Viessmann Boiler Repairs

[Snagglefoot]

I’ve posted on my Viessmann boiler before and here is my latest posting. These boilers are very common in Europe. They have a computer controlled injection fan. Then, the gas, being propane or natural gas is ignited in a drum shaped combustion chamber / heat exchanger. There is a black seal at the top of the drum. You can see it if you remove the front cover of the white cabinet.

That seal seals between the exhaust piping and the combustion chamber. If it starts to leak you will see drips of acidic water come down from the seal area and there will be a slight gassy smell, especially when the boiler stops running.

You remove the plastic top at the top of the boiler. Pull the plastic top off and the you can see the rubber seal against the stainless steel drum. Pull out the old seal. Clean the metal lip. Insert the new seal and make sure the metal of the boiler slips into the slot of the seal. Replace the white piece and insert the four screws to hold it down. As usual I am assuming you are a licensed boiler tech or gas fitter. Hope this helps someone. Here are some pics.

 

[Snagglefoot]

FUBAR

 

[LazyDog]

Why not add a bead of high temperature silicone on the outside of the seal. How often are you having to replace it???

 

[sloinker]

Not familiar with that boiler. B&W, Combustion Engineering, Tangentially fired, water tube with drum is more my speed.

 

[LazyDog]

The only thing that I can think off that is wearing out the seal is the boiler temperature. Has the boiler been adjusted using a combustion analyses tool??

 

[JohnnyG]

Stupid design! That seal could be made out of Teflon or some other high temp elastomer. Even Ceramic rope packing would be better than that.

 

[Snagglefoot]

The only thing that I can think off that is wearing out the seal is the boiler temperature. Has the boiler been adjusted using a combustion analyses tool??

No but it has a computer controlled fan and gas valve and it will deliver at up to 170 F and as low as 130 F depending on the demand. Currently the water goes to four places; the in-floor heat in the insulated slab of the basement, the in-floor heat in the two car garage with an insulated slab, the DHW stainless steel water tank, and a water-to- air heat exchanger in the furnace. Normally the house is heated with a heat pump and at 27 degrees outside temp the propane boiler feeds the heat exchanger instead of the heat pump.

 

[Snagglefoot]

They sell these in the USA as well. They are wall mounted and very compact. Mine does not have item 6 and 7 and instead those items are external to the boiler. Enjoy.

 

[facility1]

call manufacture.there maybe a improved gasket, see what they say ,, natural gas when burned has carbonic acid in it,or by-product of combustion. reaction due to moisture in breaching vent,,possibly when installed put a bead of ceramic burner caulk around outside of gasket fitting surface,,do you have proper draft up chimney vent/air flow out,as this can be a cause of condensation (sweating) in breaching running back down stack causing this problem,,,what is your stack temperature going out??

 

[Snagglefoot]

call manufacture.there maybe a improved gasket, see what they say ,, natural gas when burned has carbonic acid in it,or by-product of combustion. reaction due to moisture in breaching vent,,possibly when installed put a bead of ceramic burner caulk around outside of gasket fitting surface,,do you have proper draft up chimney vent/air flow out,as this can be a cause of condensation (sweating) in breaching running back down stack causing this problem,,,what is your stack temperature going out??

Thanks for the posting. This is a condensing boiler with 95% efficiency. The acidic water condenses inside the stainless steel boiler drum and is collected at the bottom of the sideways sitting drum. The incoming water runs through the coils built into the wall of the drum and even though the water is warm, it’s much cooler than combustion gas and energy is extracted from the gas forming carbonic water with a pH of about 3. It’s extremely corrosive. The water leaves the boiler to the drain. So yes, the material of the seal is exposed to carbonic acid. The chimney rises about a foot above the boiler and the turns horizontal. It is a plastic tube which is designed to exit the house horizontally and meets the codes. Any sweating is small change compared to what is going on in the boiler chamber. Thanks for the ideas.

 

[Snagglefoot]

I forgot to mention, the boiler and the original seal is 12 years old. By the time it needs a another seal. The boiler will be at the end of its useful life.

 

[facility1]

seems like it maybe a draft problem,,possibly install a small vented inducer fan,though it may slightly affect your efficiency,in other words increase air flow through furnace ,may want to install a barometric flow meter (manometer) to see if in complance to the manufactures specs, as a horizonal breaching may not have enough flow as opposed to vertical up draft to remove combustion by products fast enough thus causing build up of carbonic acids. re calibrating your burner will be necessary.

 

[Snagglefoot]

seems like it maybe a draft problem,,possibly install a small vented inducer fan,though it may slightly affect your efficiency,in other words increase air flow through furnace ,may want to install a barometric flow meter (manometer) to see if in complance to the manufactures specs, as a horizonal breaching may not have enough flow as opposed to vertical up draft to remove combustion by products fast enough thus causing build up of carbonic acids. re calibrating your burner will be necessary.

This boiler has a positive pressure multispeed computer controlled fan injecting the propane. It’s item 3 on posting #8, burner blower, so it has plenty of “draft”. It’s a condensing boiler. It’s designed to make carbonic acid as the exhaust gas condenses to remove more energy from it. Certainly it’s not like grandpa’s boiler.