Aluminum High Voltage Wiring

Alan (California Radiant) Forbes

I service a few steam boilers for steam rooms in commercial gyms, the kind that are electrically powered. The manufacturer says to use only copper conductors because aluminum can degrade and start arcing at the connections, even with the paste that’s supposed to prevent oxidation. 

We worked on one yesterday - 240 volt, 3-phase, 87 amps - that over a few days had stopped steaming.  Aluminum conductors were used. It’s a big facility and we have yet to find the main circuit breaker. My question is that could this be a symptom a using aluminum wire?

mattmia2

Aluminum should really terminate in to aluminum lugs weather it is a terminal or a splice block. If the terminals on the boiler are copper or brass then they won't be rated for aluminum(at least under modern listing, there were old non-aluminum terminals listed for aluminum and that is where much of the aluminum wiring problems came from). The aluminum expands more with temp changes than the copper or brass block which over time crushes the aluminum and makes the connection loose. That is why it says copper conductors only. As long as it is properly transitioned to copper before it connects to the terminals or flying leads on the boiler it should be fine. That doesn't preclude an incorrectly made connection failing somewhere. As long as the transition is made properly the boiler doesn't care what brought the electrons there.

109A_5

Hello @Alan (California Radiant) Forbes
Aluminum wire's thermal expansion coefficient, greater than Copper works the connection loose, then it eventually burns up. Aluminum wire is bad news where its temperature due to current flow and ambient conditions can vary greatly. Crimping properly helps, but it is best avoided unless NEC allows it.

Also in an environment where it can corrode easily it does not do well either.

hot_rod

A tripped breaker could certainly indicate a failed or high resistance connection. Usually you can smell trouble when the terminals start over-heating or arcing.

I wonder that under the cover of a steam chest running temperatures over 200F adds to the stress on the connection as @109A_5 mentioned.

A good thing to add to their bi-yearly service agreement Check and maintain critical connections.

Many of the high voltage transmission wires are aluminum. Utility companies monitor connections at transformers and re-closers constantly with infrared cameras. I knew a gal that did that for a living. She had a utility company van with a skylight for poking the camera out at the poles.

mattmia2

Virtually all modern feeders and utility wiring is aluminum. Aluminum wire is fine if it is terminated properly.

The wiring from the heating elements and the terminations at the elements needs to be engineered for that environment. The field terminations are in an area shielded from that heat otherwise the field conductors would have to be high temp wire and derated for those conditions.

Putting that black goop on aluminum wire doesn't make it ok to terminate it in a non-aluminum rated terminal although i think they were doing that in the 80's.

ChrisJ

109A_5 said:

Hello @Alan (California Radiant) Forbes Aluminum wire's thermal expansion coefficient, greater than Copper works the connection loose, then it eventually burns up. Aluminum wire is bad news where its temperature due to current flow and ambient conditions can vary greatly. Crimping properly helps, but it is best avoided unless NEC allows it. Also in an environment where it can corrode easily it does not do well either.

Aren't almost all power lines and high tension lines aluminum? 

hot_rod

A megger is a handy meter for troubleshooting connection and insulation breakdown

STEVEusaPA

Get out your thermal imaging camera…

109A_5

ChrisJ said:

Aren't almost all power lines and high tension lines aluminum?

Yes and they are most often out in free air and not bundled. And if a connection fails it won't burn down your house or building. Residential service entrance cables are also mostly outside or underground, Sub-panel feeders are are sized so they won't warm up much with the normal loading.

Aluminum branch circuits caused many house fires... Lesson learned, at least by the NFPA, NEC. Utility's have other rules and codes appropriate to them.

Teemok

Are transition fittings made? A lug for aluminum wire that has a safe transition to a copper lug?

Jamie Hall

Aluminium is used in grid conductors and most house drops for a simple reason: although you have to use a larger wire size, it is a good deal less expensive and a lot lighter. The utilities have various connection devices which are designed to be used for aluminium wire which don't loosen ... as badly (though as someone pointed out, they still partrol for hot spots).

mattmia2

Teemok said:

Are transition fittings made? A lug for aluminum wire that has a safe transition to a copper lug?

You just need an aluminum splice with separate lugs for the copper and the aluminum.
This is for small gauge wires, larger lugs of this type have been used to splice larger conductors for decades:
https://www.kinginnovation.com/en/products/Connections/Mechanical-Connectors

EBEBRATT-Ed

Aluminum is fine under most conditions. But it has to be installed and terminated correctly. Has to have aluminum rated lugs etc.

