non-barrier pex in snow melt system - ross

ross

ross

Frankenmuth snow melt

There is an interesting article in the July 2002 Public Works magazine about a snow melt system installed last summer at Frankenmuth, MI. One thing that concerned me about the system is that they elected to go with a non-barrier pex because the boilers "have stainless steel burners and corrosion-resistant copper tube heat exchangers with bronze headers." What do you think about this? Would you really feel comfortable skipping the O2 barrier? The boilers are roof-mounted Raypak outdoor boilers, with all parts "rust protected." They used aluminum distribution manifolds, hard coated both interior and exterior to military standards Mil-A-8625. There's no mention of the pump materials.

Mark Eatherton1

The biggest concern I'd have...

is the fact that they have aluminum in a copper system. Wherever aluminum, even one molecule, comes into contact with copper, it sets up a wicked disimilar metal mix, eventually boring a hole through the copper, letting all the inside stuff to spill out to the outside stuff if you get my drift.

As for the rest of the system, provided they have a regular monitoring and maintenance program for the corrosion inhibitors in the system fluid, the lack of an 02 barrier should not be of concern.

Aluminum headers eh...

ME

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hr

Sounds like it's too late!

I would advise the barrier pex. You really do not want any O2 getting into that system. Glycol is a wonderful product, when used correctly. The correct glycol hydronic anti freeze products have inhibitors. The inhibitor packages are comprised of a list of chemicals but the most important is the oxygen inhibitor ingrediant. It can be used up quickly if O2 is allowed to enter the system.
The good news is it can be tested, and inhibitors boosters added as they get used up.
I would test this system fluid at least once a year, twice yearly would be wise considering the tube!. It is much better to add boosters than suffer the consequences of glycol gone bad. It will destroy a copper tube boiler in short order if it slips in to the acidic ph range.
Hopefully the system was cleaned and flushed before adding the glycol, and good quality mix water was used, or you have two strikes against you right away.
Have them send a fluid sample for a complete analysis, would be the best advise you could give them.
Dowfrost HD has an enhansed booster pakage for systems with copper components, if a replacement is required.
Demineralized water is highly recommended, either DI, distilled or RO treated water.

A copy of this free guide from Dow would be a nice gift. #180-01332-598-AMS call them at 800-447-4369 for a copy

hot rod

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hr

No, no not aluminum!

I hope the hard coating, whatever it is is glycol and inhibitor proof. Automotive anti freezes are formulated for aluminumn components. They use silicate based inhibitors. Bad news for HVAC use. The low turblent flow in hydronic systems will cause the silicates to coat and foul the heat transfer surfaces i.e. copper tube hx. Hard on pump seals also.

Does the boiler hum, resonate, moan, jump around? These can be signs of the hx walls getting coated and loosing their ability to transfer the energy from the flame to the fluid. Not unlike the sound from an old water heater filled with hard water build up.

If you do have exposed aluminum in the system contact Dow or other chemical suppliers for the proper transfer fluid to work with all your components. I'd check it ASAP to protect the systems and owners investment.

hot rod

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Mike Kraft

Working @ the car wash.............

We have two DIY car wash joints in our area.Both are Raypak and both have poly-B tube.The one system has all schedule 80 PVC boiler piping.(pretty strange looking).The manifolds are in front of the "bays" under man hole covers.These manifolds are also schedule 80.There is a chemical feed tank which has automotive anti-freeze.

The other car wash I was a sub for the mechanical sub.(Just a piping fool)This car wash is also Raypak and poly-b.This is piped in CU.The manifold feed and returns are schedule 80 PVC and transitioned to CU in the mechanical room.This system is protected with Hercules Cryotek.

cheese

Mark Hunt

Aluminum

Well, kiss the manifolds good-bye.

If I have learned nothing else at "The Wall", I have at least learned this. Hotrod knows more about glycol than anyone I have ever talked to.

Do what he says, but I have to agree with HR. It may already be too late.

Mark H

Duncan

Frankenstein snow melt

Sounds like your referring to the Gene Wilder version. I saw the Boris Karloff version with an Eveready Bunny twist: a 1970s non-barrier pipe snowmelt. It uses black polyethylene tube with a cast iron Burnham boiler. Amazingly, it still runs and doesn't percolate

Sludge usually settles at the point of slowest water velocity, the widest part of the river: the boiler. It settles to the bottom of the cast iron sections, right where the fire meets the iron. That pretty well puts the kibosh on heat transfer, sending lots of wasted heat up the vent.

This one has a nice coating of fine iron oxide (rust) everywhere. Even on the bottom of all the piping.

What do I think of it? Sounds like they had a tight budget and went the low-cost route. With the long, long, runs of snowmelt system tubing, you can save some bucks up front using non-barrier tube. I've also heard that bronze headers are less apt to leak or break, but that's second hand information, I can't say if it's true or not. I suppose the smaller headers of a fintube boiler might be an advantage as far as sludge settlement if they're wet wall headers (but maybe not).

I would NOT feel comfortable with non-barrier tubing. For any inaccessible part of any system that can't be removed or repaired, I like to go with the most bulletproof material possible/practical. Given its tensile stretch properties and corrosion resistance, and considering maximum system temperatures, that would be a quality PEX. You never know who's going to do what to the system in the future, so I feel better going with the best with for stuff you can't get to.

I guess they'll use the money they "saved" for glycol maintenance. Or repairs.