New Home HVAC System

[IXLR8]

I am looking to purchase a home that just had an all new HVAC heat pump system installed. It was installed by 'one of the most reputable and respected' companies in the area. The attic is full of soft duct work that is sagging and pinched off by at least 70% in several spots. If I buy the house, I am going to have to find a way to fix it. Hard duct work seems to be a thing of the past. Although what jk96 posted is a thing of beauty and I wish an install like that was done on the home I am looking at.

 

[Sigarms]

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.

Most guys in NC in my area will run hard rectangular duct as their primary supply and return run, with collars to run flex to the outlets from the primary (more guys are going round hard duct on primary for new installs which actually does make more sense). What most guys don't do is run hard round pipe from the primary to the outlets. In an unconditioned space, prefer wrapped ductwork instead of lined (different opinions on conditioned spaces, but will only help if insulated).

At the end of the day, it's the little things that adds cost to the job, particularly with hard ductwork.

 

[jk96]

Most guys in NC in my area will run hard rectangular duct as their primary supply and return run, with collars to run flex to the outlets from the primary (more guys are going round hard duct on primary for new installs which actually does make more sense). What most guys don't do is run hard round pipe from the primary to the outlets. In an unconditioned space, prefer wrapped ductwork instead of lined (different opinions on conditioned spaces, but will only help if insulated).

At the end of the day, it's the little things that adds cost to the job, particularly with hard ductwork.

Main trunks are lined inside. All hard round off the main trunks. Unlined or wrapped but it is all in conditioned space.

 

[jk96]

Also can't stress enough about good air sealing and insulation. Our home blower door tested at 1.92 ACH50 on the last test I ran when I determined additional improvements would be hard to come by and quit there. A couple days ago when our area was part of the rolling blackouts I was seeing posts on fb from friends who's homes were loosing 10 to 15 degrees in an hour of no heat. Turned ours off to test and took 1 hour 45 minutes to drop 3 degrees. Was negative 18 outside.

 

[ponytug]

Also can't stress enough about good air sealing and insulation. Our home blower door tested at 1.92 ACH50 on the last test I ran when I determined additional improvements would be hard to come by and quit there. A couple days ago when our area was part of the rolling blackouts I was seeing posts on fb from friends who's homes were loosing 10 to 15 degrees in an hour of no heat. Turned ours off to test and took 1 hour 45 minutes to drop 3 degrees. Was negative 18 outside.

That's fantastic! Congratulations!

All the best, Peter

 

[Sigarms]

Also can't stress enough about good air sealing and insulation. Our home blower door tested at 1.92 ACH50 on the last test I ran when I determined additional improvements would be hard to come by and quit there. A couple days ago when our area was part of the rolling blackouts I was seeing posts on fb from friends who's homes were loosing 10 to 15 degrees in an hour of no heat. Turned ours off to test and took 1 hour 45 minutes to drop 3 degrees. Was negative 18 outside.

You're the rarity, not the norm, in that your house is sealed tight, but you have also have a HRV for fresh air. I also did notice some of that round hard pipe. You were right in he might of got the load wrong, but the ductwork is nice.

That's the thing about mini splits, other than the ceiling recessed model, there is no way to bring in fresh air. You can buy dedicated fresh air ducted units from certain mini split manufacturers, but for residential use they are rare and ultra expensive. The added reality is you're still using ductwork on a new system which is kind of defeating the purpose of using a ductless mini split to begin with.

I see mini splits as having some great advantages in certain applications, but where unitary split product is now, at the end of the day, if you have the space for ductwork on a new home build, I don't see the advantage to mini splits. If I put a small "parents cottage" by our house on our land, I'd have no qualms using a 2 or 3 zone multi zone mini split system to save on indoor space (and it would be the high heat option in the multi zone selection).

 

[Wakey]

The electronic filter has been replaced with MERV 16 media filter and UV light.

That sounds like something to read up on.

 

[Sigarms]

That sounds like something to read up on.

And check your pressure drop after you install that MERV 16 on an existing system, and that's assuming the duct is sized properly.

 

[truckdiagnostics]

Mini splits are great until they need to be fixed. They are ok for small rooms homes garages. Once you zone, they are a bear to fix and finding someone that really knows how they work! and doesn't end up throwing parts at it, good luck. Fortunately they are reliable.

