any hvac guys here?

[jeff84]

ok so my hvac system was poorly designed. all the air gets dumped in 6 very short runs. there are also two much longer runs and guess what those rooms are always either hot or cold.


so I want to install booster fans in those two ducts.   I have read a little online about it.  I am getting some conflicting info.



some say you can wire the fans right to the board using the 120 eac or  hum connections.  well those are the only two I have open. some people say you need a relay or a relay and a fuse for each fan.  in order to get them to kick on and off with the main air handler.


so can I wire them right to the board?  and if I can can I wire them in parallel or series to just one of the open spots?  or should I put the boosters on separate circuits? 



if I am just totally wrong in how this is done someone stop me before I fry my board

[humanshield]

I have a gauge set and can replace my air handler and compressor outside....but I've never messed with booster fans.

My guy feeling would be that if you used relays you'd be fine. Not sure if the board could support that much more load directly though. And none of the HVAC forums will help because all they want to do is tell you to get a professional for anything beyond what size unit you need.

[niz76]

Like Humanshield stated, using relays would be the safest option. A fused connection even better.
In my ten years as a Maintenance Supervisor for large apartment complexes, HVAC was a huge part of my job. We didn't subcontract anything out so it was all on us (me).

I have often replaced expensive and complex boards with the older trusty mechanical contactors (use fuses!). Are these booster fans 110v? You could use the low voltage wires that activate the air handler to activate a contactor (switch) running one leg of the power supply (110v)...

Ask 10 HVAC guys for the solution to this issue and I'm sure you'll get 10 different answers! Did I mention to make sure everything is fused??

[niz76]

Just another quick note- something to check out; Many of these air handlers were shipped with the blower motor on 'Medium' speed. Some installers will switch the connectors over on the relay so that the blower motor is running in 'High speed', but some don't. Check your wiring diagram (usually located on the back side of the air handler cover once you get it off) and be sure that your blower motor is running at high speed!

The black wire running off the blower motor is usually the high speed wire but make sure to check out your diagram! In this diagram here, it's the wire that's running to "cool")

[niz76]

*DISCLAIMER*

Ok, I gotta add this; Please keep in mind that I am a 'get er done' kinda guy so while what I'm recommending may work just fine, and I've used these methods many times over the years with good results, it may not be the absolute most professional way to go about it. Apartment maintenance is kinda the "Wild West" so to speak. So, if someone a little more professional comes along like oldgeek with a better solution you may want to take his advice over mine. 

*DISCLAIMER OVER*

[humanshield]

Good to know there are numerous people here with HVAC knowledge to ask when members run into an HVAC issues

[tvnacman]

Well, I can say the booster fans are a band aid not a solution. I would look into balancing the air flow.

Starting with basics is the answer, how many tons is the system? How many CFM of air is it moving? What size is the duct and what is the static pressure?

Booster blowers will force more air to one area and steal it from another.

Fuse the fans!!!!!!!!

John

[jeff84]

yes stealing air from another area is what I want to do. the room closest to the unit in the winter will be 5-8 degrees warmer than the thermostat setting while the rooms I want to use the booster fans are consistently 5-8 degrees cooler than the thermostat setting.

and I already have booster fans and plenty of wire lying around.


my air handler is a single speed blower

[oldgeek]

jeff84

Slap them in using a 9340 style relay The coil is 24 volts (standard HVAC control voltage)

If you have a digital thermostat the green wire from it should have 24 volts in both heating and cooling mode, so you can use the green wire at the air handler along with the (C) common wire which is usually blue or brown to energize the relay for the boosters.

If the boosters are 110v use power from a recpt in the attic if there is one. You should also consider a couple dimmers inline to vary the motor speed if the motors you have will work with a dimmer.

[jeff84]

Pin # 1 - Connect the EAC-1

Pin # 3 - Connect to neutral terminal block on board AND neutral to fan

Pin # 2 - Connect to Black Wire (Hot) Coming into Furnace

Pin # 4 - Connect to Hot Wire out to Fan


ok so I have my wiring down. so I am assuming I need to just pull my 120 from the door switch so the relay is switched off with the rest of the unit. should the fuse be between the 120 input and the relay, or between the relay and the fan?

[jeff84]

the unit and ductwork is in the basement. can a single relay be used to switch on two fans assuming it is rated accordingly. THIS is the relay I will be using. each of the fans draw less than 1 amp

[jeff84]

ok I found the booster fan for dummies solution

link

[jeff84]

upon further research, in conjunction with the booster fans adding a few cold air returns in strategic places will greatly improve things.

now I live in a single story home that has a finished basement and an open stairway. so whoever set up the hvac system must have assumed that the big open stairwell would be all the return air needed. it is for the common area of the house. there are no return are vent anywhere.

in the basement there is no ceiling. one day I planned to install a drop ceiling but you know money. so simply cutting holes in the floor of the rooms that need more return air would make the private rooms not so private.

so I want to put in 3 RA vents on the wall near the ceiling on the main level. could I simply cut a hole in the drywall, install grate, and cut a hole in the floor inside of the wall directly under the installed grate? or would that compromise the integrity of the wall?


or do I just need to vent the rooms back to the common area and not directly to the basement where the air handler is located 

[jeff84]

also the bathroom is pretty much directly above the air handler and can be as much as 15 to 20 degrees difference than the thermostat setting. would reducing the diameter of that run help send more air down to the longer ones? this room has no return air but is always the coolest in the summer and warmest in the winter

[FrankenMech]

Your blower probably has all the airflow that is needed. Use the register dampers in existing registers to regulate airflow. If your registers do not have built-in dampers consider buying some that do. Unfortunately people will 'fiddle' with them.

Otherwise, -just put some duct damper valves in all of the ducts and use them to regulate flow as required.

Like these:
www.homedepot.com/p/6-in-Damper-D-6/100396929

Or these:
www.homedepot.com/p/SPEEDI-COLLAR-6-in-Take-Off-Start-Collar-with-Damper-for-HVAC-Duct-Work-Connections-SC-06D/202542804

Shut the dampers by half in those places with plenty of airflow and go from there. Restricting the airflow in short runs will force more air through the longer runs or runs with more bends. The advantage to duct dampers in the line is that they can be adjusted and even tightened so that people can't mess with them as easily.