New Home HVAC System

[riptides]

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That's a stunningly beautiful pic.

 

[jk96]

That's a stunningly beautiful pic.

Thank you.

 

[Popgadget]

One of the reason that mini splits are typically so efficient is the technology that they use. Both indoor and outdoor fans are variable speed as is the compressor. The expansion device is a needle valve operated by a stepper motor. The entire process is monitored by a micro processor that continually adjusts all parameters according to the load. This can provide efficiency that exceeds a closed loop geothermal system depending on the actual equipment used.

Having said that, the downside is that unlike a conventional heat pump with an orfice or basic TX valve, they are much more difficult for a “generic” technician to diagnose and repair.

In the real world this means the percentage of a repair being made on the first trip is slim compared to a conventional system.
And then there is the question of parts for units that are 10 years old.

There is always a cost for being on the cutting edge.

 

[Sigarms]

I would guess at least 75% of HVAC contractors for retrofit applications do not do a full manual J load (at best, perhaps a block load)./QUOTE]

Ours actually did a manual J. Came out to 7 tons. Upgraded to 8 he said for airflow. After the fact he did admit he had not done many homes with spray foam. Also the cathedral ceiling (26 ft) and all the windows throughout the home threw him off as well. He seemed shocked we were only running stage 1 and no backup heat in zero temps the first winter. In reality we probably needed 5 tons without heat strips or 3.5 to 4 tons with heat strips on sub zero temps.

Apparently he didn't do his manual J correctly when he put in an 8 ton system and it appears a 5 ton would of worked. Oversizing by 3 tons shouldn't be your issue. Hopefully he made it right.

Nice room! Whenever I'm dealing with something new that I'm not certain of, I'd be making phone calls to ensure my butt is covered.

Have a homeowner right now filing a complaint on another contractor. 2 ton system went into a 650 sqaure foot house because the homeowner wanted it cooler in the summer time so the guy thought more AC was the answer.

You have a 4,500 sq ft house where it appears that 5 ton will suffice. We bought our house used, built in 1988. 3,500 square feet, lots of windows on the first floor, we need every bit of 7 tons between 3 systems. Before we bought the house I went over the ductwork. It was perfect.

This is why load calculations are so important. Garbarge in, garbage out per the data as most guys just go by 600 sq ft per ton and add or deduct 1/2 ton between "good" and "bad" on the insulation and if they don't come up close to the "general rule" they freak out and try to change the data to what makes sense to them

 

[jk96]

Apparently he didn't do his manual J correctly when he put in an 8 ton system and it appears a 5 ton would of worked. Oversizing by 3 tons shouldn't be your issue. Hopefully he made it right.

Not really but in the long run it worked out. Really big credits from the electric coop per ton for geo offset most of the extra tonnage expense. Biggest headache was figuring out how to make it work to prevent short cycling and high indoor humidity while he drug his feet about downsizing the units. I figured out how to trick the units zone percentages so it never called for 2nd stage. That and some slight zone bleeds took care of the short cycles. In the end I have a pretty efficient system. Running stage one only my loop is oversized a bit now so loop temps don't draw down much in the winter or up in the summer giving more delta t. Additionally in the winter we don't have a need for backup electric heat. I will give him credit on the duct work. Some of the nicest hvac duct I've seen done in residential.

 

[kf4uda]

I would like to thank everybody for posting their experiences and opinions. Definitely some great feedback here. I will use all of your feedback when it comes time to meet with the HVAC contractor to ask questions.

 

[kenmac]

No matter what brand ,or type system you choose. Be sure it's a clean install. In other words clean copper line sets, flow nitrogen during brazing, and proper vacuum, etc, will determine how long your investment last

 

[ustmd]

There is a builder I follow on Youtube--Matt Risinger.

He builds high end custom homes here in the Central Texas. He is very focused on modern building science and energy efficiency. He is doing a series on the remodel of his personal home and he is using a mini split type system for the home:

Mitsubishi HVAC At My House - Full System Tour - YouTube

The video is a little long, but he walks through his thinking along with providing the load and energy analysis.

