convert single to dual zone?

[inetquestion]

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?

---------------------------------------------------------------- HVAC:

Vendor: Lennox CONDENSOR: 10AC42-3P EVAPORATOR/HEAT: 80MGF3/4-100A-1 Approx: ~15 yrs

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---------------------------------------------------------------- HOUSE:

- 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.

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Regards,

-Inet

[.p.jm.]

Braveness, stupidity, and money ( to replace the system you just broke ).

IOW - you don't.

[inetquestion]

malrescuesite.com/

Dear Paul,

This unit suggest the prior point is merely conjecture and lacking fact:

Only do this in spare time... Lessons available when you are available. :P

-Inet

[.p.jm.]

!!!

Knock yourself out.

When you're available, that is :-)

[Stormin Mormon]

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.

[John Gilmer]

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 original thermostat.

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!).

[Grumpy]

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 systems. 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!

[Steve]

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.....

[.p.jm.]

He must be an EE ! :-)

[Steve]

Ya think??

[Lp1331 1p1331]

Google "EWC damper system", and "Maverick damper system" There are also others, but those two are the most common for resi use in my area. Larry

[Don Ocean]

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 King]

That much is apparent...

[jamesgangnc]

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.

[Grumpy]

Hey Steve when you got it why not you can't take it with you

[bp]

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.

[Tony Hwang]

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.

[danny burstein]

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.

[bp]

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 , 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

1-thermostat-based solution.

[Steve]

Start with a correctly sized and properly installed duct system.

Its not about padding the bottom line, its about doing the job right *the first time*

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.