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We haven't really changed any siding or anything else on my house since we've moved in that would have any big affect on the AC. Your mention of the heat load/loss is good advice. Some of the contractors have mentioned that they will perform this.
I'm wondering, though, just how accurate is this? It seems to me that this could be somewhat error-prone because some things seem hard to calculate. For example, does it take into account the type of siding (ie, vinyl vs. wood vs steel) or the color of the siding (dark vs light color)? How about when my kids go outside and forget to close the door behind them? (I know, this isn't good .... but it happens).
It seems to me that this heat load/loss calculation SHOULD have been done when the house was built, and if it was it was botched. What's interesting is that some of the contractors have suggested a 3 ton unit and others suggest a 3.5 ton unit. Perhaps this calculation will provide the real answer, I don't know. But it just seems that there might be a large margin of error.
I'm somewhat inclined to error on the side of conservatism and go with a 3.5 ton unit regardless of what the calculations state. But what is the downside if I oversize it? Will this affect the degree of de-humidification it can perform?
3.5 mfd and a 3 mfd. They put two capacitors in the indoor unit?
It sounds like they didn't know which one to put in?
Either way that's way more expensive than the actual capacitor. $100-$120/hr is normal rates for around me and a trip charge $10-$30 is normal here. Capacitor price maybe $20-$40 and they usually markup 100% so $40-$80. Low end $150, high end $230. Sounds more to me like they should be on the low low low end though if they left without it working.
Connected: 2-6 wires with easy disconnect clips. 5 minutes including checking to see if the capacitor is dead for each.
She is going to contact Visa. That was the price for the parts alone. They charged $80 to install. They applied a coupon to the $80 trip charge. I think she is going to get a new unit, as hers is about 15 years old.
I'm a complete novice. I'm having a new house built. Today I spent an hour in a model home that is the same size as my house will be -- 1642 sq ft, 9" ceiling, one story. It was right at 85 degrees outside, pretty mild, but it was 76 degrees inside. The AC unit (Amana Distinctions Heat Pump) was running like mad the entire hour I was there and the temperature never got below 76.
Is this normal?? I've been living in apartments for the better part of two decades and I've grown used to leaving the climate control off during work and then coming home and putting it on and within an hour the place is 72 degrees even if it's 102 outside. I know I can't expect that kind of comfort in a house, but 76 seems high for the unit running nonstop and it only being 85 outside. It sounds like the best it could do if it were hot outside (high 90s or low 100s) is mid-high 80s or worse.
Am I missing something?
By the way, the model home had standard fiberglass insulation, while I was considering opting for the open-cell foam -- but I'm worried about that too because they say they downsize the HVAC with the foam.
I don't care about cheap electric bills if the drawback is mid 80s all summer long. Thanks!
I'm wondering, though, just how accurate is this? It seems to me that this could be somewhat error-prone because some things seem hard to calculate. For example, does it take into account the type of siding (ie, vinyl vs. wood vs steel) or the color of the siding (dark vs light color)? How about when my kids go outside and forget to close the door behind them? (I know, this isn't good .... but it happens).
It takes into account almost everything.
This is the website details for Manual J 8th Edition version run for the program just to give you an idea of the many variables that are accounted for. The other very minor ones may make fluctuations but you're working in .5 ton increments of 6000 btu's. Through carefully choosing equipment that meets your needs through the performance data provided from the mfg's you can get something extremely close, at least for HVAC and hand grenades.
Quote:
MJ8 also accommodates homes that have exceptional architectural features and life style accessories such as:
Dwellings that have limited exposure or no expo*sure diversity
Homes with large south-facing glass area or rooms with unusually large glass area
A thermally isolated solarium
Customized internal load estimates
MJ8 is sensitive to an increased variety of issues re*lated to construction materials and methods including:
Fenestration loads for glass rated by the National Fenestration Rating Council (NFRC)
Improved duct load models
Improved methods for estimating the effect of internal and external shading devices, including insect screens
Infiltration estimated based on blower door test
Sensitivity to latitude and altitude
Sensitivity to skylight glazing material, curb construction and light shaft construction
Heat gain sensitivity to roofing material, roof color and the use of radiant barrier
Heat loss and gain for log walls, structural foam panels, aerated autoclaved concrete block, insulated form concrete panels, brick walls, concrete walls, wood foundation walls, and any other types of walls and insulation options
It seems to me that this heat load/loss calculation SHOULD have been done when the house was built, and if it was it was botched. What's interesting is that some of the contractors have suggested a 3 ton unit and others suggest a 3.5 ton unit. Perhaps this calculation will provide the real answer, I don't know. But it just seems that there might be a large margin of error.