 

[RoyKing]

A tight well insulated house with with geothermal with all the ductwork in condition areas is easy to keep running if a large house use two units, keep duct pressure low with adjustable registers and balance the house. A electronic air cleaner on return removes all odors and a heat exchange for fresh air and keep the house under positive pressure. In some areas a humidifier might be needed. If you like hot steamy showers vent it outside

 

[Popgadget]

A tight well insulated house with with geothermal with all the ductwork in condition areas is easy to keep running if a large house use two units, keep duct pressure low with adjustable registers and balance the house. A electronic air cleaner on return removes all odors and a heat exchange for fresh air and keep the house under positive pressure. In some areas a humidifier might be needed. If you like hot steamy showers vent it outside

When I built my house 35 years ago, it was pretty much as you described. Urethane foam from under basement slab to the 2nd floor ceiling joists. All ductwork in conditioned spaces and open loop geothermal with electronic air filter. I’m on the third heat pump since then, each one has been an improvement over the previous one. The current one is a ClimateMaster with variable speed blower, multi stage compressor (but not variable) and modulating water valve. The electronic filter has been replaced with MERV 16 media filter and UV light.

But if I were to do it today, I would take a hard look at mini-splits. They are where the cutting edge of efficiency is now, and offer multi zones without the penalties of trying to zone ductwork. There are certainly disadvantages to them, but in many cases they are the way to go.

 

[Sigarms]

There is a builder I follow on Youtube--Matt Risinger.

He builds high end custom homes here in the Central Texas. He is very focused on modern building science and energy efficiency. He is doing a series on the remodel of his personal home and he is using a mini split type system for the home:

Mitsubishi HVAC At My House - Full System Tour - YouTube

The video is a little long, but he walks through his thinking along with providing the load and energy analysis.

I watched the video.

If you walk into a Harley store and ask what kind of bikes they have for sale, and you walk into a bicycle shop and ask them what kind of bikes you have for sale, are you going to get the same product? Best analogy I can put it is both a motorcycle and bicycle is known as a "bike", but the two are no where close to each other in that they both have two wheels.

What I don't like about the video is 4 things...

1 - You call a residential HVAC contractor and ask them for a VRF system, good chance they won't know what you're talking about. 25 years ago, residential mini splits where known as the "new fangled inverter compressor system". I honestly don't know of one "VRF" system that was installed by a residential contractor. Last job I did in VRF was about $157,000 in equipment alone.

2 - You CAN zone a two story house with one unitary split product ducted HVAC system. Do it all the time in NC, it's call zoning.

3 - For the equipment cost Mr. Risinger can put in his home on the Mitsubishi, I have little doubt he could do a geothermal system for his house with ductwork (which we had those kind of attics in sub 3,000 sq foot house in NC LOL).

4 - For the ducted unit in his attic, he could of went with a unitary split product inverter system with a higher efficency, but that would defeat the purpose of Mitsubishi creating the video.

Ductless / ducted mini split = inverter compressor with multiple indoor head selections, metering device generally at the outdoor unit, 208/230 single phase (can be used in commercial applciations as well, particularly for low ambient conditions)

VRF = inverter compressor, multiple indoor head selections, metering device generally at the indoor unit, 208/230 3 phase (although some single phase systems starting off at 3 ton but heat pump only where the system can only do heating or cooling, not both at the same time). For most in the HVAC industry, VRF is 3 phase equipment that is capable of heat recovery, which means multiple indoor units can heat and cool at the same time).

It appears Mr. Rissenger is using a city multi on one outdoor unit, which is VRF, but single phase. In 25 years, I've never sold a Mitsubishi S series for a residential application like Mr. Rissenger is using because you'll never get your ROI on that unit in a residential application (then again, if the unit is free, no complaints I'm sure).

