Mitsubishi hyperheat mini-split (multi-split) questions

[aunsafe2015]

Two questions:

1) I know that Mitsubishi hyperheat units maintain full heat capacity down to 5 deg F or something like that. But is there a limit to the temperature differential that they can maintain? For example, assuming you have an appropriate sized unit, would it be able to maintain a room at 74 degrees F even when it is 10 degrees F outside?

My existing, ducted split system was having trouble keeping it above 68 when it was 10 outside (of course, if I allow the system to turn on the aux heat strips, then it has no problems going above 68).

2) Suppose you get the outdoor unit model MXZ-5C42NAHZ that can support 5 indoor units. According to submittal data (http://meus1.mylinkdrive.com/files/MXZ-5C42NAHZ_Submittal.pdf), it can ramp all the way down to 6000 btu cooling, and 7200 btu heating.

Suppose for your indoor units, you have 5 x MSZ-FH12NA (standard wall unit). According to submittal data (http://meus1.mylinkdrive.com/files/MSZ-FH12NA~MUZ-FH12NA_Submittal.pdf), these units can ramp all the way down to 2500 btu cooling and 3700 btu heating.

My question is this: Does the minimum running capacity of the outdoor unit (6000/7200) control the minimum capacity that the indoor units can ramp down to? Or can multiple indoor units be running at below 6000 btu, so long as the total of the running indoor units equals the 6000 btu minimum of the outdoor unit?

In other words, could two indoor units be running at 3000 btu each to reach the minimum 6000 btu of the outdoor unit? Or does the 6000 btu minimum of the outdoor unit dictate that, whenever an indoor unit is running, it must be running at at least 6000 btu?

Thanks in advance!

 

[PoorOwner]

1) how warm you can get will depends on how well insulated your room is. I am guessing your ducted unit take the air from the hallway that maybe drafty and colder than the room.. The minisplit recycles the heated air in the room. It will probably shoot out around 100 degrees heat when conditions are ideal (not like -14F or something), so how warm you can get would depend on how much heat loss is through the room.

2) This is good observation, and is why they say multizone units are never as efficient as individual single zone units. The compressor pumps out 6000 BTU at the minimum, if one room is using it, the minimum BTU of that room we can assume can be pretty close to 6000 BTU It could lead to short cycling in small rooms (but not the end of the world). Hopefully you are usually using in at least 2 rooms so in that case it would share that minimum 6000 BTU into 2 rooms.

 

[justinjoyal]

You already have a ducted system? Why would you switch to ductless ??

 

[aunsafe2015]

You already have a ducted system? Why would you switch to ductless ??

I'm asking because I'm thinking about moving, and many of the houses I look at are older and will need a new HVAC system (and possibly new or repaired ductwork), so I'm just trying to figure out whether I would replace with something like I've got in my current house, or if I would replace with a multisplit.

Another big draw of a multisplit for me is that I would be able to independently set the temperature for each room. That alone could persuade me to abandon a ducted system that needs to be replaced anyways.

Anyways, thanks for the responses. Would love to hear more--especially anecdotal stories about hyperheat units being able to maintain 74-ish degree interior temperatures even when sub-20 degrees outside (and yes I recognize this is completely dependent on insulation, etc., But nevertheless would value hearing people's experiences!).

 

[finn]

I have a Mitsubishi mini split, but only went that way because the house has in floor radiant and no ductwork.

If you have ducting in place, a conventional system is better, having lived with both.

The wall hung head is sort of ugly, and a dust magnet, and mini split filtering is limited. The ability to heat or cool one room is nice, but can’t you achieve the same thing on a conventional system by closing individual registers?

 

[Jackfre]

I like the way you are thinking and removed all the ductwork in my home and recently did the same to my daughters house when her furnace went out. The issue was the very poor quality of the existing duct work. One of the biggest benefits of the mshp is the ability to zone the building. In the six years we have been here, I have not run the heat upstairs. I do run the fan only and cool the upstairs in the summer. Something to consider in your research. I installed the highest efficiency single unit in the main living area. That was 12 hspf and 25 seer at the time. Upstairs I installed a dual. That was 16 seer and I think 9.5 hspf. When we remodeled I added another single downstairs, again at very high efficiency. The efficiency of the multis is improving, but I found that I could buy the dual and a single for the price of a triple. As well, look at your lay-out. It may just be easier with multiple units rather than a multi. I especially like the redundancy. If a unit goes down when it is 100* I can get around it. I will say that you are thinking correctly in asking the "how low will it go" question. The most important issue with a modulating piece of equipment is not how high it will go, but how low. Continuous operation, even at a low rate, distributes the air to adjoining spaces. I do not know precisely the answer to your question, but I do know that with my mini's the consistency of temperature in both heating and cooling is excellent and my electric bills are moderate. Oh, and one other benefit of eliminating the old ductwork. We got two closets and storage under the staircase.

