I have two American Standard heat pumps which have been getting progressively more noisy over the past three years during the cold seasons. When first installed in our new home three years ago, we did not have the loud "flushing" noise we have had this season. I had the guy who installed the units originally inspect them and he keeps telling me the had to have made the same noise three years ago if they were working properly then as he seemed to think they were working properly now. He even took the cover off the compressors outside and manually cycled the valve which when activated, made a noise similar to someone flushing a vacuum activated toilet at a public restroom. The valve he actuated was the one that defrosts the coils during temperatures in the 20s to 30s. His explaination was convincing but the fact is...the noise was not there in past seasons like it is now. Not being an expert but mechanically knowledgeable, I asked him to check the refrigerant level for my own satisfaction, which he did, and he said it was right where it should be. When the specific valve is cycled, the noise radiates throughout the plumbing going from the compressors outside to the units beneathe the home in the crawlspace. Could it be air trapped in the system? Hope you can explain or help me troubleshoot. Bob in Kentucky

I'm having a home built and the builder uses a gas furnace and a AC unit. Due to the price of LPG, I feel it would be better to have a heat pump and use the gas furnace as a backup. The problem is that the builder does not offer the option to get a heatpump installed instead of just an AC unit so I will most likely need to do the conversion at a later time. Can anyone tell he how hard this is?? Is it just a matter of getting a new outside unit and a new thermastat or is there more involved? Thanks!!