Mitsubishi Minisplit Controller + Horizontal Ducted SEZ Condensate Pump Questions

[toonerpro]

Hi,

I have been trying to get an answer from my installer (ultimately through Mitsubishi) for weeks now and unfortunately have nothing from them. We recently had a SEZ/SUZ combo installed and some things have been bothering me.

1) In cooling/drying mode, I'm 99% sure it's a condensate pump humming away 24/7 no matter if it's actually calling for cooling/generating condensate. It's most noticeable in drying mode when the temperature drops below the threshold and the fan stops so all you can hear is the pump. It sounds like it's grinding away, non-stop. I'm no HVAC expert, but running a pump dry is just bad practice. How can this not result in premature component failure if I have the unit in AC mode from May - Sep, and the condensate pump runs 100% of the time despite needing only short bursts of cooling that entire time? Not to mention it's surprisingly loud. This extra humming noise is only present during cooling and drying, and starts as soon as the unit kicks into that mode until a few minutes after the whole unit is shut off at the controller level (suspect evacuating any leftover condensate). On top of all of this, is there any real need for a condensate pump anyway if the unit is installed in the attic and the drain line comes out and down to the ground level outside? I haven't looked around close enough to see how the condensate flows out of this unit.

2) This is my controller PAR-40MAAU - (can't post links, but here's the filename from Mitsubishi) SB_PAR-40MAAU_202004.pdf. The cutsheet here claims dual setpoint, but I have found no indication for how to enable/use it. The manual talks about single/dual setpoint modes and setback mode as well. I don't fully understand the difference between them, but either sounds like they would help add some flexibility to this otherwise very basic and rigid controller. My controller has a setback mode option to enable/disable it in the options, but doing so has no impact on the modes available for selection. It seems to do absolutely nothing.

I am familiar with the function settings in the service menu, and I have toggled things such as allowing the fan to stop when the heating request ends, so if there's something else in that maze of function codes I can set to adjust either of the above options I would be thrilled to know. They seem to keep these function setting descriptions quite secret.

These are the units that were installed.
SUZ-KA18NAH2-TH
SEZ-KD18NA4R1-TH

Any help would be appreciated, thanks in advance! If you need more info/pictures/etc, let me know. The unit overall is quite nice, but the controller and documentation are abysmal.

[toonerpro]

bump on this one, anything would be a step up from what I've gotten from the contractor or Mitsubishi directly

thank you

[pecmsg]

The manufactures will not talk to the end user. You have to go thru a qualified contractor.
As far as the pumps YES they run all the time while calling for cooling.

[FlyersFan]

Yes the pump will run whenever it's in cooling or drying mode whether the system is calling or not. If you're 100% positive that the unit is being drained by the gravity drain have your contractor unplug the pump. If the drain is hooked to the clearish blue outlet you're using the pump. Dual setpoint is only available if the equipment is programmed for it and not all Mitsubishi equipment is, I just can't remember about the SEZ.

[FlyersFan]

To follow up, the SEZ doesn't support dual set point so you won't get that option in the PAR-40. The only way to get a dual set point auto mode you'd have the use an MHK2 controller which has software that will allow dual set point auto mode.

[toonerpro]

Thanks everyone, the pump one blows my mind because it's not actually always calling for cooling and yet it still runs 100% of the time. It's strictly dependent on the controller being in cool or dry mode. When I toggle the function setting (27 maybe?) for the fan to stop when cooling calls stop, the fan shuts off but the pump still grinds away. Seems to be lazy programming and reliability killer long term on that pump. I'll have to push the contractor for an answer on the connection (or crawl around in the attic myself).

For the controller piece, I don't understand how the SEZ tells my controller (that is dual set point auto capable) that it can't run with dual setpoints but the way to get dual set point auto is to change the controller? On a side note, in the options I have two options to toggle - one to turn auto on/off and the other to turn setback mode on/off. Turning auto mode off removes it from the cycle of modes on the main screen. Turning setback mode on or off does nothing. Is this also because of the SEZ/controller pairing?

It's very frustrating to not have any clear indication of what controller/unit combos are capable of what from an end user perspective. I was afraid of getting the adapter for a 3rd party controller out of fears I would lose out on certain functions, or dumb down the mini split and lose efficiency.

[FlyersFan]

Don't think of the pump like a regular condensate pump. There's no reservoir to collect water then pump out, it's designed to run constantly and just sling water up into a gravity drain. If you're not using the pump outlet it's always good to unplug the pump because it will sling water out of the top port if the drain line starts to back up.

The PAR-40 controller works for a multitude of residential and commercial indoor units and it gets its initial information from the indoor unit and will only give the features that are available on that particular indoor unit. For instance, that indoor unit has a minimum cooling set point of 67° so you cannot lower the set point below 67°.

Auto mode stuff: Since the indoor unit doesn't support dual set point auto you won't get that option on the controller. In single set point auto mode the controller "tells" the indoor unit it's in auto mode and the unit will switch into cool mode when the indoor temperature is 1°C (1.8°F) above set point and stay in cooling mode until it drops far enough to go into heating mode. This is the same for all of Mitsubishi's wired controllers.

The MHK2, which is a Redlink wireless controller, has a different logic built in to be able to give you a dual set point auto mode because it never tells the indoor unit it's in Auto mode. Say you have it set to Auto with a 68° heating set point and a 73° cooling set point. If the indoor temperature goes above 73° the MHK2 will tell the indoor unit that it's in cooling mode, not auto, and the unit will stay in cooling mode even if it's not calling until the indoor temperature drops low enough to kick into heat mode. Once it's in heat mode the MHK2 communicates to the indoor unit that it's in heat mode, not auto.

I know it's all a bit convoluted but that's the best description I can come up with.

[toonerpro]

Thanks again, I kind of suspected this thermostat was more dependent on the unit itself vs a traditional thermostat.

The pump design I get too, but what is strange to me is that it runs even when the unit isn't running. 100% it should run all of the time when the coil is cold and fan is on, but the only way to get it to stop is to completely turn off the controller and wait the 3-5 min that it pumps any leftovers out. Otherwise when the unit goes idle in dry/cool, it will run constantly. For example, the setpoint is at 23C, it hits ~21C and stops the drying cycle. Fan stops, outdoor unit/compressor stops, but the pump continues. It could cool down overnight and be 18C inside and the pump will still be running because the controller is "on" and in either dry or cool mode. I would think it should behave just like me turning off the controller - pump for a few minutes after the unit shuts down and then stop.

Thanks for all of the explanations