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Central HVAC alternatives needed

Posted by macvirtualasst (My Page) on
Sun, Aug 14, 11 at 15:54

Hello all! We are building a new home on a tight budget and are looking for alternatives to a central HVAC system. We are on electric and don't have gas. We are at 3000 ft + altitude in an area that gets cold winters with temps averaging around 20 to 32 degrees on the coldest days. We are getting two wood burning fireplaces and to supplement and for summer cooling are considering ptac or pthp units or split systems or possibly just portable heaters and a/c units. The home is a basement, main and small loft and we are going to well insulate it. We need the best bang for our buck but are on a tight budget. We were quoted 8,250 for a 2 ton Trane heat pump with 3 zones. I think that is quite expensive and would love to find alternatives...

Thanks!


Follow-Up Postings:

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RE: Central HVAC alternatives needed

mac

what is location?

if you have ruled out geothermal, then I would look at Carrier's recently introduced Greenspeed Heat pump.

BTW,on new construction, a homeowner should budget somewhere between 7-10% of home price for HVAC.

IMO

Here is a link that might be useful: Carrier Greenspeed HP


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RE: Central HVAC alternatives needed

Thank you
We are in Western NC
On a super tight budget but I'll check out your link, thanks!


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RE: Central HVAC alternatives needed

Mac

Very familiar with western NC area/weather/climate.

Not certain that the Greenspeed would be cost effective.

I personally would go with conventional HP system. You do want to qualify your dealer's experience/expertise with zoning controls.

I am listing below a few basics regarding heat pumps.

there are three equally important components-quality HVAC, the install by dealer, and probably the most overlooked and disregarded is the ductwork system.

these are my minimum specs for a new HP system. both outside and inside units should be replaced to have a properly matched system.

15 SEER, 12.5+ EER, 9 HSPF
best matching VS air handler
full BTUs in both cooling and heating for your rated size
R-410a refrigerant(same as Puron)
scroll compressor preferred
electronic demand defrost preferred
thermostat with "dehumidify on demand" feature
staged backup heat strips
new and correctly sized refrigerant lineset
10 yr warranty compressor and parts

you want a thorough inspection of your ductwork system. size, overall condition, supply and return lines, insulation qualities, leak test, etc.

any hot/cold spot issues in your home should be addressed.

I would only use authorized dealers for the various brands that provide quotes. see mfg websites.

I would look at Trane/AmStd,Rheem/Rudd,Carrier/Bryant.

I would not purchase a new HP system that did not have electronic demand defrost.

IMO


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RE: Central HVAC alternatives needed

Something you need to check.

You will want to be sure that any "non traditional" solutions to your heating and cooling will pass the required code for occupancy certificate and getting a mortgage. You may be required to have a furnace.


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RE: Central HVAC alternatives needed

Julie
No furnace here.

I would not recommend propane at all.

OP is in all electric situation which is quite common for rural areas in NC as well as gated golf course community developments.

HP systems work very nicely for this area both for climate and cost of electricity.

IMO


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RE: Central HVAC alternatives needed

Right - no furnace. But the point remains that in NC, you can not just have some alternative system. You must have something real and conventional. I suppose you could get away with electric strips only as a backup to a wood burning stove. I mean technically electric strips alone should still meet code.


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RE: Central HVAC alternatives needed

If you don't have ductwork installed and an air-source electric heat pump you will probably regret it.

Get an air-source heatpump and insulate well.


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RE: Central HVAC alternatives needed

Neohio

This is new construction in WNC.


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RE: Central HVAC alternatives needed

This is three rooms? Consider skipping the ducts altogether and installing heat pump mini splits.


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RE: Central HVAC alternatives needed

Thank you everyone. I was out of town and did not have internet access. I appreciate all your feedback. I did communicate with our mechanical codes inspector and he did say we needed to have a system that could heat up to 68 degrees, be permanent, and the vents/ducts? needed to be at least 3' off the floor. He did say ptac/pthp units would work but that we needed one for every living space. i am not sure how "living space" translates in a house with an open floor plan with multi function rooms. @ionized: It's not three rooms, it's a basement, main and loft. The only two rooms that will be sealed off are the bedroom and a room in the basement.


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RE: Central HVAC alternatives needed

I wouldn't have mini splits at all for nice new construction.

The problem with one system with zoning controls is usually finding a qualified HVAC dealer experienced in this area.

Make certain you vet his qualifications.

IMO


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RE: Central HVAC alternatives needed

"I wouldn't have mini splits at all for nice new construction."

