Question about glycol

RayWohlfarth

We suggested installed glycol in a small office building's hydronic heating loop. The customer had frozen coils several times. The owner called and cancelled it, saying it would create leaks throughout the system because the piping was thirty year old black iron. An expert advised them not to do it. Is that true? Will glycol create leaks? Thanks

Mad Dog_2

From my experience..no!  I've used that Cryotek for over 35 yrs never an issue.  Maybe some cheaper or corrosive mixtures are harmful.  Mad Dog 🐕 

pecmsg

No, a weak solution of glycol and water does no damage. The PH level must be checked and adjusted accordingly.

If it did how is it used in ice rinks that hold 1000's of gallons?

EBEBRATT-Ed

Agree with the above posts. Glycol can be a headache and the PH has to be checked it can turn acidic but Ice Rinks are a perfect example as @pecmsg mentioned.

Freeze stats should be used on the coils but the control techs in this era don't always do what they should do.

In the old days with pneumatic controls if the freeze stat tripped you would send the NO heating valve wide open, shut down the fan and close any OA dampers to prevent a freeze.

Would it be possible to repipe and just use Glycol in a new piping loop that just serves the coils with a heat exchanger in between so you don't have to glycol the entire building?

WMno57

Glycol doesn't wear out, meaning it doesn't lose its freezing protection. The additive package of corrosion inhibitors (CIs) do wear out. CIs must be compatible with all components in the system
True for automotive and hydronics. Automotive is ethylene glycol and hydronics is propylene glycol. They both include additives for corrosion protection. There is no lifetime ethylene glycol for automotive. Some last longer than others, but eventually the corrosion inhibitors lose their ability to protect.
In automotive you usually flush and fill. In hydronics you can do annual testing and replenish the corrosion inhibitors as needed.
Many race cars don't use glycol. Straight water has better heat transfer. Water makes less of a mess on the racetrack.
I like EBEBRATT-Ed idea of not glycoling the entire system, just the freeze prone items.

RayWohlfarth

Thank you sirs I appreciate it Isolating the coils would be expensive as they are also the pipes that feed the perimeter baseboard heat. I appreciate the suggestions

pecmsg

@RayWohlfarth
There is no need to keep the freeze protection very low. Even a little goes a long way. The issue if as you get near the freeze point the solution gets thick. That in turn doesn't play well with pump seals. I'd rather replace a seal or 2 then frozen coils and pipes!

RayWohlfarth

Great point @pecmsg Thanks

hot_rod

Define the word “leak”
That green fuzzy meringue build up you see around connections that have had glycol added is that a leak? Or only if it drips on your head?

The integrity of the threaded connection has much to do with it.

DowFrost is a PG
DowTherm is an EG

Larger systems that do not have potable water interface often chose DowTherm.
lower cost, better heat transfer.

EG has been used for aircraft deicers due to cost, but it also breaks down quicker than PG in the bio ponds and can be flushed down drains.

once inhibitors are added either PG or EG it become a higher toxicity, EG more so. I certainly would not drink hydronic PG

although food grade PG is in your toothpaste and many food products 

We had a Dow glycol engineer on Coffee with Caleffi years ago, he talked about the various pros and cons

Maybe a better wording is it is “more prone to leaking out of some connections”

For example, put glycol and press connections in the search box above for some real life experiences 😮

hot_rod

Keep in mind the pump spec also. This example for a 200' loop of 3/4 copper

retiredguy

@Ray, my concern with glycol is that it makes the water more slippery and could potentially seep out of any connections that are not perfect. Also, consider what all the other guys have written. I would rather have a weak glycol solution which would be less slippery and still offer freeze protection.

hot_rod

Somewhere between 20 and 50% is reasonable.

Although look at the particular brand. 50 % from one brand to another can have different protection numbers. The bargin brand 50% is a different freeze number than the more expensive brands.

I noticed Grundfos has add a glycol % to the hydronic pump spec. I think that translates into below 50%?

Also a water hardness spec of 15 gpg.

Although "lower than approx 15 gpg" leaves some room for interpretation.

RayWohlfarth

Thanks @hot_rod As usual, you are still teaching me LOL
@retiredguy Thats a great point. I am just concerned I will get that call on a Friday afternoon telling me there's water everywhere. Thanks

pecmsg

RayWohlfarth said:

Thanks @hot_rod As usual, you are still teaching me LOL
@retiredguy Thats a great point. I am just concerned I will get that call on a Friday afternoon telling me there's water everywhere. Thanks

If that happens I'll guarantee it's been leaking for months.

hot_rod

RayWohlfarth said:

Thanks @hot_rod As usual, you are still teaching me LOL
@retiredguy Thats a great point. I am just concerned I will get that call on a Friday afternoon telling me there's water everywhere. Thanks

A glycol crystal ball is needed to predict if there could or will be some seeping if glycol is added Probably find one on E-bay!

