Can you say suck suck suck suck

[slctech]

100% MAU Unit

Dunno why so do not ask, but outdoor air damper proving switch by-passed with a ziptie.

Building not used for a few years and now new project being started and need heat. One of our new guys thinks something wrong with VFD since 50hp blower motor running waaaaay too slow, VFD driven by duct static. So new tech decides to switch over to bypass!

In addition to the loud scream of four slipping belts in unison coming to life he hears a deafening SLAM...he shuts everything off and I get the panic radio call!

I rush a few miles to this building and here is what I found....dohhhhhhhhhhhh! LMAO!! Looks small but that duct is 10' by 3'.

I think someone a few years back forced the dampers open since they were jamming and ziptied the proving switch. We since had that decent earthquake back in March and I wonder if the dampers did not work themselves closed from the jigglin of the earth? Either case that motor proved she could suck a golf ball through a hose if she wanted!

[BBeerme]

D'oh !!

[ehsx]

Rarely find dampers stroked and operating properly, especially on the coast.

At least looks like a fairly easy fix.

[71CHOPS]

Thats funny, I bet he about crapped his pants when that thing collapsed! Lol!

[BBeerme]

I can tell a funny story. Actually, it wasn't the least bit funny. If I was prone to a heart attack, it would've happened during this experience . . .

Probably only ~3 years into the trade. Contractor working at a large 'installation'. Barely understood pneumatics at the time. LARGE ducting. As in you can stand up in the duct work. Supply fan in a room by itself. Outside air dampers and return dampers in another 'small' room by themselves; dampers each maybe ten feet tall and 6-8 feet wide. Probably a 100 hp supply fan, can't remember for sure. That's the setup.

Here's what happened . . .

Can't remember the call, probably something along the lines of building pressure not proper or simply not economizing proper. If memory serves, the OA dampers were fully open, and the return air dampers were fully closed. Long story short, I disconnected this one little teeny tiny 1/4" tube from the actuator for the OA dampers. They slammed shut.

Now picture this:

A 100 hp supply fan sucking against 'nothing'.

When those dampers slammed shut, obviously, I was standing right in front of them, because that's where the actuator is. Those OA dampers heaved and ho'ed. In that nano second, I could see all of those opposed blade dampers cutting loose and cutting me to shreds.

I saw myself in a very painful death.

I can't say I saw my life flash before me, I only saw me in pieces.

A second or two later I put the that little teeny tiny hose back on the actuator.

Since then, I have had great respect for the simplest of things in this trade.

[R600a]

That there blower could suck the chrome off a bumper!

Sent from the Okie state usin Tapatalk

[2sac]

Dat dere is what dey call oil canning

[Artrose]

I can tell a funny story. Actually, it wasn't the least bit funny. If I was prone to a heart attack, it would've happened during this experience . . .

Probably only ~3 years into the trade. Contractor working at a large 'installation'. Barely understood pneumatics at the time. LARGE ducting. As in you can stand up in the duct work. Supply fan in a room by itself. Outside air dampers and return dampers in another 'small' room by themselves; dampers each maybe ten feet tall and 6-8 feet wide. Probably a 100 hp supply fan, can't remember for sure. That's the setup.

Here's what happened . . .

Can't remember the call, probably something along the lines of building pressure not proper or simply not economizing proper. If memory serves, the OA dampers were fully open, and the return air dampers were fully closed. Long story short, I disconnected this one little teeny tiny 1/4" tube from the actuator for the OA dampers. They slammed shut.

Now picture this:

A 100 hp supply fan sucking against 'nothing'.

When those dampers slammed shut, obviously, I was standing right in front of them, because that's where the actuator is. Those OA dampers heaved and ho'ed. In that nano second, I could see all of those opposed blade dampers cutting loose and cutting me to shreds.

I saw myself in a very painful death.

I can't say I saw my life flash before me, I only saw me in pieces.

A second or two later I put the that little teeny tiny hose back on the actuator.

Since then, I have had great respect for the simplest of things in this trade.

I did a similar, almost major uh oh when I was a youngster, on a smaller constant volume air handler. The one set of pneumatically actuated return dampers was malfunctioning. No outside air. The damper was about 4x8, and mounted in the mechanical room wall to bring return air directly to the air handler from the conditioned office space.

I intended to check the function of the pneumatic damper actuator first, and the first thing I did was remove the branch line from the actuator. And, of course, just my luck, the damper closed almost immediately. Every particle of dust, sand, dirt, mouse snot, you name it, was immediately sucked through every crack and crevasse in and around that set of rapidly bowing dampers. I thought the air handler was trying to jump off the pad.

Luckily, I immediately put the branch line back on the actuator and the damper slowly opened before the wall caved in.
Lesson learned. Never again.