If the mfg of the equipment says not to use it then it is a violation to use it.

Pretty much almost every house has an aluminum service drop. And the electric range , dryers and other large loads use aluminum do to cost and weight.

ChrisJ

@EBEBRATT-Ed

That's my take on it as well. I personally think aluminum is perfectly fine when installed properly.
But if the equipment says copper only, it's copper only. They didn't put that because they own stock in copper.

JUGHNE

Did the install instructions state that the entire circuit had to be copper or just the connections to the unit?

I have gotten around that by having the aluminum spliced to the copper near the equipment in a separate JB and then running copper to the equipment. I splice these with compression connectors which are about 3" long, the same connectors the utility uses.

IMO, the issue with AL connectors that close to the elements is that the heat from the element conducts thru it's copper connections back to the terminal block and then to the AL wire/connection.

The same happened in many light fixtures in houses, oversize bulbs with the fixture tight to the ceiling would conduct that heat thru the copper and melt the insulation on the house wiring. Changes a few years ago dictated more heat resistant "Romex" and new designs in light fixtures.

Years ago some AC cond units had wire pigtails connected to the line side of the contactor, mainly because AL was being introduced into house wiring. Electrician was to wirenut his feeders to these pigtails.
Perhaps this passed the AL/CU connection liability to the electrician, not the HVAC manufacturer.

Alan (California Radiant) Forbes

@JUGHNE Their instructions say:

90°C copper wire is required for generator connection.

So, it seems specific that the connection at the boiler use copper connectors. This particular installation did what you outlined, @JUGHNE. They ran aluminum wire to the disconnect at the boiler and then copper to the appliance itself.

EBEBRATT-Ed

@Alan (California Radiant) Forbes

If they spliced the aluminum to the copper in a separate JB and went into the equipment with copper that is perfectly acceptable provided, they used connectors that are suitable for aluminum and copper (marked CU/AL)

The other connector that can be used is a Burndy "split bolt". They differ from regular split bolts in that there is a spacer that separates the aluminum and copper wire, so they don't touch.

The other issue is temperature of the termination which is difficult to explain and sometimes confuses me. As you said the instructions state 90 deg C copper.

This means the copper wire must be type THHN which is rated at 90C (there are other insulations rated 90C but THHN is the most common)

It also means that THWN, TW etc other copper wiring rated at lower temps cannot be used.


Now we get to wire size. The safe way is to size the wire at 60C even though it is 90C wire.

This is sure to cause a debate but it is the conservative approach not seeing the entire install

mattmia2

JUGHNE said:

The same happened in many light fixtures in houses, oversize bulbs with the fixture tight to the ceiling would conduct that heat thru the copper and melt the insulation on the house wiring. Changes a few years ago dictated more heat resistant "Romex" and new designs in light fixtures.

Note that most of those fixtures say "use 90 c conductors" and most non-electricians ignore that.

ratio

I've always wondered if (properly sized) XHHW-2 with pins would meet the requirement of 'copper conductors'. The termination is the only place where Cu vs Al should be an issue.

I have rejected electricians work when they fed a unit with Al against the nameplate, but I didn't get to talk to his inspector to hear his opinion on pins vs pulling in new wire.

EBEBRATT-Ed

@ratio

What are "pins"??

mattmia2

ratio said:

I've always wondered if (properly sized) XHHW-2 with pins would meet the requirement of 'copper conductors'. The termination is the only place where Cu vs Al should be an issue.

I have rejected electricians work when they fed a unit with Al against the nameplate, but I didn't get to talk to his inspector to hear his opinion on pins vs pulling in new wire.

What do the ones for large wire look for? I know there are pins sometimes used on low energy wiring that are commonly called "bootlaces" and those wouldn't solve the expansion problem. In this case there is also the ambient temp problem.

mattmia2

Isn't xhhw just 90c pex insulation for wet environments?

ChrisJ

mattmia2 said:

ratio said:

I've always wondered if (properly sized) XHHW-2 with pins would meet the requirement of 'copper conductors'. The termination is the only place where Cu vs Al should be an issue.

I have rejected electricians work when they fed a unit with Al against the nameplate, but I didn't get to talk to his inspector to hear his opinion on pins vs pulling in new wire.

