Central Vac Runs Randomly

[redpoint5]

Central vac turns on randomly, but mostly just stays off if it's off, or stays on if it's on.

There is a 24v low current transformer that energizes a sense circuit at each outlet of the central vac. Plugging in to the outlet shorts the circuit causing voltage to drop to near 0v, triggering the vac to turn on.

In my mind, the 24v holds open a normally closed SPST relay, preventing the vac from running. Shorting the 24v allows the relay to close and turns the vac on.

The simple stinkin board costs $145. I'm thinking either the relay, or the transformer is the culprit (there isn't much else on the board). How do I test this, or should I just throw a $5 relay at it and see if that fixes it?



This dumb part should be like $20. Also, the failure mode shouldn't be "run". Also, it shouldn't fail.

[oil pan 4]

Sounds like it's designed to fail.
I would start at the relay. If the 24v transformer died, it wouldn't come back.

[redpoint5]

Measured 21.5v AC across the open terminals that trigger the vac to turn on. It's rated at 24v, so I'm not sure if that indicates a problem with the transformer or not. It's 90% of rated output. If my theory is right that the voltage holds open the relay, it may simply be the voltage drop that occurs holding that relay open (dumb design if that's actually how it operates).

A good design would have the relay normally open, with a voltage applied causing it to close and turn on the vac. In other words, component failure should cause the vac to remain off, not switch on.

The only reason I can think of to have a component failure trigger the vac to turn on is that there is a manual switch for the vacuum. If component failure occurs, I can still switch the vac off manually, and switch it on as needed.

My worst fear would be taking a week vacation somewhere and having an 800 watt vacuum running continuously the whole time. Would probably burn up the vac too.

Anyhow, I know nothing about vac design and could come up with a better product in my sleep. Don't know how these companies that have 1 job can suck so bad. My products would suck very good.

[freebeard]

My worst fear would be taking a week vacation somewhere and having an 800 watt vacuum running continuously the whole time. Would probably burn up the vac too.

I would assume it's on a fused circuit? Break the circuit and fear not.

[redpoint5]

Yeah, on a mostly dedicated circuit.

When I first started diagnosing the issue a couple years ago, I had it on a smart switch and would just turn it on as needed. I tore apart every vacuum outlet until I figured out how the thing works, and discovered it wasn't a short in the wiring causing it to come on.

[redpoint5]

Whelp, I found a $42 board and $10 shipping. I guess I'm willing to pay $52 for a whole board instead of mucking around with ordering a relay, desoldering the old one, soldering in the new one, and possibly still having a malfunctioning control board.

Relay would have cost me $10; $2 for the part, $8 to ship.

Funny how annoyed I get having to open an app on my phone to start the vacuum rather than just push the switch on the handle.

The house also has a hidden vacuum port that triggers the central vac to turn on when you open it. It's meant to sweep the kitchen, open the inlet, and have everything disappear. Would be nice to have that going again.

[freebeard]

This is a feature that was introduced in Fuller's 1947 Dymaxion house.

[redpoint5]

Originally Posted by freebeard

This is a feature that was introduced in Fuller's 1947 Dymaxion house.

I'm on the fence about central vac. If you've got it already, then I'm for it. Nice having a nearly silent vacuuming experience. Nice having a lighter weight carpet attachment.

When your system sucks because it stopped sucking and you have to discover that monkeys made an improper joint in the attic, that sucks. When the thing turns on randomly because the controller board was made by monkeys, that sucks. When your garage port doesn't work because monkeys didn't spend the extra 15 minutes to complete the installation, that sucks. Otherwise, it's great!

I cut out an access in the drywall under the stairs primarily to facilitate home theater installation. Today I needed to access the area again (adding 4 ATMOS speakers), and decided to clean up that space. Of course, that's where the builders disposed of everything from bent nails, bits of drywall, various trash, and sunflower seed shells. Used the central vac to clean it up. Kids might like having that secret space to play in, so I might as well get it cleaned up.

Turns out ideal speaker placement involves math, not just putting them anywhere. Tonight I plan to do the math, trace out where they'll go, and run the speaker wires. Bought the speakers 2 years ago on a sale, so I'm just now getting A Round Tuit. Best guess is I've got two grand into my home theater, and countless hours, and some extra holes in the drywall from measuring once and drilling twice.

Other projects this weekend was reinstalling a gutter downspout that blew away in the wind because monkeys installed it. Putting up 2 sections of fencing that blew down because monkeys installed it. Learning audio theory from Youtube.

[freebeard]

Fuller's system was powered by air passing over the top. It would have been engineered like a car and factory built.

Kids might like having that secret space to play in, so I might as well get it cleaned up.

I was going to suggest a bolt hole/safe room, bu it might be hard to get them to come out and clean their room.

I had to swap microSD cards in the Raspberry Pi because reasons, and now running Ubuntu instead of Raspberry OS, the ads are back in Ecomodder and Youtube.

OTOH the spell checker is working again.

[redpoint5]

Got the new control board, installed it, and it didn't work. Vacuum ran continuously with nothing plugged in. As usual, when I hit any setback at all, I walk away and start a new project.

A week later, I get my multimeter out, really scrutinize how the whole thing works, then start taking voltage measurements to see if they agree with my expectations. For some reason it took me that long to realize I could keep the vacuum motor disconnected as I tested the relay.

Shorting between the 2 spade terminals, I could hear the relay click and measure 120v AC at the motor terminals. It did this reliably.

I connected the motor and reassembled everything, and it's working perfectly. Strangely, the original unit is passing my new testing methodology too.

The Russian saying is that problems avoid those who are capable to solve them. Now that I know precisely how the whole thing works, the gremlins have moved on.