DPelletier
Well-known member
- Joined
- Oct 23, 2012
- Messages
- 170
Flex-Duct Sizing/Installation
- Thread starter Social_Joe
- Start date
True enough. Nice work; no insult intended. 
DPelletier
Well-known member
- Joined
- Oct 23, 2012
- Messages
- 170
Joe, e-mail with layout sent.
Dave
Dave
OccupantRJ
Well-known member
To contribute to this thread, I went with round snap- together duct for my shop system, as I used it after a flood situation once, and was familiar with it. Easy to obtain and assemble, and fairly inexpensive from Noland Company. My unit is a 2.5 ton heat pump with 1000 to 1100 cfm IIRC. It was used, and had 14 inch takeoffs, so I went with that, stepping down later to 12, 10, and finally 8", in succession. There are ten 6" short runs of flex outward and down from the main trunk, which is run through the shop attic, dumping downward into the room. Four are in the 14" section, and two each in the other sections, for a total of ten 4x 10 outlets The trunk will have sealing mastic, along with vapor barrier duct insulation wrap. I have a 2 foot long return duct from the room straight out the wall to the unit. Flex connectors were also used to reduce noise and vibrations from the unit into the metal of the ductwork. Am I anywhere close to having a decent distribution system here? I will try to post up pics later when I can.
pseudorealityx
Well-known member
DPelletier
Well-known member
- Joined
- Oct 23, 2012
- Messages
- 170
Yep, all the numbers work and the installation sounds well thought out; especially the sealer and wrap.
Dave
Dave
OccupantRJ
Well-known member
Thanks to both of you for your input.
OP
Social_Joe
Well-known member
Update:
I built the base and set the plenum in place as a mock up.
1.5" Conduit, with 5 runs of #6 two new dual pole breakers
Then a problem arose. One time prior the blower had acted odd and needed persuasion to start. This only happened once so I didn't think too much of it as the unit had sat and it happened at a quick turn off/on cycle. Well it started doing it all the time right after I got it moved and set up in the final location. Occasionaly if I spin the fan just right it'll catch the start impulse and go, otherwise it just sits there, moves an inch, pauses, moves an inch...
I have one of the high-efficiency GM (by Regal Beloit) X13 motors that are notorious for frying the thermistor in the integrated electronically commutated motor (ECM) control module on the back of the motor. After some tests, it was confirmed that was the issue. A new module is $280, a new motor with module attached is $550.... yeah for a 1/2 hp blower motor and it's not even variable speed.
I've ordered some 1 ohm 20amp thermistors and hopefully soldering a new one in solves the problem. If not, I'm going to backdate the AHU to the old style PSC 1/2HP 1075cfm motor along with installing a separate fan relay and capacitor (contained in the module for the ECM motor). $100 for the motor+$7 cap + $24 relay sure beats the other options.
That slowed down the duct process, but I did visit my local sheet-metal guy yesterday with my plans, a basic list, etc and he's working the numbers and promised me a quote the Monday after the holiday.
I built the base and set the plenum in place as a mock up.
1.5" Conduit, with 5 runs of #6 two new dual pole breakers
Then a problem arose. One time prior the blower had acted odd and needed persuasion to start. This only happened once so I didn't think too much of it as the unit had sat and it happened at a quick turn off/on cycle. Well it started doing it all the time right after I got it moved and set up in the final location. Occasionaly if I spin the fan just right it'll catch the start impulse and go, otherwise it just sits there, moves an inch, pauses, moves an inch...
I have one of the high-efficiency GM (by Regal Beloit) X13 motors that are notorious for frying the thermistor in the integrated electronically commutated motor (ECM) control module on the back of the motor. After some tests, it was confirmed that was the issue. A new module is $280, a new motor with module attached is $550.... yeah for a 1/2 hp blower motor and it's not even variable speed.
I've ordered some 1 ohm 20amp thermistors and hopefully soldering a new one in solves the problem. If not, I'm going to backdate the AHU to the old style PSC 1/2HP 1075cfm motor along with installing a separate fan relay and capacitor (contained in the module for the ECM motor). $100 for the motor+$7 cap + $24 relay sure beats the other options.
