Dockside Chat - Mitsubishi ductless heat and A/C...PING HVAC experts

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nat
03-29-2012, 12:20 PM
Does anyone have any first hand experience with the Mitsubishi ductless units ?

I'm back to work on my mancave/fish camp ( after a 6 month delay for prostate cancer treatment) OUCH !

http://www.thehulltruth.com/dockside-chat/349940-mancave-thread.html

I'm planning on using these units for the lower intial cost and lower utility cost.

http://www.mitsubishicomfort.com/en/consumer/product-solutions/product-showcase


My concern is with the icynene insulation on the backside of the roof deck ?

How can you control the attic temps ?



I will have 1200 sq ft heated and cooled, 2 x 6 stud wall and icynene insulation, 9' ceilings


PP1
03-29-2012, 12:37 PM
I know you asked for an expert, but I'm here anyway ;)

Lower initial costs.....not so sure about that. You will need a head in each room you want to condition. From what I have seen the mitsubishi is one of the recommended brands. Apparently having a good installer is one of the key issues with these.

I have a 2 story house and put them in the upstairs rooms last spring. Very happy with how well they have worked, both with keeping it cool and the few times that I needed heat this winter.

baypro21
03-29-2012, 12:40 PM
How many rooms? Those units work well as long as you are not trying to heat or cool a room that doesn't have a unit in there.

When it breaks not every tech will know everything about them. Also you could be in a situation where parts will have to be ordered. That may not be a big deal if you have other units in the house (but I doubt you will have more than 2 for the size cave you are talking about).

Like most things, those systems work great til they don't. I prefer a whole house ducted system. As far as mini splits, those Mitsubishis are good. So are Fujitsu's.


MacCTD
03-29-2012, 01:20 PM
Put one in a while ago, it has been great, exceeded my expectations.
http://www.thehulltruth.com/dockside-chat/336703-mitsubishi-mr-slim.html

ScarabChris
03-29-2012, 01:39 PM
They have them in the cottages at the Bimini Big Game Club and they suck. It takes forever to cool the room down and if it's a super hot sunny day you will be lucky to see the room at 78 degrees.

Maybe the hotel has them rigged like this but either way, I hate them!

Mist-Rest
03-29-2012, 01:50 PM
Proper installation is key. Of course sizing is also critical.

I have a Sanyo Tri zone down here in an open style contemporary because there is no other way to cool the house. It has been a very good unit for coming on 20 years. The new units you're looking at can also heat and run as a dehumidifier only.

CARV
03-29-2012, 01:56 PM
They have them in the cottages at the Bimini Big Game Club and they suck. It takes forever to cool the room down and if it's a super hot sunny day you will be lucky to see the room at 78 degrees.

Maybe the hotel has them rigged like this but either way, I hate them!

Nothing you can't cure with a little Bud Platinum and some whiskey drinks. How's your head?

edwardh1
03-29-2012, 02:32 PM
not an expert but they work very well in many carribbean motels on the islands. quiet and less vibration than the amana carrier motel units in the us that are NOISY and shake and jump

beachbum43
03-29-2012, 03:33 PM
I had 2 Mitsubishi units installed in my office and they have worked great for 3 years. One is in a storage room we turned into a conference room. The other is in the reception area that we could never keep cool because of the door always being opened and a large storefront window.

The units have been very reliable.

ESSRTEE8
03-29-2012, 06:50 PM
I've used the Sanyo units in my computer rooms for the past 20 years. Current setup was installed in early 1999 and ran 24/7 until last year. One of the 3 units went south and had to be replaced due to lack of parts. The other 2 still running for 13 years.

I just installed a 2 head fujitsu split a/c heat system in my house. Haven't turned it up yet, electrician has to come back and hook it up.

Gunner's Daughter
03-29-2012, 07:25 PM
Paul Smith CJ Services (HVAC) cjservices@cableone.net 228-539-0842 office
228-861-1271 cell ---This guy know it all. Use him on the commercial side but does residential as well.

jeremyj
03-29-2012, 07:30 PM
If you are going to go ductless, then Mitsubishi is the way to go. They are the only one I could find support for. Ours are installed on mobile labs that travel the US, so support (regardless of where the lab's at) is key for us.

nat
11-16-2012, 09:55 AM
bumping this old thread from 03-29-12 for more discussion


Update

currently building a new home with the primary HVAC systme being mini splits

using open cell foam / non vented attic R-30 (should be 7 1/2" foam)

all conventional HVAC systems are required by code to have a register in the attic to heat and cool the closed attic space.

No flow through vents are allowed in the ceiling per the local building codes

seems like a problem to force conditioned air into your attic when the only place it has to escape is around light fixtures back into your living area ????

