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Started By
Message
New Construction HVAC question
Posted on 11/1/18 at 7:15 pm
Posted on 11/1/18 at 7:15 pm
I'm building a 1 story 2550 sf home in South BR with 10'-12' ceilings throughout. I plan to be in home approximately 15 yrs at least. There will be a 500 sf bonus room above garage, but I won't finish that out for a couple years.
HVAC contractor and builder recommend a single stage 5 ton unit (Lennox) with 3 zones (master suite = 1 zone, common areas = 1 zone, and other bedrooms = zone) OR I could do 2 separate systems (3 ton and 2 ton)...cost for either option is roughly the same. For about $3k more, I can also upgrade to a 2 stage 5 ton with zones.
My concern with single stage zoned setup is short cycles and dumping excess air back into plenum leading to shorter equipment life. Is this valid concern, or has technology and equipment improved to help prevent this? HVAC contractor says will have motorized dampers, a barometric bypass damper, and kill sensors to prevent coils from freezing, etc.
Is the combined 3 ton and 2 ton system setup better than a single stage zoned setup?
Is the $3k upgrade worth it to have 2 stage speed with zones?
I appreciate any feedback. Thank you
HVAC contractor and builder recommend a single stage 5 ton unit (Lennox) with 3 zones (master suite = 1 zone, common areas = 1 zone, and other bedrooms = zone) OR I could do 2 separate systems (3 ton and 2 ton)...cost for either option is roughly the same. For about $3k more, I can also upgrade to a 2 stage 5 ton with zones.
My concern with single stage zoned setup is short cycles and dumping excess air back into plenum leading to shorter equipment life. Is this valid concern, or has technology and equipment improved to help prevent this? HVAC contractor says will have motorized dampers, a barometric bypass damper, and kill sensors to prevent coils from freezing, etc.
Is the combined 3 ton and 2 ton system setup better than a single stage zoned setup?
Is the $3k upgrade worth it to have 2 stage speed with zones?
I appreciate any feedback. Thank you
25
Posted on 11/1/18 at 7:21 pm to Joshkdixon
Lennox?
First, find a new contractor.
First, find a new contractor.
Posted on 11/1/18 at 7:26 pm to Joshkdixon
Trane or Carrier or gtfo.
And I would always prefer 2 separate units. Youll be happy one works when the other breaks
And I would always prefer 2 separate units. Youll be happy one works when the other breaks
This post was edited on 11/1/18 at 7:27 pm
Posted on 11/1/18 at 7:27 pm to Joshkdixon
Jmho
You are staying put for 15 years. Invest in top end, high eff. equipment. I'd go two stage with a three ton and the two ton. (Your numbers).
I'd also plan for the upstairs bonus room. Equipment type?
Perhaps you might want to rough in the drain and line sets now to facilitate the system installation down the road.
Go Trane
You are staying put for 15 years. Invest in top end, high eff. equipment. I'd go two stage with a three ton and the two ton. (Your numbers).
I'd also plan for the upstairs bonus room. Equipment type?
Perhaps you might want to rough in the drain and line sets now to facilitate the system installation down the road.
Go Trane
This post was edited on 11/1/18 at 9:25 pm
Posted on 11/1/18 at 7:34 pm to LSUSkip
That was another concern, although they have since quoted others...Goodman, Rheem, Tempstar, Amana.
Posted on 11/1/18 at 7:35 pm to Joshkdixon
I would go with two separate units. Simpler design. And you will be glad you have two units when one goes out. Lennox is same quality as Trane or used to be.
I wouldn’t put a Carrier unit in my enemy’s house, to quote a contractor I knew. I feel the same way. I designed hvac for eight years fwiw.
I wouldn’t put a Carrier unit in my enemy’s house, to quote a contractor I knew. I feel the same way. I designed hvac for eight years fwiw.
Posted on 11/1/18 at 7:35 pm to Cosmo
Go with the two units 3 & 2 ton. I have the same square footage you referenced, and my builder suggested 2 units. This set up is more energy efficient and cools the home much better in the summer months than one unit & the money you save on the utility bill is worth it.
Had a single unit on my previous home with the same square footage and the utility bills were significantly more.