 

[u3b3rg33k]

Two questions:

1) I know that Mitsubishi hyperheat units maintain full heat capacity down to 5 deg F or something like that. But is there a limit to the temperature differential that they can maintain? For example, assuming you have an appropriate sized unit, would it be able to maintain a room at 74 degrees F even when it is 10 degrees F outside?

My existing, ducted split system was having trouble keeping it above 68 when it was 10 outside (of course, if I allow the system to turn on the aux heat strips, then it has no problems going above 68).

2) Suppose you get the outdoor unit model MXZ-5C42NAHZ that can support 5 indoor units. According to submittal data (http://meus1.mylinkdrive.com/files/MXZ-5C42NAHZ_Submittal.pdf), it can ramp all the way down to 6000 btu cooling, and 7200 btu heating.

Suppose for your indoor units, you have 5 x MSZ-FH12NA (standard wall unit). According to submittal data (http://meus1.mylinkdrive.com/files/MSZ-FH12NA~MUZ-FH12NA_Submittal.pdf), these units can ramp all the way down to 2500 btu cooling and 3700 btu heating.

My question is this: Does the minimum running capacity of the outdoor unit (6000/7200) control the minimum capacity that the indoor units can ramp down to? Or can multiple indoor units be running at below 6000 btu, so long as the total of the running indoor units equals the 6000 btu minimum of the outdoor unit?

In other words, could two indoor units be running at 3000 btu each to reach the minimum 6000 btu of the outdoor unit? Or does the 6000 btu minimum of the outdoor unit dictate that, whenever an indoor unit is running, it must be running at at least 6000 btu?

Thanks in advance!

Yes, and yes.

#1 - assuming you have the appropriate sized unit. if you've done load calcs, then you already know! I believe the hyper-heat models have vapor injection, which allows them to reach a higher delta-T

#2 - 6k minimum is the minimum flow from the compressor. so that 6k BTU worth of refrigerant has to go somewhere. Where it goes depends on black magic the OE doesn't share, but it's related to oil return to the compressor (minimum velocity in the tubing), and capacity of the units. I would assume that two 9k heads would be able to operate at 3k output with enough flow to return oil to the compressor.

if you have ductwork, why not upgrade to a new heatpump? I assume yours is old. I talked a friend in CT into a 3 ton VRF split with communicating thermostat and according to him, his utility bills have never been lower in the winter months, his home temps more stable, and it's super quiet.

 

[aunsafe2015]

I have a Mitsubishi mini split, but only went that way because the house has in floor radiant and no ductwork.

If you have ducting in place, a conventional system is better, having lived with both.

The wall hung head is sort of ugly, and a dust magnet, and mini split filtering is limited. The ability to heat or cool one room is nice, but can’t you achieve the same thing on a conventional system by closing individual registers?

My understanding is that closing individual registers doesn't really work very well, and that closing registers can throw off air flow and pressure design elements, making the system operate less efficiently.

As for filtering, I could install a separate unit to take care of that. Might even install a whole house dehumidifier like an ultra Aire xt105. I hate high humidity!

Also, I'd probably only do a multisplit for the second floor. (And keep a ducted system on the first... Partially to avoid the wall warts). It's really the bedrooms I want individual temperature control over. I would probably keep my kitchen, dining room, and living room all at the same temp even if I had individual control over those rooms.

 

[aunsafe2015]

Yes, and yes.