They've been around for a long time. However people are just now starting to understand. The more expensive power comes the quicker they'll come to realize. It's catching on though. More importantly in getting the heat load/loss is that you use those numbers to setup the air distribution system so if you set it at 75F the whole house is 75F. Not so easy and the contractors that can do that charge for it. The only real way for the homeowner to have proof and have a leg to stand on is a blueprint of what your home needs. Otherwise your just assuming the technician that shows up to fix it can guesstimate if it's too big or small.
Quote:
Originally Posted by rochoz
I'm somewhat inclined to error on the side of conservatism and go with a 3.5 ton unit regardless of what the calculations state. But what is the downside if I oversize it? Will this affect the degree of de-humidification it can perform?
The worst thing about over sizing is the system cycling more often on and off which is where the wear and tear happens. Also the de-humidification is a problem if you're in an area that is humid. Somewhere like Arizona wouldn't be as much of a problem. The multistage system are designed to take care of both humidity and higher heat loads. Single stage systems don't have that flexibility.
I'm a complete novice. I'm having a new house built. Today I spent an hour in a model home that is the same size as my house will be -- 1642 sq ft, 9" ceiling, one story. It was right at 85 degrees outside, pretty mild, but it was 76 degrees inside. The AC unit (Amana Distinctions Heat Pump) was running like mad the entire hour I was there and the temperature never got below 76.
Is this normal?? I've been living in apartments for the better part of two decades and I've grown used to leaving the climate control off during work and then coming home and putting it on and within an hour the place is 72 degrees even if it's 102 outside. I know I can't expect that kind of comfort in a house, but 76 seems high for the unit running nonstop and it only being 85 outside. It sounds like the best it could do if it were hot outside (high 90s or low 100s) is mid-high 80s or worse.
Am I missing something?
By the way, the model home had standard fiberglass insulation, while I was considering opting for the open-cell foam -- but I'm worried about that too because they say they downsize the HVAC with the foam.
I don't care about cheap electric bills if the drawback is mid 80s all summer long. Thanks!
No I don't think you're missing anything. Many times in the model homes they'll have every light on along with all the blinds open and curtains pulled back? I like the foam and it has the secondary benefit, besides smaller heating/cooling loads, of sealing the home tight. Sometimes a fresh air system is installed on these because you actually don't exchange enough outside air with indoor air. 25% the volume of the home/hr. This is good because when setup with something like a enthalpy sensor you can bring in just what you need and on cooler days just run the fan and bring in all outside air not using the cooling system at all.
Just an example if 20 60 watt light bulbs are on in the model that's 1200 watts which is about 4100 btu or 1/3 of a ton. With the radiant heat coming in from the windows it may top over 1/2 or more depending on the type of windows and # of them. That's a pretty big difference of probably good for a few degrees cooler. In general you'd rather have the smallest system that keeps you comfortable and runs constantly. Doesn't sound effcient but until the HVAC system equalizes out the most expensive time to use it is from the second it starts and the longer it runs till that equalization the less it cost to run till stablized. Then usually it'll run for 5/10/15 minutes or whatever then shuts off. Many two stage systems are desinged to run constantly on low and if you cut them down say over a few degrees from where it's at the higher stage kicks in. There are 4 things to look for in air comfort. Air circulation, humidity control, drybulb temp and filtered air with toxins from inside the home expelled or diluted.
As above the heat load/loss calculations are the only true way for you as a homeowner to have proof of what you need. It doesn't always have to be the same contractor or homebuilder to do the calculation either. For the $ there really is no better backup than a load/loss calc. It would be like having your house built without blueprints IMO. I'm a little partial though.
