Mitsubishi H2i Performance info
Well we installed a Mitsubishi Hyper-Heat system back before the snow storm, and I’ve been keeping some stats in order to analyze performance and costs. We have had relatively mild days and nights here in Brooklyn so it’s gonna be tough to get real world cold temp data– which is what I’m really interested in because in colder temperatures the roof unit has to work harder, and obviously uses more energy to grab BTUs out of the cold air and more importantly push these BTUs to the airhandler inside. I’ve kept some pretty detailed records of: 1) outside temp 2) room temp 3) air intake at blower temp i.e. Return temp 4) air output at blower temp i.e. Supply temp I’ll crunch what I can for those interested and post a screen shot of the excel data sometime soon. But in the mean time let me just say that in these mild temperatures the H2i system performs as expected. There are a few variables here, but just to ke it simple: 1) I’m measuring the performance of only one air handler — SEZ-KD12NA4i — this is a 12K BTU, in ceiling, short duct unit — it’s mounted in a 18″ cock loft, blowing almost directly through ceiling and into room below — two additional rooms are being heated by proximity, all in all aprox 375-400 sq/ft — I’m using a two-stage thermostat which coordinates with the inverter system — stage-1 (inverter) gradually ramps heat output to set point, over about 30 minutes when OAT is 45F — stage-2 (full on) ramps heat output to set point, over about 15 minutes when OAT is 45F 2) at ANY outside temperature between 27F-54F — the inside air handler is remarkably consistent — the room temp is kept right at 70F with fluctuation of +- 2F — the blower’s intake is always 70F no flux — the blower’s highest output is kept right at 113F right at discharge. Temp rise of 43F — the blowers highest output 5 feet away from unit is 96F no fluctuation. Temp rise of 26F So the all important temperature rise is about what you would expect, at least from my reading of the available online literature. The 43 degree rise is remarkable but it is being measured right at the air discharge. So room air is coming in at 70 degrees, passes through about 20 inches of air handler, and is discharged at 113 degrees F. REMARKABLE! So the above leads me to believe the H2i system actually works as described in the literature at mild temperatures. BOTTOM LINE: To keep the inside temperature as CONSISTENT as above data shows, the roof unit must be varying the refrigerant flow, and pushing just what’s needed past the air handlers coils for ANY OUTSIDE TEMPERATURE. This is obviously what is to be expected for an INVERTER HEAT PUMP…. But not the most important part of the calculation. What I really want to know (now that I see the system works as advertised) is HW MUCH ENERGY IM USING with the heat pump, so I can compare to the resistant heat system I was using before the upgrade. This is a bit harder to calculate, as the H2i is an INVERTER system which varies the amperage at the condensor/compressor and pushes different amounts of refrigerant through the system as needed. I have an idea how to calculate the electrical usage from the data I have… But it will take some time. BEFORE ANY OF THE HVAC PROs chime in here, YES I know the electric usage can be MATHEMATICALLY backed out from the specs of both the airhandler and the condensor—- But I’m trying to do this a bit differently to see real world performance. Anyway, if anyone gives a damn, I’ll post more observations at a later date..
jjq
in Heating and Air Conditioning 9 years and 8 months ago
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petec | 9 years and 8 months ago
So how did this system do through the recent freezing cold weather?
jjq | 9 years and 8 months ago
I don’t think the Nest compromises the Mitsubishi’s performance…. It’s just an expensive alternative to the standard Mitsu control which I did not buy. I would not buy another nest– until they unlock all the info the unit samples, and gives a little more programming control like the ability to program a group of set-points for different outside temperatures.. Ie: if it’s 30F outside give me thermostat schedule *A* inside, if it’s 50F outside give me thermostat schedule *B*. But admit I have nothing to compare the Nest to. The Nest is hooked up to a proprietary Mitsu interface (hardware) that controls the inverter functionality. So I essentially have three states of the system when “on” — on, inverter (VRF) & off. The VRF does what it’s supposed to do. It delivers 15 minutes of refrigerant per cycle (2 cycles an hour) gradually increasing the refrigerant volume which flows past the air handler. Obviously gradually increasing the temperature of the air flowing out of the unit. This gradual flow of refrigerant obviously also linearly increases the amperage of the outside unit– I can tell this because the outflow temp at airhandler goes from about room temp F-113F over 15 minutes in VRF mode. While “On” mode delivers 113F in about 3 minutes. More refrigerant equals more heat equals more $$$$. Any increase in room temperature needed after the VRF cycle is augmented by an “on” cycle for what ever time is needed to get the room to thermostat set-point. The picture I posted above is a screenshot of the nest/inverter cycle. The red bars are full-on, the orange bad are VRF, and the white bars are off. The internal fans seem to cycle independently of the increase in refrigerant. How does the standard Mitsu thermostat cycle? Thanx.
