HELP- HVAC Sizing and Electronic Dampenes

[joeyjr]

We recently purchased a 20 year old (3) story home in NC.
The first floor has a 2 year old 12 SEER Carrier unit that needs no attention.

The 3rd floor (approx 750 of converted attic space w/ R-30 insulation) is being serviced with ducts tapped into the homes original 2nd floor gas HVAC unit (which resides on the 3rd floor). Several HVAC contractors have recommended one large system utilizing two thermostats (one for each floor) and the use of electronic dampeners. Others have recommended just adding a simple 1.5 ton heat pump and leaving the existing 2nd floor unit alone until it quits working. While a third option was to add the new heat pump and replace the older 2nd floor unit with a new unit as well.

Why is there such major disagreement among HVAC contractors on the use of the systems utilizing two thermostats and the use of electronic dampeners?? Is a 20 year old system worth taking a risk on??
Thanks

[airworx]

knowledge.

installing a zoning system will lower installation and utility cost.

[-80guru]

Yes yes use zone control. In the future you may want to consider one system for the whole house using zone control.

[AllTemp]

Originally posted by joeyjr
Is a 20 year old system worth taking a risk on??
Thanks

I would not want to put any money into a 20 year system if it were me sir.

Not sure I followed your zoning issues but I would certinaly entertain accomplising this with some mechanical design and new equipment.

There is nothing worst than a partial old sytsem and a new making things work... Man makes me fell il thinking about it if it were my house...

REPLACE IT, find a company that agrees with you... The guy that wants to baby the 20 + year old along get rid of him.

[tinknocker service tech]

alltemp is right
why zone off a 20 year old system it will be one problem after an other. this would be a big mistake get someone new

[joeyjr]

I'm sorry if I was not clear on the options.

OPTION 1: One NEW larger system for the 2nd and 3rd floors utilizing two thermostats (one for each floor) and the use of electronic dampeners.

OPTION 2: Add a simple 1.5 ton heat pump for the 3rd floor and leave the existing 2nd floor unit alone (until it quits working.

OPTION 3: Add the new heat pump for the 3rd floor and replace the older 2nd floor unit with a new unit as well.

Why is there such major disagreement among HVAC contractors on the use of the systems utilizing two thermostats and the use of electronic dampeners??
Is a 20 year old system worth taking a risk on??
Thanks Again

[tinknocker service tech]

misunderstood
zone systems work well and with newer equipment you will get the same result as two systems in most cases
they are used all the time and work quite well

[joeyjr]

Thanks for the reply. The zoned system with dampers seems like a good idea, however of the six HVAC contractors I spoke with only one swore by it it while the other five swore at it.
Maybe a case of people being reluctant to technology and change.
Thanks Again

[sarge]

Originally posted by joeyjr
Thanks for the reply. The zoned system with dampers seems like a good idea, however of the six HVAC contractors I spoke with only one swore by it it while the other five swore at it.
Maybe a case of people being reluctant to technology and change.
Thanks Again

Which contractor do you think is up to date with the latest training and technology?

[Black Adder]

I use California Economizer zoning all the time, what is the problem with a twenty year old system, are we talking about the ducting or the units? If units are 20 yrs. old time for replacement, I have no problems using 20 year old ductwork.

[joeyjr]

No problem with the 20 year old system at this time. I was just considering changing that unit out giving it's age and that ANY PROPOSED CHANGES will require moving a wall to allow the new unit(s) to meet code for clearances. If the single unit multi zoned systems work well that may be a good option. Thanks for the reply.

[classicrock4you]

SIZING IS CRITICAL IN ZONING!!!!

During the summer the third floor will run 2 or 3 times as much as the second floor, so you can run into a situation
with a 3 ton unit with a 1 1/2 ton load for long periods of time. Make sure that you get proper advise from the damper manufacturer for optimal humidity removal. The will probably advise reducing the system by 1/2 ton

Remember that the load on the second floor will be much less when you condition the third floor. A 2 1/2 load could easily drop to a t ton ot less.

This is a great application for a dual speed unit

[rabadger]

Remember when trying to compare, if you don't do your homework first and know what you want and what is needed
you will have a hard time comparing bids. All contractors no matter what the trade have things in common.

1. They all have families to feed
2. They all have found products and different ways of
doing things that come up with the same results.
3. They have all been brow beaten on price so much by the
consumer that price is one of the most important
things.
4. When the consumer goes strickly for price comfort
suffers.

Zoning is great stuff when applied correctly. Figure a way to compare apples to apples.

[Black Adder]

With a dedicated zoning system, you will have to use a bypass damper to ensure that when only one zone is calling for heat or cooling the system will still move enough air to stop freezing up or over heating. Along with this you will install a LAS (leaving air sensor) to shut down the compressor and leave the fan running if the temp is too low or high. California Economizer works well with this system. I agree with the previous post that sizing is a major issue with zoning and should be carefuly worked out.