ByPass Zoning tech question.

[easybend]

I read all the manuals (mastered Manual J unabridged version) for HVAC and 90% of my questions were answered. Unfortunately, few of my concerns were not clearly explained in the Manual D.

The book tells you to use a bypass duct for the "extra" air when you implement multiple zone sections. That makes sense. The book also tells you that the bypass in not necessary if the equipment can be controlled (can adjust the airflow for the equipment).

This is what I am speculating. Tell me if I am wrong: If one is using a single speed or multiple speed furnance/airhandler, the bypass is required, because the equipment cannot dynamically change the rate of air going through. Now if the solution incorporates a variable speed furnance/airhandler the bypass is optional or not required, because the machine somehow (I do not know how) adjusts the airflow.

Can someone please tell me if I am correct in my assumptions? In addition, if I am correct how the furnace does know to adjust the airflow when one zone is closed for example. I cannot figure this out, because I have never done this part of HVAC and my situation cries for no bypass, because there is no space.

[eberrong]

Carrier Infinity zoning systems require no bypass. This system is fully intgrated...the condenser, air handler, thermostats, and zone controller all talk to each other. That is how the the airhandler knows to adjust the flow based on the thermostats and what zones are calling for cooling/heating. You can also set limits for the amount of flow (CFM's) in each zone based on the noise level it produces.

[beckservmngr]

Zoning can be a great thing, and can be very disasterous all at the same time, depends on the installer. with thaqt said, you are right, and you are wrong. The zoning required depends a lot on the ductwork itself, and how many zones. if you only have two zones, and the ductwork can be adequetly sized, you do not need a bypass.(it also depends on the zone dampers used.) if three or more zones are there, u must have a bypass, along with freeze protection, and temperature limit controls installed.

It all goes off of CFM, no matter what, whether you have a 3 ton variable drive, or multi speed, you still have to meet that 1200 cfm requirement.

[easybend]

eberrong
That's a smart approach. Are they well document when it comes to installation? I don't know much about Carrier.

beckservmngr
"if you only have two zones, and the ductwork can be adequetly sized, you do not need a bypass." - I have hard time agreeing with this. If we agree that the adequetly sized ductwork for two zones is 1.25 times the regular size. Both zones require almost equal amount of air. The 25% of air will go to the open zone, but where will the rest of the 75% air from the closed zone go?

[jrbenny]

Well, a bypass damper is not a must. It depends not only on your duct size but the zone controller. Trane zoning as well as Carrier Infinity zoning does not require a bypass. A bypass is prohibited on Carrier Infinity zoning. They both use a relief and staging strategy to ensure proper airflow through the equipment.

A bypass only ensures the register noise is minimized. Dumping hot/cold air into the return does nothing but put you closer to an equipment temperature limit. Airflow may be increased through the equipment, but you are dropping/lowering your entering air temperature. In turn, your discharge temperature is pushed closer to an equipment limit.

You should not be using a bypass to maintain airflow through the system. Your ducts need to be sized properly to ensure correct airflow through the system.

[beckservmngr]

Originally posted by easybend
eberrong
That's a smart approach. Are they well document when it comes to installation? I don't know much about Carrier.

beckservmngr
"if you only have two zones, and the ductwork can be adequetly sized, you do not need a bypass." - I have hard time agreeing with this. If we agree that the adequetly sized ductwork for two zones is 1.25 times the regular size. Both zones require almost equal amount of air. The 25% of air will go to the open zone, but where will the rest of the 75% air from the closed zone go?



That is where the adequatly sized ductwork comes into play. you have to size each zone to be able to handle 75% of the cfm. please, do research, the zoning system we use has the documentation for what I have posted. We do not agree that 1.25 is adequatley sized, if not haveing a bypass.

[easybend]

Hmmm, I'm lost here. According to Manual D the bypass has to handle 80% of the extra air if the closed zone is fully closed. If the zone does not fully close the bypass should handle the difference.

My 1.25 was a rough number according to Manual D guide. It seems incorrect to size a duct to handle additional 75% of air. That would throw off everything else.