 

[Sigarms]

Mini splits are great until they need to be fixed. They are ok for small rooms homes garages. Once you zone, they are a bear to fix and finding someone that really knows how they work! and doesn't end up throwing parts at it, good luck. Fortunately they are reliable.

Thing is, if you use a mini split for a whole house with a multi zone, you should use refrigeration ball valves on both liquid and suction line to each head, so if a head needs to be serviced, you can keep running the system while the system is being serviced. Reality is, 98% of those getting multi zone systems never get those ball valves because they are very expensive (2 per each indoor head).

At the end of the day, a condensate pump for a mini split is 6 times more expensive than a conventional condensate pump. When you go multi zone with 4-8 heads, if you want to do it right, there is a crap load of money just for prevention of issues.

Honestly, as far as fixing, go to any manufacturers website for dealers to service the equipment, and you should be good to go. 20 years ago I knew a guy who wouldn't touch them. Now he's actually pretty good at it. Anything new, people are afraid of, but mini split inverter systems we're being sold when I got into the industry close to 30 years ago, and they are here to stay.

The reality is with mini splits being tied business wise to American unitary split products, you'll see more of these in the future (think gas furnace with coil, being abled to be tied into a mini split outdoor unit along with other indoor heads). That's where the market is going in the next 20 years.

FYI - R22 is no longer to be produced or imported in the US as of the beginning of this year. Starting in 2023, R410 equipment manufacturers can no longer make equipment which uses R410A (including mini splits). Another 20 years after that, perhaps R410A will be illegal. Point being, put yourself in the manufacturers shoes and it's a no win situation.

 

[truckdiagnostics]

Thing is, if you use a mini split for a whole house with a multi zone, you should use refrigeration ball valves on both liquid and suction line to each head, so if a head needs to be serviced, you can keep running the system while the system is being serviced. Reality is, 98% of those getting multi zone systems never get those ball valves because they are very expensive (2 per each indoor head).

At the end of the day, a condensate pump for a mini split is 6 times more expensive than a conventional condensate pump. When you go multi zone with 4-8 heads, if you want to do it right, there is a crap load of money just for prevention of issues.

Honestly, as far as fixing, go to any manufacturers website for dealers to service the equipment, and you should be good to go. 20 years ago I knew a guy who wouldn't touch them. Now he's actually pretty good at it. Anything new, people are afraid of, but mini split inverter systems we're being sold when I got into the industry close to 30 years ago, and they are here to stay.

The reality is with mini splits being tied business wise to American unitary split products, you'll see more of these in the future (think gas furnace with coil, being abled to be tied into a mini split outdoor unit along with other indoor heads). That's where the market is going in the next 20 years.

FYI - R22 is no longer to be produced or imported in the US as of the beginning of this year. Starting in 2023, R410 equipment manufacturers can no longer make equipment which uses R410A (including mini splits). Another 20 years after that, perhaps R410A will be illegal. Point being, put yourself in the manufacturers shoes and it's a no win situation.

CO generation? You run a generator to make electricity, sell it back to the power company and use the heat from the engine to make hot water in your plant. Mini splits up here don't make as much sense as they do down south. You just can't beat forced air gas heat. With that said good refrigeration techs up here are hard to come by.
Changes in HVAC for office building is going to be interesting as now they want more outside air changes. That is going to bring a lot of most warm air into the building.
From what I am getting from the kid is they are using a heat pump and cooling towers on the roof. In the winter getting the air changes is pretty simple, how do you do that in the summer and how do you do that with a mini split.

 

[Sigarms]

CO generation? You run a generator to make electricity, sell it back to the power company and use the heat from the engine to make hot water in your plant. Mini splits up here don't make as much sense as they do down south. You just can't beat forced air gas heat. With that said good refrigeration techs up here are hard to come by.
Changes in HVAC for office building is going to be interesting as now they want more outside air changes. That is going to bring a lot of most warm air into the building.
From what I am getting from the kid is they are using a heat pump and cooling towers on the roof. In the winter getting the air changes is pretty simple, how do you do that in the summer and how do you do that with a mini split.

Mini splits are huge in Canada, which is further north of you.

