How hard is it to install a gas hvac central air?


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Old 01-07-19, 11:12 AM
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How hard is it to install a gas hvac central air?

Iím very handy I used to be a residential carpenter and am now an instrumentation and Controls tech and an electrical journeyman apprentice.
I am also overly cautious when Iíve never done something before and am a little worried about doing it myself, but I just got a ballpark estimate from and HVAC guy and it was a lot more than I want to pay!
Iíve only added duct runs from an existing trunk line, but Iím hoping with a little instruction and or direction I could do it myself.
Can anyone give me any information or direction to help me decide if itís worth doing it myself? Currently there is no system, itís all electric and expensive so I definitely need to do something!
 
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Old 01-07-19, 11:33 AM
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The Furnace Book is a good start. https://www.amazon.com/Furnace-Book-.../dp/1418410888 and lots of pay info here: Furnace Book

That is the install itself but you first need to do sizing and planning. Manual-D etc. https://www.energyvanguard.com/blog/...Manual-J-S-T-D
 
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Old 01-07-19, 11:52 AM
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You're all electric now. That means you'll need all ductwork, gas line, electric for the furnace and the condenser, refrigerant lines between the two and someone to charge it.

As you're contemplating this install..... keep the warranty factor in mind. Many manufacturers only warranty equipment installed by their trained techs. Not so much with furnaces as with A/C systems.
 
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Old 01-07-19, 12:34 PM
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"urrently there is no system, itís all electric and expensive so I definitely need to do something!"

Running air ducts in an existing house can be very expensive.

Unless you have very costly electricity and specifically want to switch to natural gas, look into mini-split heatpumps.

This type of system can reduce heating costs by 1/3 to 1/2 or more. The best ones can maintain full capacity down to 0f and below.
 
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Old 01-07-19, 01:08 PM
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K,
You say you are all electric but you also mentioned you've added duct runs. Is this in your house or on another job. If you have ductwork installed already I would think in your case it could be doable.

Starting from scratch with no installed ductwork would depend on the layout of the house and access to rooms and floors. Being a carpenter is sure a step in the right direction to gain access to the needed areas.

Duckwork requires some special tools but installing is pretty straight forward for the most part. You're into electrical now so that's a plus. You can contract out to runs the refrigerant part of running and evacuating the lines. The compressors come precharged.

Just my thoughts, hope this helps a little.
 
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Old 01-07-19, 01:49 PM
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Great help guys, keep it coming! So just to clarify that yes there is no duct work at all in my current house, it was a different house I owned that I ran duct work from an existing trunk line.
Also the trunk line would be an almost straight run, with minimal remodeling that I was already going to do.
One big question i have is how much it will save me to do it myself? I know we canít post prices but what percentage do you all think I would save by doing it myself?
 
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Old 01-07-19, 02:59 PM
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There's a lot to it including studying theory on load calculations and duct design.

it's not diy friendly.

if you take this on, at the very least contract out the gas lines, venting, refrigeration work (if adding a/c) -> requires special tools and you can really hurt yourself and/or destroy property if you mess up.

I wouldn't take this on myself.
 
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Old 01-07-19, 06:07 PM
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First you’ll have to determine equipment sizing, then duct sizing. There is no rule of thumb here, there are calculations to be done.
Once you do that there are fuel lines to run. They will require permitting and inspection.
Your local code may require a permit to install a furnace.
You’ll need specific tools, such as sheet metal tools, pipe wrenches, pipe threading equipment if your using iron.......
You’ll need items to commission the furnace like a manometer, combustion analyzer, and meter........
A host of other items if you plan on a/c as well.
Online equipment is likely going to have no warranty. Definitely not if it’s diy installed.
 
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Old 01-07-19, 07:52 PM
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Speaking for myself it's impossible to say how much you could save. When you get your estimates did they break down and itemize the parts or stalk and labor.

You know right off that you're going to save the labor or at least most of it. Depending where you are and the rates there and the permits needed and how right you can buy the equipment, and if you can buy it at all without a license.

I'm in MA and you have to be licensed to gas pipe and even licensed to work with sheet metal now in the last couple of years. So it depends what you need for licenses and permits how much you can do yourself plus the specialized tools you'll need which aren't cheap.

Only you can answer how much you'll save after all the running around trying to get what's needed and trying to get help when you get stuck if it's worth it.

Years ago we used to figure the price of the stock and double it and that was the price for the job. That would cover our labor and stock markup and we could sleep at night but the contractors today sleep just fine charging what the market will bear so all I can recommend is to get a few estimates but make sure you compare apples with apples and just don't take the cheapest because it is the cheapest.

What you want to do is going to require a lot of work to be sure and also to be considered is quality differences in equipment.
 
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Old 01-07-19, 08:30 PM
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"You’ll need items to commission the furnace like a manometer, combustion analyzer, and meter........"

I'm betting most furnaces aren't commissioned with a manometer let alone a combustion analyzer.

"turn it on and run"
 
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Old 01-09-19, 08:57 AM
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Thanks all!

Iíve decided to go other routes on saving on my electric bill. Extra insulation in attic, new siding with additional insulation under it, possibly a pellet stove with a blower, LED bulbs and fixtures, strategically placed motion sensor light switches,insulate the garage better(it is under the house), take out radiant ceiling heat and baseboard heaters, then install cadet heaters. I also have a mini split heat pump that I bought for a different house and never installed it, that I could put in as well.
Thanks again for everyoneís advice and input.
 

Last edited by Kmurd; 01-09-19 at 09:01 AM. Reason: To add more content
 

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