[easybend]

"You should not be using a bypass to maintain airflow through the system. Your ducts need to be sized properly to ensure correct airflow through the system."

I'm not saying you guys are incorrect, but that is the opposite of what the Manuals are saying.

[beckservmngr]

one of those things, go by the book, or go by experience?

Good luck with what you decide. Peace easybend

[easybend]

Cool. Thanks. One thing I just learned, I love Carrier Infinity. Seems very nice and I like the fact that it does not need a bypass.

[jrbenny]

Originally posted by easybend
"You should not be using a bypass to maintain airflow through the system. Your ducts need to be sized properly to ensure correct airflow through the system."

I'm not saying you guys are incorrect, but that is the opposite of what the Manuals are saying. Apply the mixed air equation to this design. What happens to the mixed air temp with each pass through the heat exchanger?

[easybend]

So what you saying it the air will heat up to the point where it will reach some limit that the exchanger has and possibly damange the exchanger. Makes sense.

Funny thing. I just called like 5 distributors for Carrier Infinity in New Jersey and 4 of them would not sell me anything anyway. I thought capitalism was the advantage of N. America. Look at XXX. They will sell you anything.

<<<Don't link or put DIY sites in your post.>>>

[Edited by jrbenny on 10-18-2006 at 02:45 PM]

[jrbenny]

Infinity is only sold to program dealers in my market. It's not unusual practice.

[easybend]

I will not comment on that.

[azulikit]

I have put in a few zones and I use a electronic bypass that seams to work very well. I know some in this area use what is called a dump zone but How can you control the temp in a zone when you cannot close that zone when the tstat is satisfied. In this area almost all the ductwork is in an attic so there is room for the bypass there.

[easybend]

Looks like I may need to do what you are suggesting, because the Carrier Infinity distributors do not distribute to people like me.

[jramunni]

Originally posted by jrbenny
Well, a bypass damper is not a must. It depends not only on your duct size but the zone controller. Trane zoning as well as Carrier Infinity zoning does not require a bypass. A bypass is prohibited on Carrier Infinity zoning. They both use a relief and staging strategy to ensure proper airflow through the equipment.

A bypass only ensures the register noise is minimized. Dumping hot/cold air into the return does nothing but put you closer to an equipment temperature limit. Airflow may be increased through the equipment, but you are dropping/lowering your entering air temperature. In turn, your discharge temperature is pushed closer to an equipment limit.

You should not be using a bypass to maintain airflow through the system. Your ducts need to be sized properly to ensure correct airflow through the system.

Well said jrbenny...I few things I would add.
Bypass consideration is somewhat different when zoning with trunk dampers verses branch dampering. With trunk dampering you typically need a bit more bypass capacity to keep register noise at bay compared to branch dampering which is typically more forgiving and creates less register noise. This has to do with the constant volume of trunk duct that still needs to be pressurized; this acts as an energy absorber when dampering at the branches. When you trunk damper, the blower energy is focused on one section of duct only.
A second consideration has not yet been mentioned. Many of the benefits of zoning occur due to a controlled increase in static pressure in the supply duct.
One benefit is the increased air flow delivered to the zone that is under a higher load than the rest of the home and is requiring more capacity (sun, people, lights or thermodynamics).
A second benefit is the lower volume and velocity of air across the equipment allows for more BTU transfer including latent capacity (increased dehumidification). So now we have more colder/dryer or warmer air being push with more velocity into the area of the home that is under the heaviest load.
The third benefit is the increased throw from the register that creates a more effective cycle. The more room air we make contact with the more mixing occurs and the less unused conditioned air we allow to fall or drift into areas of the home that don't need it(1st floor/basement).
Im my world paying extra for a system that slows the blower down and eliminates all of these advantages is a mistake.
We are also very much against a "Blow By" method of controlling air flow. This goes against the objective of zoning and allows over conditioning of zones.