That slowed down the duct process, but I did visit my local sheet-metal guy yesterday with my plans, a basic list, etc and he's working the numbers and promised me a quote the Monday after the holiday.
OP
Social_Joe
Well-known member
Re: Need assistance sorting blower wiring
Ok... so... I ordered an AO Smith 1/2 HP 3 speed PSC motor to replace the failed ECM motor. I also ordered the run capacitor Grainger recommended for it as well as a Normally Closed / Normally Open Fan Relay to make it work. I've poured over countless explanations and diagrams, but I'm still not 100% sure of how to integrate all these things together with the AHU. I went with the NC/NO relay as opposed to a SPDT relay so that the fan will always get power when the heating coils are on (just an extra layer of safety). If you guys with the know how could look over the following and help me... I'd greatly appreciate.
New motor installed... sure looks nice.
Wiring diagram for motor. It's set for CCW which is correct for my AHU and I want to set the speed tap for medium (matching the old motor speed).
Current mess/status of the AHU. Yes I have a mounting bracket for the cap and will mount it to the case along with the relay. I'm wanting to use the 24V speed tap wire from the control board to trigger the relay. I've already connected the yellow feed wires together... and that's about as far as I've made it.
My motor
http://www.grainger.com/Grainger/ww...ch&Ntt=4KA37&N=0&GlobalSearch=true&sst=subset
The run cap
http://www.grainger.com/Grainger/ww...ch&Ntt=2MDV6&N=0&GlobalSearch=true&sst=subset
The SPNO/SPNC relay (it's actually a White-Rodgers... I have no idea what "Steveco" is)
http://www.grainger.com/Grainger/ww...ch&Ntt=1N185&N=0&GlobalSearch=true&sst=subset
Ok... so... I ordered an AO Smith 1/2 HP 3 speed PSC motor to replace the failed ECM motor. I also ordered the run capacitor Grainger recommended for it as well as a Normally Closed / Normally Open Fan Relay to make it work. I've poured over countless explanations and diagrams, but I'm still not 100% sure of how to integrate all these things together with the AHU. I went with the NC/NO relay as opposed to a SPDT relay so that the fan will always get power when the heating coils are on (just an extra layer of safety). If you guys with the know how could look over the following and help me... I'd greatly appreciate.
New motor installed... sure looks nice.
Wiring diagram for motor. It's set for CCW which is correct for my AHU and I want to set the speed tap for medium (matching the old motor speed).
Current mess/status of the AHU. Yes I have a mounting bracket for the cap and will mount it to the case along with the relay. I'm wanting to use the 24V speed tap wire from the control board to trigger the relay. I've already connected the yellow feed wires together... and that's about as far as I've made it.
My motor
http://www.grainger.com/Grainger/ww...ch&Ntt=4KA37&N=0&GlobalSearch=true&sst=subset
The run cap
http://www.grainger.com/Grainger/ww...ch&Ntt=2MDV6&N=0&GlobalSearch=true&sst=subset
The SPNO/SPNC relay (it's actually a White-Rodgers... I have no idea what "Steveco" is)
http://www.grainger.com/Grainger/ww...ch&Ntt=1N185&N=0&GlobalSearch=true&sst=subset
Last edited:
OP
Social_Joe
Well-known member
Thanks to the assistance/knowledge of my friend that services CNC Mills for a living (works with 3 phase 480 all day) and programs their controllers, the new motor is installed and working. That involved alot of text messages.
Yay... now back to ductwork.
Yay... now back to ductwork.
OP
Social_Joe
Well-known member
Yep, L1/L2 runs to a dual pole 60Amp and L3/L4 runs to a dual pole 30Amp just as you suggested. I used #6 for everything including the ground since I had enough to do it after moving the AHU from the other side of the shop to where it is now, within 12' of the panel.
Thanks again for the help with that issue.