HVAC Frustration. Need Advice

[ano]

Insulation is a great this, but I think this thread is focused on controlling zoned systems with home automation equipment. 
 
 

I am a bit surprised that in 3000 sf you need so many different zones.  I think you are going to have your 3000sf twice as split up as my 6000sf house.

 
The reason for zoning is not simply because I can't keep my house all at an even temperature, although its partly about that, its more about using energy most effectively.  Why cool down rooms I'm not using? And those rooms change during the course of the day.  Yes, I could get up a ladder and adjust the vents several times per day, but that is why I use automation.

 

[IndyMike]

Hello Ano,
 
A zoned system can increase efficiency if the system was designed for zoning (dedicated zone runs and a reduced size furnace/cooling system).  If your ductwork was not designed to be zoned (central dampers) you will require a barometric bypass which detracts from the efficiency. 
 
Your HVAC was designed to heat/cool a 3000 sq foot house.  It requires a specific airflow across the heat exchanger/A frame to maintain efficiency.  If you zone down to a 750 sq foot room, that same airflow must be maintained.  You will wind up dumping the excess airflow through the bypass valve (back into the intake or into a dump zone).  You can achieve comfort, but not efficiency.
 
I have a 4000 sq foot 3 level home with 2 zones (basement/1st floor - zone1; second floor - zone2).  The ductwork was designed with separate trunk lines to each zone.  This allowed us to "undersize" the furnace/AC and it is efficient.  On the flip side, my system does not have the capacity to heat/cool the both zones at the same time (hottest/coldest days).  Since we don't typically use the upper and lower levels at the same time, it's a reasonable compromise.
 
When I was researching my system (2000) I came across some Bryant literature that indicated they were working on a "proportional" zone system.  The system would proportionally open/close dampers and vary the blower speed to achieve the proper air flow to the zones without requiring dedicated trunk lines.  I'm not sure what became of this approach.
 
 

 

[ano]

This was discussed a bit earlier.  The zoning systems presently offered by Carrier, Trane, Bryant and a few others are not "your fathers zoning system" so to speak.  They DO NOT require a bypass valve and DO NOT require a set amount of airflow across the heat exchanger.  The blower fans are continuously variable from full speed to a low speed.  In addition, the compressor can be scaled back as well. The top Trane unit actually contains two compressors, one 50% the size of the other.  If cooling requirements are low, the small compressor kicks in, otherwise the big compressor runs.
 
These things are pretty amazing. The contractor was telling me the system has the capability to provide cooling to one zone, then provide heating to another zone, then back to cooling. Also, zones don't have to be completely off or completely on, they can be any percentage on.
 
My house wasn't designed for zoning, but as it turns our, three large ducts return to the furnace, and these just so happen to also be the three zones I'm going to use.  In my case its Family Room, Kitchen, and three bedrooms. Each zone is roughly 650 sq. ft.  For me I'll probably use one of two scenarios often; Full cool in the bedrooms where my home office is and reduced cooling in the kitchen and family room I don't use during the day, OR no cooling in the bedroom, and full cooling in the kitchen and family room I use in the evening. The bedrooms gets lots of sun exposure in the day, the family room gets lots of exposure in the evening. 

 

[apostolakisl]

Insulation is a great this, but I think this thread is focused on controlling zoned systems with home automation equipment. 
 
 
 
The reason for zoning is not simply because I can't keep my house all at an even temperature, although its partly about that, its more about using energy most effectively.  Why cool down rooms I'm not using? And those rooms change during the course of the day.  Yes, I could get up a ladder and adjust the vents several times per day, but that is why I use automation.

 
 
I think your title says it all, hvac frustration.  I was merely pointing out that you might not be frustrated with your hvac if you had better insulation.
 
When I hear you talking about 8 tons of cooling with as many as 6 zones in a 3000sf house, I have to believe that something is wrong with the big picture.  Unless you are needing every room in your house to be a different temp for reasons not including efficiency, then putting a system like that is not the way to become more efficient and not the most cost effective way to be comfortable.  You will spend far less keeping your entire house at 74 degrees 24/7 then swinging rooms up and down in temp during the day as you predict you might be in them or not.  
 
For example, my house is twice as big (6000sf), and has only 8 tons, which is just actually more than has proved to be necessary judging by the run times at high/low speed.  I have 12 foot ceilings and I live where it is 105 degrees every day during the summer, sometimes for 3 months continuously.  My house is 74 throughout except at night when I chill the master down to 70.  My biggest electric bill ever in 3 years was 3300kwh.  I also have mostly led lighting which I am sure helps.
 