My system is designed to NOT force conditioned air into the attic

If needed by code I was prepared to use flow through vents between the attic and living area.

My question

any HVAC contractors or residential contractors ever cross this bridge ?

it seems our local building dept hasn't seen this type system used for a whole house


I don't plan on installing a seperate unit to condition the attic......

but

I may have to become involved in the learning curve at the buidling dept......

davedowneast
11-16-2012, 02:01 PM
"all conventional HVAC systems are required by code to have a register in the attic to heat and cool the closed attic space."

I'm having trouble comprehending this statement. The building department says it's code that you have to condition a space because it's insulated? Any code that I've ever read said "living space" or something like that. Building an "envelope" home is the way to go IMOP. If required, you could install a multiple zone unit and make the attic space one zone.

I'll be curious what the contractors on hear have to say.

As far as Mitsubishi is concerned, they are as good as Ductless systems get. There's a very large parts and equipment distribution system for them in this country.

nat
11-16-2012, 03:03 PM
correct

the local county code requires a sealed attic with a foam insulated roof deck to have a duct outlet in the attic to condition the attic space.(conventional system)
the mini split units are not designed to match the requirements of the conventional system that has duct work in the attic space

That is the problem, they are not familiar with this type ductless system and the codes don't accommodate the ductless setup.

Im my case the attic would not have direct conditioning, but would maintain a temp from the radiant transfer of household temperature through the ceiling

they don't allow cross through vents from the attic to the living space

trying to get some feedback from areas that have worked through this application

docters oarders
11-16-2012, 03:25 PM
I thought florida had some strange codes .
Is the foamed in deck with no vents for flotation or something. Do they want your house to float when it floods J/K
Can you get a copy of the local code that says all of this and post it. Most codes have exceptions

davedowneast
11-16-2012, 07:31 PM
I remember talking with the rep from Icynene in the Wilmington, NC. She was the rep for the whole SE. One of her biggest obstacles was educating countless county code enforcement agencies.

Has anyone been able to explain the need to condition unoccupied space?

YeahBuoy
11-16-2012, 07:54 PM
Maybe to eliminate the possibility of mold? Just a guess?

neckbone
11-16-2012, 07:55 PM
From what I understand, yes, if you're doing new construction with foam insulation under the roof deck, you do have to condition the space. As YeahBouy said, the reason for conditioning it is to remove moisture, thereby reducing the mold issue. In order to remove moisture, you do need to return air to the A/C coil. So, since you'll be adding a supply, you will need to add a return as well to remove the humidity.

As for the mini splits, Mitsubishi and Fujitsu are the best, and are very equilivent in price to most of the others. Mitsubishi offers a 7 yr warranty on the compressor and parts if you purchase from a Mitsubishi Diamond Contractor. I believe Fujitsu is 7 on compressor and 5 on parts. Most of the others are 5yrs or below. They are amazingly quiet, and the inverter compressor will provide the correct tonage of cooling required at the time. They also can have multiple head units on each outdoor unit, but I'm sure you've seen that already. I wish I had an answer for you on using splits when you're using foam insulation.

I would see if you could get in touch with the Mitsubishi tech support and ask them. I'm sure they've run into people foaming in their entire home and using mini-splits. Just found the number. Inside sales: 877-391-5550, or better yet, try the Applications department: 800-433-4822, option 3.

One more thing with foam insulation, code requires that if you use the attic for equipment, or for storage, you need a fire barrier.

THT Mod 7
11-16-2012, 10:52 PM
but

I may have to become involved in the learning curve at the buidling dept......

and my inspector is a bull lesbian with an attitude and no scrotum


Is this really necessary??????

nat
11-17-2012, 04:51 AM
if you could please remain on topic and not derail this thread

nat
11-17-2012, 05:04 AM
From what I understand, yes, if you're doing new construction with foam insulation under the roof deck, you do have to condition the space. As YeahBouy said, the reason for conditioning it is to remove moisture, thereby reducing the mold issue. In order to remove moisture, you do need to return air to the A/C coil. So, since you'll be adding a supply, you will need to add a return as well to remove the humidity.

As for the mini splits, Mitsubishi and Fujitsu are the best, and are very equilivent in price to most of the others. Mitsubishi offers a 7 yr warranty on the compressor and parts if you purchase from a Mitsubishi Diamond Contractor. I believe Fujitsu is 7 on compressor and 5 on parts. Most of the others are 5yrs or below. They are amazingly quiet, and the inverter compressor will provide the correct tonage of cooling required at the time. They also can have multiple head units on each outdoor unit, but I'm sure you've seen that already. I wish I had an answer for you on using splits when you're using foam insulation.

