Rattling conductors in EMT conduit

[brentm]

So I had a heat pump installed....

Long story short, the two phase wiring has some weird issues in EMT. When the compressor kicks on, it draws about 80 amps and the conductors rattle inside the EMT conduit briefly. Just on the initial start, then it drops down to around 10 amps. EMT runs from the panel, over the ceiling, and then pops down into the crawl...

Best I can research and I confirmed with the HVAC guys, that the conductors repel eachother magnetically at that high of amp draw which causes the brief moment of rattle.

Two techs came out; the first put in a "hard start" capacitor on the heat pump... didn't make much difference. The second was the manager and he validated my suspicion and we scratched our heads and he there wasn't much he could do. The installation looked good and it was just an artifact... pretty much told me to live with it.

The rattle is brief (about 1 second) but it's annoying as heck. I can hear it upstairs while I'm on my computer, and also very much when I'm working on the garage. The best way I can describe it, is the sound you hear on TV/movies when being "buzzed" in at a prison or a locked room for about 1 second in length.

I'm considering calling them tomorrow and asking them to fix it, which will likely involve pulling new conductors that are twisted. Unless any of you have a clever fix.. we already pulled the conductors tight/tested and again with slack in the conduit/tested. No difference..

So is my OCD in overdrive here or does it seem reasonable to ask them to fix the issue permanently? This will be like my 4th call on the issue and I'm starting to get a little self-conscious about the whole thing. My only real leverage is I still have an outstanding balance on the heat pump.

[Structo]

What is EMT?

About six years ago I had a heat pump and new air handler installed in my home.
Bryant pump and Carrier handler. (same parent company)

To save money I installed the new 30 Amp circuit.

It consisted of 10-2 Gauge Romex from the breaker panel to a safety switch box on the exterior of the house where the heat pump is.
The wire is ran overhead in the garage and out to the switch.
So no conduit other than from the switch to the pump.

Anyway, I haven't heard what you describe and the heat pump we got was the most efficient one at the time and it uses Puron refrigerant.(R-410A)

Although the pump has the familiar buzzing and anti-freeze cycles that most have.

[FUCHSAUDIO]

EMT is metal electrical conduit (pipe).

[brentm]

Yeah, I'm not positive, but I think some romex cable has a slight twist in the sheath.....

I thought about doing this myself, but I'm not sure how much length I'd lose if I did install a twist in the conductors. They ran 3 separate conductors that lay flat next to eachother inside the conduit...

I'm not sure what your amp draw is on start up, but it's probably pretty high like mine. We have a Carrier also...

I'm going to crawl under the house now to see if there's a slack loop or if it's all inside conduit. The EMT was a nice touch, but it sure is noisy!!! Like I said, it's a split second of noise, but enough to bug the crap out of me with my noise OCD. I chase rattles, lubricate squeaky door pins, shim plastic molding in my car to avoid rattles. I have one rattle in a combo amp I've been unable to cure... I think there's a void in the speaker baffle plywood...

After giving it some thought overnight, I'm going to call the HVAC company and politely ask them if they'd pull that wire back and install a twist in it. I don't mind the startup noise outside, but it's a bit strange to hear it throughout the house.

Here was an interesting page I found on wiring a house for low EMF. Wonder if some of the concepts like this would be good for guys like us who hear artifacts in the power while playing guitar.

http://www.eiwellspring.org/DMH-Wiring.htm

[Structo]

Yeah, noises bug me too.

I can see why they may have used conduit, as it helps when fishing wires for a circuit.

That article is interesting but as we know by wiring heaters in amps, when you twist the wires you lose about 1/3 in length.
So you use more wires.

Never heard of twisting Romex.

I have heard of using a "Soft Start" capacitor which helps to lower the initial current draw.

Maybe the conduit itself is rattling because it is not secured properly along it's length.
Another thing it could be is the condenser jumping a bit when the coolant is first circulated.
Can you stand by the handler when it is energized?

But just like light bulbs, turning them on is when they usually burn out.
The shock of that current is what does it.

In searching for answers through Google, it appears that twisting the separate wires is the way to go.
It was not clear if just changing to Romex would cure it.


http://tinyurl.com/8ru7qup

[brentm]

Well, I called them today and they said they would schedule something for after the holiday weekend. I'm starting to feel a little conspicuous, this will be the 4th time they've come out to address this issue.

Here's a video of it... This is better than me trying to describe what it sounds like.

https://vimeo.com/channels/385626

Checked all the straps and fittings and everything is snug and tight. My first thought was to just fill that conduit with that spray foam. Initially, I worried that the sheath of the cablewould eventually wear off over time and short to ground. But the electrician said the wire has some pretty "advanced" coatings on it and it wasn't likely.

Under the house, there's a box where it changes to UF type romex (not sure on extact term).. also not sure why they didn't just run that the whole distance.