Bypassing should always be considered, but you need to have a good understanding of zoning dynamics before you go there.
If you are going to have to use a bypass on a variable speed ECM motor (that increases RPM when zones close) you must size it properly to provide the least amount of bypass cfm that maintains an increased supply static and a maximum cfm to the calling zone. This is critical for both maximum comfort effectiveness and protecting the ECM controller from high return air temperatures.

[easybend]

If you are saying, branch zoning is more forgiving because of the extra space to spread out the pressure I came to an idea that might work for my situation. Since I want to zone out a basement room only I can put the zone damper in the branch for that room only and forget about the bypass.

Something else comes to my mind when talking zones and I have to ask, because it bothers me now. Is it possible to add a zone damper to the branch of the zoned room only? Meaning there is one zone that has a damper and the rest of the house is free without any zone dampers? Sort of like a 1.5 zone setup. If I close the room zone, the extra air goes to the rest of the house. The only problem is Zone control panels for sale say: 2 or 3 zones. I am wondering if this is a valid setup.

[beenthere]

I doubt you called 5 Carrier distributors, more like dealers.

This thread is real close to step by step instructions.

[easybend]

lol. My mistake. Their website provides dealers. No distributors.

[comfortdoc]

Call a professional with zoning experience. They will be able to evaluate your home and give you options to set the system up properly for your needs.

[easybend]

Well the pro that came to install this suggested no zoning, so that's why I decided to master this on my own. I know how to size the ducts for my zone setup and all. My only challange was the bypass, because there is many different opinions on the subject.

And btw, I treat myself as a professional. I don't want to complain, but the second pro guy that came to install this did not know what Manual J is.

[jrbenny]

Originally posted by easybend
And btw, I treat myself as a professional. Treat yourself how you like, but we have to follow the site rules. At this point, I don't believe that we've crossed the DIY line. Let's see how it goes from here.

[eberrong]

Go here...
http://www.residential.carrier.com/

and enter your zip code. See if you have a "Factory-Authorized" dealer in your area. This is how I found a decent contractor (also got lots of help from this forum).

[jramunni]

Originally posted by easybend
If you are saying, branch zoning is more forgiving because of the extra space to spread out the pressure I came to an idea that might work for my situation. Since I want to zone out a basement room only I can put the zone damper in the branch for that room only and forget about the bypass.




What is the reason to seperate (zone) the basement room.

We do manufacture a zone panel (AloneZone) that allows damper control in one zone to limit the conditioned air when it is no longer required. This zone thermostat would control only the damper and not the equipment.

Only available through a liscenced contractor.
I will say that it is simple enough that even a pro that doesn't know what manual J is could install it succesfully.

jr

[easybend]

jramunni,

So it looks like I was not far off.
The reason to seperate the room in the basement is obvious. This room is on a lower level comparing to the rest of the conditioned space. So pure air temperature difference (level zoning). Will your panel work with Honeywell ARD round dampers? If so can you sell it to me?

If you can't sell it it's OK I still have some choices. My point was to avoid bypass ducts if I can. Now I know Carrier Infinity provides that solution, but it's harder to buy if you're not a contractor. I really hate that part about this profession, because it's so unpatriotic. It slows down the development of the country.

Worst case scenario I will buy the Carrier stuff through a HVAC friend of mine and problem will be solved.



Eberrong,

I spoke to a Factory Authorized dealer in my area and they redirected me back to Carrier. I’m talking to a product manager there, so let’s see what happens. Thanks for a tip.

[jramunni]

eberrong

You can not use the Hnwl damper on our panel with out adding a DC relay. Our dampers are air driven and are controlled by 24vdc solenoids that send either pressure (40"wc) to close dampers or Vacuum (-40"wc) to open dampers.

We do manufacture an interface panel that allows contractors to use our dampers with other panels. We could use this same technology to operate motorized dampers from our 24vdc signal.

Unpatriotic...now that's a different twist. I will pass along your concern, we would hate to be contributing to a lack of progression in this great country.

jr

[easybend]

I was reffering to this "secret" profession. Secret comparing to others. I did not refer to anyone here btw. Mostly local "professionals".