Basement Fan Coil - Blows Cold Air with L6006C

NTL1991

Hello,

I'm trying to get a small basement workshop fan coil working right. It's a Beacon Morris HB-18 (13K BTU) hot water coil, and I've got the fan motor switched with a Honeywell L6006C1018 that's strapped to the supply pipe immediately before the fan coil.

The problem is that once the thermostat is satisfied, the fan coil blows cold air for about 5 to 10 minutes after the zone valve is closed. I've tried adjusting the temperature and diff to no avail.

Is there a better way to control this fan coil? The fan coil doesn't have any tappings, so I'm stuck with a strap-on control for now, unless there's a better way. Would an electronic control keep tighter control of the switching of the fan motor?

Thanks,
Nick

njtommy

You can turn the temperature setting up on the control or you can install a relay that turns the fan on and off when the t-stat calls for heat and turns off when the t-stat is satisfied.

NTL1991

If I used juat a relay, the fan would come on even if the supply water to the coil wasn't sufficiently hot, which would still give me cold air, right?

Unless I still controlled the fan with the L6006, but used a relay to provide power to the L6006, which would prevent the fan from running until the low limit of the L6006 was reached, and when the thermostat was closed, it would close the relay, removing power to the L6006 and, in turn, the fan motor. Right?

Thanks,
Nick

Bob Bona_4

When you pipe a fan coil, you put a T on the return piping to accept an immersion well. The aquastat goes there. Coil gets hot then fan comes on. Works ok in garages, but you still get the fan overrun until the piping cools.

You can control it better with a Honeywell fan center and a Taco HAFC201 control. This will give you adjustable delay on fan "on" and immediate off after call. You wouldn't use the aquastat anymore.

NTL1991

Excellent info, Thanks Bob.

I would like to pipe a T in for a proper immersion well, and after looking at the spec sheet for that control, it looks like it would be perfect for what I'm after.

Would a HAFC101 work as long as I installed an aquastat? I wouldn't need the pipe exercise, freeze protection and fan-on delay.

I think part of my problem is also the fact that the L6006 is installed on the supply instead of the return.

Thanks again,
Nick

Bob Bona_4

Yes, the 6006 on the supply only exaberates the problem. But, if you use the HAFC201, with the fan on delay, you eliminate the aquastat and the lack of real time control.. Use the longest delay- I think it was 4 minutes? Let the coil get good and hot. Then, when the call is over, the fan goes off immediately. It's only a few bucks more than the HAFC101.

I swap out the typical 2x4 j box on the unit heater and put on a 4x4 box, and mount the Honeywell fan center there.

NTL1991

Thanks again, Bob.

I'm wondering if 4 minutes would be enough to get the boiler up to temperature. It's an older (10 years) Burnham Oil-Fired with a Boilermate. It's a cold-starter.

But then again, the boiler doesn't often see room temperature during the winter.

Nick

Bob Bona_4

The whole HAFC thing was borne out of a job I wanted to flush out the nasty glycol and protect the system from freezeups. Included was a garage Modine. Necessity is the mother of invention