I'm sure they would have ran it like you did Structo, but there are two bedrooms above the garage so there's no attic space to run that line.[/url]

[Structo]

Is that it at 20 seconds?

Almost sounds like arcing.

Probably the camera's mic though.

I wouldn't spray any of that foam in there. It is messy as all get out and it gets where you don't want it fast.

Can you tell where in the conduit the wire is slapping the metal?

Don't feel bad about calling the service tech.
You paid for an expensive product and they have to satisfy you.

I had them out to our house about six times to correct the fan speed on the handler.
Six different techs couldn't figure out why it was blowing so hard it sounded like a jet taking off.

Finally I was so mad that I called the guy that sold me the system and told him to come and tear it all out.....he came around then.
Finally the sixth guy installed some kind of relay that slowed it down......

[brentm]

Ya that's the noise. The whole conduit overhead and behind the camera makes that sound. It seems worse around the bends. Weird huh?

Those fan blades do make some sound cutting the air. Mine sounds a bit like a prop plane. I was researching mods to quiet it down. Ours only has two blades. Most upper end models seem to have three fan blades.

Are you talking about the outside unit (heat pump)?

In my case it was the air handler inside the house that had the problem.

[roadkingbluzs]

Check name plate on unit to see what start load and running load are. Seems excessive at 80 amps. May be the unit itself. This is not an acceptable condition , especially when electricity is the issue. Over time this may turn into a major issue. Is the unit fused ?

[LeftyStrat]

brentm, seeing the quality molding around the door, and knowing you live in Seattle, I suspect you live in one of the older neighborhoods in Seattle. What you hear is the Viking Poltergeist Rattle. Get your wife to bleach her hair, eat lot's of Lutefisk this Christmas, and the sound will go away.

[passfan]

I would be curious to know the nameplate amps , the size wire , and the size breaker in the main panel. Did a licensed electrical contractor do this work or the AC contractor ? Is the AC contractor licensed to do his own electrical ? In Florida they are allowed to do their own hookups on the units but must call electrical to do a total run out to the unit.
Seeing conduit running inside your house pisses me off. There are ways even in a 2 story house to get wire to the other end and if you had a crawl space then someone should have "suited up". A 10 amp run load with an 80 amp surge seems out of place and the conduit seems awful small.

[cbass]

I don't know about the rattling but I belive i would have made them found another way than running condiut through my house even if it meant patching some drywall.

A heatpump should draw around 3x its running load at startup.80 amps seems like a lot.Im wondering why it doesn't trip the breaker.I suppose its not pulling tht much amperage long enough to trip.

Improper freon pressure can make for hard starts.

If the unit keeps going through capacitors demand a replacemet.Your contractor will likely give you the run around.Call the manufactuer and demand a replacement..Trust me if they aren't right from the start you will have nonstop problems.
I'm not a hvac guy but I own 12 heatpumps and do most of the maintenence on them.

I know nothing about your contracter but agoodmajority of HVAC contrcters are scammers.They take advantage of peoples lack of knowledge and could care less about doing a quaility job.For what these guys get an hour and the tiny investment in tools they have I wouldn't feel badabout calling them everyday till its right.

[brentm]

Thanks for the responses!!!

I looked on the nameplate but I didn't see the max amp draw. I know his fluke measured 80 on the initial inrush. It seems high, but the run is pretty long (probably close to 80-100 feet) so perhaps that has something to do with it?

I did get the buzz fixed. Pulled out the cable at the LB and twisted the wire and put a piece of electrical tape around the bundle about every 5 feet and reran the cable.

40 amp breaker. The wire in the conduit is #10 I believe. I don't believe that inrush of 80 amps will trip the breaker as it's pretty instant. But it was enough to make those conductors jump around. When he pulled the cable out, I inspected for nicks in the wire and found none.

On the asthentics... It's ugly, there's no getting around that look of conduit strapped to a wall. The bedrooms above the garage, floor joists running the wrong direction, and access to the crawl, it would have meant drilling through several studs and some drywall work. But, it's a garage, and at least it follows lines and doesn't come down the middle of a wall somewhere. I'll probably paint it white and watch it disappear from my field of vision.

-Brent

[Structo]

First of all, glad you got rid of the noise.

A few years back my parents had an AC unit added to their gas forced air furnace.
They had to add a circuit for it.
The furnace is in the garage.

They still had the old screw in type fuse box so at that time they had it converted to a breaker box.

Their home was a single level ranch style so the electrician ran the wire up through the attic and came out the side wall above the AC unit.
They then ran the wire down through conduit to the AC unit.

You could paint your conduit to the same color as the garage to make it not so obvious.

[passfan]

If it's #10 wire on a 40 amp breaker , that is the reason why AC contractors should not be allowed to make their own runs. By NEC rules that is illegal. If it's #8 wire it's too big to go in a 1/2" conduit. Pulling it out and taping it to get it to stop rattling is a first for me in my 30 years of being an electrician. You should report the guy to your local building authority.