I would see if you could get in touch with the Mitsubishi tech support and ask them. I'm sure they've run into people foaming in their entire home and using mini-splits. Just found the number. Inside sales: 877-391-5550, or better yet, try the Applications department: 800-433-4822, option 3.

One more thing with foam insulation, code requires that if you use the attic for equipment, or for storage, you need a fire barrier.


appreciate the info from everyone


on the return air issue, the method they are conditioning the attic here is with a register in the duct system , in the attic, the only return air flow is through the cracks around recessed lights or other fixtures in the ceiling.So in reality, on one hand they won't allow air flow from the attic and at the same time, they ignore the indirect airflow that is the result of a duct vent in the attic. with the return air in the living area cross through vents are essential IMO

you can go in a house with this type setup, get a ladder and put your hand up to a recessed light and feel the airflow while the system is running


I have spoken to three mitsubishi diamond dealers and none of the three had any clue about this type insulation/HVAC configuration.

I spoke with an insulation contractor that has been working with the county building dept while they adopt new energy codes and he mentioned the fire code was the reason that no air flow vents were allowed between the living area and attic, a fire retardant coating must be sprayed on the foam to slow down ant fire/flames that contact the foam surface.
it's really a latex paint with lab tests that show it slows down a fire.

kinda like 5/8" fire sheet rock is a 20 min fire barrier

crazy thing is one county over (just across the state line in Fl) the flow through vents are required by code.

davedowneast
11-17-2012, 05:19 AM
If mold is the only reason for the code, why not a stand alone dehumidifier?

FYI, the houses I did that were "envelope" built, had whole house ventilation with a heat exchanger bringing in fresh air and exhausting the stale air. The main problem of foam insulation is being too tight and trapping humidity, thus the fresh air intake. The exhaust is from bathrooms and kitchens, I would think the attic could be added to that system.

I am away from home and my computer, so I don't have links to my favorites.

Carolina Custom
11-17-2012, 06:24 AM
I built a house 2 years ago in NC with all spray foam insulation and mini splits as the only HVAC system. The inspectors pretty much just left us alone, since they really did not know much about either the insulation or the mini split system. House is insulated under the roof deck. There is no insulation above the ceilings, and no vents from the living space to the attic. I would say at the most, there is no more than a 5 degree difference in the living space to the attic, either winter or summer. I am sold on both the spray foam and the mini split system. I will never build another structure with forced air HVAC.

edwardh1
11-17-2012, 06:27 AM
many many caribbean motels use only mini splits- all Japanese made - Mitsu invented them I think, sanyo and many other make them, very very quiet inside unlike the carrier and ge units that are in many american hotels. Many also have remote controls for the ceiling mounted units.

nat
11-17-2012, 06:44 AM
I built a house 2 years ago in NC with all spray foam insulation and mini splits as the only HVAC system. The inspectors pretty much just left us alone, since they really did not know much about either the insulation or the mini split system. House is insulated under the roof deck. There is no insulation above the ceilings, and no vents from the living space to the attic. I would say at the most, there is no more than a 5 degree difference in the living space to the attic, either winter or summer. I am sold on both the spray foam and the mini split system. I will never build another structure with forced air HVAC.

do you know what your relative humidity is ?

is there any mold growth in your attic ?

would you share your energy costs in the summer months July, August ?

Carolina Custom
11-17-2012, 08:17 AM
Nat,
Humidity in the summer is like most of the south, sopping wet. Fairly low in the winter months. No mold in the attic, the air up there is pretty much conditioned, we get some air transfer around light fixtures etc. We really did not make any attempt to isolate the attic space from the rest of the house since the attic is part of the "envelope".

We built with 2x6 framed walls and filled the wall cavities with foam, and the roof deck has 8" plus of foam. House is on a slab, 2 story, footprint is 30 x 30, so 1800sqft of conditioned space, plus the attic since it is in the envelope. We also have a galvalume metal roof, which reflects a lot of the summer heat.

House is all electric. We are a family of 3, and our highest electric bill thus far has been a little over $100/month. We went with very good windows, doors, appliances etc for max energy savings. Our last house was a remodeled 1920's structure that was horribly energy inefficient, so I went to extremes to get our energy usage down on this house. I am very happy with the outcome.

nat
11-29-2012, 08:06 AM
just FYI on this job

sat down with the head man @ the county building inspection dept

He said the county codes do not adaquately address foam insulation, so they are behind the learning curve

also

on the A/C system

I got 3 quotes from mitisubishi "diamond" dealers in my area
1 26 seer 9000 BTU
1 23 seer 12000 BTU
1 19 seer 24000 BTU

$11,800
$11,100
$9,200

another quote from a non-diamond dealer

$8100

I guess some dealers have higher over head


foam insulation is too damn high !



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