[BBeerme]

I did forget to say how slow the dampers opened up after re-attaching the tubing, it was like an eternity.

Mouse snot. That's s funny one!

I did a similar, almost major uh oh when I was a youngster, on a smaller constant volume air handler. The one set of pneumatically actuated return dampers was malfunctioning. No outside air. The damper was about 4x8, and mounted in the mechanical room wall to bring return air directly to the air handler from the conditioned office space.

I intended to check the function of the pneumatic damper actuator first, and the first thing I did was remove the branch line from the actuator. And, of course, just my luck, the damper closed almost immediately. Every particle of dust, sand, dirt, mouse snot, you name it, was immediately sucked through every crack and crevasse in and around that set of rapidly bowing dampers. I thought the air handler was trying to jump off the pad.

Luckily, I immediately put the branch line back on the actuator and the damper slowly opened before the wall caved in.
Lesson learned. Never again.

[pctech]

what happened to it in the first place that the proving switches are bypassed i would have looked in to it to see if it could be fixed properly

[slctech]

what happened to it in the first place that the proving switches are bypassed i would have looked in to it to see if it could be fixed properly

Dampers are seized, someone forced them open, disabled the pneumatic actuator, and zip-tied the damper proving switch. God only knows who and when.

Dormant building for years. Finally for what ever reason a project is started up there. Building has probably 12 VAV boxes, all calling for heat. SCADA department starts up system and notice VFD is barely driving. SCADA department sends work order out. New tech gets request and shows up at this building. In his defense, one of hundreds out here, so no tribal knowledge or experience with this one. He verified that motor is crawling. For whatever reason, new tech, flips switch from AUTO to HAND for local system control, and then flips the switch from VFD to BYPASS, and the racing sqeeeeeealllllll of belts screaming and the KAAAAAAAAAABAAAMMMMMMM!! I guess dust and debris kicked up like crazy and had all settled by the time I got there.

I am thinking that since this building experienced an explosion, reason it was off line for many years, and a major earthquake, both may contributed to loosening up the jammed dampers and they worked themselves closed.

I am not blaming the new tech, he made a mistake, that frankly anyone could have made, even myself. But this would have never had happened, if someone did not zip-tie off an interlock, shameful.

[Roof Monkey]

Reminds me of something 35 years ago when I was younger & dumber. I was in a warehouse that was too hot. The warehouse had one very large roof exhaust fan in the center of the building. The fan was supposedly running, but the damper was closed tight. Young me grabs a lift, goes up under the damper, and tried to push them open. They didn't budge, so I took a harder swing at the blades, and they popped open with a bang. Of course, my hand was still moving upward, and I just missed the spinning fan wheel by an inch. It also sucked my hat right off my head, and I was lucky I didn't fall off the lift.

[Poodle Head Mikey]

A free standing Department Store. I worked on one of their buildings. Two Centravacs in the penthouse along with a 150+HP blower. The 'return plenum' was a concrete block room 25' square and 15' high. With a Huge Friggin WALL of outside air dampers.

During construction the workers were cold or something in the penthouse - so they pulled the OA and the RA dampers tightly closed and wired them to stay closed to keep out the wind.

On start-up day the blower came up to speed and the pressure difference pulled the top 4-5 courses of 12" block walls right into that plenum room. It was pretty darned amazing. <g>

PHM
---------

100% MAU Unit

Dunno why so do not ask, but outdoor air damper proving switch by-passed with a ziptie.

Building not used for a few years and now new project being started and need heat. One of our new guys thinks something wrong with VFD since 50hp blower motor running waaaaay too slow, VFD driven by duct static. So new tech decides to switch over to bypass!

In addition to the loud scream of four slipping belts in unison coming to life he hears a deafening SLAM...he shuts everything off and I get the panic radio call!

I rush a few miles to this building and here is what I found....dohhhhhhhhhhhh! LMAO!! Looks small but that duct is 10' by 3'.

I think someone a few years back forced the dampers open since they were jamming and ziptied the proving switch. We since had that decent earthquake back in March and I wonder if the dampers did not work themselves closed from the jigglin of the earth? Either case that motor proved she could suck a golf ball through a hose if she wanted!

[71CHOPS]

I was working on a 1,000 ton chiller one time.....forget what I was doing, prolly trying to get the head pressure up or something.

Decided to pinch off the discharge of the 125HP pump. Started slightly closing the butterfly valve, then all of a sudden, BAM!! It slammed shut. The braided stainless vibration isolator blew up like a balloon!! I about sh!t my pants, and almost died getting off the ladder to the disconnect!! It was late at night, and I was alone...never told anyone about that one!! LOL!!