What do the ones for large wire look for? I know there are pins sometimes used on low energy wiring that are commonly called "bootlaces" and those wouldn't solve the expansion problem. In this case there is also the ambient temp problem.

This is what I pictured but I've never seen them for larger than 10 or 12 gauge wire.
I think the voltage rating on them is 600v or so but they're tin plated copper.

ratio

Maybe I should have said reducing pins. Basically what Chrisj showed, but for larger size. Burndy AYP & others. Unfortunately, what I found in two minutes of googling on my phone is that Burndy had Al pins for aluminum & Cu pins for copper. The only one I saw that was dual rated was the AYP series, & they're Al body, so no go. Maybe I just answered my own question.

EBEBRATT-Ed

This is what I would use. I assume with an electric boiler we are talking larger wire like #8 and up but maybe I am wrong.

Intplm.

Alan (California Radiant) Forbes said:

I service a few steam boilers for steam rooms in commercial gyms, the kind that are electrically powered. The manufacturer says to use only copper conductors because aluminum can degrade and start arcing at the connections, even with the paste that’s supposed to prevent oxidation. 

We worked on one yesterday - 240 volt, 3-phase, 87 amps - that over a few days had stopped steaming.  Aluminum conductors were used. It’s a big facility and we have yet to find the main circuit breaker. My question is that could this be a symptom a using aluminum wire?

@Alan (California Radiant) Forbes California

I wonder what the manufacturer says about using "Naolox" or similar for this type of issue?

Jamie Hall

I think it could, @Alan (California Radiant) Forbes , but I wouldn't bet on that being the problem or even the only problem. Do you have an infrared camera? If so, and can see the connections, see what the temperatures are.

And preventing oxidation is only one part of the puzzle -- loosening of the connection dues to expansion and resulting deformation of the wire is the other part.

mattmia2

Jamie Hall said:

And preventing oxidation is only one part of the puzzle -- loosening of the connection dues to expansion and resulting deformation of the wire is the other part.

In fact the oxidation normally doesn't become a problem until after it loosens from the differential expansion.

EBEBRATT-Ed

From what I understand now They are saying using "Alnox" or whatever you want to call it is no longer required on aluminum conductors even though it has been required for years. At least for new work.

But as far as I know if you want to use it you can and I often use it on Copper conductors as well in a wet or damp location.

fastd

In 42 years in the electrical trade in NYC my experience with Aluminum wire has been consistently negative, including seeing the main risers, and the Aluminum conduit they were in, in a pyramid at the bottom of the riser shaft, in one office building. My advice: bite the bullet and use copper, and sleep better at night.

rick in Alaska

As far as your boiler issue though, did you do a running amp test and voltage check? I would think if it was a problem with the aluminum wiring being "loose", then the current draw would be higher.
On a side note. I worked on a 3 phase laundry mat boiler boiler once where I had the maintenance guy turn the power off to it, and I just happened to have my new contact sensor, so I tested it and found it to still be live. The guy was positive he turned it off, but after some investigating, we found it only turned off part of the power to it. We started chasing wires and found another circuit panel behind some water heaters and was able to power down the rest of the unit. He would have just reached in and started working on the boiler,
because he thought it was dead.
Trust, but verify. I don't even trust an electrician to tell me a circuit is dead without checking. Also had that happen.
Rick

ChrisJ

rick in Alaska said:

As far as your boiler issue though, did you do a running amp test and voltage check? I would think if it was a problem with the aluminum wiring being "loose", then the current draw would be higher.
On a side note. I worked on a 3 phase laundry mat boiler boiler once where I had the maintenance guy turn the power off to it, and I just happened to have my new contact sensor, so I tested it and found it to still be live. The guy was positive he turned it off, but after some investigating, we found it only turned off part of the power to it. We started chasing wires and found another circuit panel behind some water heaters and was able to power down the rest of the unit. He would have just reached in and started working on the boiler,
because he thought it was dead.
Trust, but verify. I don't even trust an electrician to tell me a circuit is dead without checking. Also had that happen.
Rick

And never trust a glow stick, or whatever they're called.

mattmia2

rick in Alaska said:

As far as your boiler issue though, did you do a running amp test and voltage check? I would think if it was a problem with the aluminum wiring being "loose", then the current draw would be higher.
On a side note. I worked on a 3 phase laundry mat boiler boiler once where I had the maintenance guy turn the power off to it, and I just happened to have my new contact sensor, so I tested it and found it to still be live. The guy was positive he turned it off, but after some investigating, we found it only turned off part of the power to it. We started chasing wires and found another circuit panel behind some water heaters and was able to power down the rest of the unit. He would have just reached in and started working on the boiler,
because he thought it was dead.
Trust, but verify. I don't even trust an electrician to tell me a circuit is dead without checking. Also had that happen.
Rick

From ohm's law, e=ir, if r goes up and e stays constant than i has to go down, not up.

