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I'm living in the Northeast of the US, so my ac/heat units are 12 years. My current setup is like this: Heat-pump on unit outside the house, and a furnace unit in the attic.

The heat was not able to produce enough heat. So I hired a person to check on my HVAC system. So he mentioned the following which I don't fully understand, and recommended a full replacement. I have attached the pictures as well, can I delay the replacement by another year or two.

  1. The coil inside furnace might be leaking.
  2. On the heat-pump unit, The thermostatic expansion valve (TXV) caused stress to the compressor. The refrigerant pressure from the is too high and too low.

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  • Do you need a new furnace/AC now or can you put it off? Sure. Either one works for me as I sit here comfortably in my heated house, watching the snow blow. If your HVAC guy says you'll need it in the next couple of years, you probably will. But, we put our guy off for more than 5 years before replacing our furnace/AC unit that were 25 years old when they finally went to the bin. What you need to do is determined by how much heat you're getting right now and if that's satisfactory to get you through the winter. We can't answer that for you.
    – FreeMan
    Commented Nov 14, 2021 at 21:54
  • How do the heat pump system and the furnace in the attic play together? Is the attic furnace the backup/auxiliary heat for the heat pump system (which do not work below ~35 deg F)? Are there one or two thermostats?
    – SteveSh
    Commented Nov 14, 2021 at 22:55
  • And what fuels your furnace that's in the attic? Oil? Natural or propane gas?
    – SteveSh
    Commented Nov 14, 2021 at 22:56
  • The furnace use electric. Commented Nov 15, 2021 at 2:14
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    @SteveSh I think it always try to get heat form the heat pump, and then the attic furnace as a backup. Commented Nov 15, 2021 at 2:15

2 Answers 2

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If the heat pump system does not keep the house warm when the outdoor air temperature falls, the problem is probably in the indoor fan unit. Inside that unit should be the back-up heating elements that are energized by the 2nd stage of the thermostat. There may also be an outside air temperature sensor that will sometimes shut off the outdoor unit(compressor) and allow the 3rd stage heating elements to be energized. Just exactly how the back-up coils are utilized is dependent on how the thermostat and controls are wired.

If the description you gave is what the HVAC tech said I would never call him back and try to find another company to service my heat pump. The TXV will not put a strain on the compressor. Before you make a decision to replace that heat pump get another opinion. Heat pumps normally last much longer than 12 years.

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  1. Try another technician. Or two more. There are a lot of technicians who are out of their element when diagnosing unusual problems or multiple problems. No harm in getting multiple opinions and going with someone you think you can trust.
  2. If there is something wrong with the thermostatic expansion valve or with any other part that can easily be replaced the technician should explain to you how he diagnosed the problem and why he thinks it should be replaced, and how much that will cost. You can then decide based on cost whether it's time to buy a whole new system or just keep the old one a live a few more years. The technician should not scare you with "too high too low" and not enough information to make a good decision.
  3. "Might be leaking"? Again .. nothing but fear and no information you can use. It's hard to find tiny leaks but just scaring you won't help. If the system pressure is too low he should A) look for obvious sources of a leak, around the connections and valves. B) Refill the system and then you measure how long it takes for it to leak out again. If it's a year or more you weigh the costs of recharging it repeatedly versus replacing it and you choose the timing. If it's less than a year ... it's time. He needs to give you the information to make a wise decision.

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