Iron Pipe used in High Efficieny SS Boiler Installation

[MajrTom]

It's been just over 8 years after new construction installation of a Peerless Residential High Efficiency Boiler. Two years ago we stated having issues with the igniter going out. The same company that installed came out to do maintenance and supposedly cleaned inside the boiler unit. This lasted about a years. Problems resurfaced and the boiler, expansion tank and one of the zone pumps all ended up failing within a month of each outer. The Installer/Service company said the unit was no longer made and can only give me a percentage off the cost of a new "similar" unit. I acquired a guy from the Near West Chicago Suburbs that almost exclusively works on the famed Bungalow boilers, local churches & school boilers. When he looked over the installation he almost immediately pointed out that the installer used a $1.50 "Iron Tee" at the expansion tank. According to his explanation of metallurgy, the Tee should have been Brass. The dissimilar metals caused corrosion causing the SS Coils and Expansion Tank to corrode and fail well before normal life expectancy.

I brought this point up to the original installer who swears the dissimilar metals are NOT a problem and refuses to help me recover any of my cost. I'm in the service business myself (computers), I've done appliance repair, auto repair, etc. and I tend to believe the new guy over the original installer. I've combed over the Peerless Installation Manual with nothing stating water line material requirements. I'm assuming there is something in the Illinois Plumber Codes stating this but am not an expert in this stuff. As a DIY guy, I'm hoping you can defuse me, or better yet, point me in the right direction to finding out if I'm right or wrong.

Thanks for your time on this matter.

Tom

 

[Jadnashua]

The expansion tank is likely made of steel...iron pipe is compatible with it as the primary component of both is iron. Corrosion inside of the boiler circuits of the iron normally is not an issue unless there are leaks, as without a constant addition of dissolved oxygen from the fill valve, after a short timeframe, all of the 'air' is exhausted in the system by either the air scoop or it turned to rust. Once it's all gone, things internally will last a very long time. Constant addition of fresh water, though, and they can degrade fairly quickly. An iron T in this case probably has nothing to do with the boiler issues. Rust caused by constant additions to the system water supply, though, could cause rust to flake off and potentially clog things, and in the affected item itself, cause it to eventually dissolve into rust particles.

You'll potentially get dielectric issues when the materials are different...SS=mostly iron, iron pipe=mostly iron...thus, no dielectric current.

Normally, the potable water and the water in the heating system are separate for safety reasons, and the ET would be connected to the boiler, closed, system. It's possible you may have a second ET on the potable side, and if there's an iron T there, there shouldn't be! Whether it would clog up the heat exchanger in the boiler, maybe, but that system gets flushed out each time you use hot water. It could cause that joint to fail.

 

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[Dana]

The problem is that it's an "open" system, using potable water in the heating loops, which is very corrosive on iron components since it's constantly being replenished with oxygenated water. If it went 8 years with iron circulation pumps before they failed you're lucky!

In many states open systems aren't even code-legal (for lots of reasons), and there is really no good reason to go with an open system. It's not really about using a cheap tee (which can corrode and fail, not a problem), it's the issue of having an open system in the first place.

Corrosion on the water side of the system is not going to create issues with the igniter, but corrosion or grit brought in by the potable water can take a toll on pumps and zone valves, etc. If the expansion tank wasn't rated for potable water, it could fail early. Going bad after only 8 years is a bit early, but it's failure is not related to iron fittings or dissimilar metals.

Without model numbers it's a bit difficult to dig up any manuals or other data on that boiler. But since you have a heating history on the place you're now in a position to use it's fuel consumption against weather data a for measuring the heat load, so that any replacement would be appropriately sized. Converting an open system to a closed system usually isn't too tough, but if it has gritty corrosion or other detritus dragged in by the potable water, it's worth installing a good filter on it.

 

[MajrTom]

The expansion tank is likely made of steel...iron pipe is compatible with it as the primary component of both is iron. Corrosion inside of the boiler circuits of the iron normally is not an issue unless there are leaks, as without a constant addition of dissolved oxygen from the fill valve, after a short timeframe, all of the 'air' is exhausted in the system by either the air scoop or it turned to rust. Once it's all gone, things internally will last a very long time. Constant addition of fresh water, though, and they can degrade fairly quickly. An iron T in this case probably has nothing to do with the boiler issues. Rust caused by constant additions to the system water supply, though, could cause rust to flake off and potentially clog things, and in the affected item itself, cause it to eventually dissolve into rust particles.

You'll potentially get dielectric issues when the materials are different...SS=mostly iron, iron pipe=mostly iron...thus, no dielectric current.

Normally, the potable water and the water in the heating system are separate for safety reasons, and the ET would be connected to the boiler, closed, system. It's possible you may have a second ET on the potable side, and if there's an iron T there, there shouldn't be! Whether it would clog up the heat exchanger in the boiler, maybe, but that system gets flushed out each time you use hot water. It could cause that joint to fail.

