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Bearis

05:29PM | 07/29/04
Member Since: 07/28/04
5 lifetime posts
Bvhvac
In the process of buying a home and after living in an apt in NYC I've realized how little I know about basic home care. I have some initial questions on central ac installation.

1. What "kind" of central ac should I get - floor vents versus ceiling vents - one generator versus two....? I live in NY and the house is a two story colonial (plus usable attack) with 2600 sqft.

2. How long does the project usually take from start to finish?

3. What would a reasonable cost be.

Thank you

tomh

06:07PM | 07/29/04
Member Since: 07/01/03
558 lifetime posts
I am a bit confused by your post. First you ask what kind of HVAC system you should have, then you tell us the place is 2600 square feet with an attic.

Like most of us, you are not making a purchase decision based on what kind of AC is present, you want to know what will best meet your needs? or the system does not include AC?

Lets start over.

Have you bought a place?

What kind of HVAC exists now?

Are there ducts?

How many stories is the strucuture you need to cool?

What is the heat or cooling load?

A professional HVAC contractor should start with calculating a heat load to determine you heating and cooling needs. This, plus the limitations in installing a system and duct work, and the quality of the system you choose, are going to determine the price. What you need to do first is to get preliminary information on what type and size system you need, what efficiency you want to pay for, and what the scope of duct work and so forth you are going to need.

I consider this a 2-part bid process. You need to ask an HVAC contractor for an initial bid and learn what its going to take. Then bid the project equally to several contractors to find the best price/service point.

There are far to many variable to say what this project should cost. An new furnace and AC system can be installed in 2 days or 2 weeks depending on what duct modifications or installation are required.

Thats my best answer. Back to you.

Bearis

06:51PM | 07/29/04
Member Since: 07/28/04
5 lifetime posts
tomh,

the house (which im in contract at the moment) is a 1902 colonial with a non-finished basement, two main floors and an attic with a bedroom and full bath which Im sure we will use at some point for guests or future kids.

The house does NOT have central ac.

I did not notice any ducts though that does not meen there are none. I just did not notice any. Im going with the engineer on saturday so will look then.

Not sure how to measure the cooling load. Aside from the house being 2600 sqft and wanting to pretty much cool all of it (certainly the two main floors plus attic), not sure what else. I guess being in NY cooling will be needed from may through oct.

I think your idea of getting someone in first to get details and price and then bidding it out to 3 or 4 other is great.

By the way, I have seen that there are systems now with little whole (size of tennis ball) in the corners of the ceiling which are used for central ac. How are those versus more conventional vents? and should they go on the ceiling or floor.


Anonymous

09:56PM | 07/29/04
Sounds you are starting from scratch with air handler, ducts, AC and new heating system. Existing house may use a boiler or radiators, we don't know. I am going to answer as someone with enough knowlege of HVAC to be dangerous, but at least I have been in your position needing to find out what was needed. While you have your engineer on Saturday, pay particular attention to the existing electric system. You may have an old 60 to 100 amp knob and tube with fuses or upgraded breaker system. Central AC is going to require at least a 200 amp service. So that may be your first expense.

Any good heating contractor will do a heat load that considers, not just floor space, but things your house has, like large single pane windows and a lack of insulation. You need a larger unit than say someone in a new house with well insulated and nearly air-tight walls and windows. The system is specific to your climate zone, and your house. You may want to condider a single central system or a split system. Depending on your budget, it may be better to separately heat and cool the upstairs via an air handler in the attic, and the downstairs from the basement using 2 smaller condensors outside. This avoids excavating walls for ducts, and may simplify some aspects of installation. This is something to discuss with an expert in HVAC.

Like we said before. The first bid is educational. I hope he gets the job, but at least he is going to give you an education. Be sure to ask for a heat load calculation, and whether it is better to install a central, or split system. Then get bugetary estimates for that. Once you know what is needed, make sure your bid requests, consistently ask for the same grade and size of equipment and duct installation from any competing companies. Dont try to compare a SEER 15 Carrier Infinity or Lennox system to someones SEER 10 Ruud or Janitrol. Do your homework on this and decide what efficiency and quality you want to pay for initially, with the trade-off being lower operating and maintenance costs for higher efficiency and quality.

Take your time to do the education and bids. The work can be done in a couple weeks depending on what you decide, and whether you need to upgrade electric and gas services. Start Saturday with an evaluation of the electric service. Build on your knowlege of brands and quality available, so you can discuss this intelligently with a HVAC salesperson or contractor. Do a heat load to determine size, and decide whether you need a central or split system. Finally bid the job using equal quality and size criteria....And don't forget to post back here so we can hear how you are doing. We can all learn.

tomh

07:11AM | 07/30/04
Member Since: 07/01/03
558 lifetime posts
I tried to reply last night, and you will just have to believe it was a great answer, but the system logged me off and didn't post the message. Here it is more briefly.

While your engineer is out on Saturday, check the electric capacity for the house. Upgrading to central AC may require a 200 amp service. If the house is still served by knob and tube wiring or even a breaker upgraded to 100 amps, your first project may be an electric service upgrade to allow you to consider central AC.

Since there is no existing ductwork you are looking at a complete system. Even though you may have heat by a boiler, a central AC unit is going to entail an air-handler, furnace, evaporator, condensor and ducts runs. Square footage is not so important in sizing as "HEAT LOAD" This is a function unique to your house and is based on volume (floor size and ceiling heights), and will be affected by less insulation and large single pane windows likely in this older structure. Your system will likely be larger than one designed for new construction of the same size.

Something to consider is whether its better to install 2-zones or a single central system. A separate unit serving upstairs and another serving downstairs has the advantage of not requiring vertical supply plenums to be installed in the the walls or in chases. In other words, one system mounted in the attic serves the upstairs zone, and a second unit serves the downstairs. Duct runs are easier, and you only heat or cool the part of the house in use. So, during the day you may run only the downstairs zone. At night the upstairs. Tends to be efficient, as well as easier to install. This is an option to discuss with a knowlegable HVAC contractor.

Once you decide on the necessary size and zone configuration, you need to decide what quality and efficiency you want to buy. This will take some homework and research. Higher quality and efficiency has higher initial costs, and long-term operating cost savings. With the above information you can put out a bid specification to several contractors. You want bids based on equal quality, efficiency, size and installation. Actual installation should be able to be completed in 2 weeks or less, but you may have to upgrade electric service first.

As you can see, its not a simple project, and one thing leads to the next. You are at least a few weeks away from someone being able to tell you what this will cost, and how long it will take. Most important, I hope you will continue to post back, so we can all learn something from your experience here.
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