#1 - assuming you have the appropriate sized unit. if you've done load calcs, then you already know! I believe the hyper-heat models have vapor injection, which allows them to reach a higher delta-T

#2 - 6k minimum is the minimum flow from the compressor. so that 6k BTU worth of refrigerant has to go somewhere. Where it goes depends on black magic the OE doesn't share, but it's related to oil return to the compressor (minimum velocity in the tubing), and capacity of the units. I would assume that two 9k heads would be able to operate at 3k output with enough flow to return oil to the compressor.

if you have ductwork, why not upgrade to a new heatpump? I assume yours is old. I talked a friend in CT into a 3 ton VRF split with communicating thermostat and according to him, his utility bills have never been lower in the winter months, his home temps more stable, and it's super quiet.

Who makes a residential 3-ton VRF? I thought those were mostly commercial/apartments?

Isn't a VRF basically the same as a multisplit, except you don't have a separate lineset from every single indoor unit back to the compressor?

And as noted above, one of the big reasons I'm thinking about not upgrading to a better ducted heat pump is because I'd like individual temperature control over some of the rooms, and I haven't seen a ducted system that does a great job of that (but could be wrong).

 

[yeldogt]

Have have a mix in my homes ... I did my first mini split about 15 years ago .. about the same time I did my first 2 speed HP in a home with 3 zones. I recently upgraded a house with a 3 head Mitsubishi and a 5 speed carrier HP w/zoning.

In a perfect build where space is not a problem (for the ducts) -- a properly designed duct system .. especially zoned with variable blower and compressor would be my pick.

Unfortunate, that I'm an old house guy who especially loves old stone or brick -- most built before central heating was available. Good heating and AC is always a space challenge when I build.

#1. This is all equation of what's the heat load. How much heat do I need for this room at a given outside temp .. add up the rooms to get the building load. Same for equipment -- what's the BTU output as the temperature outside drops. Since most HP's will start to loose capacity as the outside temp drops -- it's common to see resistance coils in the air handler to make up the difference. Modern (the best) HP don't have this problem -- they can maintain output down into single digits ... My Carrier 5 speed HP does not have any backup resistance coils and was humming along last month in 2 degree weather w/ hot air coming out of the ducts.

2. Mitsubishi keeps some of the inner workings secret -- they simply give you parameters. My three head system works very well at template times to control humidity -- a difficult thing for any system to do. 5/6k of cooling/ heating is not a lot even going into a well insulated home.

I have used single mini split HP's in lofts and single story (one room) additions -- it's great way to condition a difficult space. In my newest build I'm doing a conventional ducted (zoned) carrier system in the main stone building and will be using a multi heat Mitsubishi seem for the two room two story kitchen addition and for a loft in the main building that can't get ductwork for.

Every situation is different. The VS compressor had changed the game in both the mini split and conventional ducted systems. Zoning is even easier with the newest systems ... I'm using the Carrier 5 speed vs going to a full modulating (Greenspeed) ... mostly for cost as the 5 speed gets me where I need to be.

 

[justinjoyal]

2. Mitsubishi keeps some of the inner workings secret

Why would they be any different than other units ? Mini-splits are not rocket science...

 

[yeldogt]

Why would they be any different than other units ? Mini-splits are not rocket science...

They don't give any info on the workings as the OP is asking -- how a single unit that's able to handle less vs what the outside unit is able to provide.

Watching how my units are woking -- I thing they just loop the extra around to another unit thats not running.

 

[aunsafe2015]

They don't give any info on the workings as the OP is asking -- how a single unit that's able to handle less vs what the outside unit is able to provide.

Watching how my units are woking -- I thing they just loop the extra around to another unit thats not running.

So you think the indoor units are able to run at a lower BTU than the minimum required by the outdoor unit? I.e., the 6000 min required by the outdoor unit can be shared among multiple indoor units running at less than 6000?

 

[yeldogt]

So you think the indoor units are able to run at a lower BTU than the minimum required by the outdoor unit? I.e., the 6000 min required by the outdoor unit can be shared among multiple indoor units running at less than 6000?

That's how they work -- they share --- with VS compressor it's not always putting out the max. My one place has hydronic heat in most of it .. but I use the mini in one room for a bit of a boost (the other two units are off) .. so I can tell it sending some heat to the units that are off when the single unit is only calling for a tiny amount. I think that's how they must do it .. I'm guessing.

It's a rare occurrence -- typically most people keep them on -- so it's rare that they all don'e need some output from the compressor.

 

[theoldwizard1]

I'm asking because I'm thinking about moving, and many of the houses I look at are older and will need a new HVAC system (and possibly new or repaired ductwork), so I'm just trying to figure out whether I would replace with something like I've got in my current house, or if I would replace with a multisplit.