Reality is with large organizations, it seems inherent that the engineering department always does a palm in the face when marketing puts out a video.

All that said, what I am excited about in the HVAC industry is when a manufacturer can produce a VRF system (metering device at the indoor unit) in a heat recovery system in a single phase unit (where multiple indoor units can heat and cool at the same time). To my knowledge, only one manufacturer has one out as I just described, and it's not Mitsubishi. But the reality is for the money, if it were my house or my parents house and I was going to spend that kind of money for efficency, it would be geothermal. 2nd best option would be inverter unitary split product (which actually why Mitsubsihi got into bed with Train and these kind of business relationships are happening HVAC industry wide).

Lucky to the video is from Texas. In my part of NC, in general, the heat load can easily exceed the cooling load, which increases the money on the equipment for heating by itself.

 

[Steppenwolfe]

There is a builder I follow on Youtube--Matt Risinger.

He builds high end custom homes here in the Central Texas. He is very focused on modern building science and energy efficiency. He is doing a series on the remodel of his personal home and he is using a mini split type system for the home:

Mitsubishi HVAC At My House - Full System Tour - YouTube

The video is a little long, but he walks through his thinking along with providing the load and energy analysis.

I follow him as well... pretty sharp guy who is always looking for what's new. He reminds me of Mike Holmes sort of, in the sense you probably can't afford to do this in your house, but this is what should be done. I find it to be a good measuring stick...

 

[Steppenwolfe]

I watched the video.

If you walk into a Harley store and ask what kind of bikes they have for sale, and you walk into a bicycle shop and ask them what kind of bikes you have for sale, are you going to get the same product? Best analogy I can put it is both a motorcycle and bicycle is known as a "bike", but the two are no where close to each other in that they both have two wheels.

What I don't like about the video is 4 things...

1 - You call a residential HVAC contractor and ask them for a VRF system, good chance they won't know what you're talking about. 25 years ago, residential mini splits where known as the "new fangled inverter compressor system". I honestly don't know of one "VRF" system that was installed by a residential contractor. Last job I did in VRF was about $157,000 in equipment alone.

2 - You CAN zone a two story house with one unitary split product ducted HVAC system. Do it all the time in NC, it's call zoning.

3 - For the equipment cost Mr. Risinger can put in his home on the Mitsubishi, I have little doubt he could do a geothermal system for his house with ductwork (which we had those kind of attics in sub 3,000 sq foot house in NC LOL).

4 - For the ducted unit in his attic, he could of went with a unitary split product inverter system with a higher efficency, but that would defeat the purpose of Mitsubishi creating the video.

Ductless / ducted mini split = inverter compressor with multiple indoor head selections, metering device generally at the outdoor unit, 208/230 single phase (can be used in commercial applciations as well, particularly for low ambient conditions)

VRF = inverter compressor, multiple indoor head selections, metering device generally at the indoor unit, 208/230 3 phase (although some single phase systems starting off at 3 ton but heat pump only where the system can only do heating or cooling, not both at the same time). For most in the HVAC industry, VRF is 3 phase equipment that is capable of heat recovery, which means multiple indoor units can heat and cool at the same time).

It appears Mr. Rissenger is using a city multi on one outdoor unit, which is VRF, but single phase. In 25 years, I've never sold a Mitsubishi S series for a residential application like Mr. Rissenger is using because you'll never get your ROI on that unit in a residential application (then again, if the unit is free, no complaints I'm sure).

Reality is with large organizations, it seems inherent that the engineering department always does a palm in the face when marketing puts out a video.

All that said, what I am excited about in the HVAC industry is when a manufacturer can produce a VRF system (metering device at the indoor unit) in a heat recovery system in a single phase unit (where multiple indoor units can heat and cool at the same time). To my knowledge, only one manufacturer has one out as I just described, and it's not Mitsubishi. But the reality is for the money, if it were my house or my parents house and I was going to spend that kind of money for efficency, it would be geothermal. 2nd best option would be inverter unitary split product (which actually why Mitsubsihi got into bed with Train and these kind of business relationships are happening HVAC industry wide).

