Longer and quieter
If your old system was oversized, the first thing you’ll notice is longer cycles. A correctly sized heat pump runs for longer stretches on a July afternoon and shuts off less often. That is the point: long cycles pull water out of the air.
Bluffline Memphis Heat Pumps sizes every system from a load calculation, and this note covers what to expect from May to September.
What normal looks like
| What you notice | What it means |
|---|---|
| Runs most of a hot afternoon | Correct size; doing its job |
| Shuts off less often | Fewer starts, less wear |
| Quieter outside | Especially on two-stage and variable speed units |
| Supply air a few degrees warmer at low speed | Variable speed running slow to dry the air |
The house gets drier, slowly
Indoor humidity drops over days, not hours. Carpet, furniture and drywall hold water and release it gradually. After a week of real summer weather, a reading around 45 to 50 percent at your normal setpoint is a good result.
If it doesn’t
Readings that stay above about 55 percent for days point to something worth a look: the fan setting, the airflow, a leaking return duct or, rarely, the size. The humidity guide explains each.
Settings to check
A few settings make the biggest difference in summer:
- Fan on AUTO, so water on the coil drains instead of evaporating back into the house.
- Dehumidify mode on, if your thermostat has it.
- A steady setpoint; big daily swings cause short catch-up cycles.
- Cooling mode, or AUTO with heating and cooling setpoints a few degrees apart.
The thermostat setup guide walks through each menu.
The filter
A new system’s filter clogs faster in its first months as it catches dust stirred up by the work. Check it after a few weeks and change it on schedule after that, more often in summer and with pets.
Outside
Keep the outdoor unit clear: trim plants back to the maker’s clearances, keep grass clippings and mulch away from the coil, and don’t let a sprinkler hit it. A gentle rinse with a garden hose once or twice a season helps.
The condensate drain
A heat pump pulls gallons of water out of the air on a humid afternoon. Check that the drain line outside is dripping when the system runs. On attic units, glance at the secondary pan; it should be dry.
If the system ever stops cooling and the pan has water, the float switch did its job and the drain needs clearing.
Spring and fall are different
The hardest humidity weeks are often the mild, rainy ones in May and September, not the hot ones. On a 75-degree wet day the house needs little cooling, so a single-stage system runs short cycles and the thermostat is satisfied before much water comes out.
What helps in those weeks
- Close the windows on muggy days, even if the temperature outside feels pleasant.
- Lower the setpoint a degree or two for a day, so the system runs longer.
- Use the dehumidify mode if your thermostat has one.
Two-stage and variable speed systems handle these weeks best, because they can run long at low output.
Noise and the neighbors
A new outdoor unit usually sounds quieter than the one it replaced, especially at startup.
If you hear rattling, buzzing or a hum that wasn’t there on install day, a loose panel or a line set touching the wall is the usual cause, and it’s a quick fix.
The bill
Compare the summer bill with the same months last year, not with the previous month, since July and August are always the peak. A higher SEER2 rating and correct sizing usually show up as a lower cooling bill.
Reading your MLGW bill after a heat pump shows how.
When to call
Some things aren’t normal and are worth a call:
- Humidity stays above about 55 percent after a week.
- A room can’t keep up on the hottest afternoons.
- Ice forms on the indoor lines or the outdoor unit in summer.
- Water appears in the attic pan or on a ceiling.
- A new noise, smell or tripped breaker.
The lifespan guide covers the care that keeps a heat pump running for years.