hawaiismurf | 9 years and 8 months ago
why dont you unplug the nest since its compromising the performance of mitsubishi? use the normal mitsubishi control, and install a mitsubishi controller and use the mitsubishi iphone app.
jjq | 9 years and 8 months ago
I’m using a Nest thermostat to set room temperature, a wireless thermometer with digital base station to measure opposite side of the room (from nest) temperature and remote sensor (for outside temp) and two digital meat thermometers ($10/each on Amazon) which measure air output at blower and aprox 5 feet away from blower. I took samples every 5 minutes (well, really every time the Nest called for a new heat mode)for three hours at three different outside air temperatures– 30, 40, 50 Degrees F– for about 8 days. At this stage, main purpose for the above work was not to compute effciency(power usage) but to understand how the heat pump works, and especially to understand the real world implications of the INVERTER function/algorithm I’m writing a post now on general performance– but just to leak the bottom line– 1) the NEST thermostat affects usage the most — My air handlers are set to come ‘on’ ONLY 50% of the time — basically remaining off from 9am-4pm, and 10pm-5am (“early on” warms room before set target) — so this is where the most SAVINGS occur — SELECT AND PROGRAM THE PROPER THERMOSTAT — the basic $80 Home Depot thermostat will perform 95% of the (expensive) Nest functionality and will also do rudimentary outside unit diagnosis (the Nest can’t do diagnosis on Mitsu) 2) the INVERTER ALGORITHM keeps the system blower cycling from “Off”, “PARTIAL ON” & “FULL ON” — on average and Depending on outside air temperature, and weather conditions — within those hours the thermostat is set to “ON”, the inverter cycles the blower OFF about 15min an hour, PARTIAL ON 30min hour, and FULL ON about 15min an hour — UNDERSTAND THE “PARTIAL ON” INVERTER CYCLE — Partial on=Variable Refrigerant Flow (VRF) — this is where the remaining savings occur Anyway, I’m gonna post a better, and a little clearer analysis of how the INVERTER system works sometime later this week.
hawaiismurf | 9 years and 8 months ago
jjq, what type of thermometers are you using for your measurements? I have a Mitsubishi City Multi and am interested in doing similar analysis. Incidentally, I have found the system to perform very well in a well-insulated home with triple pane windows. In general, at temperatures close to freezing, I use only 2 of 5 indoor zones. My monthly electricity usage (For all household purposes), is about 0.5 kwH/sq ft / month
jjq | 9 years and 8 months ago
I wanted to add another post on my observations after a week or so with the Mitsubishi H2i system. This is kinda a pre-useful observations post, just to organize my thoughts on what might be important to members like me, who are trying to sort out all the various, sometimes conflicting reviews, specs, performance metrics, and operational characteristics of cold climate INVERTER type heat pumps. INVERTER is the key word here, because as I quickly found out– this is where the real energy savings occurs– Not only energy savings (in terms of BTUs or Dollars) but also where my pre-purchase knowledge was most limited. I also just want to point out– I’m no expert on this or anything else to do with HVAC or heat pumps. These posts are simply one guys “real world” observations. I’m trying to answer questions which I had BEFORE I installed the system. Questions and answers which may be obvious to some, but we’re still obscure to me even after a year of research, conversations with multiple HVAC people, and reading everything I could on the subject. After about 10 days of on-site observation– I’ve answered some basic questions about Inverter heat pump mechanical operation– but several associated energy efficiency questions still linger in my mind. I gotta admit that even as the H2i units went in, I was still skeptical that they could produce the kind of heat I need for two floors of my 3,000 sq/ft limestone. I mean, 140F degree steam heat, or 100F degree resistance heat is way different than 96F degree air sourced heat. WAY DIFFERENT. The above tactile difference between STEAM, ELECTRIC and HEAT PUMP heat sources can not be emphasized enough and deserves a complete post sometime in the future. But now I’m NOT looking specifically at heating comfort, but energy/cost (savings) and more importantly, just how an inverter heat pump ACTUALLY achieves its advertised goals. Almost everything I read before the installation implied that heat pumps alone WOULD NOT BE ABLE TO HEAT a home in this area of the country. Truth is, every HVAC guy I talks to also said the Conventional heat pump system would work great at temperatures above 35 degrees, but would fail in colder weather. That’s why we went with a cold weather heat pump system, described as delivering 100% rated BTUs even when the outside air temperature is 5 degrees F. There’s a list of cold climate heat pumps here: http://www.neep.org/initiatives/high-efficiency-products/emerging-technologies/ashp/cold-climate-air-source-heat-pump