If you look inside the Iron or "Black Steel" Tee & Nipple you can see significant corrosion (rust). Per the original installer, we were told to release fresh water via Pressure Valve into the system to keep the pressure at around 20#'s, which was done on a regular basis and tells me this is NOT a closed system. The Expansion Tank failed due to corrosion build up perforating the diaphragm. According to Watts (Expansion Tank Mfr) all plumbing attachments should be

The problem is that it's an "open" system, using potable water in the heating loops, which is very corrosive on iron components since it's constantly being replenished with oxygenated water. If it went 8 years with iron circulation pumps before they failed you're lucky!

In many states open systems aren't even code-legal (for lots of reasons), and there is really no good reason to go with an open system. It's not really about using a cheap tee (which can corrode and fail, not a problem), it's the issue of having an open system in the first place.

Corrosion on the water side of the system is not going to create issues with the igniter, but corrosion or grit brought in by the potable water can take a toll on pumps and zone valves, etc. If the expansion tank wasn't rated for potable water, it could fail early. Going bad after only 8 years is a bit early, but it's failure is not related to iron fittings or dissimilar metals.

Without model numbers it's a bit difficult to dig up any manuals or other data on that boiler. But since you have a heating history on the place you're now in a position to use it's fuel consumption against weather data a for measuring the heat load, so that any replacement would be appropriately sized. Converting an open system to a closed system usually isn't too tough, but if it has gritty corrosion or other detritus dragged in by the potable water, it's worth installing a good filter on it.

You bring up a couple good points, the installer swears it's a closed system, but then why am I manually adding water via pressure valve to keep pressure at 20#'s? The Expansion unit failed due to a perforated diaphragm (rust buildup), the igniter was being extinguished from pin hole leaks in the SS coils spraying water into the chamber. The inside of the Zone Pump is coated in rust. And you can see significant corrosion on the Black Steel Tee & Nipples... The Boiler Mfr states its not a manufacturer defect because all of the seams and welds are intact. I just know I'm out about $8,000 for replacement boiler, parts and labor after only functioning 8 years - what Hi-Efficiency is that?

 

[Jadnashua]

IF you're constantly adding water...the system has leaks. Thus, you're constantly adding oxygen to the system. You can't have essentially raw steel/iron in that type of system - it will rust. A closed system that doesn't leak does not need constant additions of water, and iron pipes can last eons in that case. But, throw in fresh water with its dissolved gasses, and you're going to be adding fresh oxygen and things will rust. Rust CANNOT happen if there's no oxygen in the system. ANy that gets in there from the initial fill will quickly create a patina of rust, but once that oxygen is converted to iron oxide (rust), it doesn't magically create more oxygen, and the water becomes essentially inert.

A closed system with a properly sized and functioning expansion tank and no leaks will not lose pressure and need constant additions. In that case, you won't rust things out. FWIW, unless you have a 3-story or higher building, your system doesn't need 20psi...there needs to be enough pressure so that the elevation change doesn't drop the pressure at the high point where things could flash to steam. Pressure will change at 0.43#/foot elevation, so you need enough to keep it positive at the high point so you can't boil things. If you had radiators on the floor, and two stories, from the boiler to the high point, it might be 15', so 15'*0.43#/foot = 6.45#...most boilers put in a fudge factor and are designed for a minimum of about 14-15psi to help also account for the suction side of the pump.

What most people call an open system would have potable water coming into the boiler, running through some radiation, then being used in say your shower or other hot water points, constantly being refreshed rather than a typical boiler where the hot water is recirculated into radiators or some other heat distribution system. A typical water heater is an open system, a typical boiler is not. AN open system would be street pressure, a boiler would not. If the heat exchanger in your boiler is spraying water, it's definitely shot.

 

[Dana]

If you say there are pinhole leaks in the HX, that's the problem. The boiler is basically toast and must be replaced.

Without model number information it's impossible to compare how your unit fared compared to others, but you should be able to get 15 years AT LEAST out of a decently modulating condensing boiler with minimal maintenance, and 25+ years is not out of the question.

Don't just accept an HVAC contractor's proposal for a replacement. Amost all boilers currently installed are oversized to the point that they don't operate as efficiently or last as long as they would if right-sized. Take the time to go over the gas billing to perform fuel-used based heat load calculation. No heat load calculation is perfect, but a fuel use load calc is a MEASUREMENT, albeit with a not-super-precise measuring instrument. That is at least a stake in the ground by which you can assess any proposed equipment.

Also take the time to measure up your radiation, to ensure than it won't short-cycle itself into low efficiency and short lifespan on zone calls. The napkin math on that lives here. It's pathetic just how many modulating condensing boiler there are out there that are so oversized for the radiation than they can't modulate at condensing temperatures with short-cycling themselves to an early demise.