Key is you need to look at heating capacity and know what the unit will give you at it's full load and at what outdoor temp (most 12K systems will only give you about 8k at of heat at 5F outside air temp, but some of the same size systems will give you anywhere between 12-17k of heat down to 5F or 0F outside air temp (and these systems generally cost more because you're paying for the heating, not cooling). This is why you run a load to determine what KIND of system you want and explain to the end user what that system will give them at what outdoor air temperature.

The reality is gas furnace and oil heat feels warmer due to the discharge temp over a heat pump. Ironically enough, even though I'm in NC, many unconditioned spaces require more heat than cooling even in my neck of the woods. Yes, a gas furnace does give better heat, but only because the discharge air temp is generally hotter and feels "warmer" (that said, the best heat IMO for cold temps is hydronic heat). Thing is, what's easier to run, electrical or gas lines? Better yet, in an existing structure, do you have room for the new ductwork if you want to use a unitary split ducted system?

On multi zones, yes, it's simpler further down south of me when the heating load doesn't exceed the cooling load and you don't have to worry about sizing for heat.

It seems most of your post pertains to commercial applications where residential mini splits may or may not fit the bill for single phase equipment.

That said, just did 3 multi zone mini spit sysstem with 11 indoor heads primarliy for cooling in certain offices. Long story short, it's a band aid for ductwork and package equipment that wasn't laid out right to begin with, and years later, the owners wanted to address "spot cooling".

Ever deal with a girl in one office and a guy in another office in the same building and they can't get the right cooling or heating in each office (these people are generally up the food chain in the organization)? In the grand scheme of things, a mini split offers a cheap alternative depending on what's there in a commercial application.

Like I said, mini splits can be a great product for speciffic uses. I'm just not a fan of "whole home systems" using ductless.

 

[3Ts]

When I had our house built, I required the contractor to provide a manual J calculation. What a mess that turned out to be. It was done after the sub had installed the system. The sub did not have the software to do it and borrowed another company's computer to do it. Didn't get the values right - not even the right geographical area.

I can do heat and cooling loads thru walls and roofs based on a closed box (no wind, shade, solar heating, etc). What i don't know is the heat loss thru the concrete slab (no insulation under it). The manual J as I understand it takes into account the orientation of the house to the movement of the sun, shading, soffit overhangs, etc.

So, my question is: how does one go about getting a manual J calculation done?

 

[Sigarms]

When I had our house built, I required the contractor to provide a manual J calculation. What a mess that turned out to be. It was done after the sub had installed the system. The sub did not have the software to do it and borrowed another company's computer to do it. Didn't get the values right - not even the right geographical area.

I can do heat and cooling loads thru walls and roofs based on a closed box (no wind, shade, solar heating, etc). What i don't know is the heat loss thru the concrete slab (no insulation under it). The manual J as I understand it takes into account the orientation of the house to the movement of the sun, shading, soffit overhangs, etc.

So, my question is: how does one go about getting a manual J calculation done?

Find someone experienced with Wrightsoft. Guys who know what they are doing will guarantee their load calculation. Thing is, training and software isn't cheap, so don't expect someone to do it for free.

Generally, for residential retrofit quotes, a block load is done vs a room to room load (if a load is done at all). When it's new contstruction, a room to room is generally done for the manual J and a manual D for ductwork sizing / layout.

 

[3Ts]

Find someone experienced with Wrightsoft. Guys who know what they are doing will guarantee their load calculation. Thing is, training and software isn't cheap, so don't expect someone to do it for free.

Generally, for residential retrofit quotes, a block load is done vs a room to room load (if a load is done at all). When it's new contstruction, a room to room is generally done for the manual J and a manual D for ductwork sizing / layout.

Thanks, I'd no idea as to the name of the software. I expect to pay for it but don't know what is reasonable, is $200 about right for the manual J?

 

[mikester]

Mini splits are great until they need to be fixed. They are ok for small rooms homes garages. Once you zone, they are a bear to fix and finding someone that really knows how they work! and doesn't end up throwing parts at it, good luck. Fortunately they are reliable.

That goes for everything these days. That's another reason why I installed two single systems instead of one multi-head. I also have baseboard heat as backup and a woodstove as another backup when there is no power.

