What is involved in converting a single zone HVAC to a dual zone
system using one compressor? Given all my existing parts will remain
and no new condensor or evaporators will be added, I assume it will
require a baffle/damper to direct the air to up/down/both areas
depending on which thermostat get triggered. What parts best suit
this type conversion? Is there an intermediate circuit board which
would be required?
Approx: ~15 yrs
- Built in 1995
- 2200sf with existing thermostat on lower level.
- Evaporator and heater (gas) are in the attic.
- All vent lines are very accessible in the attic.
On 15 June, 14:37, .p.jm.@see_my_sig_for_address.com wrote:
This unit suggest the prior point is merely conjecture and lacking
Only do this in spare time... Lessons available when you are
It's a bit of a challenge. A single zone HVAC is designed to move some
number of BTU per hour. If you cut the conditioned area down, the
cooling might not work as well. Also, you'd reduce the air flow
through the indoor coil, which creates other problems.
It's the kind of project a handy engineer might want to install.
The concept is simple: you have a "controller" (which may well be a
dedicated PC) which has as "inputs" the temperatures in the various rooms
and the outlet temperature of the air handler.
The "outputs" would be control of dampners to the individual rooms, and the
main "call" for the whole AC system.
"Nice to have" would be control of the fan speed.
The system would have to open dampners and control the fan speed to keep the
air handler outlet temperature within desirable limits. Likewise, the
temporarily "un-conditioned" zone might have some limits to keep it from
getting TOO hot or cold.
It would also have to do some "reasoning" to determine whether a sensor or
dampner (or fan or ???) isn't working properly.
Of course, it would have a "failsafe" mode whereby all the dampners would
open, the fan goes into default mode, and demand is controlled by the
It would be a fun project to "program."
I know the dampners are availble "mail order" but one might have to do some
scrambling to get the I/O to your computer. But once you have done that
it's SMOP (Simply a Matter of Programming!).
Yes it could be done but it is not advisable
first it would need modification of refrigeration system itself
second your cost for operating such system would be very high
you would be better of hiring some one and installing two independent
Be aware that on single compressor with two zones, will be running
practically all the time
at full capacity if you running single zone or both.
Additional parts: electro mechanized dampers, relays, Hot gas bypass CPR.
Stay with what you have!
Unless he wanted to invest in a 2 stage system with a variable speed blower,
and even then, he would have to completely redesign the ductwork from
scratch, as well as the control system.......we are talking about some
serious green here.... in the neighborhood of $15K - $20K. But... if he's
got more dollars than sense.....
Have you seen the new Air Cooling system that is super energy efficient
that is now being advertised nationally. It is free...After you read all
the fine print and buy the first one. It has 2 Gel packs that you
refrigerate and then stick in the portable system that blows air over
them, thus cooling the room.. Get this guy to buy them as them he can
zone 2 areas. I am sure you can also heat those Gel Packs in the oven. I
I think this system is full proof as it is union made in China. ;-p
Dpn't forget super Energy efficient. Kind of like the Amish heaters.
The plain english version of many of these answers is you really
can't. Your system is sized to handle your whole house. Forcing it
to only do one half or the other is not effecient and may even damage
it. The proper solution is to get a variable speed system in
combination with zone controls. Or get 2 systems. I prefer 2 systems
because it costs about the same and when one breaks you still have
part of the house getting heated or cooled.
To revisit an old thread from 17 Jun 2010, jamesgangnc wrote:
None of the local dealers I've talked to, including those who do
commercial work, seem to have much knowledge about active residential
zoning systems unless you have upwards of 3000 sq. ft. to handle. Any
brochures on zoning systems I've read to date seem to suggest they
just close off ducts when the local zone temperature setpoint is
reached. That would seem to be a hazard if they aren't paying
attention to total air flow requirements.
Are there systems that can rebalance air flow while maintaining
minimum/maximum air flow requirements for A/C? Perhaps something
involving anemometers mounted right in the ductwork?
I'd be looking for something that can seamlessly integrate with a
LENNOX Signature Series variable-speed air handler and a
single-capacity 2-ton A/C unit for a 1900 sq.ft. 3-storey condo.
I am no expert by any means but multi level small space, small a.c unit
makes this a challenge. Unless you have unlimited budget Bo wonder
hardly any one shows interest. Even if it is done, the result may not be
to your satisfaction. Again due to multi level small space, small a/c unit.
I've been through a similar situation myself, and have spent quite
some time with licensed, experienced, insured, and qualified
local hvac installers. Both of them...
Well, a couple more.
They all basically said it couldn't be done at anything approaching
a reasonable cost. (They did give me valid estimates for the
type of work they were recommending, but this involved commercial
grade controls and dampers and multi stage /variable output units).
I then asked about mini-splits. Only one of them had any experience
installing them and he said "yeah, that would work". One or two
of hte others said that I'd be the first install, but they'd be
willing to give it a try.
Due to finances we've had to hold off. They understand and we're
still on good terms. Maybe next year. We're hoping...
Anyway, a mini-split system might make sense for you. The big
brand name is Mitsubishi's "Mr. Slim" but there are plenty of
other good quality units. As with anything of this sort, once
you're thinking about decent equipment, 90 percent of the
success is based on good installation.
Very few intallers have experience with mini splits, so it's
something you should mention to them.
Knowledge may be power, but communications is the key
I've made it perfectly clear to these companies that price is the last
consideration and function the first. I ended up buying more system
than they recommended. (The iComfort thermostat is a boon.) I would
have thought they would have shown more initiative in suggesting
alternatives to pad their bottom lines.
As a clueless layman <G>, I would have thought this problem wasn't in
principle all that hard to address if you were willing to accept a
less than perfect solution. Provided you can keep total air flow
around 800CFM-ish for the 2-ton unit, should you not in theory be able
to apportion the flow anywhere it's called for? The farther you are
over the local temperature setpoint, the more air flow you get
(subject to practical maximums based on local ductwork configuration)
Where possible, the rooms farthest under their local setpoints would
be closed off entirely. This sounds to me like something a very low
end microcontroller could handle..
The absolute max total CFM the air handler can push through appears to
be in the neighbourhood of 1100CFM. (So sayeth my anemometer as
measured at the individual registers.) So in principle there would
appear to be some considerable leeway in how many extra CFM you can
pump through some individual registers and steal away from others. If
I'd gone for the two-stage A/C unit (much louder apparently than the
single-stage one), then it could operate at a considerable lower
capacity when fewer zones are calling for cooling.
Such a system isn't going to be perfect in all circumstances because
clearly some rooms are going to get over-cooled just to prevent the
system as a whole from icing up. But I would have thought it should
be a lot better than the 6C+ temperature differential I have now from
floor to floor and room to room with a traditional dumb
Start with a correctly sized and properly installed duct system.
Its not about padding the bottom line, its about doing the job right *the
You still haven't answered the right questions... remember we can't *SEE* it
through the computer.
The whole idea is for your home to be comfortable, and have no more than 1
degree temperature difference between any 2 rooms.
1100cfm from a 2 ton air handler?? your not getting the humidity control or
efficiency out of the system. btw.. 2 stage systems are high end systems,
and are almost virtualy silent when installed correctly.
not if the system and ductwork are correctly designed, sized, and installed.
Zoning isn't the answer. getting it done right is.
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