Another big draw of a multisplit for me is that I would be able to independently set the temperature for each room. That alone could persuade me to abandon a ducted system that needs to be replaced anyways.

I am a big fan of mini-splits for many reasons, BUT their cost to install in multiple room can kill you ! A 3 bedroom is going the need 3 air handlers, period. That runs up the price a lot, even if they are sharing one compressor. Large open areas will need more than 1 air handler. Kitchens can be a challenge because there is typically no high wall space.

If you can get over the installation costs AND you plan on living there a long time AND you have a reasonably high A/C requirement, then it might be worth the cost.

BONUS : During a power outage a moderately sized generator (5000W) can cool a couple of small rooms.

 

[Jackfre]

I am a big fan of mini-splits for many reasons, BUT their cost to install in multiple room can kill you ! A 3 bedroom is going the need 3 air handlers, period. That runs up the price a lot, even if they are sharing one compressor. Large open areas will need more than 1 air handler. Kitchens can be a challenge because there is typically no high wall space.

If you can get over the installation costs AND you plan on living there a long time AND you have a reasonably high A/C requirement, then it might be worth the cost.

BONUS : During a power outage a moderately sized generator (5000W) can cool a couple of small rooms.

1 evap/bedroom. Not necessarily. You can go with the small air handler units and pick up two or maybe three bedrooms with one. Be very careful in positioning the unit if you go this way as the small air handlers have VERY low static pressure capability. The control is only one room as well, so the other rooms get what they get, but that can be balanced.

 

[PoorOwner]

1 evap/bedroom. Not necessarily. You can go with the small air handler units and pick up two or maybe three bedrooms with one. Be very careful in positioning the unit if you go this way as the small air handlers have VERY low static pressure capability. The control is only one room as well, so the other rooms get what they get, but that can be balanced.

Here bedroom with jack and Jill bath is popular. I always wondered if I can have one and it will eventually cool the other bedroom ? (Putting in one bedroom but not the bathroom)
6000 btu may be too small to do the job but 9000 is too big for one bedroom.
For Mitsubishi I know the 6 and 9 is almost identical.

It doesn’t seem to flow out to the hallway too well

 

[justinjoyal]

They don't give any info on the workings as the OP is asking -- how a single unit that's able to handle less vs what the outside unit is able to provide.

Watching how my units are woking -- I thing they just loop the extra around to another unit thats not running.

Gotcha.

One would have to calculate the BTU output of a given head, but they say they *can* go down to 2500 btu, but is that possible only under certain conditions, etc. ? I'm thinking it's something along those lines.

I am a big fan of mini-splits for many reasons, BUT their cost to install in multiple room can kill you ! A 3 bedroom is going the need 3 air handlers, period. That runs up the price a lot, even if they are sharing one compressor. Large open areas will need more than 1 air handler. Kitchens can be a challenge because there is typically no high wall space.

If you can get over the installation costs AND you plan on living there a long time AND you have a reasonably high A/C requirement, then it might be worth the cost.

BONUS : During a power outage a moderately sized generator (5000W) can cool a couple of small rooms.

It depends on the floorplan and on open/closed doors.

In houses with large, open areas, where mostly just the bedrooms are separated, if people keep their doors open, it can work just fine. Of course if the doors are kept shut, forget about any cooling/heating.

 

[u3b3rg33k]

Who makes a residential 3-ton VRF? I thought those were mostly commercial/apartments?

Isn't a VRF basically the same as a multisplit, except you don't have a separate lineset from every single indoor unit back to the compressor?

And as noted above, one of the big reasons I'm thinking about not upgrading to a better ducted heat pump is because I'd like individual temperature control over some of the rooms, and I haven't seen a ducted system that does a great job of that (but could be wrong).

Look at any high end heat pump model that uses the word "inverter", and has a mandatory communicating thermostat. You're not going to get 10+ stages out of a standard 7 wire setup. His is a lennox XP25 I believe. VRF stands for variable refrigerant flow. Some of those are compatible with zoning, but this is really best for floor by floor zoning, not room by room.

By the way, the way you get full heat output at cold temps with an inverter unit (mini or full size split) is actually by them running the compressor (and maybe the outdoor fan, too) past 100% of nominal speed (and probably having vapor injection). in effect it's a bigger unit than the nameplate says. The efficiency penalty for this is minimal compared to using backup heat.

