Need advice on installing air conditioning on my home (1 Viewer)

[yotadude520]

So I’m in the process of getting quotes to add A/C to my house and I need some advice.

The house is currently equipped with a gas furnace and a swamp cooler on the roof. I’d like to keep the swamp cooler since it works well most of the year. The setup I’d like to have is add a evap coil above the furnace and a condenser on the roof. The A/C would be run off of the same blower motor from the furnace. My house is 1100 square feet but has a 250 square foot addition that has no ducts going to it.

I’ve had 3 quotes so far. Each guy has told me something different. I’d like to keep the furnace because my budget is tight and it seems to work well. The first guy is okay with me keeping the furnace, but after running a heat load recommended a 3.5 ton unit. The second guy ran a heat load test and recommended that I replace my furnace and do everything and advised against me keeping my current furnace (which works well) and said they wouldn’t do the work if I kept it. He also brought up a good point that my furnace return air might not be able to handle A/C so we’d have to add another. This was also the most expensive of all three quotes.

The third guy was a very straight shooter, seemed knowledgeable and recommended that I get a 2.5 ton unit because my furnace wouldn’t handle anything bigger and it was designed for the house without the addition. He also noted that the first two guys did their load tests using a room that doesn’t get any A/C since it has no ducts therefore shouldn’t have been used in a load test.

My questions are

A) do you think that adding an evap coil without replacing the furnace is a good idea?

B) any input on anything that I’ve been hearing? I really liked the first salesperson as a person, the second guy not so much but seemed thorough and the third guy was a straight shooter who seemed logical and knowledgeable.

This is a huge decision and I would like advice from someone who’s NOT trying to sell me something! Any input would be much appreciated.

Thanks so much guys!

 

[Mungrol]

Completely different environment and use I guess. My house has a furnace and no a/c since we are up here in the NW. It is fine most of the year but would be nice to have A/C several weeks a year when it is quite miserable.

So I am looking at the ductless units. That way I can have A/C in the 4 rooms I want and not really worry about the rest of the house. They also double as heaters which will allow me to go with my radiant floor heating in the two lower units of the house, remove the furnace and still get heat to the bedrooms via the ductless when I need it. And the Ductless ends up being far easier to install, and is more affordable than having my furnace upgraded to a A/C and Furnace unit.

So not sure if you have looked into the ductless units but you may want to. Especially if you are saying that like me... you really only need it at certain times since the swamp cooler is sufficient most of the year. I have even seen ductless units that are DIY if you are handy. I would go that route but they are usually only for one area and I want to have 3 or 4 areas on ductless.

Just a though and sorry about not being able to answer your direct questions.

Cheers,

 

[yotadude520]

No problem! Appreciate the input @Mungrol

I'd rather have an A/C unit use the existing ductwork since well it works and having mini splits in all the rooms would be kind of a PITA and not very efficient (atleast not here in AZ).

I have thought about adding one to the room that doesn't have a duct going to it but that's about it. But as an update to the thread I think I am going to go with the third guy. The company he works for is local, has great reviews and he's been doing it for a long time. I trust him the most out of the three.

 

[Weedhopper]

Mitsibishi makes little fan coil units that you can put almost anywhere.

My parents sold their house and the new owner used them. Independent of the existing heating.

A little fugly looking but a little landscaping hides them well.

 

[yotadude520]

Mitsibishi makes little fan coil units that you can put almost anywhere.

My parents sold their house and the new owner used them. Independent of the existing heating.

A little fugly looking but a little landscaping hides them well.

Yeah I've seen them before - definitely neat! I would do one of those for the room with no current ductwork but I don't see the need for the rest of the house since the heater works well and the ductwork is solid - but I appreciate the input!

 

[Jprice]

Not a lot of experience with Swamp Coolers but I do know ductwork.


A) do you think that adding an evap coil without replacing the furnace is a good idea?
~Not if the sizing is mismatched. Your current furnace is only delivering so much CFM, and if it is paired with an Evap coil designed to have more, then you will have issues of freezing up.


B) any input on anything that I’ve been hearing? I really liked the first salesperson as a person, the second guy not so much but seemed thorough and the third guy was a straight shooter who seemed logical and knowledgeable.
~As far as the load calculation, the guy who said that the one room should not be counted because it didn't have a duct, could be right but probably not. Does that room exchange air with other parts of the house that is getting conditioned? If so, then it absolutely is a load that is a part of the larger load of the whole house. But again, I hate to say that he is wrong without knowing more details. Will you be adding a duct run to this room?

