HVAC folks, come on in! Converting to central air questions

[IronWing]

Current setup:

• Forced air natural gas furnace (45 years old and no problems)
• Roof mounted down-draft swamp cooler (two years old)
• Furnace and cooler share duct work
• "Cookie sheet" dampers block the ducts from the furnace or cooler depending on season

Desired setup:

• Forced air natural gas furnace
• Roof mounted down-draft swamp cooler
• Central air unit
• Ability to switch between swamp cooler and A/C without too much hassle. Switching would be seasonal with cooler in spring and fall and A/C during the humid monsoon season

Questions:
Do modern central air units generally have their own air handler or do they share a blower with the furnace?
Can the entire A/C unit live on the roof?

What I'm thinking of is some sort of T junction in the ductwork on the roof with a damper system to allow me to choose whether to use the A/C output or swamp cooler.

 

[justoh]

Sorry, all i have is a kevin smith reference. I just use a fan.

 

[Mayne]

how big is your home. square footage? Where do you live? Need to answer some simple questions first. I'm a gas fitter.

 

[mikeford]

Visit the HVAC forum, its mostly contractors and VERY touchy about non pro babbling, but its where the solid info lives.

This place.
http://hvac-talk.com/vbb/forumdisplay.php?1-AOP-Residential-HVAC

 

[Mayne]

I install furnaces and a/c's in Canada. So ask away.

 

[Mayne]

such a shame. I could of saved you lots of money. oh well.

 

[drnickriviera]

such a shame. I could of saved you lots of money. oh well.

Your avatar is the perfect expression. Don't respond back in 17 mins, oh well, tough luck :jackiechan:

 

[nickbits]

They share a blower.

 

[Billb2]

Do modern central air units generally have their own air handler or do they share a blower with the furnace?
Can the entire A/C unit live on the roof?

What I'm thinking of is some sort of T junction in the ductwork on the roof with a damper system to allow me to choose whether to use the A/C output or swamp cooler.

AC units use the existing furnace blower but have an evaporator in the furnace plenum and a compressor/condenser/fan in a separate unit that can be mounted pretty much anywhere.

There's a little more to it, but that's the basics.

 

[Red Squirrel]

I never understood swamp coolers, don't those create humidity? I could see them being useful for data centres but not living quarters.

If your furnace is 45 years old it may be time to consider a replacement simply because a new one will be more efficient. It may or may not be able to handle central air as well, but I think that more has to do with the size of the plenum for the evap coil to fit in. You will probably need a new thermostat too, one that has AC and heat mode, but that's fairly trivial to replace. May need to run a new cable (5 wires vs 2 if I recall).

You also need a double pole slot in your panel for the breaker that will power the outside condenser/compressor unit. I think they use a 30 amp.

 

[feralkid]

I never understood swamp coolers, don't those create humidity? I could see them being useful for data centres but not living quarters.

If you lived here you'd understand.

 

[BUTCH1]

I never understood swamp coolers, don't those create humidity? I could see them being useful for data centres but not living quarters.

If your furnace is 45 years old it may be time to consider a replacement simply because a new one will be more efficient. It may or may not be able to handle central air as well, but I think that more has to do with the size of the plenum for the evap coil to fit in. You will probably need a new thermostat too, one that has AC and heat mode, but that's fairly trivial to replace. May need to run a new cable (5 wires vs 2 if I recall).

You also need a double pole slot in your panel for the breaker that will power the outside condenser/compressor unit. I think they use a 30 amp.

"Swamp coolers" take advantage of the fact that when water evaporates it takes some heat along with it, it's in fact VERY useful DEPENDING ON WHERE YOU LIVE, in the SW they work well due to the extreme temps but very low humidity, in the SE they are next to useless as FL, GA, LA all have extremely high humidity and using a swamp cooler in those areas will not work, part of the cooling effect from an AC is the removal of excess moisture in the air.

 

[IronWing]

Update: The central air was installed Thursday. New furnace, added compressor unit on roof, barometric dampers to block swamp cooler duct when furnace/AC in use and block furnace/AC when swamp cooler in use. Cool, dry, and comfy. It's hard to get used to the windows being closed all the time but dry is nice.

 

[Mayne]

Update: The central air was installed Thursday. New furnace, added compressor unit on roof, barometric dampers to block swamp cooler duct when furnace/AC in use and block furnace/AC when swamp cooler in use. Cool, dry, and comfy. It's hard to get used to the windows being closed all the time but dry is nice.

Glad to see it worked out for you. Make sure to change your filter every month.

 

[alkemyst]

Current setup:

• Forced air natural gas furnace (45 years old and no problems)
• Roof mounted down-draft swamp cooler (two years old)
• Furnace and cooler share duct work
• "Cookie sheet" dampers block the ducts from the furnace or cooler depending on season

Desired setup:

• Forced air natural gas furnace
• Roof mounted down-draft swamp cooler
• Central air unit
• Ability to switch between swamp cooler and A/C without too much hassle. Switching would be seasonal with cooler in spring and fall and A/C during the humid monsoon season

Questions:
Do modern central air units generally have their own air handler or do they share a blower with the furnace?
Can the entire A/C unit live on the roof?

What I'm thinking of is some sort of T junction in the ductwork on the roof with a damper system to allow me to choose whether to use the A/C output or swamp cooler.

What's the budget?