What would the $$ be to redo any joints that would leak or seep?

Maybe adding freeze stats on the coils is a better option. That is common on hydroair units installed in attics.

I think Dan Foley had a post on that option years ago, here.

hot_rod

RayWohlfarth said:

Thanks @hot_rod As usual, you are still teaching me LOL
@retiredguy Thats a great point. I am just concerned I will get that call on a Friday afternoon telling me there's water everywhere. Thanks

Brad White had a clever analogy on glycol back about 18 years ago here on HH.

WMno57

Glycol in hydronics is somewhat OK if it is maintained every year. The included inhibitor additive package MUST be compatible with everything in the hydronic system, and the local water.

DexCool is a great ethylene glycol for cars with aluminum engines and radiators. Except for the one GM V6 model that had intake manifold gaskets incompatible with DexCool's Organic Acid Technology inhibitor package. GM had control of and knowledge of everything in their line. They had testing labs and thousands of engineers. GM still screwed up.

How could a contractor possibly know if the additive package of their locally available propylene glycol is compatible with everything in an existing hydronic system? How would they even know compatibility with a soup to nuts new system where they spec everything?

So yes, I believe Glycol should be avoided in buildings and hydronic systems if possible.

https://forum.heatinghelp.com/discussion/190758/new-boiler-or-strip-heaters-in-existing-heat-pump-air-handlers/p1

hot_rod

How could a contractor possibly know if the additive package of their locally available propylene glycol is compatible with everything in an existing hydronic system? How would they even know compatibility with a soup to nuts new system where they spec everything?

I see the brands now promoting multi metal formulas.

EBEBRATT-Ed

Seldom if ever need more than a 30% mix in most areas.

Jamie Hall

I wonder... if the problems are really all that bad... how often do you have to add coolant to your truck's radiator? Running at 190 F and 15 or 20 psi?

jumper

I worry about something galvanized inside. My experience with glycol in chilled water is that glycol is somehow consumed. Of course that adds fresh inhibiter.

mattmia2

So the summary is glycol will corrode things if you don't maintain it, it flows better than water(but has a higher viscosity), and doesn't evaporate so it can find leaks that water didn't.

Note that hydronic systems are usually copper, brass, iron, and steel. Not a big deal for compatibility. The o-rings and other synthetic rubber components are a bit of a wild card but they are a bit of a wild card with water and chlorides too. The manufacturers frequently don't pick great materials to begin with.

mattmia2

Jamie Hall said:

I wonder... if the problems are really all that bad... how often do you have to add coolant to your truck's radiator? Running at 190 F and 15 or 20 psi?

2 years to 5 years depending on how its additives are engineered.

hot_rod

mattmia2 said:

So the summary is glycol will corrode things if you don't maintain it, it flows better than water(but has a higher viscosity), and doesn't evaporate so it can find leaks that water didn't.

Note that hydronic systems are usually copper, brass, iron, and steel. Not a big deal for compatibility. The o-rings and other synthetic rubber components are a bit of a wild card but they are a bit of a wild card with water and chlorides too. The manufacturers frequently don't pick great materials to begin with.

It’s the low surface tension that can lead to leaks. At room temperature glycol surface tension is 1/2 that of water. It goes lower as you heat the fluid

It seems both crimp fittings and Victraulic struggle with glycols. The make up of the rings or gaskets?
We had trouble with the green fiber washers on the glycol solar systems. Months down the road green fuzz appeared on many of those connections. Connections that held 80 psi water tests with no problem.

mattmia2

I'm thinking the chemical compatibility of the synthetic rubber compounds. This mainly comes from my noticing that faucet washers are made of compounds in not recommended column for water and chloride.

It is hard to say with the composition gaskets if it was a synthetic rubber that was incompatible with glycol that was used in the composition or that it just didn't conform well enough to hold the more fluid glycol. I suppose compressed air would tell you.

hot_rod

mattmia2 said:

I'm thinking the chemical compatibility of the synthetic rubber compounds. This mainly comes from my noticing that faucet washers are made of compounds in not recommended column for water and chloride.

It is hard to say with the composition gaskets if it was a synthetic rubber that was incompatible with glycol that was used in the composition or that it just didn't conform well enough to hold the more fluid glycol. I suppose compressed air would tell you.

As I recall Viega wanted you to used a different o-ring on solar glycol systems. Maybe a combination of the glycol and potentially 300 plus degree stagnation temperature. I think it was a grey colored o-ring. Or as they call it a sealing element, they don’t use the word o-ring.
Or is that two words😏

RayWohlfarth

Wow thank you all. m getting a real education on glycol
@hot_rod Loved the Brad White observation