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Forced Air System

2K views 46 replies 8 participants last post by  user_12345a 
#1 ·
So i think with the new house we are buying we are going ot have a force air system installed. We are gutting the entire home so installing ducts will be a little easier. THere is currently a boiler with baseboard heating. We don;t like the baseboards everywhere and want central A/C so we will be removing the baseboards. A few questions. We wil be hiring a professional( just to install the forced air system) but would like some feedback/advice as to make sure they are being honest and fair.

1. If removing the baseboard heat we will still need to keeo the boiler for our water system?
2. We will need to buy a furnace when getting the forced air system installed?
3. We will need to buy A/C equipment that ties into the furnace which is condensor and evaporator coils?
4. Is there a concensus on best brand furnaces and A/C equipment?
5. I would like to have separate heat/AC control in some rooms. I think that is zoning and would require separate t-stats??? I'm think about 5-6 seprate zones. Would that add huge cost to system?

Thank you very much for any feedback.
 
#4 · (Edited)
I figured it would be zoned a little better than just a basic up/down.

OK, it's your choice. You will need to scale back the number of zones you can control unless you're willing to install a very inefficient bypass system. The general idea for providing for zone control is to have someone that is very familiar with duct sizing to design the system since zoning a system that doesn't have oversized ducting would risk doing damage to the equipment. It generally takes a combination of oversized runs and adding more runs than normal. Getting the right person to design it is key. Experience in doing that and references would be nice.

Of course there are two stage ac units and furnaces so that's another consideration but it can get expensive and sometimes less reliable than going with controlled dampers.
 
#7 ·
If you want the ultimate in comfort AND efficiency you may want to look at a high end Lennox Harmony III zoning system coupled to a SLP gas modulating furnace.

The furnace is 98% efficient and can modulate down to 30% of it full blast firing rate. You do not need a in-efficient bypass damper system as the furnace modulates with the zoning system demand and adjusts the furnace fan speed to suit.

Unless you live in Texas and have very expensive AC costs you can use a cheaper 2 stage AC and get good results.

There are very high end modulating ACs also but I doubt AC is as important in New York vs Florida and Texas.

The only concern I have with some of these non name brand, not been in biz a long time other zoning systems is whether they will be in biz 15-20 yrs down the road.

If they go out of biz you have a huge problem.

Lennox and Carrier both have high end zoning systems and will never go out of biz as they are HUGE wealthy old school companies.

For hot water you can use a electric tank or thru the wall gas hot water heater or tankless heater.

https://www.lennox.com/products/comfort-controls/zoning/harmonyiii
 
#10 ·
I think York got a bit of a bum rap as they are actually pretty good units. They have been around for over 35 yrs.

A 2 stage AC will run at 66% of its full blast power on 1st stage and then 100% on 2nd stage. That way it runs longer and de-humidifys your air better which is very important in Florida. I doubt you need that in NY.

It works off the thermostat. When it cuts in it runs on 1st stage and if it cannot keep up and the temp rises another 1 deg F then 2nd stage cuts in.

Personally I don't see why people need zoning unless you are very rich and are building a new house and can have the ductwork properly designed for it.

A full blown Harmony III and SLP furnace can be over $10,000 plus more for AC. However there are LOTS of very rich people in the US where money is no object and they want the ultimate in climate control and comfort.

For the average person a good basic 1 or 2 stage high efficiency furnace w/o a expensive ECM variable speed fan plus a good quality AC is all you need.

Unless you are very fussy and want your temp control within 1 deg F all the time and are willing to pay a lot for zoning then I don't see the need.

We all have to go outside and to work and don't have that level of comfort at work so what is the big deal. Like I said if you want to spend lots of $$ then go ahead.

Like the Dude in the video said, the more complicated you make it the more the repairs cost.

Lennox, Carrier, Trane are probably the 3 top dogs.

York is good and so is Goodman. I put a 2 stage Rheem high efficiency furnace in my Sister's house and have no problems and I don't want to aggravate her.:vs_OMG::vs_mad:

Rheem is good also. As the price goes down then the sound of the units go up as they are not as heavy built so if sound is a issue then the 3 big dogs are the quietest IMO.
 
