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Posted by Bubba on August 19, 2006, 3:57 pm
On Sat, 19 Aug 2006 09:28:25 -0400, "Murdentech" <j. murden@ insight
bb.com> wrote:
>
>>I am going to be ripping out my oil furnace and installing a heat pump
>> and am about to pull the trigger on an Amana (Goodman) 3.5 ton and
>> variable speed AHU. From what I can tell, they come with a flowrater
>> instead of a TX valve. Three items I hope someone can help with:
>>
>> 1. Can someone confirm that the "flowrater" is not a TX valve and is
>> just an orifice arrangement in place of the TX valve? What do they do?
>>
>Flowrater is a standard piston, or fixed orifice. TXV is theral expansion
>valve. It adjusts the refrigerant flow based on system load and increases
>efficiency at less than maximum load.
>
>> 2. A majority of the Amana ARI ratings say " + TXV " in the AHU
>> column. I assume this means that a TX valve was installed in the AHU
>> for the test. Why would they do this when the standard unit comes with
>> a "flowrater"? Will it improve both heating and cooling performance?
>>
>The TXV at the indoor unit will improve latent heat (moisture) removal in
>the cooling mode. The indoor metering device has no function in heating
>mode. The metering device for heating mode is located in the outdoor section
>of the heat pump. Notice that heating performance is not rated in SEER,
>rather it is rated in COP (Coefficient of performance). The outdoor metering
>device is installed at the factory (TXV or fixed) and is not field
>changeable.
>
>> 3. If I go with a unit with a factory flowrater, should I insist that
>> they install a TX? I would use the unit 93% of the time for heat.
>> What does the TX improve and how? Any downsides to a TX (moving parts,
>> longevity, etc.)?
>>
>A TXV can improve cooling performance. Some ARI rating require the TXV to
>meet the standard. There is a downside to a TXV. It is more difficult to
>adjust the charge. The TXV can become stuck and cause performance issues.
>Goodman has had problems with their TXVs in some applications. The TXV costs
>more to install.
>
Jeff,
Just curious. I havent seen the problem with a TXV being more
difficult to adjust the charge?in fact, seems a lot easier. Quite
frankly, with 13 SEER here now, I think the piston flow rater crap
needs to disappear. What problems have you found with adjusting the
charge on a TXV?
Bubba :-)
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