You really should be able to do very nicely with 2 zones, maybe 3 in a house that size.  Assuming you have bedrooms upstairs you put all of those together on one unit.  Downstairs probably has living areas and a master.  You might zone the downstairs unit separate the living areas from the bedroom.  I would spend less on the hvac and look at spending a lot more on the other things.  I think you'll find in the end you are more comfortable, more efficient, and spend the same or less up front.

 

[apostolakisl]

This was discussed a bit earlier.  The zoning systems presently offered by Carrier, Trane, Bryant and a few others are not "your fathers zoning system" so to speak.  They DO NOT require a bypass valve and DO NOT require a set amount of airflow across the heat exchanger.  The blower fans are continuously variable from full speed to a low speed.  In addition, the compressor can be scaled back as well. The top Trane unit actually contains two compressors, one 50% the size of the other.  If cooling requirements are low, the small compressor kicks in, otherwise the big compressor runs.
 
These things are pretty amazing. The contractor was telling me the system has the capability to provide cooling to one zone, then provide heating to another zone, then back to cooling. Also, zones don't have to be completely off or completely on, they can be any percentage on.
 
My house wasn't designed for zoning, but as it turns our, three large ducts return to the furnace, and these just so happen to also be the three zones I'm going to use.  In my case its Family Room, Kitchen, and three bedrooms. Each zone is roughly 650 sq. ft.  For me I'll probably use one of two scenarios often; Full cool in the bedrooms where my home office is and reduced cooling in the kitchen and family room I don't use during the day, OR no cooling in the bedroom, and full cooling in the kitchen and family room I use in the evening. The bedrooms gets lots of sun exposure in the day, the family room gets lots of exposure in the evening. 

 
Just realize, that the upfront cost on these units which pick up an additional 10 or 20% efficiency can more than double the price.  You can easily spend many many thousand of dollars to drop your electric bill by 10 or 20 bucks per month.  Certainly the hvac guys love selling the number one top of the line model because the profit margin is a lot higher.
 
And just to be clear, all units do require a minimal air flow over the evaporator.  Except for units like the mitsubishi continuously variable compressor, all of these units will put at minimum a certain number of btus of cooling freon to the evaporator, if there is insufficient heat (warm air from the house) blowing over the evaporator, you will force the tev to clamp down, raising the burden on the compressor, the coil might freeze up, and liquid freon might get past the protection mechanisms and return to the compressor and damage it.
 
Partially opening dampers is fancy and nice, but I doubt you will notice much difference from it.  The honeywell board also flips back and forth from heat to cool if one zone is calling for heat and another calling for cool.  It also runs 2 speed compressors and 2 speed fans.  I don't have a zoned system at home, I have 3 2 speed units.  I can't hear them, I can't feel them, I have no idea when it is on high or low.  And it is always the same temp.  The trick is, good insulation means less need for HVAC.  Less need for hvac means no high speed air flow, just a little trickle.  Good insulation also means that the temp next to the wall is the same as in the middle.  All of this means no drafts and air that is just the same everywhere.  

 

[picta]

The reason for zoning is not simply because I can't keep my house all at an even temperature, although its partly about that, its more about using energy most effectively.  Why cool down rooms I'm not using? And those rooms change during the course of the day.  Yes, I could get up a ladder and adjust the vents several times per day, but that is why I use automation.

 
I have installed a zoned system in my old 2500 sf house using dampers and RCS 6 zone controller connected to homeseer. This was a retrofit solution, and whatever insulation the house had, that was that. The benefits of "before and after" were very clear. Besides savings on electric bill (about 40% drop) it had other benefits. The most awesome was the outside air intake. We ran it every day at the optimal point in time that would be either the coldest in the summer or the warmest in the winter. Every bedroom had its own zone, so if you wanted to take a nap while kids are playing games, you could cool/heat the bedroom fast using most of the air and then turn it off and not be bothered by the sound of the forced air when the other rooms call for it. We also had a small office full of equipment and the door to it was locked during the day. It could get 20 degrees hotter there than in the rest of the house, so when it got its own zone, it was frequently the only room using the air. The compressor was basic without variable fans, so there was a bypass valve installed. That was the most difficult part, but as a bonus we also got a whole house filter which had a noticeable effect on the air quality. The dampers were easy, inserted in the flexible ducts before each room's register. It helped that we had an attic and the crawl space.

