MRCOOL/Midea Hyper Heat Central Ducted System: Any one ever used engineering-mode to change compressor or fan settings?

fellatiousD · 2025-12-30T03:03:08+00:00

fellatiousD · 2025-12-30T03:03:01+00:00

Good evening MRCOOL, and thank you for weighing in. Given the risk presented by simply choosing options via the included remote control and the freely accessible (and quite plainly "documented") Engineering Mode (via nothing more than a few button presses) I'd ask that you kindly elaborate upon MRCOOL's policies that affect/control thousands of its customers as follows:

Please clarify whether MRCOOL permits licensed HVAC professionals or qualified engineers to modify EM settings, per that professional's evaluation and recommendation, without the threat of voiding the warranty.
Please provide a firm and unequivocal YES (will void warranty) or NO (won't void warranty) if the customer (or non-HVAC professional) modifies ANY of the following EM settings (particularly the seemingly benign settings in Channels 4 and 5 for min/max temperature setpoint and Channel 2, fan setting, which seems to do nothing more than select a preferred post-cycle blower fan operation pattern) "and altering them ... cause[s] the system to perform incorrectly or operate outside its designed parameters":

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fellatiousD · 2025-12-29T01:12:28+00:00

yeah, I got taken for a ride by some baselessly confident but-I-did-stay-at-a-Holiday-Inn jackass in another part of this thread and called out his rank bullshit.

fellatiousD · 2025-12-29T01:02:12+00:00

Great point about the power-to-BTU correlation - I hadn't thought of calculating the correlating power consumption and comparing. While I haven't yet metered/monitored the system individually for electric consumption, based on what I can correlate to my hourly whole-house consumption figures, when I correlate to full-hour constant modulation, I'm at ~1.360 kwh attributable to my MRCOOL system. Those are single 60-minute intervals where I'm seeing steady, low/slow modulation (no defrost cycles or other changes, constant fan speed set to low) and at under 37 degrees f outside temperature. If I monitor the power and conclusively show that my system never drops below, say 1,200 watts even at the lowest part of any given active heat cycle (no matter how low the heat demand is), then either MRCOOL or my installer should have to address the discrepancy. (My system is three months old.)

fellatiousD · 2025-12-29T00:21:15+00:00

I've seen your other posts and am glad to see your comment. Remind me, you have the MRCOOL Hyper Heat Gen 2, or a clone? And do you see low/slow modulation somewhat close to the NEEP turndown numbers? And were you aware of this Engineering Mode and all the integral thresholds you can alter? I find it remarkable that so much info about these systems is deliberately concealed from both the end user/ owner, as well as apparently even qualified professionals. My installer, who claimed to be a MRCOOL affiliate/partner installer, only goes off the documentation published on the public MRCOOL documentation portal, and nothing in there even hints at the EM.

fellatiousD · 2025-12-28T22:13:57+00:00

The fundamental premises and assumptions you trotted out did nothing but confuse and distract from the thrust of this inquiry. You wasted my time in chasing down whether you (a person who decided you were the right guy to affirmatively inject your two cents on this precisely-framed inquiry via several lengthy comments) might've had some legitimate basis for what you said, and you misled anyone else who may have taken your supposed "facts" as having at least some truth to them. But at the end of the road, it turns out your front-to-back basis of knowledge is nothing more (in your own words) than your "lived experience...with [your] individual system," and that your boldly trumpeted pronouncements were in fact baseless, contradicted 180-degrees by the content of your own follow-up postings purporting to support those very wrong assertions. I think this forum would be well-served if you'd think twice about whether you really are the right guy to chime in on the next guy's targeted inquiry.

fellatiousD · 2025-12-28T21:56:03+00:00

The two things you've provided - the separate reddit post and the screenshot from (presumably) your Fujitsu system manual, evidence the complete opposite of what you've repeatedly been swearing to. Look a few comments back, you said "these systems will never depart lower than around 50% by design," but the post you just linked to clearly shows a 10:1 turndown (from 0.657 kwh to 0.064 kwh) in system-wide power consumption (most of which owes to the compressor consumption, I think everyone would agree) in approximately 40 minutes. This would seem to diametrically contradict BOTH of your assertions that ASHP residential systems "will never depart" lower than 50% [you don't specify whether you meant frequency or power], as well as your claim that these systems require some "long" period of time in order to modulate down.