So with the understanding that the average NYC “cold” temperature is around 27 degrees, installing the heat pump, in my mind, was/is an expensive gamble. And although the jury is still out on COLD TEMPERATURE operation, I think I have some interesting observations on how these units perform at mild temperatures– say 30 – 50 degrees F. I’m NOT gonna post much of the temperature data I’ve collected over the last week or so, because I’ve found out — “your mileage will vary.” And vary a lot for what seems even the most minor items. In addition to the advertised COP, EER, SEER, HSPF of these units, their performance (both power consumption and general operating mechanics) is affected so much by the following three classes of variables, that in my view, it’s almost useless to convey specific measurements, electrical and temperature observations: 1) Direct ENVIRONMENTAL variables — such as outside air temperature at any specific time, home insulation and room envelope (closed doors, windows, construction materials), whether it’s sunny or cloudy outside, the type of thermostat being used, scheduling of thermostat — these are obvious variables and are not to be underestimated 2) Placement of room THERMOSTAT and measurement thermometers — How and where ambient air temperature is measured directly affects the thermostats performance — the thermostat directly controls whether the compressor is ON or OFF — “on” or “off” is a BIG DEAL. It is the NUMBER ONE major contributor towards how much electricity is being used 3) INVERTER algorithm and operational characteristics — this is the bug-a-boo. It’s a big black box that will affect 90% of your electric bill — it affects how the compressor cycles through heating stages and associated power consumption I just wanted to mention something about COP, EER, SEER, HSPF. Yes the math to compute these metrics is pretty easy and it’s pretty easy to extrapolate a weeks worth of data out into a seasons worth of performance data and costs. Understand ahigher metric is a better metric is just a start. But it’s not the math that’s important to me. Much like BTUs in terms of kilowatts, one needs a real world idea of how much heat (in human tactile terms) a 3,000 watt/10,000BTU electric heater generates, before one can fully understand the output of a heat pump system in terms of say, 19 HSPF, or 4 COP. It’s the relative understanding that’s important before the abstract metric. With the above in mind, I am going to try to convey some more general but hopefully useful data/observations in a future post which will look at the above three classes of variables a little more closely and in context of my installation. Thanks for listening.
cmu | 9 years and 8 months ago
You know steam man, when you try to refute something technical & specific, as in my post, saying ‘you’re wrong’ and pointing to an article is just plain ….. Where am I wrong? There’s nothing magic about efficiency numbers, anyone with any understanding of simple math can do it.
Augustiner | 9 years and 8 months ago
This looks also good for live energy monitoring: http://neur.io/ I’m also happy with my H2i – but when it’s really cold the energy draw rises quite a bit. It’s best for mild winters like this one.
kenzdesigns | 9 years and 8 months ago
Really appreciate this, keep it coming!
presidentstps | 9 years and 8 months ago
You could get one of these electric usage monitors and hook them up to the circuits driving the heatpump and air handlers to get real data? I thought about doing it just for fun myself but couldn’t justify the cost: http://www.theenergydetective.com/prohome
steam_man | 9 years and 8 months ago
cmu, you are incorrect. For your edification: http://www.powerknot.com/how-efficient-is-your-air-conditioning-system.html
cmu | 9 years and 8 months ago
All that matters is the heat output (btu) per energy input (kW). There’s no objective reason heat pumps have COP and ACs have EER (and, anyway, you can convert one to the other.) And of course, neither is real-world accurate, which is why ACs also have lower SEER ratings. Isn’t comparing to resistive coils trivial: 1kw=3,7xx btu. (COP=1)? What’s would be interesting about OP’s post is a cost comparison to gas heat.
steam_man | 9 years and 8 months ago
jjq, Heat pumps aren’t measure in terms of efficiency (like a regular AC) so do your research in order to understand how to compare to your resistive heat coils. Send me the data when you have it. I’ll try and help you make sense of it. Great post and thanks for being a mechanical geek. You’re in good company. -S.
cmu | 9 years and 8 months ago
I think your electric bill might be an indication of usage. Can you tell us what it is before & after? fwiw, my boiler quit on monday. Before it was fixed, I turned on my cheapo Freidrich Breeze unit (the DIY model) which is rated 12000btu and it kept my parlor floor at 68 when the outside temp was at freezing.
petec | 9 years and 8 months ago
jjq, thanks for posting your experiences. the data is great and very useful to someone trying to figure out how to upgrade an hvac system.