Modulation and boiler water chemical treatment

Voyager

I have two questions not really related:

1. What water treatment is recommended for a Triangle Tube Challenger Solo CC50s? The I&O manual says that water should not have chlorine (my well water is not chlorinated), should have pH between 6.5 and 8.5 (good here at just above 7) and hardness less then 7 grains/gallon (mine fails here at 10 or slightly more grains/gallon). I tested both pH and hardness with test strips so the accuracy isn’t super, but I believe the water softener salesman said my water hardness was 12 GPG several years ago so the strip agreed fairly closely with that. My boiler water source comes off before the softener, so my boiler is not getting treated water just straight from the well. What would you all recommend for a hardness treatment for this boiler? I believe the CC50 is entirely copper in the water path and my system is in-slab pex so the only iron in my system is the two circulators. Everything else is brass or copper.

2. I have found no way to know at what modulation the CC50 is firing. I assume there is a diagnostic mode in the controller that would show this, but I see no discussion about this in any of the manufacturer literature. Only the way to force the burner into low fire or high fire for combustion testing. I would like to learn more about the algorithm used for modulation control, but a fair bit of searching has not located any good articles on this. If anyone knows of a technical article that covers modulation algorithms, I would love to read it. I assume they use some combination of ODR and probably the rate of temp change of the return water, but that is just a guess. Anyone know for sure how these burners modulate and what inputs they use in their modulation calculations?

Jamie Hall

On question 1 -- your water quality is good to go, You might want to add a corrosion inhibitor, but I'm not sure you even need that.

Question 2 -- someone else -- not my field at all.

hot_rod

That water is a bit too hard for boiler fill.

I'd suggest that you will have no warranty on the boiler if in fact you fill with 10- 12 GPG and the manual states 7 max. Most manufacturers state 5-7 GPG as ideal.

7- 10.5 GPG is considered hard, 10.5 and up considered extremely hard water.

TDS is a good test also as it shows all the ions + and - in the water, chlorides are something to watch for in stainless and aluminum boilers, note the manufacturers limits.

Softening the fill water would pull the hardness down but raise the TDS due to the ion exchange process in a softener.

Blend in some RO or DI water to pull the hardness # down.

Adding hydronic conditioners is a good idea also, they will lock up some of that hardness, although you may already have scaled some of the surfaces, a cleaner, good fill and conditioner if you want to assure good fluid condition.

Here are some fluid requirements from a handful of manufacturers.

Also some examples of failed boiler HX due to water conditions they were filled with.

NY_Rob

The mod-cons can only use the sensors they have available, but the algorithms in the control board can vary and change with new board revisions based on customer and field tech feedback.

Typically the ODR sensor (usually a simple NTC 10K thermistor) input to the controller board determines your SWT setpoint based on your ODR curve. The SW and RW temps are monitored and once the delta between them narrows the boiler will start to modulate down (via the neg-pressure gas valve and variable speed inducer fan) based on rate of rise to prevent overshooting setpoint.

I've had three different control boards in my HTP mod-con since June 2016 install. Each time they have improved the algorithm to react faster to RWT changes to prevent cycling and shutdown on short term setpoint overshoot.

It looks like your boiler has a 3.8:1 turndown, some boilers have up to a 10:1 nowadays which really helps on small zone installs.

Jamie Hall

On the water quality. There is a remarkably fine balance between hardness, specifically defined and measured in terms of calcium and magnesium harndess, and total dissolved solids, which isn't the same thing at all, and corrosivity of the water.

Hardness, strictly defined, does create scale, which is to be avoided. However, it does not, by itself, cause corrosion, and it does provide a very effective buffer system to control pH.

Ion exchange softened water is remarkably corrosive, and lacks any buffering. For this reason, if ion exchange softened water is used in a boiler, my recommendation would be to add anticorrosion treatment -- whatever is recommended by the boiler manufacturer. This should be tested and adjusted from time to time.

@hot rod_7 's suggestion of using a mix of RO or DI water (which is very aggressive) and your tap water is a good one, if you desire to go that route. A mix of 3 quarts of RO or DI water to each gallon of tap water should bring your measured hardness down into the range suggested by the manufacturer without raising total dissolved solids or other nasties.

Voyager

hot rod_7 said:

That water is a bit too hard for boiler fill.

