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Another 10/13 ?

As mentioned by Techman, you may need greater starting torque with the TXV.

With a capiallry tube system, the system pressures caneasily equalize during the compressor's off cycle. This is not necessarily the case with the TXV.

Some TXVs allow system pressures to equalize during the off cycle, while others do not. Compressors that are used on TXV systems that do not allow system pressures to equalize (at least not very quickly) must be able to start with substantial pressure differentials across them. These compressors are usually equipped with start capacitors and associated starting relays.

Most TXVs are avaiable with permanent bleed ports, which allow the system pressures to equalize during the off cycle. The larger the bleed port percentage, the more quickly the system pressures will equalize. The bleed port percentage typically ranges from 5% to 40%.

Some TXVs are equipped with an RPB (Rapid Pressure Balance) feature which allows the system pressures to equalize faster during the compressor's off cycle.


  • Robert O'Brien
    Robert O'Brien Member Posts: 3,280

    removing a furnace w/ 10 SEER cased coil and replacing with hydro-air handler/boiler/indirect. The condensing unit is also 10 SEER and 2 years old. Customer does not want to trash condensing unit unless absolutely necessary. What is the feasibility of using existing condensing unit with a new 13 SEER air handler?

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  • don_182
    don_182 Member Posts: 69
    Go for it

    Other then maybe needing to make a speed adjustment at the
    blower for for better humidity control...that too depends on where you live, I see no problem at all.

  • Techman
    Techman Member Posts: 2,144

    You "MIGHT" also need a hard start kit if the new evap has a TXV.
  • Look into the past

    and you will see that 10 SEER equipment would turn into 11 or 12 SEER with the substitution of a larger evap coil and/or a TXV addition. Also blower-off delays, etc. ARI books and OEM manuals should give you that info!

    I just find it hard to believe that last year they had 13 SEER equipment from orfice fittings and now hardly anyone has the same rating unless you go TXV!?!

    Not that I'm against TXV's, it just seems that the OEMs are taking advantage of the situation, just like the EPA regs. How much money has been made off recover, recyle and reclaim?? New refrigerants??

    Don in MO
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