 

[yotadude520]

Not a lot of experience with Swamp Coolers but I do know ductwork.


A) do you think that adding an evap coil without replacing the furnace is a good idea?
~Not if the sizing is mismatched. Your current furnace is only delivering so much CFM, and if it is paired with an Evap coil designed to have more, then you will have issues of freezing up.


B) any input on anything that I’ve been hearing? I really liked the first salesperson as a person, the second guy not so much but seemed thorough and the third guy was a straight shooter who seemed logical and knowledgeable.
~As far as the load calculation, the guy who said that the one room should not be counted because it didn't have a duct, could be right but probably not. Does that room exchange air with other parts of the house that is getting conditioned? If so, then it absolutely is a load that is a part of the larger load of the whole house. But again, I hate to say that he is wrong without knowing more details. Will you be adding a duct run to this room?

Hi Jprice - thanks for the thoughts!

A) The first two guys were recommending 3 & 3.5 ton 14 seer units. My furnace puts out about 80,000 BTU's and that isn't enough for either of those units. I think a 2.5 ton be okay and work well.

B) The last room doesn't really exchange air with the other rooms. There's no return air or duct in there. It was originally a patio that was enclosed and made into a separate room. The main idea is that we're going to be running off of the capbiltiies of the furnace and how efficient that is/it's return air rate. The furnace does heat the house pretty well, with the exception of that room. There are no ducts going there and the closest one is behind a wall like 15 feet away. I'd say it's pretty safe to say that the room wouldn't have any load on the system whatsoever.

 

[Jprice]

Hi Jprice - thanks for the thoughts!

A) The first two guys were recommending 3 & 3.5 ton 14 seer units. My furnace puts out about 80,000 BTU's and that isn't enough for either of those units. I think a 2.5 ton be okay and work well.

B) The last room doesn't really exchange air with the other rooms. There's no return air or duct in there. It was originally a patio that was enclosed and made into a separate room. The main idea is that we're going to be running off of the capbiltiies of the furnace and how efficient that is/it's return air rate. The furnace does heat the house pretty well, with the exception of that room. There are no ducts going there and the closest one is behind a wall like 15 feet away. I'd say it's pretty safe to say that the room wouldn't have any load on the system whatsoever.

Is the door to the patio room always closed? If so, then yes, it would not really need to be included in the load calculation. If it is open or if it has any kind of louvered vents or even if it is an interior door "hollow", then it absolutely would contribute to the load of the house, as air is free to pass back and forth and within a pressurized system would be getting conditioned air from the rest of the house.

As far as tonnage goes, go with as close as you can to what the load calculation calls for. Going over or under will only cause headaches later on.

Final note, as concerns the return air. Increase the size or add another if you can. You can never have too much return. It always confounded me why contractors so often install the bare minimum when it comes to R/A. Also, adding a return air in the rooms you occupy most will add to the comfort in those rooms.

 

[yotadude520]

Thanks for the info - I think I'll get some more quotes before I make a decision.

 

[Hack]

First off a disclaimer: I'm not a HVAC tech or engineer. So take this from my experience having two heat/AC systems installed by 'experts'.

The concern over the present furnace size really seems to be over the existing plenum/blower capacity. You will need sheet metal work regardless due to adding the coil to your existing system. But will the CFM of the blower be capable of handling the added AC system?

You want to keep your existing swamp cooler, is its sheet metal separate from the current furnace setup?

Where is the present furnace located? Is it in the attic (most-not all-homes in the south/southwest are)?

Do you have sufficient electrical capacity to add an AC system?

If you have the option to get interruptible electric, you might consider it. You will save some money on electric cost over the long term.

If your 'extra room' was a former patio, you probably have a sliding door to access it (most likely, you leave the door open. Right?). Or perhaps the sliding door was removed. If it also has lots of large windows, it will effect the selection of either a heating or cooling unit, if you choose to condition the air in that room. A simple solution (but perhaps not the 'best') may be to just add a large ceiling fan to that room. And a space heater.

The most efficient system, IMO, is one where the heat blows (or rises) from the floor, and the cool blows down from the ceiling. In my main house (two story colonial, 2300 sq ft) my furnace is in the basement and the AC is also attached to it. I have a Trane 3.5 ton AC unit and a Trane 80k BTU forced air furnace. Both high efficiency. The blower is a variable speed DC unit, that I run 100% of the time. It's speed varies depending on the temperature inside the house. I set the thermostat at 70 degrees in the winter, and 68 in the summer. It's comfortable right now, and the outside temp is -6 degrees. In the summer, I keep the shades drawn upstairs.