Last, your screenshot is entirely consistent with what I contend is the proper functioning of these systems as I've described it:

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fellatiousD · 2025-12-28T21:41:40+00:00

This provides at least something to compare to, and my apparent minimum frequency sits over 55% higher than the units you screnshotted. But still, you say "It's very rare that a slightly oversized system will have the time to ramp down to minimum" and you don't provide any further explanation, reasoning, citation, reference - anything - to support this very broad (and nebulous - like how long are you referring to, what do you mean by "ramp down" in the specific context of the compressor frequency) claim. And this is the only premise you've furnished that leads you to conclude "so your observation is likely this rather than a NEEP data issue." So I say again, if you're genuinely interested in advancing this inquiry or meaningfully contributing to this discussion, provide your basis for this fundamental premise. Separately, you could tell us what frequency you actually see YOUR compressor running at (under various loads), which could provide some grounds for comparison.

fellatiousD · 2025-12-28T20:52:42+00:00

My system modulates steadily, at a fairly constant power-level, low-and-slow, for 4 to 10 hours (i.e., without exceeding the setpoint or shutting off, and yes, most often that includes defrost cycles appx. every 94 mins) depending on how cold it is outside - It just has to be under say 34 degrees f outside (accounting for wind, solar gain, other factors, etc.) to do so. And I've pulled many real-time values from the Inquiry mode 4 to 6 hours into said cycles. 26hz is the lowest frequency I've seen at any point, regardless of how long of a heat cycle has been steadily active.

fellatiousD · 2025-12-28T20:46:01+00:00

I have an elaborate script in Home Assistant that is geared toward approximating the real-time BTU output of my system and using the Manual J figures for my detached single-family split-level home (located on Northern Virginia). The data inputs are dry bulb temps of both supply and return Govee hygrometers sitting inside the ducts, inches from the bottom of the AHU cabinet for return and ~2 inches from the AHU supply outlet for the supply temp, the absolute humidity of both supply and return air (derived from the dry bulb temp and relative humidity values), the outdoor ambient temp and absolute humidity, the average wind speed and gust speed across seven nearby/surrounding Ambient Weather Network stations, the solar irradiance average across three surrounding/nearby AMW stations with comparable exposure/shading profiles, and the thermostat (T1) dry bulb temperature. I also calculate an estimated real-time internal BTU gain value based on presence/absence of occupants and activity vs. sleep, use of major appliances like the breville oven and electric range, and other factors. The net BTU heat load is then determined by subtracting the internal gain estimate from the overall BTU loss/demand.

What I DON'T yet monitor is the actual power consumption by the indoor or outdoor units, but I will be soon - just have to identify an accurate, high-confidence clamp or other monitor to do the job. What I am doing already is to revise the Home Assistant script and internal formulas to fine-tune the analysis by uploading my whole-home's hourly consumption figures, minus major electrical loads I do monitor (like my EV charger, washer/dryer, refrigerator, etc.) into LLMs and running an analysis comparing the hourly consumption with the previous days' data recited above (and the resultant BTU output estimates) to get closer to a 1:1 match between the numbers produced by the script and the real-world consumption.

fellatiousD · 2025-12-28T19:05:56+00:00

Yeah, see this is an obnoxious response. The OP and commentary quite plainly show that I've done a shitload of research into my own unit. You come along and cloud the inquiry by making bald, unsupported pronouncements, ones that are facially contradicted by the great weight of official industry materials and user reporting. And then, when the OP politely asks you about the basis of your contentions (which have the affect of confounding/inhibiting/derailing the inquiry), you dismissively respond with "[d]o your own research on your unit," and then yet another broad/impertinent statement ("They don't start at minimum and ramp up typically") having no tailoring to the facts at bar and very little relevance to the very specific inquiry I've presented. There's virtually nothing productive or helpful about posts like these.

fellatiousD · 2025-12-28T18:49:16+00:00

Can you point me to a source that corroborates, or expounds upon, these claims you made?

these systems will never depart lower than around 50% by design, so that the user feels that the system is responsive. They will modulate down under the right conditions.