Au contraire, it is the perfect time when the walls are open to run the tubes and electrical. The thought of never having leaking, nasty ducts to deal with should make most people giddy. The absence of pressure differentials to suck unconditioned air suck into and blow conditioned air out air of the house is too cool for school.


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RE: Central HVAC alternatives needed

Ionized - you could do ducts in conditioned space and retain all the advantages of a centralized system.

The disadvantages of mini are pretty numerous but the number one is that trying to find a service person in a heat wave or cold snap in W NC might be extremely difficult. It might not but that would be a big issue in my book.

So this is a one bedroom house? You would need a mini split for each floor and each bedroom at a minimum (so 4 for what you describe if it is just 1 bedroom). So a traditional 4 bedroom, 2 story house would need at a minimum 5 units but it is unlikely that one minisplit could cover the entire first floor. There are standards for this but I think they are sometimes inspector's opinions.

NC has one of the strictest HVAC codes regarding air distribution. No 1 system unzoned 2 story houses allowed. In fact, it is apparently pretty hard to not have 1 system per floor in the latest revision.

So even with central, you might have to have 3 units. But - you can just do electric strips which would be the cheapest option - if you can still find the thermostat controlled electric baseboards that were all over NC in the 70s.

I am building an inexpensive vacation home in NC and I am doing 2 units for 2 floors. This one is 1000 sqft per floor.

How big of a house are we talking here?


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RE: Central HVAC alternatives needed

So far, with partial heating season and a lot of cooling behind me, I am not seeing the disadvantages of mini splits. They are quiet, throttle capacity well, dehumidify well, and are inherently zoned. In my house, that last thing is saving me a lot of money. I know that I can get qualified people to work in them here, but in case I have a problem, I lose at most, 3/7 of my system while I am waiting for repair. That is a positive point for me as it gets pretty darned hot where I live.

I understand that these are often much more complicated than systems typically seen by install and repair personnel, but maybe the OP will be lucky and find a nearby tradesman that is really proud of keeping up with current technology, and can see that this is probably going to become more the norm than ducted systems.


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RE: Central HVAC alternatives needed

Ionized - I'd love to hear some sq footage, location, install cost and operating cost.

Some of the disadvantages from the top of my head are no NG, no humidification and more visual components. None of which may matter to you or a lot of people. I am also guessing that for a system as good as yours, you are looking at additional upfront money.

The best comparison for someone building new would be ducts in conditioned space and a seer 15 or better heat pump. I'm not sure there is going to be significant savings but I could be wrong.

It is worth remembering that Europe and Japan live in smaller spaces so minisplits make a little more intuitive sense and then they live in older dwellings making the retrofit more appealing. Just because these things are used there, does not make it better. Also, we have NG for a large percentage of the country and we are the Saudi Arabia of NG.


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RE: Central HVAC alternatives needed

David_cary, the expense of back-up heat is a factor that I tend to forget because I don't have a need for it, mea culpa. I am in the Gulf South. I would tend to think that humidification is a small issue for a tight house in a cold climate. Dryness in winter is very dependent on infiltration of outside air. If you control that, you will not have such dry air. Trust me, I know about cold climates too. I grew up in a house with an oil-fired hydronic system. I moved 5 times in 15 years between different cities, hot and arid to cold or humid, before I moved to South LA a decade ago.

As far as efficiency goes, my worst of three systems is supposed to operate at SEER 17.5, and HSPF 8.9. The 1:1 systems are rated better, some over SEER 20. Obviously, I do not have to subtract duct losses from that. I appreciate the ability to put ducts within the house envelope, but you can still get pressure differentials from room to room that push air out and suck it into the house.

Yes, some people don't like the units hanging on the walls. There are many alternatives to that now, but I have 7 of the old-fashioned wall units. The only place I would change in my house is the dining room. It is a small room and it is obtrusive there. I should have used a ceiling cassette in there. They do cost more and are less efficient.

I have 7 rooms totaling 2000 sq. The mini split install cost me about 15K. That was about $2000 more than a 16 SEER (2-stage) system with all new ducts in the attic and under the house. My house is a 1950 raised, wood-frame house that probably could have been built in 1920 for the construction techniques. It must have been conservative builder. It is notable that the house still has all the doors and walls that it ever did. (I have none of that open floor plan nonsense. If I am going to stay married, I need to be able to get away from my wife sometimes and she needs doors to slam when she gets mad at me.) We only seriously heat or cool rooms that we will be in. We are not home much either, and we are working in the kitchen a lot when home. The life style has a lot to do with our decision.