At my lake house, I have hot water baseboard heat (just had a new boiler installed - $6k - ouch) and the AC (1.5 or 2 ton unit - not certain) is separate with the air handler located in the attic. The ductwork is all above the ceiling. Granted my lake house is less square footage (about 1200), single story, and on a crawl space. The heating is on three zones, the AC is not. But the system provides better, more even temperature control in either hot or cold weather, over the one in my main house.

Lastly, talking to a salesperson, is one thing. Taking with an installer (the person who's actually going to do the work), is probably what you should do next. The installer can give you a better insight as to what's all going to be involved in your particular job. Salespeople sell the job, then assign it to an installer. Who on occasion comes out and says: 'WTF???'

 

[yotadude520]

First off a disclaimer: I'm not a HVAC tech or engineer. So take this from my experience having two heat/AC systems installed by 'experts'.

The concern over the present furnace size really seems to be over the existing plenum/blower capacity. You will need sheet metal work regardless due to adding the coil to your existing system. But will the CFM of the blower be capable of handling the added AC system?

You want to keep your existing swamp cooler, is its sheet metal separate from the current furnace setup?

Where is the present furnace located? Is it in the attic (most-not all-homes in the south/southwest are)?

Do you have sufficient electrical capacity to add an AC system?

If you have the option to get interruptible electric, you might consider it. You will save some money on electric cost over the long term.

If your 'extra room' was a former patio, you probably have a sliding door to access it (most likely, you leave the door open. Right?). Or perhaps the sliding door was removed. If it also has lots of large windows, it will effect the selection of either a heating or cooling unit, if you choose to condition the air in that room. A simple solution (but perhaps not the 'best') may be to just add a large ceiling fan to that room. And a space heater.

The most efficient system, IMO, is one where the heat blows (or rises) from the floor, and the cool blows down from the ceiling. In my main house (two story colonial, 2300 sq ft) my furnace is in the basement and the AC is also attached to it. I have a Trane 3.5 ton AC unit and a Trane 80k BTU forced air furnace. Both high efficiency. The blower is a variable speed DC unit, that I run 100% of the time. It's speed varies depending on the temperature inside the house. I set the thermostat at 70 degrees in the winter, and 68 in the summer. It's comfortable right now, and the outside temp is -6 degrees. In the summer, I keep the shades drawn upstairs.

At my lake house, I have hot water baseboard heat (just had a new boiler installed - $6k - ouch) and the AC (1.5 or 2 ton unit - not certain) is separate with the air handler located in the attic. The ductwork is all above the ceiling. Granted my lake house is less square footage (about 1200), single story, and on a crawl space. The heating is on three zones, the AC is not. But the system provides better, more even temperature control in either hot or cold weather, over the one in my main house.

Lastly, talking to a salesperson, is one thing. Taking with an installer (the person who's actually going to do the work), is probably what you should do next. The installer can give you a better insight as to what's all going to be involved in your particular job. Salespeople sell the job, then assign it to an installer. Who on occasion comes out and says: 'WTF???'

Thanks for the reply Hack!

The swamp cooler is on the same ductwork as the heating furnace. The furnace is located in it's own room in the hall way. So basically you have the swamp cooler on the roof, and it forces air down through the furnace duct and then through all the vents. When it's time to use the furnace, you place a cookie sheet on the bottom of the swamp cooler than kick the furnace on. The air travels up, hits the top of the swamp cooler, then goes down into the ducts.

The idea would be to have A/C in between the two with a damper above the A/C coil so when the A/C kicks on using the furnace blower motor, it will shut off the swamp entrance so the cold air doesn't escape through the swamp cooler.

There is sufficient power to add A/C, and the room without ducts (the old patio) currently has it's own A/C unit in there. What I'm looking to do is very popular in homes here and the unit that I would be getting wouldn't be putting out too much load on my furnace. It would essentially be the furnace blowing A/C through the same ductwork with the same blower motor and intensity. It will be like the furnace kicking on but instead of hot air you get cold A/C. The trouble is finding the right evaporator coil that will work with the fan.

 

[Bob Morazes]

Help me out here.
Is your problem the stuffy house?
Then the AC is not circulating well enough. So better balance between supply and return air ducts, bigger fan, fan slipping on belt, change the speed of the fan through different size pulleys.
Or is it your sick with the AC on. Get your ducts cleaned, and get one of the more expensive filters that kills the most allergens.
Hope that helps
Bobmo