TXV replacement
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kevin9408
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Comments (2)I hope he used a Heat Pump application TXV, as they incorporate an Internal Bypass ball-check-valve that allows the refrigerant to bypass the TXV when the Reversing Vales shifts the direction of the refrigerant flow. There is normally a strainer screen at the entrance of the TXV, it could be clogged or there is excessive moisture in the refrigerant causing the TXV to freeze up & blocking flow. He should have checked the system for moisture, & if need be, pulled the charge & after installing an oversized Heat Pump application dryer, double or triple evacuated the system. - udarrell...See MoreQuestion about variable speed blowers and txv's
Comments (4)"Given that all these systems are 15 SEER with variable speed air handlers and txv's does it matter much if they are over sized?" -- Yes. Oversizing decreases efficiency (off/on cycles often cost more money as well). What is the area (in sq. ft.) of the upstairs? They may have oversized it slightly since it is upstairs and heat will rise. "When the air handler slows down, what exactly happens? Does the liquid freon remain under pressure after the compressor stops [I'm assuming that the compressor is constant speed on/off] and then slowly release into the evaporator coil as needed?" By slow down, do you mean during an off cycle? After the compressor turns off, the coil will still remain coil for some time. During dehumidification mode, the air passes air slower over the coil, thus increasing latent (humidity removal) capacity. "Given that all these systems are 15 SEER with variable speed air handlers and txv's does it matter much if they are over sized?" Oversizing is oversizing; however, the variable-speed blower can increase humidity removal by slowing the blower down during a call for dehumidification. "In other words, will I still get the dehumidification that I need, and also keep my power bills low if the units are oversized by 1/2 to maybe even a full ton?" Oversizing SIGNIFICANTLY can run up power bills and hurt the ability to remove humidity. Being 1/2 ton oversized may require you to set your thermostat a bit lower, but I don't think you'll see any major issues. Remember, nominal capacities aren't always actual capacities. If your duct leaks, you lose capacity. Sometimes coil matchups change capacity from what the unit is rated at. (i.e. 22,000 btu's instead of 24,000 btu's). It's really all guesswork from here without seeing a copy of the load calculation, if one was performed....See MoreHeat pump not right
Comments (1)Well, I had three psychometric data sheets at 350-cfm/ton/ 400-cm/ton & 450-cfm/ton that showed the unit well under 5- nominal tons. "The nominal tonnage will always vary considerably as the Total Heat Enthalpy conditions through the evaporator vary." I lost all my work when I closed a window instead of a TAB! I won't redo them, bad hands & fingers. I got 19.4-F Subcooling - 241-psig SCT 109 minus 89.6= 19.4SC. That is still too much but is probably due to the lighter than rated Btu/hr heatload. Lighter heatloads don't boil off R-22 as fast therefore the TXV slows to maintain Superheat setpoint & more of the R-22 will be in he condenser resulting in a higher SC. At 350-cfm/ton nominal tonnage was 3.5-ton 42,228-Btu/hr;/ @400-cm/ton 4-ton or 48,260-Btu/hr & 450-cfm/ton 55,882-Btu/hr.(5-ton 60,000) Depending on the nominal Rating of your unit, here is what a nominal 5-ton system would deliver at these conditions: 2,000-cfm 400-cfm/ton. Air entering coil 80db 67wb Air leaving coil 61db 57.6wb Total cooling 60,111 Btu/hr or 5.01 ton of heat transfer Sensible 42,631 Latent 18,086 (SHR) Sensible Heat Ratio 0.70 Indoor SA/RA delta-T 19-F Condensation Rate 17.07-lb/hr - udarrell ====================== DISCLAIMER: I assume NO legal responsibility for how anyone uses information I provide. All HVAC/R work should always be done by a licensed Contractor! This information is only placed on my pages & here for your understanding & communication with contractors & techs. You alone are liable for what you do! Federal Refrigerant Licensed - Retired Long Time Licensed Contractor. - Darrell Udelhoven Here is a link that might be useful: Latent Heat Removal...See MoreReplace TXV or replace entire coil?
Comments (5)What a mess. As long as the same hvac company is involved,you will continue having problems. If the warranty alows you to choose repair company,it's obvious what you need to do. Choose a company who agrees the coil worked well and will again as long as it is equiped with 410a control. Convince the warranty company they choose an inept contractor and needs to dump them in favor of one who can properly diaginois the problem. Based on past perormance,the problem may have nothing to do with the coil. You don't want to sink any of your money in this unless you have written assurance of cost and satisfaction....See Moresktn77a
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