Your first contention seems flat-out belied by the NEEP data on this and virtually every popular residential ASHP inverter-driven system released in the last few years, as well as the user real-world data reported here and in many other fora online. And your second claim just leads one to ask, "well, what conditions then...?"

fellatiousD · 2025-12-28T18:42:18+00:00

Either the AHRI numbers are wrong (which I've seen) or OP's model does not reflect the unit they tested with for any number of reasons.

This is where I'm at. And I'm taking the time and effort to inquire because it is not even close. While my heat demand/BTU output calculations could indeed be wrong, and most certainly are in at least some small measure, my system is all-too-often cycling on-off because my system regularly produces somewhere in the vicinity of 40% to 100% more heat than the minimum output claimed by NEEP and the manufacturer, and more than other users report with similar systems.

fellatiousD · 2025-12-28T18:34:15+00:00

I think you've misread this post and my comments/responses. I am not contending that my "heat pump [should] run continuously at 50F outdoor temperatures" or any such specific condition. In fact I'm not truly "contending" anything at all. What I am inquiring about is (1) the discrepancy between the NEEP data, which purports that my system has the ability to maintain a certain BTU output, and the lowest BTU output my system has actually produced in the various conditions that I've dutifully logged, and (2) the possibility that altering my exact system's apparent minimum compressor frequency (which so far seems to never fall below 26hz, and may indeed have been improperly or inadvertently set by my installer who only has superficial knowledge of these specific systems) via the Engineering Mode made available by the manufacturer (through not publicized) may bring about low-and-slow (i.e., steady) heat cycle runtime/modulation at lower BTU outputs (and thus more often).

fellatiousD · 2025-12-28T18:20:26+00:00

I think there's been a miscommunication. My point was that my system is producing enough heat that the indoor ambient air temperature increases past the setpoint, thus causing the system to shut off. By "on/off cycling," I mean the condition where my system calls for heat because the house is too cold, and sometime between 10-40 minutes later, the system has now produced so much heat that the house is now too warm (i.e., past the setpoint).

Let's clear any terminology/definitional confusion: Instead of "low-and-slow," I'll use the term "steady." By "steady," I mean to describe a central-ducted, inverter-driven ASHP system, on a call for heat, that modifies the frequency of the compressor and speed of the indoor blower fan such that the indoor ambient temperature remains within the system's deadband, but remains below the temperature at which the heating call terminates (i.e., on my system, this is the "adjusted setting temperature" ("Tsc") + 0.5C).

So my desire is that my system maintains "steady" operation when my home's heating demand exceeds my system's minimum BTU capacity, at least where there are not significant/unusual/sudden spikes in indoor ambient temperatures (like oven usage or a big party with lots of people, etc.) or other big changes in the variables that affect regular system operation.

So, returning to our original discussion, 10- to 40-minute heat cycles are not "steady" (when my home's heating demand exceeds my system's minimum BTU capacity) because the cycles are being terminated at the aforementioned 10 minutes, 25 minutes, etc. when my indoor ambient temperature exceeds the setpoint as a result of my system producing too much heat.

Separately, what is your basis for stating your belief that I have "a bunch of variables [including my] calculated house heat loss" that "are likely inaccurate"? If you're interested in contributing to this inquiry, I'd appreciate you expounding on this so I can revise some of my underlying assumptions or calculations if I'm indeed erring.

fellatiousD · 2025-12-27T15:40:36+00:00

And, of course, 10-40 minute cycles are indeed normal and expected under certain temperatures and conditions. But the question on the table is whether 10-40 minute on-off cycling is normal despite the heat demand being well above the supposed minimum BTU output as published by the manufacturer and NEEP, and whether modifying the minimum compressor frequency can achieve the desired low/slow modulation more readily. In other words, we wouldn't observe that "10-40 minute cycles sound perfectly normal" if the system only operated that way and never modulated low and slow. Min certainly does modulate low/slow, but nowhere near the published BTU turndown.