#11 ·
Makes sense, really does. So I'd want three zones as we have a full basement, 1st floor with LR, Dining, Kitchen and 1BR and upstairs with 4 BR. I think 3 zones makes sense.

Are you saying all furnaces will hav an ECM variabe speed fan but not to get an expensive one or you have the option not to have one at all? Thanks for the help.
 
#12 ·
Never completely discount separate a/c systems, one for top floor and other for 1st floor and basement. That's the traditional method around here. Upstairs areas have a way of staying warm enough year around without any help so heating isn't a consideration but cooling certainly is.

That way also has something to say for having somewhat of a backup system when if/when one goes down.
 
#14 ·
It could probably cost less, depending on the equipment you are considering for a well designed zone controlled installation versus two separate systems. Bounce that off the man giving you an estimate on your system, you may be surprised.
 
#15 · (Edited)
If the air duct system is designed right and everything is properly commissioned, you won't need zoning in most cases. Especially in heating mode.
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Doing a separate system for each floor drives up costs and increases the likelihood of having oversizing equipment. Most furnaces start at 40k btu/hr and a/cs start at 1.5 tons -> so looking at 3 tons and 80k btu minimum which is a lot for most houses not in extreme climates.

A separate system for the second floor is likely to be installed in the attic with ceiling vents. Attic ducts lose a lot of heat - heat from the ceiling is not very comfortable.

-------------------

You should know that the typical forced air isn't as comfortable as hot water and you should seriously look at just replacing the baseboard rads and using mini-splits for cooling.

It takes a really skilled contractor (among other things) putting in a really good duct system and the smallest 2-stage or modulating furnace that will do the job to get forced air right.

Most systems are terrible - they provide short noisy blasts of hot air and the heat isn't distributed evenly.

Zoning is much easier on hydronic than forced air.
 
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#16 ·
Thank you very much!!!!! So maybe we will keep the baseboards for heat and figure out whether we want a ducted AC or mini split system for the AC. When you have a split AC sytem is it a 1to1 where you can only have one head unit( that you mount on the wall) to one compressor or one compressor will can take care of a few wall mounted units? Thank you.
 
#17 ·
A multihead mini can do multiple indoor units off of one outdoor. Either ducted or other types of indoor head.
A conventional split is just one to one.
First step you’ll have after deciding on what type of system you want is determining proper size via a manual J calculation.
 
#18 ·
You can have an outdoor unit installed that can be hooked to multiple heads.

If you want ducted a/c, can look at a high velocity system to reduce or eliminate the need for bulkheads.

In this, you should get the boiler looked at because if it needs to be replaced.

New rads + boiler + mini-split or duct system all together could be very expensive.

It may make sense to go forced air after all - especially if you end up with ducted a/c.

Not anti-forced air, was just bringing up different options.
 
#20 · (Edited)
Here is what I would do:
Get rid of the baseboard units.
Get rid of the boiler. If it heats your domestic hot water, buy a water heater.
Buy a furnace, connect it to the new ductwork, and have them install an A coil. It will cost about $300 and you can add on AC easily later.
Buy no better than a 2 stage furnace. Anything more will cost more for a slight efficiency improvement. Also, getting the latest tech means expensive proprietary parts that won’t be in a repairman’s truck.
If you really like the Lennox dealer, their stuff is good. The problem with Lennox is parts availability for repairmen who don’t sell Lennox. Any HVAC guy can get parts for most brands except Lennox the same day. If he is not a Lennox dealer you wait weeks for Lennox parts. It sounds crazy until Christmas Eve when your heat is out and the Lennox dealer can’t get to you.
Have dampers put in every supply duct so you can adjust it to your comfort level. Zoning can be done if you want to spend a lot.
 
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#22 ·
The decision to zone or not needs to be made in the planning stages - impacts the way the ducts are done.

For 2-stage furnace i wouldn't have more than 2 zones and would get a zoning panel that keeps second stage off unless both are calling - split house evenly.
 
#24 ·
May be easier to do 2 separate systems, maybe only zone one.
Is the third zone a below ground basement? They often only need a little bit of heat and a dehumidifier. It’s a much different environment then the above grade spaces of the home. Should be on a separate system anyway.
 