Matt_67

Actually a loose connection causes amp draw to go up because of the voltage drop across the bad connection.

mattmia2

Matt_67 said:

Actually a loose connection causes amp draw to go up because of the voltage drop across the bad connection.

The supply voltage does not go up. It can not cause the current draw to increase on a resistive load like this. On a motor load it can cause the motor to draw more current as it tries to draw the same power at a lower voltage but you need a reactive load for that to happen.

realliveplumber

rick in Alaska said:

As far as your boiler issue though, did you do a running amp test and voltage check? I would think if it was a problem with the aluminum wiring being "loose", then the current draw would be higher.
On a side note. I worked on a 3 phase laundry mat boiler boiler once where I had the maintenance guy turn the power off to it, and I just happened to have my new contact sensor, so I tested it and found it to still be live. The guy was positive he turned it off, but after some investigating, we found it only turned off part of the power to it. We started chasing wires and found another circuit panel behind some water heaters and was able to power down the rest of the unit. He would have just reached in and started working on the boiler,
because he thought it was dead.
Trust, but verify. I don't even trust an electrician to tell me a circuit is dead without checking. Also had that happen.
Rick

rick in Alaska said:

As far as your boiler issue though, did you do a running amp test and voltage check? I would think if it was a problem with the aluminum wiring being "loose", then the current draw would be higher.
On a side note. I worked on a 3 phase laundry mat boiler boiler once where I had the maintenance guy turn the power off to it, and I just happened to have my new contact sensor, so I tested it and found it to still be live. The guy was positive he turned it off, but after some investigating, we found it only turned off part of the power to it. We started chasing wires and found another circuit panel behind some water heaters and was able to power down the rest of the unit. He would have just reached in and started working on the boiler,
because he thought it was dead.
Trust, but verify. I don't even trust an electrician to tell me a circuit is dead without checking. Also had that happen.
Rick

We replaced 2 electric water heaters today in a 4 unit building.

Everything was labeled, but it was all labeled wrong. Every units load center was powering a water heater that wasn't theirs.

If my guy didn't confirm the power was off to the water heater he was working on, he would have been lit up good.

Matt_67

@mattmia2 Yep your exactly right. I was thinking motor circuits which isn’t the case here.

ChrisJ

Matt_67 said:

@mattmia2 Yep your exactly right. I was thinking motor circuits which isn’t the case here.

Yeah motors are weird in that sense but that's because they want to spin at  60hz.  Which comes to roughly 1800rpm (4 pole) or 3600rpm (2 pole).

Alan (California Radiant) Forbes

It turned out that the wiring was fine. The detail that fried the elements was low water.

The water level probes sit in a small cylinder separated from the main tank that houses the heating elements. The cylinder is connected to the tank with two, 1" nipples - high and low - kept separate so that the water level probes don't see the violent changes in the water level when the boiler is steaming. The cylinder had become clogged with mineral deposits that prevented the probes from properly reading the water level in the tank and the tank ran out of water.

Jamie Hall

Same thing that happens to sight glasses -- and sometimes LWCOs -- in other steam boilers! But what a mess...

Solid_Fuel_Man

Separate water level tanks connected by piping to main boiler vessel. 

That's what happened to Three Mile Island I believe. 

I've been an electrician for 20 years, and I have yet to see an aluminum wire fail due to it being aluminum. I've personally run thousands of feet of cable, XHHW, SE-R, etc of aluminum conductor. 

In the mid 70s (after ALCOA pushed for aluminum branch circuits in the 60s and the trouble started) there was an alloy known as 8000 series which largely resolved the thermal expansion issues. But the bad taste was in some guys minds.....like me with Korean cars. No matter if they are decent now, I've seen too many blown engines in the 90s. Don't trust them. 

Here is a good pic for those who are suspect of aluminum wire. This was a 30 year old disconnect on a 30A breaker for a condensing unit. I'm sure never opened in all that time.  

That's #6 aluminum on the top, and #8 copper going to the condenser which failed. The aluminum didn't have any NOALOX on it.