She is going to contact Visa. That was the price for the parts alone. They charged $80 to install. They applied a coupon to the $80 trip charge. I think she is going to get a new unit, as hers is about 15 years old.
Thank you for the input!
Unfortunately there seems to be more contractors out to make a buck at any cost in the HVAC field than there are people who like to stamp their name on quality work. I don't think it's limited to just HVAC though. That does not take away from those that do take pride in their work and do as best they can any and everyday. They just aren't as easy to find since the McMansion boom. The bottom line became more important.
Any advice for someone wanting to have central a/c installed? I've tried to read all posts in various threads about central a/c. The more I read, the more confused and overwhelmed I feel.
I currently have a forced air natural gas furnace which I'm guessing is original to the house (30 years old). My home is a split entry floor plan with just over 1500 sq ft. Most of the living is done on the upper level. I currently use a swamp cooler to cool my home in the summer. I don't know how old it is but I've lived there 11 years and think that this it the best time to consider getting central air.
After a lot of research, I've decided to look into Trane, Carrier & York.
I live in Salt Lake and it's very dry here. Currently 93 degrees & 10% humidity. A humid summer day here is when the humidity is over 35%. Temps here can reach 100+. Swamp coolers can only cool up to 20 degrees so on really warm days, it's not pleasant in my house.
I'm concerned with being too cold in the basement. Can you just close the register vents for rooms you're not using or does that screw up your cooling system?
I typically keep my swamp cooler at about 78 when I'm gone and about 75 when I'm home. I really like the coolness of the swamp cooler....when it's functioning properly. I've put-off getting central air because it seems so frigid.
I've located some autorized dealers in my area for all three makes.
Any advice as far as brands, features, price, etc? I am interested in the federal rebates but understand in order to get those, I have to get a 16 SEER.
I'm concerned with being too cold in the basement. Can you just close the register vents for rooms you're not using or does that screw up your cooling system?
In general you would want to condition the entire home. Depending on the size of the home, the error room given by vent sizes and the type of system you buy depends on how many, if any, can be closed off. Basements are hard to use air condition alone to cool because of the extremely low heat load and relatively higher humidity. Humidity doesn't sound like your issue though.
Quote:
Originally Posted by eggalegga
I typically keep my swamp cooler at about 78 when I'm gone and about 75 when I'm home. I really like the coolness of the swamp cooler....when it's functioning properly. I've put-off getting central air because it seems so frigid.
Central air is purely for comfort in the entire home or conditioned space. I'll call it envelope since homes are made to block outside ambient conditions or at least slow them down.
Quote:
Originally Posted by eggalegga
I've located some autorized dealers in my area for all three makes.
Make sure they use NATE certified service and installers. It's one of the few indicators of competent HVAC co's. Also ask if they do load calculations using ACCA standards or equivalent. It's virtually the blueprints, like with your house, for HVAC equipment.
Quote:
Originally Posted by eggalegga
Any advice as far as brands, features, price, etc? I am interested in the federal rebates but understand in order to get those, I have to get a 16 SEER.
25 year old equipment, if replaced with 16 SEER equipment, would virtually cut your power usage in half. There are many calculators to figure out ROI on the net. I suggest taking your time, as it seems you already know that, and getting everything, as detailed as possible, in your quotes. If it takes 25 companies to find one you're comfortable with then so be it. You're setting up a long term, at least 10-15 years, relationship and you want someone to do the job and if problems arise you can have an avenue to solve them with a company that knows you and your situation. I highly suggest a load calculation be done so not only do you know your heat gain but your losses also and what causes the biggest hits on your load calculation.
Those are some useful tools in understanding how HVAC systems are designed and built. I hope I was of some help to you and am more than happy to help in any other way.
...Those are some useful tools in understanding how HVAC systems are designed and built. I hope I was of some help to you and am more than happy to help in any other way.
HUGE help. I'll start by checking out all the links. Great info. Thanks so much!
I was spending quite some time on the internet for some info regarding how air condition works and came accross this website. I'm amazed of how people are helping each other here. Thats great! My question is, are we breathing in some Freon gas? Its my understanding that the basic concept of air conditioning is just taking the heat out of the indoor air thus making it cooler.
Thank you in advance.
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Adding Central Air