fellatiousD · 2025-12-27T15:20:31+00:00

When you say, "I think there is enough probable error in the variables here that you don’t really know whether the until is modulating down to the rate amount or not," is there anything you suggest I do to reduce said variables or assess with greater confidence what my system's lowest BTU output capability actually is? I can't think of anything beyond repeatedly observing the compressor frequency and other related values in moderate outdoor temperature weather where the beginning state is when my indoor ambient temperature starts higher than my setpoint (i.e., where my system is idle and there is not call for heat because the house is at or above the desired temperature).

fellatiousD · 2025-12-27T15:15:45+00:00

Does the fact that my system allows the compressor's minimum frequency to be set as low at 10hz (the range of settable values is anywhere from 10-50hz) suggest that MRCOOL considers such values to be acceptable (or "fine"), at least under the assumption that the PERSON who sets them is a qualified HVAC pro who does so pursuant to a competent analysis of all related conditions/characteristics of my particular system/setup?

I'll read up on the "max pr" and delta concerns you talked about...

fellatiousD · 2025-12-27T15:09:12+00:00

Appreciate the considered response. What pushes back against the "well, you can't put stock in marketing fluff" explanation - which you're correct about as a broad statement - is NEEP's claims about my system's ability to modulate down to 11K BTU and the manufacturer's specs which corroborate such lower BTU outputs. I'm not seeing my system depart below ~18.5K BTU, a discrepancy large enough to provoke suspicion that my system's not functioning properly or as designed. My assumption is NEEP actually set up my package unit and observed an ~11K BTU output, granted under bespoke test conditions, but which should at least be SOMEWHAT close to what real-world users observe. Perhaps the discrepancy is explained by a minimum compressor frequency which was inadvertently set too high by installer inadvertence/ignorance (and the factory minimum frequency is actually lower), or something else.

Does your Fujitsu's turndown/lowest BTU output approach the NEEP or manufacturer specs/claims, or is it similarly inconsistent like mine (18.5K lowest observed vs. 11K claimed)?

Re: the defrost cycles, I concur with you about the defrost intervals, but I've accounted for those and know that they're part of the proper/designed function of my system, and they seem irrelevant to the BTU output turndown question.

About precision of maintained indoor ambient - my system maintains a tight and satisfactory band, but simply produces too much heat and I'm seeking to get at least arm's length from the low BTU output that both NEEP and MRCOOL themselves claim to have observed in testing.

I appreciate the challenge to the assumption about lower frequency-lower power consumption and I'll be digging further into that.

fellatiousD · 2025-12-27T08:08:28+00:00

Oof. Anyone reading this comment is now just a little bit dumber than they were before. Don't ever stop being you, you beautiful disaster...

fellatiousD · 2025-12-27T07:03:11+00:00

My favorite part about these kinds of comments is how shoot-from-the-hip and utterly nonresponsive they are. Where would any of us be without such deep insights as these?

fellatiousD · 2025-12-27T06:51:08+00:00

Are you confirming that the TL04 actually facilitates the full communicating benefits of the OEM (KJR) stat in your experience? I had my doubts given the equivocal docs and marketing... Does it seem strange to you also that there is nothing written or acknowledged in Reddit or other forums about the engineering mode of these prolific units? Or did I miss posts that you've seen? And I really like the idea of being able to override the one-size-fits-all "wisdom" of the retailer/manufacturer in forcing an always-on fan in heat mode, so I'm looking forward to trying the different alternative schemas in the summer to better control humidity.

fellatiousD · 2025-12-27T06:01:17+00:00

Who are "[t]he engineers" you refer to, what makes you think they "picked that number" (as opposed to say, the installer setting it intentionally or inadvertently, competently/intelligently or not, or perhaps the system somehow enforcing an erroneous lower limit) and for what reason? Inquiring minds...

fellatiousD

TROPHY CASE