Steam coil sound

Dennis Kunkle

We have an overhead air handler in a seldom used large room that runs when, thru the computer schedule, it is needed. Because the air handler is located at an outdoor fire escape that can be very cold, it was programmed to have its steam coil valve at 100% when the unit is not running. At those times, its steam trap is very hot and functioning correctly, we believe. When the unit is scheduled to run and I go in to check the unit, the steam valve usually settles in at about 50% in fairly cold weather. The steam trap is always just warm. I can easily keep my hand on it. Does this seem correct? And when the unit is running, there is a noticeable tinkly, maybe metalic, constant sound. It's not anything rubbing like a fan blade hitting something. It's too quiet and irregular. I'm thinking steam hitting water in the coil? Is the just-warm trap a clue? The 50% open valve can't be the issue; we have VAVs elsewhere in the building with modulating steam valves with no probs. At times, the sound can be heard in the room and that's the problem. So what's the sound? It's not there when the unit is not running and the trap is hot.  

Jamie Hall

It could very well be

operating correctly; at 50% it is likely that less steam is getting in than can be condensed, and thus all the trap will ever see is warm condensate.



The tinkling sound could be almost anything -- possibly water dripping, but it is also possible that it is an expansion sound of some kind.  Does this thing have fins?  They often ring just a little bit.  Can be very exasperating to find, never mind fix!  And I have no suggestions other than listening carefully... or ear plugs!

Dennis Kunkle

OK....

....that's encouraging. We were hoping that. This is not a violent sound like steam slamming into water. We'll take a look at the coil again and investigate. Thanks.

Dennis Kunkle

The latest is....

....this: This AM, I set the computer to run the unit. Now at first, because the steam valve is at 100%, the unit does not make any sounds. After about 10 minutes, the room's zone temp is happy and the steam valve settles in at about 50% and the clicking sound begins. I took off the unit's cover on the steam coil side and sound is definitely coming from the aluminum finned coils. The coil at the top is warm, at the middle less warm and at the bottom, practically cold. So that's why the F&T trap is just warm to the touch. For fun, I over-rode the 10% outside air command to 0%. There's less clicking, but it's still there. It almost sounds to me like the coil is too big? For some background, this unit is 4 years old, but this is the first winter that we've used it for heating this room. Despite my explanations to the engineer, after the renovation, that room still had its old radiators hooked up to a stat in the room. But if we used the new unit to heat the room and turned down the stat for the radiators, the foyer and rest rooms (not fed by the air handler) would be ice cold. Now there is a remedy for that issue, but that explains why this sound is a new problem; we hadn't been using the unit for heat. We plan to turn off all of the radiators in the big room and then relocate the stat in the foyer. Right now we have half of the radiators turned off in the room. So does my "the coil is oversized" theory hold an water, so to speak?

Charlie from wmass

yes it does

can you adjust air flow? Rather then speeding up the steam, try slowing down the air so the condensate is a bit warmer as it gets near the trap.

Dennis Kunkle

Looking at the computer screen for that unit......

........(Metasys), there's nothing that I can do about the air flow. I see that the mixed air damper output is at 0%. I'm not quite sure what that refers to. Outside air? There's no relief damper.

Charlie from wmass

can the fan motor

be physically changed for a lower speed? Some things require actually mechanical changes.

Dennis Kunkle

We did that....

......at a blower coil elsewhere due to the air flow being so fast that the chilled water coil was not condensating. It was blowing condensate on to the fan. For that fix, we changed out the sheave for one twice the size. The coil immediately produced condensate that flowed out of the unit nicely. Nothing was flowing out before. But that was just basement storage at the museum. This is a large meeting room and I'd be needing engineering assistance to do that. IMO, less CFMs wouldn't hurt. That room can go from 58 degrees to 70 in less than ten minutes. Can too much air flow create the noise we have thru the low temp of the steam coil?

Charlie from wmass

Condensating is not occuring

same issue different size of the coil. It is happening inside the coil instead of outside.

Dennis Kunkle

To prove this......

.......How could I temporarily induce less air flow? The return is an opening on the top of the air handler. (It's not directly connected to the return vent in the room.) Lay some 2x4s across and constrict the air flow?

Charlie from wmass

only time I will say this advice

ise strips of duct tape. I hate to say use duct tape, but it will work this time.