 

[aunsafe2015]

Apologies for reviving an older thread, but I was recently reading on greenbuildingadvisor.com, and saw some posts from a pretty knowledgeable person that suggest the Mitsubishi multi-split setups actually have pretty poor modulation capability. So I posted a thread over there and am being informed that the individual indoor units on a multi-split setup actually do not really modulate. Link below in case anybody is interested:

http://www.greenbuildingadvisor.com...at-multi-splits-and-modulation#comment-214268

I will say, I don't want to believe it. But for the reasons stated in that forum--namely, the multi-split submittals do not list ranges or minimums, and instead list only a single operating capacity--it certainly seems that it might be true.

If anybody has definitive information one way or the other I'd love to see it. I was planning to pull the trigger on a multi-split setup within the next few months, but if I can't satisfy myself with certainty that individual indoor heads will modulate, then I will just go with the Carrier 5-stage or the Trane XV18 series.

 

[PoorOwner]

It does modulate but the compressor can only go to so low. (6000-7000 instead of 1500 or 3800 of single zone system). Sometimes you have to find a different version of submittal to get their range.

I am only familiar with the 2 zone Mitsubishi, when more than one unit is on, the higher demand one will take most of the priority and that zone will definitely modulate.

The second one (slave) tag along and using amount of refrigerant pumping from the compressor, it turns the blower on and off as needed to maintain the temperature. In some sense the slave zone acts like a traditional unit.

I also used to think it can throttle with individual EEVs, it may do that to some extent, but it does not control it as fine as we think.

 

[aunsafe2015]

It does modulate but the compressor can only go to so low. (6000-7000 instead of 1500 or 3800 of single zone system). Sometimes you have to find a different version of submittal to get their range.

I am only familiar with the 2 zone Mitsubishi, when more than one unit is on, the higher demand one will take most of the priority and that zone will definitely modulate.

The second one (slave) tag along and using amount of refrigerant pumping from the compressor, it turns the blower on and off as needed to maintain the temperature. In some sense the slave zone acts like a traditional unit.

I also used to think it can throttle with individual EEVs, it may do that to some extent, but it does not control it as fine as we think.

Do you have links to any submittals, manuals, or engineering specs you can share? The way you describe it is the way I thought it worked, but that's apparently not what some of the folks on greenbuildingadvisor believe. And the only submittals for multi-zone use indoor units that I can find are at best ambiguous regarding the modulation capabilities of the indoor units when in multi-zone configuration.

 

[yeldogt]

I have two MXZ systems in two different homes. I'm going to be using another in my new build unless something new comes out. The one home uses three 12k MSZ wall units on the 30k MXZ.. the other one 12k MSZ wall and two 12k SLZ cassettes. Yes you can have greater head unit totals ... the compressors can also exceed 100%. The goal is 60-80% ..typical.

They modulate -- The MXZ is Mitsubishi's best line .. the hyper heat. MSZ is the best head unit. GBA .....They are wrong enough that .. well -- let's leave it at that.

The key with anything is to understand what you need and what you are buying. Mitsubishi builds more than one type of system.

Now. The wall units have the most sophisticated control interaction. The ceiling and ducted units don't have the same controls ... The full air handler is being redesigned (may be out) to match how the ceiling and ducted units work.

What does this all mean. The ceiling units have a 3 speed fan and four outlets -- same with the ducted units -- 3 speed fan. The wall units have either more speeds or full VS. Mitsubishi -- does not publish some items -- because they don't want to.

When I was doing my first system -- I used the two ceiling units to replace a second floor 2T unit in my attic. This was for the second floor of a large cape cod (two big bedrooms -- one bath between the bedrooms) One ceiling in each bedroom -- I put the wall unit on the first floor in a new single story addition (slab w/ radiant). The system works -- it's amazing.

The full size air handler -- that looks like a typical USA system -- is designed to integrate with the other head units -- or have an up/down system with only one VS condenser. It was not ready for prime time 3 years ago -- so I went with the carrier 5 speed in the rest of the house.

With the three speed fans the units do shut off -- but so do the wall units depending on the inside outside temps and set temps. The three speeds just do it a bit more.