I'd suggest that you will have no warranty on the boiler if in fact you fill with 10- 12 GPG and the manual states 7 max. Most manufacturers state 5-7 GPG as ideal.

7- 10.5 GPG is considered hard, 10.5 and up considered extremely hard water.

TDS is a good test also as it shows all the ions + and - in the water, chlorides are something to watch for in stainless and aluminum boilers, note the manufacturers limits.

Softening the fill water would pull the hardness down but raise the TDS due to the ion exchange process in a softener.

Blend in some RO or DI water to pull the hardness # down.

Adding hydronic conditioners is a good idea also, they will lock up some of that hardness, although you may already have scaled some of the surfaces, a cleaner, good fill and conditioner if you want to assure good fluid condition.

Yes, I know it is too hard. I can get some DI or RO water and blend that in. However, since that is more “aggressive” water, will that cause pH or other issues?

The boiler has been in operation less than a month so scale should not be significant yet. Are there specific conditioners that you would recommend to address the water hardness?

NY_Rob

You can also descale the heat exchanger every other year or so just to keep things clean.... it only takes about an hour or so.

https://www.supplyhouse.com/Oatey-35230-Haymaker-Descaler

Voyager

I am hoping to find an additive to treat the hard water and prevent the scale rather than having to remove it later.

hot_rod

Voyager said:

hot rod_7 said:

That water is a bit too hard for boiler fill.

I'd suggest that you will have no warranty on the boiler if in fact you fill with 10- 12 GPG and the manual states 7 max. Most manufacturers state 5-7 GPG as ideal.

7- 10.5 GPG is considered hard, 10.5 and up considered extremely hard water.

TDS is a good test also as it shows all the ions + and - in the water, chlorides are something to watch for in stainless and aluminum boilers, note the manufacturers limits.

Softening the fill water would pull the hardness down but raise the TDS due to the ion exchange process in a softener.

Blend in some RO or DI water to pull the hardness # down.

Adding hydronic conditioners is a good idea also, they will lock up some of that hardness, although you may already have scaled some of the surfaces, a cleaner, good fill and conditioner if you want to assure good fluid condition.

Yes, I know it is too hard. I can get some DI or RO water and blend that in. However, since that is more “aggressive” water, will that cause pH or other issues?

The boiler has been in operation less than a month so scale should not be significant yet. Are there specific conditioners that you would recommend to address the water hardness?

Even if you put straight RO or DI water in, ph in the 6's usually, it will buffer up into the 7's within a day or two. It basically pulls some ions from the metals in the system, not causing any harm, we have tested this multiple times. We also have data from European manufacturers of DI products specifically for boiler fill.

Find a commercial window washer nearby, they use DI equipment for rinsing windows for a spot free glass. It's that droid looking device on the sidewalk with a hose connected

If concerned about aggressive water, a small squirt of boiler inhibitor give you a ph balance O2 scavenger, locks up hardness and provides a micron or two layer of film to protect bare metals.

The reason not to go low hardness is you do want a small layer of mineral to protect piping. Steam prefers 8 or so ph for that reason also.

hot_rod

A quick look at boiler water
https://www.caleffi.com/sites/default/files/coll_attach_file/idronics_18_na.pdf

Voyager

So, some DI water and a little of something like Sentinel X-100?

hot_rod

My preferred method would be to squirt a cleaner in the systems as is. Run a few days and flush, add good water, then squirt in the conditioner.

The cleaner will get you back to square 1, all clean surfaces.

Manufacturers of chemicals make that easy now with a 2 step aerosol kit, this is a Rhomar brand. This kit will handle 35 gallons or so.

Be sure the hose connection is tight as the cans empty in a few seconds, inside or outside the system

Voyager

Thanks. I enjoyed your Coffee with Caleffi webinar today. Now we just need one on boiler water management.

hot_rod

thanks for tuning in today, it was a fun presentation.

We actually did several presentations on water for boilers, guest speakers with much more experience than I. I'll see if they are archived.

Jeff Persons is a GEO expert, been using DI water for many years for filling hydronic and geo, he presented Feb 2013.

Jim Poeling is also another engineer with years of water experience, mainly large boilers, April 2015 was his presentation.

Caleffi NA manger Mark Olson 2 part Nov 2016

On the list #21, 42, 45 &46