The first cooling system in the house was a water-cooled, 3-phase system "monstrosity" (the word used by a guy that grew up in the house) of some sort. The house originally had a floor furnace. At the time of the first central system addition, the duct was a central trunk that consisted of a dropped ceiling in a hallway. Later, this was supplied along with additional ducts (some to additions and some to the original rooms) from a sheet metal plenum connected to a gas furnace in the attic with a split evaporator. The condenser/compressors that I had were two, 2-ton that were staged and used a single-speed blower.

As a side note, I am not as confident of our nation's NG supply as you are. We might be in trouble if we have to depend on the shale gas that is purported to be under our feet. I think that the amounts are way lower than estimates and the whole operation may look like a Ponzi scheme by the time we are done. The damage done from making the ground like Swiss cheese could be a nightmare.

More details are available, forgive me for being lazy and editing some earlier posts. Follows are modified excerpts from my previous posts:

My system is Mitsubishi (7 in, 3 out). On paper mini splits are more efficient due to inherent efficiency and the inherent zoned nature. We have been having pretty hot weather and with my wife out of town this week, I have been pretty much been cooling the bedroom and the kitchen with some intermittent cooling in the utility room where the exercise machine lives. Note that I am not much of a sit and watch TV type.

One thing to think about is that, many of them don't have back-up heat so you will not have any heat while they are defrosting. You also have to pay close attention to cold weather performance for the mid-Atlantic region. Cold weather performance has been getting steadily better and they claim that some are good to 0 F so you should not need back up heat in climates where other heat pumps do. I know that with Mitsubishi's current residential equipment, the 1:1 systems have better low temp performance than the multi-splits. They are more efficient too. Even if they do have back-up heat, you can kill the efficiency pretty fast if you need back-up very often.

Keep in mind that there are lots of options to the wall-hung indoor units. They cost more, but there are units that can be dropped into ceilings and others that sit on the floor. There are also short, ducted units that would solve that big room problem by splitting the supply and return. (You could also install more than one indoor unit/room.) Condensate needs to be dealt with using pumps.

Installing a mini-split through outside walls, as is it usually promoted, is pretty quick and straightforward (Read fast and cheap, straight through the exterior walls.) compared to installing a new duct system in an existing house with no existing central AC. My install was done through mostly interior walls running the lines/cables under the raised house and out to the side which was much more complicated. If I were doing this over and I had a good duct system within a house envelope, I might stick with it to save install money. The trouble is, what is a good duct system? More often than not, they are outside of the living space. In addition, they are considered good when they leak 5% of the air and they only get worse as they age. Even if the whole duct system is within the envelope, you will still get pressure differentials that can force air in or out of the house.

My system was in the attic with parts of the duct system in the attic and a trunk that was a furred-down space over the main hallway. That was both in and out of the conditioned space. The worst part was one duct that started at the AH in the attic, dropped down under the house in a chase and ran for about 30 feet before it reached the first of three floor register in an addition with a flat roof (thus no attic). It then reduced in size and ran another 25 feet under the house. That part might have been mini-splitted even if the rest of the house retained a ducted system.

In general, I think that ducted systems are trickier to design and install than mini-splits so there is more tolerance for less than careful and knowledgeable installers with mini-splits. Due to their ability to handle variable loads, choosing the right size is not as critical either. (I had 4 tons cooling plus a gas furnace before, now I have about 106% of the cooling and 60% of the heating. The heating was way oversized.) My system will handle cooling fine with the house the way it is, but I should not have trouble after I make improvements to limit infiltration and add insulation.

My installer is knowledgeable, smart, very workmanlike, and experienced (he has taught the trade for 30 years). He would have installed new ducts and a two-speed system for a lower price than the chosen mini-split equipment. I doubt that he would do my project for the same price if doing it on a similar home going through interior walls. He did not have much mini-split experience and brought in a collaborator that does, on this project because he was looking forward to a learning experience. I don't think that he lost his shirt, but I don't think he made as much as he usually does.

Mini split sellers market their good dehumidification heavily. The variable-speed-blowers and variable speed compressors should help with low-load situations. Some variable-speed ducted systems might match it.

If you have a lot of air infiltration, you will have a humidity problem no matter what you install. Ducted systems can make a passive infiltration problem into a power-vent infiltration problem under some conditions. If the leaking supply ducts are outside of the house envelope you suck hot, humid air in somewhere else to replace the leaking, humidified air. If the leaking return is sucking air in from outside, conditioned air will leave through holes elsewhere. If supplies and returns are not set up perfectly, you will pressurize some rooms and depressurize others relative to outdoors and get both at the same time.