The MXZ is a three head max system ... Overall efficiencies can be misleading. All the units are rated at the best possible spot. The other system is in a converted barn -- loft/ main living area/ big bedroom.

 

[PoorOwner]

Do you have links to any submittals, manuals, or engineering specs you can share? The way you describe it is the way I thought it worked, but that's apparently not what some of the folks on greenbuildingadvisor believe. And the only submittals for multi-zone use indoor units that I can find are at best ambiguous regarding the modulation capabilities of the indoor units when in multi-zone configuration.

https://richairductless.com/wp-content/uploads/2015/09/MXZ-2B20NA-1_Submittal.pdf

you can see in the "total range" there is a minimum when 1 head is on.
when 2 heads are both calling the compressor minimum also increases, the EEV also opens for the second zone and presumably the compressor pumps a bit more overall. They do share the BTU but the left 2 they are maximums.

EEVs don't seem to ever close completely so there is at least a little pin hole even when that circuit is off. Otherwise you wouldn't be able vacuum or pressure test the unit from that one service port.

I don't have anything in writing what the unit does, you may find something more in the service manual.

 

[yeldogt]

https://richairductless.com/wp-content/uploads/2015/09/MXZ-2B20NA-1_Submittal.pdf

you can see in the "total range" there is a minimum when 1 head is on.
when 2 heads are both calling the compressor minimum also increases, the EEV also opens for the second zone and presumably the compressor pumps a bit more overall. They do share the BTU but the left 2 they are maximums.

EEVs don't seem to ever close completely so there is at least a little pin hole even when that circuit is off. Otherwise you wouldn't be able vacuum or pressure test the unit from that one service port.

I don't have anything in writing what the unit does, you may find something more in the service manual.

That's an MXZ ... but, it's not a hyper. Not sure what that is ?? Maybe old ...

But it gives you an idea ... my memory was the low was around 4k not 5400 ... but that's cutting hairs.

 

[PoorOwner]

the X in MXZ- means it is a multi zone unit, the hyper heat have a suffix like MXZ-____AHZ.
hyper heat (now called H2i) is paired with FH heads. non hyper heat (like the one I own and posted the submittal for) usually paired with GL heads.

Here is the H2i brochure, you can see they cool at minimum 6000 and heat at 7200-7400 minimum.

http://www.mitsubishicomfort.com/si...ual/m-series_hyper-heat_brochure.pdf?fid=1010

I am not really sure how people are thinking they don't modulate, they modulate but just at the minimum the refrigerant the compressor must push about 6-7000 BTUs of it.
I am not that happy about how the slave unit(s) acts, but it is what it is.

Did you know the M series is residential grade and meant to be used seasonally, and not meant to be on 24/7 x365? If you wanted to cool something like a server room 24/7 or facility, they have the P series with lower SEER but built with "commercial grade" components.

 

[yeldogt]

In my climate they don't run 24/7 -- typical seasonal AC / Heat. I'm sure all the units are rated that way.

A server system is running all the time under load .. same with the "city" system .. that one can send heat and cool at the same time to efferent locations.

 

[aunsafe2015]

https://richairductless.com/wp-content/uploads/2015/09/MXZ-2B20NA-1_Submittal.pdf

you can see in the "total range" there is a minimum when 1 head is on.
when 2 heads are both calling the compressor minimum also increases, the EEV also opens for the second zone and presumably the compressor pumps a bit more overall. They do share the BTU but the left 2 they are maximums.

EEVs don't seem to ever close completely so there is at least a little pin hole even when that circuit is off. Otherwise you wouldn't be able vacuum or pressure test the unit from that one service port.

I don't have anything in writing what the unit does, you may find something more in the service manual.

Do you have a link like that for a hyperheat? Such as the 4C36NAHZ?

I found a similar document: http://meus1.mylinkdrive.com/files/M-Series_MXZ_Operational_Performance.pdf

Unfortunately, it does not give ranges. It only gives a single number for capacity for each indoor unit.

I'm not trying to argue with you; I'm just trying to find something definitive. And the only actual data I can find never lists more than a single solitary capacity for indoor units connected to MXZ hyperheat series.

 

[PoorOwner]

There are many days I can turn off the units here in northern California also.

I think multi zone systems have too much compromises. Installers don't tend to give you a price break installing them, and the saving on the hardware is minimal. I am seeing about $3000 for a 2 zone hardware and I can easily buy 2 9000 BTU single zone units. I haven't done the price research on the 5 zone units.

