Is this normal

mikehn

Hi all
Cleaned out my Grant oil boiler to day and wonder if anyone has any views on what I found. I have always been happy with the set up, seems to be burning cleanly and economically but at the rate the baffle plates are going I will need replacements shortly. The top plate is now extremely light and as I go down they get heavier and the lowest one is still substantial.The material I took out seems to be mainly rust!!!
Thanks
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DGOBS

looks like you maybe getting water in the flue or something to cause that amount of rusting, or your flow/return temperature is too low and your getting condensing happening within the boiler. Do you have a pump overrun stat, what temperature does this cut out at (should be 55ºC as causes the same problem)

mikehn

DGOBS wrote: »

looks like you maybe getting water in the flue or something to cause that amount of rusting, or your flow/return temperature is too low and your getting condensing happening within the boiler. Do you have a pump overrun stat, what temperature does this cut out at (should be 55ºC as causes the same problem)

Thanks, no overrun stat on system, only stat is on the module, . pipe is taken out through roof directly above burner, is sealed with heat resistant mastic but I better check it out again as if there is water passing in then it will go straight down to the combustion chamber

DGOBS

check that the terminal is the correct (vertical type assuming it's a vertical flue) and the rain hood is still in place, and flue joints if any exterior are in the right direction (not allowing rain into the boiler) periodically check your boiler interior when not in use during summer months to check if you have damp getting in

Wearb

Do you have a copy of the flue gas analysis from last service? I would be looking at temperature of flue gas. Was the size of nozzle reduced below manufacturer recommendations? I have seen similar results from people trying to cut down on usage by doing that.

jimf

we have all come across a degree of scaling from time to time but I would have to agree with others this does look excessive

JamesM

From the amount of corrosion, I would be fairly sure that this is not from condensation, but is from rainwater getting in around the flue, or dripping on the top of the boiler, or maybe a badly leaking automatic air vent, or safety valve.
Jim.

DGOBS

How would the water from an auto air vent or safety valve corrode the boiler inside?

Condensation inside the boiler would be acidic (condensate rapidly corrodes steel) and could well cause this level of damage.

scudo2

Its something I see a lot.

Condensation and rain internal in flue and/or rain on the outside of flue running down outside directly into hair line crack in concrete around flue pipe caused by heat + expansion and contraction of flue, or perished flange gasket, if fitted.

18' flue = over 55sq/ft of surface area, that's a lot of rain water been collected and running down it. !

Also low flue temperatures, but mainly rain.
I come across a lot of flooded burners after a wet summer.

JamesM

DGOBS wrote: »

How would the water from an auto air vent or safety valve corrode the boiler inside?

Condensation inside the boiler would be acidic (condensate rapidly corrodes steel) and could well cause this level of damage.

The water lands on the top of the boiler and finds its way inside through the top cover or around the flue exit - but most likely it's from rain either dripping from where the flue goes through the roof, or down the flue.
Jim.

mikehn

Where the flue pipe comes through the cladding is at the end of a 20ft run so the amount of water striking the pipe would be considerable. I have removed the existing high temperature mastic and redone the seal. I also put a dam about 1ft on the high side of the pipe exit to reduce the level of rainwater and I lowered the cowl about an inch. Hopefully that may cure the problem. I would say the rainwater cause is correct as the top plate on the boiler is also shook.
Thanks for the suggestions