 

[IndyMike]

This was discussed a bit earlier.  The zoning systems presently offered by Carrier, Trane, Bryant and a few others are not "your fathers zoning system" so to speak.  They DO NOT require a bypass valve and DO NOT require a set amount of airflow across the heat exchanger.  The blower fans are continuously variable from full speed to a low speed.  In addition, the compressor can be scaled back as well. The top Trane unit actually contains two compressors, one 50% the size of the other.  If cooling requirements are low, the small compressor kicks in, otherwise the big compressor runs.
 
These things are pretty amazing. The contractor was telling me the system has the capability to provide cooling to one zone, then provide heating to another zone, then back to cooling. Also, zones don't have to be completely off or completely on, they can be any percentage on.
 
My house wasn't designed for zoning, but as it turns our, three large ducts return to the furnace, and these just so happen to also be the three zones I'm going to use.  In my case its Family Room, Kitchen, and three bedrooms. Each zone is roughly 650 sq. ft.  For me I'll probably use one of two scenarios often; Full cool in the bedrooms where my home office is and reduced cooling in the kitchen and family room I don't use during the day, OR no cooling in the bedroom, and full cooling in the kitchen and family room I use in the evening. The bedrooms gets lots of sun exposure in the day, the family room gets lots of exposure in the evening. 

 
Sorry, should have read post #27.  I thought you were adding zone control to an existing fixed speed system.  Now I understand the cost as well.
 
I would consider Lou's appeal to look at windows and insulation.  Reducing the Heating/Cooling load normally provides the biggest bang for the buck (not very sexy though).  In many areas, the utility will offer rebates for insulation improvments.  If they don't, the State Government normally does.  Reducing the heat load will not only improve uniformity, but it will reduce the size of the required equipment.
 
Ask your contractor for a heating/cooling load analysis.  This should include allowances for the type and number of windows (glass area), ceiling area, exposure and many other sources of loading.  Many contractors (in the past) used "rules of thumb" or generalized from similar sized homes that resulted in oversized equipment.  Nothing can compensate for incorrectly size equipment.
 
Ask your contractor to provide a "pay off period" based on your local rates.  I understand that some of your incentive is for comfort.  Nonetheless, I would try to get your contractors to sign up for some sort of efficiency improvement (they really will not want to do this).  The payoff period should at least be within the equipment warrany period. 
 
I was about to post that multistage or variable speed compressors would have reduced benefits without a variable expansion valve for the refridgerent...  Just did a google search - they have them now.  Really does suck getting old and out of date. 
 
Bottom line in the above - get a good contractor.  We all love getting a good price, but it can't make up for improperly sized or installed equipment.

 

[picta]

Bottom line in the above - get a good contractor.

 
That is usually the most difficult part....

 

[mikei-ma]

ANO,
 
If you haven't pulled the trigger yet, give http://emme-inc.com/ a look.  Our angel group invested in these guys, while they don't have home automation hooks yet, they will at some point. Their system is WIFI currently. Their room-by-room solution is slick.
 
Mike

 

[apostolakisl]

Sorry, should have read post #27.  I thought you were adding zone control to an existing fixed speed system.  Now I understand the cost as well.
 
I would consider Lou's appeal to look at windows and insulation.  Reducing the Heating/Cooling load normally provides the biggest bang for the buck (not very sexy though).  In many areas, the utility will offer rebates for insulation improvments.  If they don't, the State Government normally does.  Reducing the heat load will not only improve uniformity, but it will reduce the size of the required equipment.
 
Ask your contractor for a heating/cooling load analysis.  This should include allowances for the type and number of windows (glass area), ceiling area, exposure and many other sources of loading.  Many contractors (in the past) used "rules of thumb" or generalized from similar sized homes that resulted in oversized equipment.  Nothing can compensate for incorrectly size equipment.
 
Ask your contractor to provide a "pay off period" based on your local rates.  I understand that some of your incentive is for comfort.  Nonetheless, I would try to get your contractors to sign up for some sort of efficiency improvement (they really will not want to do this).  The payoff period should at least be within the equipment warrany period. 
 
I was about to post that multistage or variable speed compressors would have reduced benefits without a variable expansion valve for the refridgerent...  Just did a google search - they have them now.  Really does suck getting old and out of date. 
 
Bottom line in the above - get a good contractor.  We all love getting a good price, but it can't make up for improperly sized or installed equipment.

 
 
Sadly, for many hvac contractors, the "rule of thumb" is if you stand at the curb and hold your hand out, how many thumbs wide is the house.  For each thumb, add 5 tons.
 
That is really not a joke.
 