 

[Sigarms]

Thanks, I'd no idea as to the name of the software. I expect to pay for it but don't know what is reasonable, is $200 about right for the manual J?

Keep in mind, Wrightsoft is only one software program out there of many out there (Wrightsoft probably is one of the most expensive ones out there, and I'm thinking that becomes a racket as well).

A room to room load will proably cost more than a block load, and I'd guess the sqaure footage would determine. I looked online, and it seems my guess was right.



Thing is, what is just as important is ensuring that you get proper airflow to each room to hit the heating and cooling criteria for each room (where manual D comes into play). There are also a lot of variables at play with new homes being built to ensure that the garbage in is the right garbarge out. My house was built in 88, 3,500 sq ft, I did the load and ductwork (to verify it was correct, as the house sat unoccupied for at least 5 years) and it came out to what I had installed, 7 tons (lots of window square footage with windows made in '88). JK96 house is a newer (I assume) 4,600 square ft house, and he figured it only needed an actual 5 tons.

After time with experience, take size, age, windows and shade and generalize the insulation, a decent contractor can get a pretty good idea with adding or subtracting to a rule of thumb guys use if needed (technically it should always be needed but the reality of money is it isn't), but with newer, tighter homes you don't need the same cooling and heating capacity for a home built today vs a home built 20-50 years ago.

The nice thing with most good inverter mini splits where heating is required is you can oversize the cooling to meet your heating criteria.

Thing is, from the same manufacturer, one 2 ton single zone mini split system will give you 25,000 BTU/h of heat @ 5F OAT, and another model from the same manufacturer will only give you 15,000 BTU/h of heat @ 5F OAT. Lots of HVAC contractors IMO only care about the SEER rating and don't look at the actual heating capacity or take the time to explain the differences to the homeowner. People think that if they get a 2 or 3 ton multi zone mini split, they are getting 2 or 3 tons of heating, and that is generally never the case.

For straight AC, it's hard to beat even a multi zone mini split, but where it gets tricky is when the heating exceeds the cooling for the same space (and it does happen often, even in my area in NC). Think about this, on most 24,000 BTU/h AC systems used, if a gas furnace is used, the size of the furnace generally starts off is 35,000 BTU/h net output for heating.

 

[Sigarms]

When I had our house built, I required the contractor to provide a manual J calculation. What a mess that turned out to be. It was done after the sub had installed the system. The sub did not have the software to do it and borrowed another company's computer to do it. Didn't get the values right - not even the right geographical area.

The irony is depending on the GC and communication between the homeowner and subs, a HVAC contractor can figure out a load, size the duct work from the plans from the builder, only to find out after the fact that the insulation and windows were changed during contruction by the homeowner and no one told him. Actual types of insulation can make a huge difference in the capacity needed for heating and cooling. I think someone here said biggest investment you can make is in insulation when it comes to HVAC, and I would agree.

I always find it amazing when a million dollar home is being built with very expensive add ons, but it's the cheapeast Dico thermostat on the wall with single stage HVAC equipment.

 

[Frankenkubota]

Main trunks are lined inside. All hard round off the main trunks. Unlined or wrapped but it is all in conditioned space.

That's what i got, underside of roof sprayed so HVAC guy says i will have a conditioned space. Insulation guy says temp in attic shouldn't vary by 5-10 degrees from living area.

 

[jk96]

That's what i got, underside of roof sprayed so HVAC guy says i will have a conditioned space. Insulation guy says temp in attic shouldn't vary by 5-10 degrees from living area.

Yours sounds just like ours. We did closed cell walls and underside of roof. Timberframe home so very little attic space. Just a very small area above the 3 bedrooms on the upper level.

I always find it amazing when a million dollar home is being built with very expensive add ons, but it's the cheapeast Dico thermostat on the wall with single stage HVAC equipment.

Sigarms house was built 6 years ago so your assumption was correct. I agree on the absurdity of how money is spent on new homes. We hit our coldest temp so far in this home the other night at minus 21. Coldest I can ever recall in this area. Units ran most of the night but rarely saw all zones calling at once and kept temp just fine. On the flip side a friend of ours had a new build high end home with frozen water lines on one wall and a bedroom over a garage that was so cold it was unusable. Would love to see the insulation job behind the sheetrock.