Buderus GB142 & mixed radiant system

Joe@buderus_2

The PH on the GB142 should be 7.0 to 8.5. If there are any questions about the fill water, we recommend Rhomar 922 treatment. A "Y-Strainer" with an 80 mesh screen is suggested on the return to help prevent the boiler from getting plugged from system debris.

Do-It-All

Water chemistry - Al heat exchangers / iron rads

Need some smarter people than me on this question:

Have a customer who wants to take advantage of all the govt grant money now coming available for energy efficiency upgrades. He's seen the GB142 and the Vitodens 200 and for his budget he prefers the GB142.

The problem is that he's got a lot of old cast iron rads in his home and the water chemistry with an aluminum core boiler is causing me to lose sleep.

We are doing a major reno to his house - an early 1900's Arts & Crafts place. He's keeping the cast iron rads on the 1st and second floors to retain the character of the house, and installing radiant in-floor in his basement.

The first floor is a high temp zone (160F) because we are not tearing out the plaster/lath over brick. The 2nd floor (frame construction) is being insulated from the outside as we re-shingle the exterior, so it will be about a 140F zone, and the basement is a low temp zone.

I feel much more comfortable steering him to the Vitodens because of the stainless steel design but he's balking at the cost.

The GB142 seems to want a max. pH of about 8.5, while cast iron seems to be happier at about pH 9.0. Is there any way to buffer the water chemistry so the GB142 and the cast iron rads will be happy? I've seen product from http://www.fernox.com/index.php?cccpage=products (recommended by my Weil-McLain rep) but I don't want to blow the GB142 or its warranty.

Any thoughts are welcome.

Paul Pollets

Water chemistry

Why not call Buderus and ask what cleaning chemical they want used in conjunction with the GB, and what stabilizer/pump lubricant and O2 scavenger for final treatment??

Normally we clean the original piping system and cast iron rads with TSP or Rhomar products, after flushing and rinsing, we top off with Rhomar ProTek.

Cleaning the system, prior to commisioning the new appliance, is critical. Most don't. It's too bad because the water chemistry will affect the boiler. No one would want the old boiler sludge-mud to foul the new appliance.



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Do-It-All

Paul,

For sure we will flush before we fill - always do.

The old boiler coming out is a copper fin-tube with big straight channels and it has not gunked up. But we take no chances and we'll be installing a sidestream filters to filter out particulate matter - we do this any time we have cast iron in a system.

I've asked Buderus but have not received a clear answer. The electronegativities of Cu and Fe are much closer to one another than those of Al and Fe, so mixing Cu & Fe in a system is generally not an issue. I just don't remember enough electrochemistry to know for sure what tolerance there is in the water chemistry to not have to worry about things in a practical sense - I'm a mechanical engineer, not a metallurgist or chemical engineer, ie. a boiler failure due to corrosion of the Al in 20 years is probably acceptable, whereas corrosion failure in 2 years is not.

Dave_4

Water Chemistry

The question is at what point do you clean the system? If it's before changing to the new boiler any good boiler cleaner is OK. If cleaning after installing an aluminum system, make sure the cleaner is safe for use with aluminum. I've tested various cleaners and some love to eat aluminum. I believe there are two approved antifreezes for the 142 and both are excellent products.

Drew
Noble Company
Engineered Fluids Division