technow (Nov 12, 2010)

Not necessarily, Piston/orifices can and do move. On a heatpump the piston is pushed out of the way in heating mode. In cooling mode the piston is forced against a seat to force the refrigerant thru the orifice. If there is trash at the seat and the piston does not seat, then refrigerant can bypass the orifice. So it could be "stuck" and not seating, something can be causing it not to seat, or its not there.


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## beenthere (Oct 11, 2008)

On some brands the piston can be put in backwards, that it won't seat properly.

.082 piston is for a very high efficiency 3.5 ton air handler condenser match, or a mid efficiency 4 ton.

Supply house may not have any old manuals to size the piston for the mismatch.


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## yuri (Nov 29, 2008)

Technow said:


> Not necessarily, Piston/orifices can and do move. On a heatpump the piston is pushed out of the way in heating mode. In cooling mode the piston is forced against a seat to force the refrigerant thru the orifice. If there is trash at the seat and the piston does not seat, then refrigerant can bypass the orifice. So it could be "stuck" and not seating, something can be causing it not to seat, or its not there.


Good to know. Too da*mn cold for heat pumps where I am so we have no moving pistons.

Always interesting to know where the vernacular comes from. Trane uses sump heater and everyone else uses crankcase heater.

Now if the Industry could combine, draft inducer, inducer, ventor fan, combustion air inducer into one term it would make life easier.


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## beenthere (Oct 11, 2008)

yuri said:


> Good to know. Too da*mn cold for heat pumps where I am so we have no moving pistons.


You have the same set up there as we have here. Just you don't have the heat pump. But your pistons are capable of moving.


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## yuri (Nov 29, 2008)

I am sure they can move but it is not something I spend time worrying about. More concerned if they get blocked by dirt. Never had one get stuck as ours just move forward once and sit there I guess. Never had a problem in over 20 + yrs of Lennox using them. TX valves are more common now but I have a orifice and prefer them. Nothing to go wrong.


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## Dak Man (Jul 4, 2015)

imo and experience and not that I care much about service any longer, but in Houston heat pumps all have txv's, no pistons. two per system. thought that was universal..??

eh.


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## WyrTwister (Jul 22, 2013)

Two expansion valves per system ? That totally went over my head . Please enlighten me .

Thanks ,
Wyr
God bless


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## Dak Man (Jul 4, 2015)

exactly as it sounds. not that down here we have a lot of heat pumps but yes, heat pump systems here are always equipped with two thermostatic expansion valves, condenser and evap. never heard of a single txv heat pump system until this thread, never gave it much thought. 

but i'm no heat pump expert either, ...or am I?  :jester:


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## WyrTwister (Jul 22, 2013)

Our oldest boy lives in the Houston area . Would think it would be a good region for Heat Pumps ? Not a great deal of need for aux heat ?

I am not a HP expert , either ( I an a DIY'er ). We own 2 , but they are ductless mini splits .

I thought a single TXV was used right before the expansion coil , on straight A/C and HP's ? 

Now , you tell me one is used at that location plus one at the condenser coil . Is it field installed or factory installed ?

I would like to learn more . More info , please .

Thanks ,
Wyr
God bless


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## Dak Man (Jul 4, 2015)

factory.

But you must realize that it's per region. American Standard high efficienyc dc blower motors are set up factory for 450 cfm as those furnaces are shipped blindedly nation wide. When we install them for our region we have to set back blower to recommended by American Standard for Houston to 350 cfm, medium low.


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## WyrTwister (Jul 22, 2013)

Interesting ..........

Thanks ,
Wyr
God bless


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## Dak Man (Jul 4, 2015)

WyrTwister said:


> Interesting ..........


 Not really, unless you're buying a system from me! :thumbsup: :thumbup:


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## supers05 (May 23, 2015)

New Ductless Split units will use single exv or txv or other metering device for heat Pumps, or straight a/c, always in the condenser. (that's why you have to insulate both pipes. Smaller package units will use a single, txv as well. You get more efficiently when using 2 on long linesets, especially on larger units. 

Cheers!


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## DOUG1111 (Apr 13, 2015)

R22 system 3.5 condenser / 4.0 AH -2 years ago I did in-place cleaning on E-vap coil - was extra dirty & mold inside cabinet. At that time I felt the coil was only 80% clean. Customer did not keep clean filters in-- Recently customer called local franchised co - they told him he needed a new coil. I went to look and recommend pull & clean coil. Priced coil & new OEM coil cost more than a new AH. Customer wanted new AH - thinking new AH will do R410A & R22 - and when condenser goes out -he could go with R410A - I ask supply house about piston- orifice size - said use .082 piston-orifice- that is what comes with a 3.5- R22 condenser unit. NUMBERS- inside temp 78* - air into return 77.1* - air out supply 64.1 - wet bulb @ air return 63.8 - low side pressure 78.7 - low side temp 52.7 - high side pressure 215.6 - high side temp 101.1 - air coming into condenser & outside temp 92.1 - air coming out of condenser top from condenser fan 107.1 -- NOT much cooling only 13 delta T split - Problems?? What to check- adjust??


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## beenthere (Oct 11, 2008)

What brand outdoor unit, and what brand indoor unit.

.082 Piston is most likely too big for the current condenser.


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## supers05 (May 23, 2015)

6*SH, 5*SC. With those temperature, you should be closer to 10*SH. 

Cheers!


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## DOUG1111 (Apr 13, 2015)

beenthere said:


> What brand outdoor unit, and what brand indoor unit.
> 
> .082 Piston is most likely too big for the current condenser.


 Outside Tempstar - Inside Goodman ARUF


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## beenthere (Oct 11, 2008)

That air handler handler matched to a Goodman 13 SEER R22 condenser, would only have a .076 piston. That .082 is for 4 tons. Get the .076 piston, and install it. That 12 SEER should be able to work much better with the right size piston.


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## DOUG1111 (Apr 13, 2015)

beenthere said:


> That air handler handler matched to a Goodman 13 SEER R22 condenser, would only have a .076 piston. That .082 is for 4 tons. Get the .076 piston, and install it. That 12 SEER should be able to work much better with the right size piston.


 THANK YOU!!!! THANK YOU!!!! .076 will do!!!


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