I think ideally if you have almost identical rooms of similar sizes and load that is usually used at the same time. Then let's see how the mitsubishi can flip flop the master / slave role and serve the 2 (or more).

 

[PoorOwner]

Do you have a link like that for a hyperheat? Such as the 4C36NAHZ?

I found a similar document: http://meus1.mylinkdrive.com/files/M-Series_MXZ_Operational_Performance.pdf

Unfortunately, it does not give ranges. It only gives a single number for capacity for each indoor unit.

I'm not trying to argue with you; I'm just trying to find something definitive. And the only actual data I can find never lists more than a single solitary capacity for indoor units connected to MXZ hyperheat series.

I can't seem to find one for the unit you are interested in, I was lucky to find that version of energy star submittal for my 2 zone unit. They don't seem to write them that way anymore, so you would have go with the brochure number of 6000 cooling and 7200 heating minimum.

by the way, if you see the FH09 head can do 1500 BTU with paired with MUZ-FH09NA outdoor unit, it does not mean at all you can get as low 1500 BTU when installed it with the MXZ multi zone system. It's nothing but a coil of copper piping with a fixed surface area and variable fan speed. The refrigerant hardware control is all done in the outdoor unit.

 

[aunsafe2015]

I can't seem to find one for the unit you are interested in, I was lucky to find that version of energy star submittal for my 2 zone unit. They don't seem to write them that way anymore, so you would have go with the brochure number of 6000 cooling and 7200 heating minimum.

by the way, if you see the FH09 head can do 1500 BTU with paired with MUZ-FH09NA outdoor unit, it does not mean at all you can get as low 1500 BTU when installed it with the MXZ multi zone system. It's nothing but a coil of copper piping with a fixed surface area and variable fan speed. The refrigerant hardware control is all done in the outdoor unit.

I know an FH09 can't do 1,500 with an MXZ. But say you had 4 of them connected to an MXZ. If all 4 were running at the same time, could they be running, for example, at 2,000 each? I previously thought the answer to that was yes. But the greenbuildingadvisor folks seem to think they would only be able to run at the rated capacity of 9,000 each.

 

[PoorOwner]

I know an FH09 can't do 1,500 with an MXZ. But say you had 4 of them connected to an MXZ. If all 4 were running at the same time, could they be running, for example, at 2,000 each? I previously thought the answer to that was yes. But the greenbuildingadvisor folks seem to think they would only be able to run at the rated capacity of 9,000 each.

I don't think so, capacity means the maximum it can be, you notice they add up to 36K BTU or very close, that's with the compressor running full capacity you will get 8,900 BTU sent each FH09 head. which draws 3,680W.

as I show you the data on the smaller unit, they do have a low range of BTU and watts to it, they just didn't bother to make that data available to your unit.

You should call the tech line tomorrow to confirm, (not through the chat, that's not so helpful)

 

[aunsafe2015]

I don't think so, capacity means the maximum it can be, you notice they add up to 36K BTU or very close, that's with the compressor running full capacity you will get 8,900 BTU sent each FH09 head. which draws 3,680W.

as I show you the data on the smaller unit, they do have a low range of BTU and watts to it, they just didn't bother to make that data available to your unit.

You should call the tech line tomorrow to confirm, (not through the chat, that's not so helpful)

So you are saying in my hypothetical, you think each of the FH09s could be running at 2,000 for a total compressor load of 8,000?

 

[PoorOwner]

So you are saying in my hypothetical, you think each of the FH09s could be running at 2,000 for a total compressor load of 8,000?

I don't claim to know what exactly happens, from what I observed in my machine, it doesn't seem the machine can divide the refrigerant precisely in the way you are thinking.

They do however have other tricks, like fan on/off, refrigerant flow on / almost off, based on temperature sensor in each indoor unit.

 

[theoldwizard1]

I think multi zone systems have too much compromises. Installers don't tend to give you a price break installing them, and the saving on the hardware is minimal. I am seeing about $3000 for a 2 zone hardware and I can easily buy 2 9000 BTU single zone units. I haven't done the price research on the 5 zone units.

I don't know how much faith you professionals put into SEER ratings but ...