One advantage of ducted systems that I have considered is their ability to use the capacity of the system in one room of the house. That might sound weird, but consider the situation of a party in your house with a large crowd gathered in the living room. Your HVAC system can be running at full capacity picking up heat from the bodies in the LR. Unless your mini split was sized for a large crowd, it might get warm in there. If you have frequent parties, you might size it that way, or install two. Most people will not do that.

If you go mini splits, don't mount a wall unit above where you will have a bed. I saw advertising that showed that and planned that but changed my mind figuring that at low speed at night the cold air would sort of cascade down over the heads and be uncomfortable. I am glad that I changed my mind about it. I don't know if that problem would occur. What I did find, since we did the installation during heating season, is that the default programming of the heat pump mode makes the units good ceiling heaters. (Predictable really. I have experience with ducted systems in predominantly cooling climates that do the same thing.) As they approach the set point the blower speed goes way down so hot air gets stratified near the ceiling even though the louvers are pointed down. Setting the blower speed manually to a slightly higher speed fixed that. Putting the indoor units above the bed would have been uncomfortable if only for that reason.

It is going to be difficult to provide any meaningful operating costs. We are changing too many things on our house so it is a moving target from one month to the next.


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RE: Central HVAC alternatives needed

David_cary, the expense of back-up heat is a factor that I tend to forget because I don't have a need for it, mea culpa. I am in the Gulf South. I would tend to think that humidification is a small issue for a tight house in a cold climate. Dryness in winter is very dependent on infiltration of outside air. If you control that, you will not have such dry air. Trust me, I know about cold climates too. I grew up in a house with an oil-fired hydronic system. I moved 5 times in 15 years between different cities, hot and arid to cold or humid, before I moved to South LA a decade ago.

As far as efficiency goes, my worst of three systems is supposed to operate at SEER 17.5, and HSPF 8.9. The 1:1 systems are rated better, some over SEER 20. Obviously, I do not have to subtract duct losses from that. I appreciate the ability to put ducts within the house envelope, but you can still get pressure differentials from room to room that push air out and suck it into the house.

Yes, some people don't like the units hanging on the walls. There are many alternatives to that now, but I have 7 of the old-fashioned wall units. The only place I would change in my house is the dining room. It is a small room and it is obtrusive there. I should have used a ceiling cassette in there. They do cost more and are less efficient.

I have 7 rooms totaling 2000 sq. The mini split install cost me about 15K. That was about $2000 more than a 16 SEER (2-stage) system with all new ducts in the attic and under the house. My house is a 1950 raised, wood-frame house that probably could have been built in 1920 for the construction techniques. It must have been conservative builder. It is notable that the house still has all the doors and walls that it ever did. (I have none of that open floor plan nonsense. If I am going to stay married, I need to be able to get away from my wife sometimes and she needs doors to slam when she gets mad at me.) We only seriously heat or cool rooms that we will be in. We are not home much either, and we are working in the kitchen a lot when home. The life style has a lot to do with our decision.

The first cooling system in the house was a water-cooled, 3-phase system "monstrosity" (the word used by a guy that grew up in the house) of some sort. The house originally had a floor furnace. At the time of the first central system addition, the duct was a central trunk that consisted of a dropped ceiling in a hallway. Later, this was supplied along with additional ducts (some to additions and some to the original rooms) from a sheet metal plenum connected to a gas furnace in the attic with a split evaporator. The condenser/compressors that I had were two, 2-ton that were staged and used a single-speed blower.

As a side note, I am not as confident of our nation's NG supply as you are. We might be in trouble if we have to depend on the shale gas that is purported to be under our feet. I think that the amounts are way lower than estimates and the whole operation may look like a Ponzi scheme by the time we are done. The damage done from making the ground like Swiss cheese could be a nightmare.

More details are available, forgive me for being lazy and editing some earlier posts. Follows are modified excerpts from my previous posts:

My system is Mitsubishi (7 in, 3 out). On paper mini splits are more efficient due to inherent efficiency and the inherent zoned nature. We have been having pretty hot weather and with my wife out of town this week, I have been pretty much been cooling the bedroom and the kitchen with some intermittent cooling in the utility room where the exercise machine lives. Note that I am not much of a sit and watch TV type.

One thing to think about is that, many of them don't have back-up heat so you will not have any heat while they are defrosting. You also have to pay close attention to cold weather performance for the mid-Atlantic region. Cold weather performance has been getting steadily better and they claim that some are good to 0 F so you should not need back up heat in climates where other heat pumps do. I know that with Mitsubishi's current residential equipment, the 1:1 systems have better low temp performance than the multi-splits. They are more efficient too. Even if they do have back-up heat, you can kill the efficiency pretty fast if you need back-up very often.

