Automate fan speed control

leafpeeper

I installed a boiler reset control last year and I'm happy with it's results. Now, also for heating operation I'm thinking about creating a control system to change the fan speed of the air handler, based on need. On cold days when the boiler is making 180-ish degree water, the control will run the fan on a high speed. On warmer days when the boiler is making 145-ish degree water, it'll run the fan on a lower speed. Just two speeds, I'd be happy with that.

The air handler is made by First Company (VHBXB-HW) and uses a ECM motor with fan speed settings that are adjusted by moving a small jumper on the pin-outs of the circuit board. I already have an idea on the control to change the fan speed using a simple 2 relay temperature controller, by monitoring outside air temperature.

Here's my question... When the temperature controller decides to change the fan speed, what issues might come about if it does so when the fan is already in operation? Is this a potential damage threat to the air handler's fan control circuit? How/what do I do to easily make the fan speed controller change speed only when the fan is >not< in operation?

Thanks in advance for any suggestions.

njtommy

I really wish Taco's hydronic fan controller was able to Run multiable fan speeds from supply water temp.

I use a Honeywell strap on style aqua stat to control my fan speed for heating. Part # type L6006C

Jamie Hall

I'd be a little cautious about changing the fan speed when it is powered -- unless I were really familiar with the circuitry and the motor and all. However, could you rig up a relay and a time delay system so that when a fan speed change was commanded, the system would power off long enough for the fan to stop, then change the relays which are in place of that movable jumper and then power it back up? Would take a bit of circuitry...

John Mills_5

Sounds like an X13 motor. 5 taps, you put 24v into the tap you want. Far as I know you can switch when on just don't power 2 taps at once. Confirm brand and maybe we can find out for sure.

njtommy

The fan handler control I have yet to see, but would like to play around with it. Just found out about them from Rich.

https://www.fanhandler.com

hvacfreak2

John Mills said:

Sounds like an X13 motor. 5 taps, you put 24v into the tap you want. Far as I know you can switch when on just don't power 2 taps at once. Confirm brand and maybe we can find out for sure.

Agree. During normal operation ECM motors are switched to different speed ranges between circulation and heat / cool speeds .

leafpeeper

It's a Genteq 1/2 HP ECM motor. Can't really get at it to see the motor tag info on it. It doesn't have a green housing, so I'm thinking it's not an X13 unit. There are 4 heat tap settings on the board (see photo).

That FanHandler ecMModulator looks interesting, anyone know how much they go for?

njtommy

On a side note when increasing fan speed for heat you may not want the highest speed. Higher fan speeds/ higher cfm can make the house feel colder do to moving the air to fast and over pressurizing the house.

In my experience with hydroair low cfm and warm supply air temp (nothing lower the 100f supply or higher then 115) really makes the house feel comfortable.

What kind of boiler are you using? And do you really need the water set point at 180?

leafpeeper

I agree with you on the higher fan speeds, the draft can make it feel cooler than it is. In part, that is why I'm interested in slowing down the fan when the boiler reset control calls for lower water temps.

The boiler is a 10 year old Burnham Series 2 (basic, non-condencing & was free ). The 180 degree water temp would only happen when the boiler reset sees outside temps well below zero, which wouldn't happen but on the very coldest days in Jan-Feb.

So, 100-115 degree air temp huh? Can't recall, but I'll have to check and see what I'm getting.

njtommy

Too hot of supply air drys the house out and causes a lot of static along with shorter run times. Too cool of supply air can make the house feel cooler then it is and cause excessive run times.

SWEI

We do this on DDC systems pretty regularly using RIB RIBMN24Q2C boards for 0-10V control. First relay turns fan on and off, second one chooses between two taps. The motors typically have four, but duct sizing almost always narrows it down to two viable options for the system.

ratio

I just came across this while perusing the ICM catalog. I think I might just have to try one out.