LG Heat Pump frustration

It might be something completely different. If the space isn't maintaining temperature, then the entire system needs to be looked at. If the air filter is clean, and there's nothing obstructing the outdoor unit, then it needs professional attention. It could be control wiring. It could be refrigerant loss. It could be a faulty thermistor somewhere (under warranty?). So, not much help to offer, unless you have the testing equipment.

You could check the thermostat sub base (one thermostat controls all?) and see if the W2 and aux/emergency terminals have wires connected. That doesn't mean they're connected on the other end.

Sorry to hear, sounds like you may be going backwards. They installed electric back up—-do you see larger electrical cables and double pole breakers (probably at least 40 amp) for the two air handlers? Were you home when this work was happening? You would think the installers would have explained the basics and even showed you what makes the electric come on (temperature difference, outdoor temperature, etc)

Also- I’d be curious if the original systems were charged properly. If your home is super tight and well insulated, I would think you wouldn’t need electric. Unless you have lots of glass. I’d be looking at the ducting to see if it’s reasonably tight. Any ice damming on the roofs?

Do you set the temperature back at night? These HP systems don’t have enough juice to make it worth it, not recommended at all

maybe another company to do an assessment. In my opinion, maybe 1/3 or less of the hvac companies have the depth of staff and interest to take this type of task seriously.

I think Jamie is on the right track with his comment that the systems may just not be big enough.

I'm not a heating pro, just a homeowner/engineer who has done the heat loss calculations for my old house in the Boston area. If I lived in upstate NY, even in a tight well insulated house, I would want at least 20 BTU/hr/sq ft heating capacity. For a 4500 sq ft house like the OP's, that would be 90,000 BTU/hr.

I would especially want at least that minimum 20 BTU/hr/sq ft if using heat pumps, whose performance gets worse at lower temps. OP has 36,000 BTU/hr + 24,000 BTU/hr = 60,000 BTU/hr installed capacity. That is only 13 BTU/hr/sq ft, and quite possibly inadequate as Jamie says.

Defrost every 4 hours for what 30 - 45 minuets at those temps might be OK might not. Time to get a tech out, inspect and possibly pull and weigh the charge.

Those are good units. It's worth having them checked for correct functioning, but… I regret to say… I'm going to bet they simply aren't big enough. It looks like they are doing what they can, though.

As @pecmsg said, what is your backup heat?

Try to split the traces onto multiple graphs. Very hard to read. What is your design load for the place? I'm guessing those are the cold climate units?

Quick check with any heat pumps is crank the fan to max and thermostat up, let it run for at least 15min as it takes a while for the unit to ramp up. Measure delta across the coil, you should see between 30F to 40F (closer to 40F) across it. If you don't see this, most likely you have a refrigerant leak. Sometimes bad ducting can also significantly reduce flow. You can get a budget anemometer from Amazon and measure airflow out of each register, add them up for a quick check. Won't be accurate but should tell you if you have major issues.

As for the aux heat, as others have said, this has to be configured. There are settings inside the installer menu on the thermostat to set it up. They are not straight forward and you might need LG tech support to walk you through it.

No, the insulation is quite adequate. It's important to remember with a heat pump that the place where heat will be absorbed (or released) is the place where the refrigerant is evaporating (or condensing, respectively) and that that depends on the pressure of the refrigerant at those locations. Consider those fittings: let us suppose that they are on a high pressure line. At high pressure, the surrounding temperature also has to be high or condensation — and heat transfer — will not happen. The refrigerant, which is a gas at this point, passes into the low temperature (relatively speaking) environment but through a pressure drop — and promptly condenses, releasing heat to that low temperature environment (your room).

Let’s take a step back here: do the units keep the thermostat on the wall at the temp you set them? I don’t think this graph is measuring room temp. But if they are keeping the setpoint, I think that changes this question substantially.

okay gotcha! That’s all we needed to know. You might be slightly undersized. Are you using set backs or keeping a constant setpoint?

While it's true that if the line set is uninsulated outside, performance will drop, it's not your problem and unless its all uninsulated you'll likely never notice it.

The temp reported by the app is probably the return air temp inside the air handler. A lot of mini split brands sense air temp at the indoor unit & call that 'space temp'. If the indoor unit fan shuts off during defrost, I feel pretty confidant that's what's going on with the 40° you're seeing.

You'll need to pop the cover to see if/which heat strip is installed (the other door, not the one with the line set going in to it). It doesn't look like the wires are large enough for the big heat strip, but I can't see them all that well in the picture so I don't want to commit to any opinion about them yet.

Also, it's kinda strange to see the wind baffles on two of the units. Around here, they're only used on cooling-only units that will be expected to need to operate in cold weather (IT closet cooling, etc.). Never seen them on a heat pump, which operates differently in heating mode (cold weather), no real benefit to them in that application.

Crank the T stat to say 85F and repeat the measurements after about 15 to 20 min.

I Agree.
get a contractor to Weigh the charge.

put your thermometer next to the wall thermostat, do they agree?

other thing I see is that low humidity, that dry an air will feel colder, more evaporation from your cold fingees and arms and such,

add humidity, but find the air leaks letting in the cold dry outdoor air, and letting out the conditioned air up thru the attic and upper walls,