The Case of the Failed 5-year-Old Boiler

RayWohlfarth

This week's case, The Case of the Failed 5-year-Old Boiler.
What caused a hydronic boiler to start to leak after only five years? On paper, it appeared to be the perfect solution to the unique needs of the building. Turns out it wasn't. I would love to know your thoughts.

https://youtube.com/watch?v=qszP9U-lOfg

Mad Dog_2

I really like your smooth  Narration .  I only have 4 of your  books. Where can I get the rest?  Mad Dog 

RayWohlfarth

@Mad Dog_2 Thanks my books are on Amazon right next to @DanHolohan Well slightly below and to the side

ethicalpaul

I’m having trouble picturing how a low flow rate due to just one zone being on could hurt a boiler.

- boiler runs when needed to maintain its temperature range
- the single zone circulates a relatively small part of that water

what causes the harm? Thanks!

RayWohlfarth

@ethicalpaul If the flow rate is too low, there will be a higher delta T and could cause damage to the boiler because of the expansion and contraction. If you look at the manufacturers installation manual, they will tell you the desired temperature rise through the boiler. This is from Weil McLain manual. Hope this helps
Ray

ethicalpaul

Thanks. Still a bit confusing to me since the single operational loop, feeding the one apartment, shouldn't have had any larger of a delta T than any other loop on any other boiler in operation.

JUGHNE

Paul, IMO because the fire is under all of the CI sections and the temp probe is only at one point of the sections, the heating would be uneven on the sections and the expansion rate varying causing stress.

Not unlike the sloped water line in a steam boiler perhaps.

ethicalpaul

So the thinking is that one or more of the sections was a different temperature than the section with the thermostat?

I'm pretty ignorant of how water "boilers" work, but don't they circulate water through all the sections?

Would this boiler have lasted longer with a primary/secondary loop setup? I don't think so but I notice this one didn't have one. Thanks for tolerating my questions!

It just seems like a boiler with a very low btu requirement sometimes...It seems like the boiler would come on when the water got to 160 or whatever, fire for awhile until it was 180, then shut down, repeat as needed. I just can't see what would kill a boiler with such a gentle usage.

Just like a boiler that was heating an indirect tank for DHW in the summer, no?

The thing that does make sense was Ray's other theory where when they turned up the thermostat in the worship areas (the other 5 zones), LOTS of 50 degree water rushed into the 180 degree boiler.

RayWohlfarth

Thanks When I spoke with the manufacturer, they attributed it to a lack flow Im not sure why Im thinking there would be a wide delta T and the expansion would be more than the boiler can handle and it leaked between the sections

ChrisJ

RayWohlfarth said:

Thanks When I spoke with the manufacturer, they attributed it to a lack flow Im not sure why Im thinking there would be a wide delta T and the expansion would be more than the boiler can handle and it leaked between the sections

I'm sure this is not simple to answer but, why do cast iron steamers not have an issue with lack of flow?

RayWohlfarth

@ChrisJ This was a hydronic boiler

ChrisJ

RayWohlfarth said:

@ChrisJ This was a hydronic boiler

I understand that 

Why isn't this an issue with cast iron steam boilers?  Most of the residential steamers are also sold as hot water boilers.  They're just a big cast iron box that holds water.


I have no way of knowing but I'm going to guess there's nothing terribly special about that larger commercial cast iron boiler?

It's not anything special like a fire tube or water tube boiler?

Mad Dog_2

I've seen how the build up of steam boiler mud and red Iron splooge, will collect and dam up in the dead ends of the boiler. This is why I NEVER want to see a plug in ANY boiler tapping below the water line: Tees with boiler drains and bushings with valves so you can flush out once a year. Also, so nice when you have to pull a hydronic zone off the bottom, Mad Dog

RayWohlfarth

@ChrisJ I think the difference between a cast iron boiler and steel is the different rates of expansion. A steel boiler will expand at the same rate as the pipe but the cast iron expands at a different rate. Thats why they use swing joints on steam boilers. that's my story and Im sticking with it

RayWohlfarth

@Mad Dog_2 I agree. I urge contractors to use a nipple and pipe cap instead of a plug. It makes it easier to remove, especially around pressure controls or a float low water cutoff

ChrisJ

Mad Dog_2 said:

I've seen how the build up of steam boiler mud and red Iron splooge, will collect and dam up in the dead ends of the boiler. This is why I NEVER want to see a plug in ANY boiler tapping below the water line: Tees with boiler drains and bushings with valves so you can flush out once a year. Also, so nice when you have to pull a hydronic zone off the bottom, Mad Dog