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Mini split heath pump question / issue

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  • Jul 18th, 2021 11:58 pm
[OP]
Deal Fanatic
Nov 21, 2013
6294 posts
4859 upvotes

Mini split heath pump question / issue

This morning, I turned on the AC on my mini split heath pump unit. When I turned it on, temperature went as high as 29°C on my baseboard thermostat. It was abviously not 29°, but we felt the humidity coming out of the evaporator (inside unit). Went out to have a look at the condensor (outside unit) and I noticed that there was no water drop falling from the drain pipe, and the fan was not running. Went back inside, turned off the system, turned it back on, and already felt te cooling temperature, confirmed by my thermostat. Got back outside, and then I noticed that the fan was running, and water drops were falling from the drain pipe.

Now, tonight, I went back to have a look at the condensor outside (temperature is comfortable inside) And noticed again that the fan is not running. Water was dropping from the drain pipe.

Question: Should the condensor fan ALWAYS run when the system is on? If so, what could be the issue? If not, I guess everything is OK since temperature is comfortable? (it's not that hot outside, but very sticky and humid air)
2 replies
Sr. Member
Dec 6, 2020
635 posts
671 upvotes
Unless the manufacturer is doing something funky with their control logic, in cooling mode the outdoor fan should always run unless you're in a low-ambient cooling situation (i.e. AC on with an outdoor temperature below 20°).

In heating mode, the outdoor fan will stop during defrost, but there's no equivalent functionality in cooling mode.

I would get the unit looked at by a tech, both for the fan issue and because you needed to power-cycle it to get cooling. If possible, don't use the unit until you can get it looked at. The compressor could be destroyed if it runs for too long without the outdoor fan running.

Good minisplits are generally intelligent enough to shut themselves down if they're in danger of permanent damage, but I wouldn't completely rely on the protection logic to be designed properly.
Sr. Member
Jan 19, 2013
631 posts
454 upvotes
Ottawa
It varies between brands....
If the system is on cool mode and the temperature is satisfied, would expect both the condenser fan and compressor to be off, indoor fan to continue to run.
If cooling in cool weather, some brands cycle/delay the condenser fan motor, while some run at the lowest speed until high side pressures reaches normal operating pressure.
Theres also sometimes a delay after the indoor unit is turned on, before the outdoor unit kicks in. 3-5min usually
Could be that when you checked the second time, compressor and fan was off from reaching set temp, and some residual water coming from drain pipe.
If its cooling as it should, nothing to be concerned about, unit should throw a code if theres something wrong.

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