Boiler Leak

Norm Harvey

Maybe its early, but help me to understand. Your using a cast iron boiler on an all radiant system where the boiler condensing is in the design engineering?

Where are you picking up the condensate to be fed to the neutralizer?

How is the system controlled?

Pictures please!

RonV

It looks like I've got a leak inside my boiler, but listen to what I've observed and give me your opinion. The symptoms include
-dark grey condensate water in my drip tube,
-the condensate water that gets through the tube to the glass container on the floor evaporates and leaves obvious copper residue (blue-green)(my flue vents are all stainless steel)
-the backflow preventer in my makeup water line appears to be operating fairly often as it seems to drip in concert with the occurance of the dirty condensate,
- there is frequently a bit of air available at the Maid-O-Mist air purge valve on top of the boiler.
- the leak seems to occur only when the boiler is cool as it doesn't have the various symptoms in the peak of the heating season, only when the weather is a bit milder and the boiler cycles less frequently
-The final and most damning evidence is that when I isolate the cold boiler it loses pressure in less than an hour.
- My other boiler, which is an identical model installed at the same time, takes a few days to lose pressure and it has crystal clear condensate.

There is no dirt or blockage in my boiler's vents (which are forced air).

My plumbing pro took a look at the condensate last year, listened to my concerns and pronounced "I wouldn't worry about it". He's an experienced hydronics guy so I believe he knows his stuff. Trouble is, I'm a born worrier and the dirty condensate has been going like that since the system was commissioned 6 years ago. So, I'd like opinions from you pros on the basic question which is, should I worry about it? Isn't it true that bringing make-up water in all the time, even in tiny doses, can also put air into my system which can promote rust in my cast iron boilers?

My system is only 6 years old and is all in-floor radiant using PEX with the usual copper zone headers, brass and stainless steel ball valves and zone valves, copper piping around the boilers, a DHW exchanger tank, a few circulators and a variety of other items in the system, including a good quality Spirovent microbubble resorber where the makeup water joins the primary loop. Oh, and the boilers are SlantFin Victory 150s which are cast iron units. Are the boilers the only part that can rust out? Is a small leak worth fixing? Is my post too long? Sorry about that.

RonV_2

Hi Norm
Thanks for responding. I know you guys like good data, so I've attached a system schematic that I drew up a while back, plus one photo showing the boiler setup.

The condensate is recovered at a T in the flue approx 3 feet from the boiler, and you may see the clear tubing in the photo.

If you need any more detail photos or info, just ask.

Weezbo

To me it sounds that it is somewhat temp dependent...

might be from an internal leak to the combustion or the torque
on the thru bolts need to be tightened.

there are oil fired boilers that have similar design.

the difference though is that the 'T' is installed 90 degrees tapped off the bottom cap of the riser . there are some other minor technicalities to this however...

i would rather have the piece that fits the boilers however they are made someplace else and are not available in America or Canada.

Norm Harvey

I'm really concerned about condensate in the boiler flues rotting out the cast iron.

I would consider a low limit aquastat on each boiler that will prevent the boilers circulator from running if the boiler water drops below a certain point, say 140 degrees.

As far as your boiler leak goes. If you isolate the boiler and the pressure drops do you see water anywhere outside or inside the boilers combustion chamber area?

RonV

To be clear, the amount of condensate is very very small. In the peak of the heating season there will be none for weeks. In warmer weather, I might see evidence of flow in the drip plate once every three weeks and that might be half a thimblefull. So the amount of condensate is not alarming to me, and the fact that it is indeed being properly diverted from flowing back to the boiler from the colder parts of the flue is good to know. The need for a T in the flue to collect condensate from further up is straight out of the boiler's manual so everything is to spec. I mention the condensate mainly as it's colour is a clue to what is going on inside the boiler, perhaps.

I have had a good look around the exterior of the boiler and found no stains or such signs of leakage. I've also had a look into the combustion chamber with a mirror and to be honest I can't see any obvious signs there either. My inside inspection was hardly exhaustive though so I might have missed something. I am not aware that the cast assembly might need to be torqued tighter. That has never been done since new. I'd bet that the manufacturer would frown on that from a warranty point of view, but is this sort of thing done?

Norm Harvey

Ive never heard of torquing tie rods and it is certainly something I would not do in my business.

If your having radiant return temperature water flowing through the boiler you can certainly have condensing within the boiler. The condensate within the boiler could be quickly evaporated but the acidity would still have a chance to work.

if the boiler is leaking or for a difinitive test, isolate the boiler, drain it down, and pressure test with air. Then you will be able to hear and/or see the leak.

Adding a low limit aquastat to stop the boilers circulator would certainly help to alleviate any condensing inside the flues.

RonV

A pressure test using air is a very good idea. Thanks Norm.