Keep in mind that there are lots of options to the wall-hung indoor units. They cost more, but there are units that can be dropped into ceilings and others that sit on the floor. There are also short, ducted units that would solve that big room problem by splitting the supply and return. (You could also install more than one indoor unit/room.) Condensate needs to be dealt with using pumps.

Installing a mini-split through outside walls, as is it usually promoted, is pretty quick and straightforward (Read fast and cheap, straight through the exterior walls.) compared to installing a new duct system in an existing house with no existing central AC. My install was done through mostly interior walls running the lines/cables under the raised house and out to the side which was much more complicated. If I were doing this over and I had a good duct system within a house envelope, I might stick with it to save install money. The trouble is, what is a good duct system? More often than not, they are outside of the living space. In addition, they are considered good when they leak 5% of the air and they only get worse as they age. Even if the whole duct system is within the envelope, you will still get pressure differentials that can force air in or out of the house.

My system was in the attic with parts of the duct system in the attic and a trunk that was a furred-down space over the main hallway. That was both in and out of the conditioned space. The worst part was one duct that started at the AH in the attic, dropped down under the house in a chase and ran for about 30 feet before it reached the first of three floor register in an addition with a flat roof (thus no attic). It then reduced in size and ran another 25 feet under the house. That part might have been mini-splitted even if the rest of the house retained a ducted system.

In general, I think that ducted systems are trickier to design and install than mini-splits so there is more tolerance for less than careful and knowledgeable installers with mini-splits. Due to their ability to handle variable loads, choosing the right size is not as critical either. (I had 4 tons cooling plus a gas furnace before, now I have about 106% of the cooling and 60% of the heating. The heating was way oversized.) My system will handle cooling fine with the house the way it is, but I should not have trouble after I make improvements to limit infiltration and add insulation.

My installer is knowledgeable, smart, very workmanlike, and experienced (he has taught the trade for 30 years). He would have installed new ducts and a two-speed system for a lower price than the chosen mini-split equipment. I doubt that he would do my project for the same price if doing it on a similar home going through interior walls. He did not have much mini-split experience and brought in a collaborator that does, on this project because he was looking forward to a learning experience. I don't think that he lost his shirt, but I don't think he made as much as he usually does.

Mini split sellers market their good dehumidification heavily. The variable-speed-blowers and variable speed compressors should help with low-load situations. Some variable-speed ducted systems might match it.

If you have a lot of air infiltration, you will have a humidity problem no matter what you install. Ducted systems can make a passive infiltration problem into a power-vent infiltration problem under some conditions. If the leaking supply ducts are outside of the house envelope you suck hot, humid air in somewhere else to replace the leaking, humidified air. If the leaking return is sucking air in from outside, conditioned air will leave through holes elsewhere. If supplies and returns are not set up perfectly, you will pressurize some rooms and depressurize others relative to outdoors and get both at the same time.

One advantage of ducted systems that I have considered is their ability to use the capacity of the system in one room of the house. That might sound weird, but consider the situation of a party in your house with a large crowd gathered in the living room. Your HVAC system can be running at full capacity picking up heat from the bodies in the LR. Unless your mini split was sized for a large crowd, it might get warm in there. If you have frequent parties, you might size it that way, or install two. Most people will not do that.

If you go mini splits, don't mount a wall unit above where you will have a bed. I saw advertising that showed that and planned that but changed my mind figuring that at low speed at night the cold air would sort of cascade down over the heads and be uncomfortable. I am glad that I changed my mind about it. I don't know if that problem would occur. What I did find, since we did the installation during heating season, is that the default programming of the heat pump mode makes the units good ceiling heaters. (Predictable really. I have experience with ducted systems in predominantly cooling climates that do the same thing.) As they approach the set point the blower speed goes way down so hot air gets stratified near the ceiling even though the louvers are pointed down. Setting the blower speed manually to a slightly higher speed fixed that. Putting the indoor units above the bed would have been uncomfortable if only for that reason.

It is going to be difficult to provide any meaningful operating costs. We are changing too many things on our house so it is a moving target from one month to the next.


 o
RE: Central HVAC alternatives needed

if the op is concerned with costs
the cost of multiple minisplits vs
heat pump should be compared.

with an open floor plan perhaps ducts
can be brought into conditioned space
via fur downs.

just a thought.
best of luck


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