Don’t go with Lennox either.
Had a single unit on my previous home with the same square footage and the utility bills were significantly more.
Don’t go with Lennox either.
Posted on 11/1/18 at 7:37 pm to Joshkdixon
If you have any bedrooms on a 2nd story then absolutely go with 2 units.
I’d consider 2 3-ton systems just to be safe. Hvac guys will almost always tell you to be conservative and 5 tons for 2500 sq ft plus a potential upgrade is not conservative at all.
I’d consider 2 3-ton systems just to be safe. Hvac guys will almost always tell you to be conservative and 5 tons for 2500 sq ft plus a potential upgrade is not conservative at all.
This post was edited on 11/1/18 at 7:37 pm
Posted on 11/1/18 at 7:37 pm to Joshkdixon
I wonder how many comments you are getting are from mechanical engineers or HVAC contractors?
Posted on 11/1/18 at 7:37 pm to Joshkdixon
wtf is this
Posted on 11/1/18 at 7:40 pm to kengel2
Licensed mechanical engineer who used to design hvac for a living.
Posted on 11/1/18 at 7:40 pm to Joshkdixon
Regardless of which you choose, Insulate the bonus room floor with foam...please, just do it...foam the attic too if you can swing it...
Pre-run line set and drain for future Mitsubishi minisplit to control the bonus room.
Zone / motorized damper systems work ok, but since you are leaving unfinished for now...I prefer the minisplit option.
Pre-run line set and drain for future Mitsubishi minisplit to control the bonus room.
Zone / motorized damper systems work ok, but since you are leaving unfinished for now...I prefer the minisplit option.
Posted on 11/1/18 at 7:41 pm to Joshkdixon
Carrier infinity system. Look it up.
Crazy crazy efficient and comfortable.
Carrier engineer here Kengel
Mechanical engineer too, btw.
Crazy crazy efficient and comfortable.
Carrier engineer here Kengel
Mechanical engineer too, btw.
This post was edited on 11/1/18 at 7:43 pm
Posted on 11/1/18 at 7:42 pm to baldona
Thanks. I was thinking of using mini split for bonus room down the road.
Posted on 11/1/18 at 7:47 pm to Joshkdixon
Zoning with a single stage that large is rarely a good idea. Your contractor better be very good with his manual j and manual d calcs to make it work well.
Posted on 11/1/18 at 7:49 pm to RadBro
quote:
Catahoula20LSU
quote:
RadBro
OP, Id listen to these guys.
And keep in my if you do 2 units your electrical price will go up due to feeding systems.
Posted on 11/1/18 at 7:51 pm to notsince98
I agree.
Your only energy conservation / comfort measures are slowing down your fan speed, scaling back the compressor, or both.
You often see low/med/hi fans speed as your only adjustment. They typically aren’t comfortable or efficient.
I’d recommend at least a 2 stage compressor.
The infinity system I talked about earlier can have 5+ stages plus 0-100% fan speed modulation.
It’s a little pricy, but if you are staying for 15 years it’s well worth it IMO.
Your only energy conservation / comfort measures are slowing down your fan speed, scaling back the compressor, or both.
You often see low/med/hi fans speed as your only adjustment. They typically aren’t comfortable or efficient.
I’d recommend at least a 2 stage compressor.
The infinity system I talked about earlier can have 5+ stages plus 0-100% fan speed modulation.
It’s a little pricy, but if you are staying for 15 years it’s well worth it IMO.
Posted on 11/1/18 at 8:08 pm to Joshkdixon
I don't have much to add 9ther than my hvac guy once told me that zoning with a single stage is a bit of a hack job. Sometimes it sorta works but zoning is really intended for variable compressors.
Posted on 11/1/18 at 8:11 pm to baldona
quote:
I’d consider 2 3-ton systems just to be safe. Hvac guys will almost always tell you to be conservative and 5 tons for 2500 sq ft plus a potential upgrade is not conservative at all.
I would not trust any "rule of thumb" he needs a accurate heat load calculation for the house, in South LA too large of a unit is worse than too small.
Posted on 11/1/18 at 8:20 pm to Joshkdixon
quote:
Lennox
Hot garbage
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