Mark Eatherton...copper tube boiler with antifreeze

Drew_2

Dave
Yes that is how chelates were to be used. They disolve and suspend the scale in the fluid. Then when it is flushed the solids leave with the fluid. Rhomar has an outstanding cleaner that will do this job. Make sure you use good water to refill the system (low solids content).

Dave_61

Mark Eatherton...copper tube boiler with antifreeze

Mark,
I have a copper tube boiler with antifreeze that was totally quiet during the heating season and is now making this resonant/groaning noise. I spoke with Drew Longnecker at Noble Co, and he said that you had experience with this same situation in Colorado.
I don't think flow is the problem as our delta T between inlet and outlet of boiler is about 10 degrees (Lochinvar says it must be below 40 deg). I have noticed that the pressure needle on the inlet gauge has been vibrating (Outlet gauge needle does not). One of the things we are thinking about is foaming.I sent some of the fluid to drew to do an analysis. The max %age it could be is about 50%.
What did you end up finding as the solution?

Thanks.
Dave Freitas

[Deleted User]

Chelates....

I induced chelates (chelants) into the mix and the humming stopped, IMMEDIATELY. What you're experiencing is microbubble steam flash at the copper tube to fluid interface. That's why you're seeing the needle jump. Check with Dennis Bellanti at Ferguson Denver, 303-320-4833.

Tell him I said hey.

ME

Dave_61

Thanks Mark

I just have a couple more questions....

Is that typically what you see that the system works fine for several months and then the noise starts?

Since my delta t is around 10 (max for Lochinvar copper tube is 40), doesn't that mean that I don't have a flow issue through the primary loop? I would think if it were a true flow issue, it would have manifested itself when the repiping was first done in January, right?

Is there any problem with the chelates corroding the copper of the piping or HX?

Thanks again.
Dave

[Deleted User]

If it were me...

Assuming that everything on the fire side is set up and working correctly, and you're not being fiddle faddled by the fickle finger of fate and excess air :-), then yes, you are correct, you're WHIPPING the water through the heat exchanger, possibly at excess velocity on some tubes.

Every noisy system I've ever seen was silent to begin with.

Watch the pH on those fluids too, and adjust with the proper chemicals and metals you're working with. Aluminum requires a completely different set up than does other typical systems.

THe nature of copper fin tube boilers (CFTB) is one of the heat exchanger being nice, shiny and new when first commisioned. I think, in an 'ideal world', you would clean the system as a whole with water and Rhomar cleaner.

Then, completely dump that cleaner and rinse.

Then, induce a perfect pre-mixed solution of prop glycol and water, preferrably deionized water, which won't be de-ionized for long, but is completely free of EVERYTHING when first induced.

Nothing to break down the corrosion inhibitor packages of the glycol.

Under this scenario, you could possibly go for a couple of years without hearing the glycol wolves, or glycol whales in heat (sound familiar?:-)) Eventually, you would build a layer of scumthing on the heat exchanger and the howling would eventually begin. It is definately btu transfer related. And it is compounded by glycol's inherent resistance to heat transfer. I've never heard it with straight water in the 1/3 of a century that I've been around CFT boilers, and I've been around the biggest ones made. Ever seen a 3.5 mill instantaneous CFT tanless boiler? I have. And it NEVER howled. But of course, it also had full modulation characteristics.

But I digress...

As for copper loss, I would suggest that you turn DOWN the flow rate to a 30 degree delta T. That won't eat copper due to hydrolysis, erosion corrosion, which I'm certain your current heat exchanger has seen (look inside the tubes under the header.) The inside tubes have the highest velocity and consequently the most damage from HEC.

Bearing that copper with the chelants could expose you to even more HEC, hence my suggest that you slow the flow to a 30 DDT. It'll only make a point or two difference in combustion/heat exchanger efficiency. Not worth the copper loss of the heat exchanger, for sure. Just make sure you don't condense an appliance that's not made for it.

Another thing I've found that will partially supress this micro bubble steam flash is increasing the pressure at the heat exchanger with static fill pressures compounded by the pump. It puts you in a postiton whereby you're breaking almost all the rules of the book about pumping away FROM the boiler, and this is probably ONLY place that I would recommend and condone this practice unless encouraged by the manufacturer, but it does suppress the boiling. This may require closing the outlet valve of the boiler, pumping away from the PONPC, but towards the boiler and staying as far below the boilers relief valve threshold setting, all while suppressing boiling action to alleviate the noise.

