Multi-zone residential system
First, forgive me for being such a novice, but I am hoping to get some help regarding setting up a multi-zone HVAC system.
Currently my house has a Dual Zone split between the upstairs and downstairs but I am trying to add two additional zones. The upstairs is about 1,000 sq ft and the system seems to work fine in that area, the downstairs however is impossible to properly heat or cool. The downstairs is about 2,700sq ft and for an easy description is divided into a north section (bedrooms) about 800sq ft a middle section (kitchen/living) about 1,000 sq ft and a south section (master bed/bath) about 900 sq ft, currently the air return and downstairs thermostat are in the south section.
Issue: Because of the way the system was designed it seems impossible to heat or cool the downstairs to a comfortable temperature for everyone. During the winter the North section becomes an freezer, the middle is somewhat cool and the south is an appropriate temperature, however if we adjust the thermostat to heat the North section of the house the other two rooms become to hot, during the summer the opposite situation occurs.
Plan: we would like to be able to divide the downstairs into 3 zones, I have been reading about numerous systems that are designed to do just this, however when talking to an HVAC professional they said it was not possible because residential systems are not built to be split because of back pressure.
Any help, feedback or ideas would be greatly appreciated.
Zoned systems in large residential applications are a pretty common thing. You could be getting into a costly investment though, so I recommend talking to some other contractors and find one that will do the job right.
The issues you are having is a common one and is primarily due to the fact many HVAC contractors often are challenged in the proper design and installation of the duct work. Add the complexities of duct zoning and it can become a night mare. You will want several good references before hiring one.
Originally Posted by jmrpaint
One alternative are systems that have multiple small air handlers connected to a single outdoor unit. Each of these indoor units is a separate zone and acts as a stand alone system with its own temp setting and such and will respond to the heating and cooling loads of the zone it is in. the other zones are not influenced by what happens in any particular zone. You can have up to eight of these air handlers connected to the outdoor unit. And the more you have the more efficient the system becomes.
These systems are known as VRV/VRF for Variable Refrigerant Volume/Flow and are offered by Daikin, Mitsubishi and Sanyo. This is what what is used around the rest of the world where energy costs are much higher than here in the US.
It is a fully communicating system and variable in the amount of heat/cool that delivered.
Zoning systems work great only when the design is correct. I am assuming you have a 5 ton system. I have done plenty of zone systems, the largest in a residence was a design load 21 tons, installed tonnage 12 . The key to proper zoning is load calculations for individual rooms, the zoning tracking the solar load from east to west and the most important great duct design. I am not a big fan of flexduct. The job mentioned above was 80% spiral pipe. Friction loss adds up quickly, and most residential furnaces only have blowers which max out at 0.5" of static. With that being said, long duct runs eat up the fans capability to deliver the air needed for each zone.
It could be done properly if you had full access to duct work and enough room in the area the equipment is located. As mentioned you would need a contractor skilled in zoning to get it right.
Might be possible to get some recommendations for a contractor through a zone mfg. Co.
EWC zone controls
Arzel zone controls
are a couple of good companies.
There is still another, single outdoor unit with multiple indoor unit manufacturer that was not mentioned; Fujitsu. You can look at the Hybrid Flex System, it can have up to 8 indoor units, with 1 outdoor unit.
I have not installed the new "Flex" systems, but have installed up to 3 indoor units/1 outdoor unit using the "Multi-Zone" products. Just FYI
If I understand your post, are you wanting to use existing equipment and zone it? or will you be changing the existing based on heat gain/loss calculations to include the 2 additional zones?
This summer I replaced to systems in my home. I removeda 12 seer,4t w/80% 125k btu furnace downstairs and a 12 seer 2t w/ 80% 40kbtu furnace upstairs. I installed an 18 seer 5t 2 stg heatpump w/ 95% 100k btu 2 stg variable speed blower duel fuel system and a honeywell communicating Envirozone 3- zone panel w/ an additional module TAZ4 for my 4th zone. It gives me 3 zones downstairs and one upstairs. Additionalyl, I installed a IAQ stat for zone 1, an EAC and Steam humidifier. Could not have asked for better comfort. Cannot accurately determine cost savings yet, as this summer we had a grand daughter doing her and her fiancee's laundry at out house with electric dyer.
The key was planning the loads and ducting. A good idea is to have the system designed by a professional, that has experience with zoning. I have installed Carrier Comfort II , EWC bmplus and honeywell zone kits. All have their advantages/disadvantages but should be used based on the CUSTOMER's needs not because I only sell brand "A". The same for equipment choice, brands are not nearly as relevant as installation.
Many choices, many opinions, just thought Id put in my two cent$. Good luck
Thanks for that Wayne. Fujitsu makes very efficient systems so they should always be considered.
Originally Posted by thrashme
To achieve comfort you need supply to match loss, right?
First step, energy audit including room by room load calc and airflow. This will give current supply and loss.
Next, can loss be reduced to match supply? Can supply be increased? Can't get these answers without step 1, right?
Once you have a clear picture of current conditions you can model improvements and see if they will solve deficiencies.
Which makes more sense to you?
- turning your thermostat back and being uncomfortable. Maybe saving 5-10%
- leaving your thermostat where everyone is comfortable. Saving 30-70%
DO THE NUMBERS! Step on a HOMESCALE.
What is comfort? Well, it AIN'T just TEMPERATURE!
Energy Obese? An audit is the next step - go to BPI.org
, or RESNET
, and find an auditor near you.