6+ years ago I moved into my current house. I installed a new AO Smith 4 section boiler and a Bock 50 gallon indirect. After about 4 years, give or a take a few months, I get a call from the wife at work.
Wife-"THE BASEMENTS FLOODING!!!!!!!!" She says in a rather panicked voice.
Me-Where's it coming from?
wife-The side of the "furnace"!!!!!
me-Crap. Go down there and close the valve going into the boiler. It is above and to the left of it.
wife-"What the #$@! is a boiler!!!!!"
wife-Oh. Wait a minute. I turned it off. Water is still coming out
me-did it even slow down?
wife-no, I don't think so.
me-f##K. go back down and shut off every valve you can reach.
wife-OK.....did it. it stopped.
I got home that night, went down into the basement, scratched my head for a minute, turned the boiler feed back on and waited.
Then I turned the domestic feed to the indirect back on. Guess it fixed itself, I thought/hoped......for a few seconds till the boiler pressure relief valve popped again.
I shut the domestic feed off again and after a few seconds the water gushing out of the "furnace" stopped.
WTF, I thought to myself? After thinking about it and experimenting a bit, I came to the conclusion that my domestic supply was pressurizing my boiler. Apparently there was a leak in the boiler water coil.
I went and dug out my bock manual and warranty info. I read back through it, a bit more carefully tha when I installed it. I found the part about checking the anode.
Anode? What's an anode?
Now I knew what an anode was.
After being bounced around a few different places, I got a hold of a bock rep and they replaced it, which kind of surprised me as I figured they'd say DIY install? pffttt. sorry.
Anyway, a few weeks later, I had my new bock. I got by just fine on my tankless coil till then.
I have performed the anode check since then. I have replaced it once and was getting ready to look at it again when I hear another panicked call from the basement.
daughter-Dad? There's water comingout of the furnace.
So I went back down, shut off the domestic HW supply and watched as the boiler pressure eased it's way back down.
Looks like I got another cracked coil. Bleep me.
I emailed the bock rep again and am waiting to hear back from him.
I am considering just living with the tankless coil. I only have one problem with the coil and that is that you do get a fluctuation in temp, but, it ain't that bad.
Also, I have another idea for the Bock.
I plan on installing radiant heating sometime in the next year or twenty. I also like to burn wood in my stove. I was thinking running some black pipe around inside the woodstove and circulating water from the bock, thereby using the woodstove to keep the bock hot. I would then use this water to heat the radiant system.
I would also circulate water from the boiler to the bock to keep it hot when I am not running the stove.
Not sure if I have the room inside my stove to do this, but, I might be able to go to a larger stove.
Am I crazy or what?
One other question.
I was thinking about just keeping the existing bock heater but plumbing it differently.
Tell me if you think this is feasible.
I run my domestic supply through the tankless coil to the indirect domestic supply. On the hot indirect out I install a T back over to the supply going to the tankless coil. I put my existing recirc pump in this. I would cap off the boiler feed and return water going to my leaky coil.
So, now I have my indirect being supplied with hot water from the tankless coil. When the indirect temp drops below a set temp, it's water gets recirculated back through the tankless coil.
This should give me the nice even temps I have come to expect from the Indirect, without having to get a new one.