A proper load analysis is worth the money, IndyMike is totally correct.  Any quality hvac guy will have someone in house that does it and it should be very detailed, however, they won't do it for free.  If they do, they either aren't doing it right or are very desperate because it takes a good 8 hours to do it, or more.  They usually cost a few hundred bucks and can be very enlightening.
 
While oversizing equipment nowadays isn't like the old because of dual speed units, it still costs you a bunch in higher costs for equipment.  With single stage units, oversizing meant short cycling, high humidity, quick temp swings, and early equipment failure.  With dual stage units, it just means that you rarely use stage 2.  But you still paid for it.

 

[tmbrown97]

My house falls in the category of using zoning to use an undersized system (a single 5 ton unit) in a 4000sq ft house in a part of the country where temps easily get up 110+ and sometimes our nights never drop down below the 80's.  But, it's a 2 story and as mentioned before - we heat/cool the areas we are in at a given time of day - plus, if you heat the downstairs, the upstairs automatically gets warmer - and if you cool the upstairs, you inevitably cool the downstairs.
 
That said, this talk of a continuously variable system has piqued my interest... last summer I threw a current sensor on my AC (This is part of Ubiquiti's mFI line) and watched how often the system was cycling and also compared it to the temperature swings in my home office - and it's ridiculous how often it runs and how much the temperature swings constantly throughout the day 

 
I have also heard a lot of people mention lately how the new standard is to be able to accomplish 20 degrees of temperature swing - so if it's 90° outside, expect to get no better than 70° inside; of course that's just asinine here because that would mean when it's 115° outside I should be willing to accept 95° inside - which I'm just not; and unfortunately in a way, we're home all day every day so there's no setting back the temperature during the day.

 

[apostolakisl]

My house falls in the category of using zoning to use an undersized system (a single 5 ton unit) in a 4000sq ft house in a part of the country where temps easily get up 110+ and sometimes our nights never drop down below the 80's.  But, it's a 2 story and as mentioned before - we heat/cool the areas we are in at a given time of day - plus, if you heat the downstairs, the upstairs automatically gets warmer - and if you cool the upstairs, you inevitably cool the downstairs.
 
That said, this talk of a continuously variable system has piqued my interest... last summer I threw a current sensor on my AC (This is part of Ubiquiti's mFI line) and watched how often the system was cycling and also compared it to the temperature swings in my home office - and it's ridiculous how often it runs and how much the temperature swings constantly throughout the day 

Screen Shot 2013-02-23 at 3.55.24 PM.png
 
I have also heard a lot of people mention lately how the new standard is to be able to accomplish 20 degrees of temperature swing - so if it's 90° outside, expect to get no better than 70° inside; of course that's just asinine here because that would mean when it's 115° outside I should be willing to accept 95° inside - which I'm just not; and unfortunately in a way, we're home all day every day so there's no setting back the temperature during the day.

 
A perfectly sized system is the one that runs 100% of the time on the 95th percentile hottest day of that geographic location and keeps the temp as desired.  
 
Agreed, 20 degree in/out differential is a stupid number, that's like the rule of thumb.  If you live where the summer rarely hits 90, that is overkill, and if you live where it hits 110, that is woefully lacking. 

 

[ano]

I had 4 contractors come out to give me a quote. Each spent almost 2 hours at my house, measuring all the window sizes, looking at the insulation, and measuring each house dimension.  This is required, because our utility requires such calculations before they will provide their rebate.  Actually each calculated it out to the tenth (or hundredth) of a ton, and the values ranged from 3.76 tons to 3.9 tons, so each recommended a 4 ton unit.  This gives me some confidance that the size is correct. 
 
Before I install the AC unit I also decided to perform an energy audit.  This is a $600 service that the utility subsidizes, so it only costs me $99.  I hope to have this done this week.  I wouldn't be surprised if they find problems like missing insulation. I'm not sure if they will tell me the AC size.  We will see.

 

[BraveSirRobbin]

Wow, for that amount of money for an energy audit, I sure hope they are going to use something like a thermal camera to see exactly where your heating/cooling is coming out/in your house!  That would be VERY beneficial IMO.

 

[tmbrown97]

Wow, for that amount of money for an energy audit, I sure hope they are going to use something like a thermal camera to see exactly where your heating/cooling is coming out/in your house!  That would be VERY beneficial IMO.

I keep wanting to buy one just for this reason - but I haven't had the spare cash laying around, although with what I pay in electricity it'd probably pay for itself before too long!
 
I did have a chance to play with one briefly and I could clearly see spots on the walls that literally had no insulation and where the attic insulation was pulled away!