How to wire for a Fan Break?

tommygags

Hi.  Can you please explain to me how to wire my thermostat for a fan break? I have forced air heat and when the system first turns on the air that comes out is cold. I was told a fan break would delay the fan to turn on to minimize the time of cold air being blown until the boiler heats the water. 

I have a navien ncb240 and an ecobee thermostat. Boiler is on first floor and air handler is on 2nd floor. The navien produces the hot water for the forced air heating

Or would it just be better to increase the speed on my recirculating pump instead? It's currently on the lowest speed. 

Thanks!

ScottSecor

I'm a little confused. You mention forced air heat, a Navien combi boiler and a air handler. I have never heard of the term fan break, probably because we don't install hot air furnaces (or I'm old school). If I understand correctly, your Navien unit produces all the heat (and dhw) for the house.

Assuming I'm correct, I would suggest a reverse acting aquastat for the air handler. This would not allow the air handler to blow cold air. You would set the aquastat say for 120 degrees and the blower would only operate once the heating coil reached this temperature. This is a simple (old school) concept that we've seen many times. I must admit that there may be something much better out there today for your system.

tommygags

Thank you! You are correct in your assumptions, the navien produces the hot water for dhw and the for the forced air heat. 

I'll look into that aquastat to see if it's worth the hassle to install. 

hot_rod

maybe it’s the cold duct work that the warmed air is traveling thru?  Most coils have a thermal fan switch that turns on the fan when it reaches a temperature. You might get a higher temperature fan switch, but you may still get a short blast of cold air?

STEVEusaPA

Is there a time delay on the air handler that you can increase to delay fan on until the temperature gets hotter?

tommygags

hot_rod said:

maybe it’s the cold duct work that the warmed air is traveling thru?  Most coils have a thermal fan switch that turns on the fan when it reaches a temperature. You might get a higher temperature fan switch, but you may still get a short blast of cold air?

Thanks! The fan kicks on as soon as the thermostat calls for heat and the cold air is at least for 30 seconds, which makes me think it's not just the cold ducts?

tommygags

STEVEusaPA said:

Is there a time delay on the air handler that you can increase to delay fan on until the temperature gets hotter?

Thanks. I'm not sure to be honest, would that be easy for me to identify?

EBEBRATT-Ed

Probably the simple fix is what @ScottSecor mentioned a Honewell aquastat strapped on the return line from the air handler model #L6006C from Supply House.com.

You wire this control to "make" on a temperature rise. Set the temperature about 115 degrees with a 10 degree differential (you can experiment for the best setting). This mounts on the outside of the pipe so you don't have to drain anything.

If you could post a picture of the air handler wiring we may be able to help more

tommygags

EBEBRATT-Ed said:

Probably the simple fix is what @ScottSecor mentioned a Honewell aquastat strapped on the return line from the air handler model #L6006C from Supply House.com. You wire this control to "make" on a temperature rise. Set the temperature about 115 degrees with a 10 degree differential (you can experiment for the best setting). This mounts on the outside of the pipe so you don't have to drain anything. If you could post a picture of the air handler wiring we may be able to help more

Thanks for providing the actual model number!  I am curious why this would be installed on the return line and not the supply line. Is this to ensure the water is the temperature I want it after it goes through the handler?

I'll try to get a picture of the wiring today. 

EBEBRATT-Ed

@tommygags

If you don't want the fan to blow cold air you want to "prove" the coil is hot before you start the fan. So you put the control on the return line

mattmia2

Does this air handler also do cooling? If the thermostat is controlling the blower in the air handler you have to make sure the aquastat only operates on a heat call, that the blower comes on directly from the thermostat on a cooling call from y or g.

(or set the thermostat to not make a fan call on a heat call and run the fan for the heat call only off of the aquastat).

tommygags

Hope these pictures help, @EBEBRATT-Ed

Thanks @mattmia2, this is for air conditioning as well. 

tommygags

Just wanted to check if you saw anything in the writing, @EBEBRATT-Ed. Thanks!

jhewings

Following up on @STEVEusaPA comment...Those 2 black boxes with red time delay potentiometers. They must be BDR and TDR. I would try to increase the time delay of the BDR, which is the one mounted to the chassis and facing out.

tommygags

Thanks @jhewings! I tried the one you mentioned on the chassis and it didn't do anything. I changed the red dial on the other one and it delayed the fan! Any issues with using this device? Will this also delay the fan for cooling? Any issues with me setting it to a minute? Thanks!

mattmia2

You should check when it is in cooling mode, but it should be wired so it doesn't.

tommygags

Awesome, thanks for confirming @mattmia2! Thanks for the help everyone!  Just curious, what the other time delay device controls?

mattmia2

Either the delay before the blower shuts off after a heat call or delay before the blower shuts off after a cooling call.