#27 ·
Keeping different areas of the house cooler/warmer depending on season doesn't really save much energy - there's no insulation between interior rooms.

In winter keeping a part of the house cold while the rest is warm can cause condensation problems leading to mold growth.

Now, if you only need a/c in one or two rooms - for sure it makes sense to go the mini-split route and forget about central.

Mini-splits do have a down side -> they're loaded with proprietary electronics. Most central units can be fixed with generic parts off the truck.
 
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#36 · (Edited)
Personally I don't like ductless mini splits except for problem jobs where there is no other alternative.

In my experience few techs know how to service them or want to and they are hard to get technical info for. Same with some parts. They also have drainage problems with the condensate from the cooling coil due to the small line plugging with bacteria.

If you have a conventional air handler or furnace and a regular AC then ANYBODY can service it and get parts easily.

Who knew life can be so complicated.:vs_laugh:

I enjoyed renting. Just call the landlord and let him deal with it.:biggrin2:
 
#38 · (Edited)
I have never seen a basement and upstairs ducting system balanced so well that both areas are pleased. There is too much variation in the heat load to ever strike a balance that works all the time. Might work where it's cloudy ever day and temps stayed around 65 year around.

Having a greater percentage of the return air in the basement and no door between it and upstairs works for me in this house we have lived in for the past 20 yrs. I tried resetting dampers from season to season and sometimes from week to week without much success. Short of a full blown zoning control and reworking the ducting sizes and adding controlled dampers, I decided to leave it alone and go with the off balanced return air method. It works reasonably well with no ill effects on backdraft through the furnace or water heater flues. YMMV
 
#39 ·
2 stories on one system works just fine for heating - when it doesn't there's an insulation/air sealing problem or a duct problem.

The loads are not that different especially if the attic is properly insulated and the house is reasonably tight. Leakage -> cold air leaking in low and leaking out into the attic can cause heating loads to be very uneven.

In the us, I bet things are done a lot worse than in canada where room by room load calcs and properly engineered duct systems are required for new building permits.

For cooling on a decent duct system it's normal for the second floor to be 2F warmer than the first.

If the ducts were done done without cooling in mind, the difference can be much greater.
 
#41 · (Edited)
Yea, if you want central AC and you don’t want the baseboard units, get a forced air system. I would not zone it. If you have dampers you can adjust them to get the comfort you want at a low cost. I fine tuned mine for a little while. Now I know where to set each damper twice per year when transitioning from heat to air and air to heat. It takes all of about 5 minutes. More AC on upper floors, more heat on lower floors.
I removed my baseboard heat and put in forced air 25 years ago. Now that I am retired, when we go away or to FL for the winter, I turn off our water at the meter. If something happens and the place freezes, only the water in the pipes will get out. With hydronic heat, you have to keep makeup water turned on and a power outage might let pipes freeze. It happened to my son at a vacant rental house, a bedroom heat pipe burst and caused almost $50k in damage. I am sitting in FL and water damage in NY is something I don’t have to think about.
 
#43 ·
(And one other thing - the a/c for the upstairs was located in the attic, and it was clearly undersized. It really struggled to keep the whole upstairs cool. Just something to watch out for: I suspect that an attic installation should be sized differently from a ground floor installation even if the square footage being cooled is the same.)
probably wasn't delivering close to rated capacity and wasn't actually undersized. duct loss, low airflow, improper charge, mismatched components kills real world capacity.
 
#44 ·
Consider heat pumps. I don't know a lot about them, but have read that they are the most efficient at heating and cooling. I've also seen them as individual units for single rooms. Besides that forced air, with natural gas is great for heating, which is what I have since it was the original installation. Requires a furnace of course. The original huge inefficient furnace lasted about 25 years. Since then I'm on my 3rd high efficiency gas furnaces in 10 years. They just don't last as long as the old robust ones did.
 
#45 ·
You have other issues at play if you’ve gone through 3 furnaces in 10 years. What is killing the furnaces? They simply don’t “wear out” in that amount of time.
Efficiency depends on electric and gas rates, plus a lot of other outside information. One or the other isn’t most efficient all of the time.
 
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