Quote:
Originally Posted by berettafan
Some background- a/c is serviced annually. tech's take is for how old the system is it's running well but he recently said aging outdoor unit causing 'very high head pressures'. not sure what that means. house is about 21 yrs old and has a sealed crawlspace with concrete floor and sump pump. air handler is in crawlspace. no insulation under flooring (one story house). generally feels very dry when I have to go down there but not sure humidity level. This morning here it was 99% humidity, everything outside wet, fog, the whole nine yards. Temp was 72 and a/c not having to run. My understanding is when cooler at night a/c doesn't run but humidity builds.
Sounds like a 2 speed HVAC would essentially include the dehumidifying function via the lower speed. How much delta is there in price vs one speed or variable speed?
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On high head pressure, normally with age the two gauges start looking at each other meaning you'd have higher suction pressure and lower discharge pressure, condition is known as having an inefficient compressor. If discharge is running high, I'd look heavily at the outdoor coil for any blockage. Typically "head pressure" rises as it gets hotter out and the airflow across the outdoor coil is insufficient. I'm willing to bet a tech has adjusted the charge in the past but hasn't cleaned coils. Checking the evaporator coil requires removing a plate from the front. After 20 years, if no one has visually inspected the inside of the coil, I'll bet there's some blockage of the fins. Blockage of the fins affects operating pressures which affects operating temperatures.
Sounds like the crawl situation is good.
2 speed doesn't make the big jump in price like a true variable speed. My cost for just the variable speed heat pump, modulating gas furnace, indoor coil and copper tubing was about 10K.
The problem now is that the switch has been made to R32 and R454B, you'll have to upgrade the fan coil in the crawl as well. R410a systems are getting hard to come by. If there is an option for 2 speed communicating where the outdoor and indoor units communicate and you have a true ECM blower that will adjust to the output of the outdoor unit, I'd go that route.
When it cools in the evening and humidity is high, your only option for dehumidification is to have the feature I mentioned in the new smart stats or turn it down yourself. My variable speed just runs on the lowest output for a really long time. If you need any advice on systems, just PM me. I'd be happy to offer my .02.