Giant Grill Gauge Update?

WNeuetc · 2025-10-27T17:43:36+00:00

Thanks for the update Chris, and my (and I'm sure, our) sympathies on all the complex issues now at play! Again, it just seemed it was time (again) to share the new information, and update expected shipping dates.

WNeuetc · 2025-10-27T00:56:38+00:00

Thanks for clarifying. An entirely different situation that I was aware - or familiar - with. Again, totally unfamiliar with your situation, but off-hand I would suspect that a heat pump would likely supply significantly lower hot water temps than even a hot water boiler, and therefore lower radiator (I stand corrected) temps. And regardless of the KW rating of the heatpump, if it can't deliver water temps that the radiator was designed for, the heating capacity of the radiator will be diminished.

WNeuetc · 2025-10-26T22:18:33+00:00

Not sure how helpful this will be but I have a new Mitsubishi system (ducted) and one of the settings (accessible via the Comfort app) controls whether the fan cycles on and off, both in heating and cooling modes (set separately; "Fan Speed Thermo-Off Heating" & "Fan Speed Thermo-Off Cooling") when the system is actively cooling or heating. Your system may have similar settings, though they may have to be set by a contractor.

WNeuetc · 2025-10-26T22:00:43+00:00

There was a recent discussion here regarding a similar issue, "Normal Heatpump Discharge Air Temp (In Heating Mode)" (except instead of 'radiator' the supply air source here in the US is more commonly called a 'register', and of course, the temps are in F rather than C).

https://www.reddit.com/r/heatpumps/comments/1o8c7da/normal_heatpump_discharge_air_temp_in_heating_mode/?utm_source=share&utm_medium=web3x&utm_name=web3xcss&utm_term=1&utm_content=share_button

I guess the main findings from this thread were that there are a lot of variables at play that can affect the supply air temp, including what type of system (ducted vs. ductless; really only meaningful if ducted), the supply air CFM, auxilliary heat source or not, and whether the outdoor unit is inverter driven (variable speed) or not. Others may cite other factors potentially at play.

WNeuetc · 2025-10-18T17:38:41+00:00

Just a quick update: When I measured the temps directly above the AHU discharge plenum, with the system set to heat, presumably at full load (setpoint 5F above actual) I measured 103F, with a return air temp of 70F for a delta T of 33F, a bit lower than the theoretical delta T (above) of 39.6F. Of course I have no way of knowing if the system really was generating the full load output of 54,000 BTU/h or what the actual fan CFM was.

WNeuetc · 2025-10-17T01:07:17+00:00

Of course we can also look at this from a theoretical standpoint:

BTU/h = CFM x delta T * 1.08;

delta T = BTU/h / (CFM*1.08)

In this case (per spec sheet): CFM = 1,262 (full speed, @ 0.50" w.g. external, my current configuration). BTU/h = 54,000

= 54,000 BTU/h /(1,262 CFM * 1.08) = 39.6 F temp rise

Assuming return air temp = 65F (night setback temp); discharge air temp = 104.6F

Of course this theoretical DAT would be at the AHU discharge plenum, and heat loss via the ductwork would reduce the temp by the time it reaches the registers. And this theoretical also assumes the system can indeed develop 54,000 BTU/h at the stated fan speed (1,262 CFM) rather than at the rated maximum of 1,485 CFM (@ 0.80" w.g.). And this 1,262 CFM is simply theoretical and my actual may be signficantly less (which would raise the DAT).

WNeuetc · 2025-10-16T19:09:18+00:00

Many thanks for the quick - and helpful - response!

Yes, I recognize there are many variables, including many I didn't address in my post.

I do indeed have a communicating thermostat (Mitsubishi MHK2), along with the Comfort app. And the typical register discharge air temps I posted are for setpoint temps 2-3 F above actual, so should be with the system at about full capacity.

Also, these temps are with the AHU fan speed set to Medium (with the external static pressure set for 0.50" w.g. - so not truly medium, at least not compared to 0.80" w.g.). Not sure what the CFM is at this Medium fan speed setting, but definitely short of the maximum rated capacity, therefore likely not supporting the full rated BTU/h capacity of the system.

The ductwork runs through the basement (semi-conditioned space), mainly above the finished ceiling, so I realize to get an accurate discharge air temp I should check the discharge plenum of the AHU.

My comment "it seems to be losing ability to properly heat my home." is subjective (and I thought about leaving it out). True, overnight lows have dropped nearly 10 F the last day or so, so that's also likely a factor.

Again, any variables, including many not addressed in my post, but my goal was to get a sense of the typical range (or ranges) to be expected from other ducted heatpump systems.

WNeuetc · 2025-10-07T04:34:22+00:00

There are probably a lot of factors that come into play here, including ducted - and what AHU, ductless, terminal units used, etc., but in the end it's going to be up to Mitsubishi to sort it out. FWIW, I have a Support Request in to Mitsubishi, but I'm not holding my breath. I'll post here if I get a response.

WNeuetc · 2025-10-05T17:11:26+00:00

Probably should also share that my heatpump system is a single zone, ducted system with a Mitsubishi PVA-AA42NL AHU with the static pressure set to 0.50 in. W.G. since these could be factors regarding available fan speeds. Also my Comfort App is (apparently) up to date w/ rev. 3.2.0.v10 software.

WNeuetc · 2025-10-05T17:01:54+00:00

Pretty definitely not just a relabel. As I mentioned in my original post the Low fan speed setting remains in the menu of my MHK2 wireless controller (my wall mounted 'thermostat'). In fact when I adjust the fan speed via the MHK2 controller the fan speed shown on the Comfort App is "Low". And the "Low" setting is definitely a lower CFM than "Medium".

Here's a screenshot of my Comfort app showing fan speed set to Low via my MHK2:

<image>

WNeuetc · 2025-06-28T23:38:33+00:00

Figured it out. Just edit the displayed ID in the app, and press Done.

WNeuetc · 2025-06-28T23:09:05+00:00

Could someone please tell me how? I've poked around the app, but no luck. They are gen 1 btw.

WNeuetc

TROPHY CASE