PDA

View Full Version : Variable speed air handler with single stage HP


Herdfan
05-15-2007, 12:43 PM
For those who have followed my issues with my zoning mess:

http://www.hvac-talk.com/vbb/showthread.php?t=137046

and my lack of cool air at the registers:

http://www.hvac-talk.com/vbb/showthread.php?t=138281

I first want to thank all those who have replied and offered advice.:)

As my HVAC contractor is getting ready to replace my single speed air handler and single stage compressor with the following:

Lennox Elite XP16 Multi-stage Heat Pump
Lennox CB31MV Variable Speed Air Handler

I have a question. It has been the opinion of almost everyone here that a zoned system needs a variable speed AH. What is the benefit of a 2-stage compressor other than possibly energy efficiency?

Will a variable speed AH work fine with my current single stage compressor?

Since my current coil is freezing due to poor airflow, how does reducing the fan speed not induce the coil to freeze?

My HVAC contractor has been cooperative throughout this entire process even though they haven't been able to fix it. I can't find any fault with their effort. So I don't want him to have to "Eat" any more than is required to fix my cooling system. It seems a Variable Speed AH is required, but I am not sure about the 2-stage compressor.

And just a recommendation to all who quote jobs: Give your customer some options. I have seen many posts here from customers who are trying to decide between different setups an quoted by their dealer. I just wish my dealer had given me options instead of just a price for what he had spec'd. If he had given me different setup options, I would probably have taken the VS/2-stage in the first place.
t527ed
05-15-2007, 02:30 PM
when set up properly unit will run most of the time on the low stage.
you will not have to move 5 tons of air thru 1 or 2 tons of ductwork.
should allow each zone to run long enough to dehumidify better.

with lennox zoning system it will cycle between high and low stage as needed by sensing air temperature in plenum.

not familiar with the arzel zoning so i don't know how they will control staging.
Herdfan
05-15-2007, 02:43 PM
with lennox zoning system it will cycle between high and low stage as needed by sensing air temperature in plenum.

not familiar with the arzel zoning so i don't know how they will control staging.

http://www.arzelzoning.com/literature/Airboss_Series_Fact_Sheet.pdf

The Arzel has a temperature sensor in the plenum, but at this point in time it is shut off as to not compete with the freeze stat.

The fact sheet indicates it will work with both 1 and 2 stage units.
dash
05-15-2007, 05:05 PM
Neither the VS or the two stage is required.We have been doing zoning since before either was available.

Systms like Infinty and Harmony Zoning ,do thing using VS and two stage that others couldn't do,that's where the value is.

I've been told Arzel can come close,using variable speed and two stage,don't know for sure.
beenthere
05-15-2007, 05:16 PM
Not required. But can enhance your comfort even more.
t527ed
05-15-2007, 06:29 PM
Neither the VS or the two stage is required.We have been doing zoning since before either was available.

Systms like Infinty and Harmony Zoning ,do thing using VS and two stage that others couldn't do,that's where the value is.

I've been told Arzel can come close,using variable speed and two stage,don't know for sure.



neither one of them are absolute must haves but they do make for a much better system without the need for bypass dampers and or dump zones.

with the technology available it is foolish anymore to zone without it.
dash
05-15-2007, 10:48 PM
neither one of them are absolute must haves but they do make for a much better system without the need for bypass dampers and or dump zones.

with the technology available it is foolish anymore to zone without it.

Then there's still a lot of foolish people!lol!


my point is ,that's not what he paid for,and if the ducts where right ,it would work fine.
t527ed
05-15-2007, 11:03 PM
Then there's still a lot of foolish people!lol!


my point is ,that's not what he paid for,and if the ducts where right ,it would work fine.


it would work fine, BUT the size of the bypass needed for a 5 ton unit with zones that small would be a big waste of energy.:cool: