Just how dirty is this heat exchanger?

Boon

Doing annual maintenance today. How bad does this look for 1 year of operation? Any thoughts?

Guy_Woollard

I think it looks good: From the discoloration in the fire area it is showing signs that it has been condensing very close to the top of the HX, which is great. To verify how clean it is, pour water down through the HX and collect what comes out the condensate trap. I don't suspect much.

Boon

Thanks Guy. Having never seen the inside of a used heat exchanger I had no idea what to expect. When I rinsed it out, it all went straight into my floor drain so I didn’t have a chance to check out any debris. I’ll note that idea for next year.

hot_rod

It's the conditions on the water side also, that you don't see that can compromise boiler heat exchangers. Either with water tube or fire tube, the same scaling mechanism applies.
Check and maintain fluid quality.

Boon

@hot rod do the treatments only prevent or can they dissolve scale over time?

Brewbeer

Boon, which boiler is that?

hot_rod

Boon said:

@hot rod do the treatments only prevent or can they dissolve scale over time?

Different treatments are used for different purposes.

Detergent based hydronic cleaners remove any oils, flux, grease dirt on both new and old systems.

Conditioners added after the clean and flush will balance Ph, lock up some hardness, scavenge some O2, provide a very thin protective film on the metals.

More aggressive acid based cleaners are used to remove limescale once it has built up inside.

The same type of acid based cleaner used periodically on tankless WHs to keep them performing and extend life.

Even a few thousands of an inch of build up reduces heat exchange and caused the flame to over-heat and stress the HX metals. Pin holes are usually found under scale deposits.

Take a sample of the water in the boiler now, test or have it tested and add inhibitors as required by the test results.

in some, very rare cases, local water may be okay for boiler fill. the manufacturers I&O should list acceptable water quality requirements.

If not, you have no warranty on the boiler HX should it fail.

These small aerosol kits make it easy to clean and treat systems, I think they do 35- 40 gallons.

Boon

@Brewbeer Lochinvar KHN; and I love this thing. You know those stickers on the front door or window that tell a fireman you have a pet or child? I'm thinking of getting one of those made for my boiler.

@hot rod Thanks. I tested the quality when I originally filled it and it was well below all the limits in the manual. pH test strips are in the mail so I'll test it again when they arrive.

NY_Rob

@Boon You have to disassemble the HX on the KHN every year?

I looked at the maint. schedule for the HTP UFT (Fire Tube) and it only requires a HX flush with descaler every 2-3yrs.
No mention of disassembling the HX on the UFT.

Boon

NY_Rob said:

@Boon You have to disassemble the HX on the KHN every year?

No. I had it open to check the burner but I was doing the annual stuff, too. The manual says the HX only needs to be cleaned if flue temp exceeds 54°F above the return water temp or if performance or combustion indicate a need. I don't even see where it gives a multi-year interval to clean it.

Anyone want to guess how many honey bees it takes to impact combustion on a KHN?

7 honey bees; 1 medium-size moth; 4 leaf pieces

[it wasn't only the debris. combustion was off, too]

NY_Rob

Oh, good to know.

Certainly not something you want to dive into often.