I built my house in 2008 in Northern Virginia, and the basement/first floor heat pump just died--compressor shorted to ground. The house originally had two 25HNA648 Carrier heat pumps (one of which was already replaced under warranty), both with duel-fuel systems with natural gas furnaces. When I built the house, I battled with the builder over sizing the units. I did a complete Manual J and came up with a total heat gain for the house of 53,000 BTUH, split between 26,000 for the basement/first floor, and 27,000 for the second floor/finished attic. The builder insisted on 4 ton units for both. I said 3 tons, but couldn't get them to budge, so instead I got two-stage heat pumps that are 4 tons on high and 2 on low so that it wasn't oversized on low stage.
Fourteen years later, I think I'm proven right. The lifetime run hours on the Infinity thermostat for cooling are 12,301 on low and 1,199 on high.
For the replacement unit, I think I want a single stage 3-ton unit instead of a multi-stage or variable unit. I also plan to go with a 14 SEER as the payback time for the higher SEER appears to be far longer than I'll stay in the house, or even the lifetime of the equipment. I only plan to be here for four more years, and don't think I'll get the payback in comfort or cost savings. Cash is kind of tight right now. Any thoughts on this plan? Is duct sizing an issue? I assume that if the ducts handled the airflow for 2 or 4 tons, it should be OK with 3. Also, the quote I received doesn't include a lineset replacement. Can't a failed compressor toss nasty stuff into the lineset? Replacing would involve ripping out some drywall in a basement bathroom and bedroom.
Fourteen years later, I think I'm proven right. The lifetime run hours on the Infinity thermostat for cooling are 12,301 on low and 1,199 on high.
For the replacement unit, I think I want a single stage 3-ton unit instead of a multi-stage or variable unit. I also plan to go with a 14 SEER as the payback time for the higher SEER appears to be far longer than I'll stay in the house, or even the lifetime of the equipment. I only plan to be here for four more years, and don't think I'll get the payback in comfort or cost savings. Cash is kind of tight right now. Any thoughts on this plan? Is duct sizing an issue? I assume that if the ducts handled the airflow for 2 or 4 tons, it should be OK with 3. Also, the quote I received doesn't include a lineset replacement. Can't a failed compressor toss nasty stuff into the lineset? Replacing would involve ripping out some drywall in a basement bathroom and bedroom.
source https://hvac-talk.com/vbb/threads/2242862-Replacing-14-year-old-Carrier-heat-pump-and-sizing-question?goto=newpost
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