Interesting factoid, I've never heard ANY of the MANY stainless steel boilers I've installed on snowmelt systems howl... but they too are mod cons, and I fully expect to hear from them as time goes on.

As for chelates effect on the CFT HXer, only the manufacturer can answer that question for sure. I ran it by the CFT manufactureres where I'd applied it, and they didn't have a problem with it.

Let us know how you make out with this situmication:-)

ME

Dave_61

Mark,

Thanks for the info.
I had increased the pressure to about 25 psi with boiler operating (drops to about 20 with it off), but no change in the sound. Our prv is set to release at 30 psi.
The pump we are using is a Taco 0010. It pumps into the boiler inlet, and there is a gate valve just beyond the pump (maybe 6-8 inches). Is that too close to the pump outlet for me to adjust the flow?
There is another valve about 8 feet past the outlet of the boiler.
My neighbor who is a plumber/heating tech came over last night and ran some water out of the hx and refilled it, thinking that there may have been some air trapped in it. It definitely made it quieter, but it still is making the vibration noise but about 50% as loud as before he came over.
Does that help narrow down anything?
When we had the boiler overheating before we put in the buffer tank, it made a howling (like mating whales, as you said),; however, this sound is different...it sounds like the BRRRR of a Mack truck running in the basement. It is not particularly loud near the boiler, but the vibration is transmitted through the floor joists, as the pipes are hung off the joists.
The fluid came back as about 30% glycol with a pH of 9.2. I tested our household water with test strips,a dn it came back between 50-100 ppm total hardness.

[Deleted User]

The only real solution...

is to add the chelantes to the mix. The boiling/howling noise will stop IMMEDIATELY, or my name's not Dennis Bellanti :-)

I seriously doubt its an air problem, because if it were, you'd be hearing it on the opposite end of the system (FCU's in the attic) and would have a complaint of a different nature.

Dave, I have spent some SERIOUS time messing around with this problem on numerous boilers, and the only Easy Button is to add the chelates to the system fluid...

That, or get rid of the reason you have the problem (glycol).

ME

Jerry_15

Great advice the cop tube boilers I that used to install had all these problems, and more. I still have to service them, but get paid for it now. I will check out the chelate solution, usually I have had to resort to down-firing the boiler, which works quite instantly for a quick fix, but...Thanks Mark.

Dave_61

Jerry,

when you say downfiring the boiler, did you mean turning down the operating temp? That did not work with mine.

Jerry_15

No - I meant slowly cracking back the gas valve on the inlet for instant gratification while it was firing until it stops howling. If you're lucky the manifold pressure was high and can be adjusted down with a manometer, and the inlet valve re-opened, but if a reduced gas flow drops the burner below spec, you will get condensation and other problems. This is a quick test, not a solution. If you leave it at the magical point where it works, someone will notice that the valve is partially closed and help you out by opening it, and you can't take the handle off a gas valve.

Dave_61

The boiler/ergomax primary loop holds probably about 75 gallons of the total 90 gallons (15 gallons are in 3 air handler zones and 1 small radiant loop).
What do you guys think about my draining the glycol/water mix from the primary loop only and then running a TSP/water solution through the primary loop for a while.
Then drain/flush with water and refill primary loop with glycol:water. This would allow me to clean HX and save me the huge job of draining the long loops with the air handlers. But at the same time I would be replacing most of the solution, thus diluting out most contaminants that may or may not be present.

Drew_2

Chelates

Use caution when using chelates. They were made for cleaning systems, not to left in the system. I'm attaching a document from Dow Chemical about where no to use chelates with EDTA.

Dave_61

Thanks Drew. But how about if I use them to clean out the boiler and then dump the water and rinse?
Do you know of any non-EDTA chelates? We just can't stand the noise.

Dave_61

Jerry,

I did crank back the gas valve, to the point of the boiler wanting to stall, and it still was making the noise. I now am convinced it is inside the hx.

Jerry_15

As I said it's a good easy test, without getting the wrenches out(you should still be sure your gas pressure is right though). You'll have to work through the other stuff now. Cop tube boilers always seem to have a plethora of interesting issues. Eliminate the negative, accentuate the positive, don't mess with Mr.in-between.

Jerry_15

Thanks Mark, and I will get ahold of some to use when all hope is lost. I will also charge appropriately for disposal. Would a good de-liming product from a janitorial supply do the same job? I have done this on flash heaters with good results, but never tried it on bigga boilers. You got me thinkin now.