Lucky to the video is from Texas. In my part of NC, in general, the heat load can easily exceed the cooling load, which increases the money on the equipment for heating by itself.

Jeez... I understood everything you said, I think... :thumbsup:

 

[Sigarms]

Jeez... I understood everything you said, I think... :thumbsup:

It can get confusing.

This is why I wasn't certain what Kenmack actually installed in his own home when he called the system a "VRF" system.

When someone calls me for a VRF system, it generally starts off at 20 tons, 3 phase, base price of at least 30-60k for the smaller jobs for equipment only (where you're able to run over 30 indoor units off of 1 outdoor unit). In the video I watched, they were calling a residential mini split system a "VRF system" which can be misleading.

Technically, a inverter compressor is a variable refrigerant flow system, but if your looking for a residential ductless mini split, I think less contractors would be confused if you just call it that instead of a VRF system.

Imagine being able to run 69 degree cooling in one room and 73 heating in another room at the same time with over 20 indoor heads off of one outdoor unit. This is done in commercial applications all the time. Currently, "residential" single phase multi zone splits (non VRF non heat recovery from what I call them) can't do that (except for one manufacturer).

The issue is with residential multizone ductless mini splits in single phase is the entire system is either in heating or cooling as you can't have both at the same time. Generally this isn't a problem. But, if you have a large house and depending on the time of day, and depending where the rooms are at, one room may need cooling and one room may need heating. At this point you're screwed because you're only going to get heating or cooling with the mini split system, not both.

Even with a conventional split system that is zoned, you will have some lag time between heating and cooling. This is why VRF with heat recovery in single phase for residential applications excites me LOL Problem is, when the do come out, you could probably put in a geothermal for less money.

 

[not2old]

Actually mini splits can exceed the efficiency of a closed loop geothermal system, and get close to an open loop. In various buildings I have an open loop geothermal, air to air heat pump with propane furnace, and mini splits. If I were to build a new house, I知 nearly certain that I would use multiple mini splits.

I have an open loop system and didn't know that it was more efficient than a closed loop. It was chosen because we have an abundance of water here. We have a 50' deep well, water at 22' and provides 55 gal/hr.

 

[Sigarms]

I follow him as well... pretty sharp guy who is always looking for what's new. He reminds me of Mike Holmes sort of, in the sense you probably can't afford to do this in your house, but this is what should be done. I find it to be a good measuring stick...

I use to love watching Bob Vila. Then I found out it's a fine line between promoting something because that's what you like vs using something because there is money in it for you. That said, it's branding and marketing, and I get it.

 

[Popgadget]

It’s at least 25% more efficient in cold climates.

 

[mikester]

I installed two 10kBTU mitsubishi cold-climate minisplits 4 years ago. So far they've worked down to -30oC, are quiet, cut my heating bill by 60%, and I now have AC in summer. I went with two small single head units because they had the highest efficiency. I installed one unit in the middle of the house on each floor.

I would not hesitate to use them again on a new build.

You will get a lot of claims over efficiency of ducted vs minisplit systems. If your you have a lazy duct installer who takes shortcuts your ducts will be a big waste of energy.

If you have a well designed, well insulated and air tight house I'd recommend an HRV/ERV which requires some sort of ducting. A small minisplit can work well for you.

 

[jk96]

If your you have a lazy duct installer who takes shortcuts your ducts will be a big waste of energy.

If you have a well designed, well insulated and air tight house I'd recommend an HRV/ERV which requires some sort of ducting.

Here's a look at some of the ductwork running off our our two geo units. HRV is tied into ductwork to distribute fresh air throught the home.

D14_5173

20150113_084447

D14_5174

D14_5177

 

[Frankenkubota]

You don't see hard ductwork much anymore. I speced it for my house. The HVAC guy said, some atticks look like a birds nest with soft ductwork everywhere, no good. In his opinion.