If you read the specs, multi-zone systems have lower SEER rating than single zone. The bigger the capacity, the more the zone, the lower the SEER numbers are.

 

[aunsafe2015]

I don't claim to know what exactly happens, from what I observed in my machine, it doesn't seem the machine can divide the refrigerant precisely in the way you are thinking.

They do however have other tricks, like fan on/off, refrigerant flow on / almost off, based on temperature sensor in each indoor unit.

Thanks for the response. It's too bad Mitsubishi doesn't provide more info. I know exactly how far a Carrier 5-stage or a Trane XV18 will modulate down. Mitsubishi is going to have trouble getting me to give them my money when they won't give similar details.

I guess at the end of the day I'd rather have serious modulation capabilities than individual room control, though both would have been nice.

 

[yeldogt]

I don't know how much faith you professionals put into SEER ratings but ...

If you read the specs, multi-zone systems have lower SEER rating than single zone. The bigger the capacity, the more the zone, the lower the SEER numbers are.

It's misleading ...

 

[yeldogt]

6k BTU -- is not very much. I can tell you mine are barely running this morning .. I'm not getting much out of each head. The outdoor fan is also barely turning (for lack of a better term)

You are also not looking at efficiency correctly -- thee (3) 23 seer units are not going to get you more efficient use if the output of the three individual units don't fall in the sweet spot -- vs where the multi unit is running.

The nice thing about the multi units is you can have the extra capacity at one head -- so the outdoor unit falls into the most efficient range vs having three units that never run in that range.

 

[Jackfre]

The inverter mshp's...all inverter equipment, has pretty much the same issue and that is, how do you test it? There is no test that can reflect what a variable speed unit is going to see in the real world, building by building. Heat Pumps and mini-splits were always tested at 47 & 17*. I believe that is still the case. Writing a specification for that equipment constitutes a fight between the legal dept and marketing. Engineering simply have their palms pointed toward the ceiling, although they know exactly what it will do in the 17 & 47* test. When the first inverters came out I spoke with one of Fujitsu's Japanese engineers. He offered that while we were seeing low 20 seers that Japan felt they were more in the 36 seer range, but we did not know how to test them. Hence, you make a claim that you can defend in court. If you get to grandiose in claiming high specs and things go side-ways on a big job, the manuf has to defend his claims. Why would they do that. MSHP's are sweeping the N American market. I know when I represented Fujitsu in the six New England states that we were growing the market frequently by 100%/yr. Even in the '08 crash, mini-splits were the ONLY segment of the hvac industry that grew. Our growth following that lovely event was in the 40-50% range and speaking with my partner from those days it is simply off the charts today and all the other inverter manuf are seeing the same performance. Why make bold claims when the performance of the equipment speaks best for itself?
Also, consider the view of the American unitary manuf. They are freaked about how their market is changing and will speak poorly about mini-splits. It is all they can do.
Aunsafe, the interior units are nothing but a coil and a fan. All the modulation is done in the condensing unit and the expansion valves are located in the condensing unit. The thermistor on the evap coil is talking to the condensing unit and telling it how it is doing. Essentially all you modulate in the evaporators is the fan.

 

[eddieK]

I'm asking because I'm thinking about moving, and many of the houses I look at are older and will need a new HVAC system (and possibly new or repaired ductwork), so I'm just trying to figure out whether I would replace with something like I've got in my current house, or if I would replace with a multisplit.

Another big draw of a multisplit for me is that I would be able to independently set the temperature for each room. That alone could persuade me to abandon a ducted system that needs to be replaced anyways.

Anyways, thanks for the responses. Would love to hear more--especially anecdotal stories about hyperheat units being able to maintain 74-ish degree interior temperatures even when sub-20 degrees outside (and yes I recognize this is completely dependent on insulation, etc., But nevertheless would value hearing people's experiences!).

While the thought process of individual conditioned rooms sounds great...not conditioning an area creates heat load or heat loss...High pressure always moves towards low pressure.

A properly ducted central system with high SEER and high AFUE is efficient and maintains the entire "envelope", keeping everything at a constant reasonable temp...In heat mode it is about warming everything within the structure, not just the air, this way the indoor temp does not fluctuate as much. Lowering the heat gain and heat loss with proper weather sealing and insulation is much more important than all the other factors.

As far as the inverter and multi zone equipment you should have a few outdoor unit capacities to choose from.