Baxi Luna HT330 (aka Laars Mascot HT 330) cleaning maintenance question- buildup


Old 11-01-12, 10:54 PM
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Lightbulb Baxi Luna HT330 (aka Laars Mascot HT 330) cleaning maintenance question- buildup

Hello all! About 6 years ago I installed a radiant floor system in my house. It's been working great the last few years (I had a hiccup or two the first couple years), but every year when I service the boiler, I am surprised by the build-up of carbon. I think it's much more than I should have in the boiler. I carefully vacuum it out and wipe down the chamber of boiler, then re-calibrate according to the manual (setting the CO2 output with combustion analyzer - usually I made only a small tweak, but it doesn't seem to stay exactly the same year to year).

Anyway, I'm wondering why I have so much build-up, or if this is "normal" for a year? This is a mod-con boiler, and also delivers on-demand hot water, so it cycles on and off a lot every time water is turned on, but still is this expected?

Advice/thoughts are appreciated! Please see the attached images to see what I'm talking about!

Thanks, jetpeach
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Old 11-01-12, 11:14 PM
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That's after a full year of service and before you clean? If so then count your blessings.
Old 11-02-12, 05:26 AM
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That is a lot of residue for one year of operation. LP will create more byproducts than natural gas. Are you getting cross contamination of flue gasses. You mentioned many cycles on hot water demands what about heating?
The unit should be running longer run cycles of 10 -20 minutes minimum. Does the control allow you to turn the fan speed down?
What is the Co when you have it set up?
Old 11-03-12, 12:43 PM
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I service a Munchkin with the same Gianoni heat exchanger about 3 times a year ...also on LP..get about that much build up each time..if that is a years worth consider yourself lucky indeed
Old 11-04-12, 11:38 PM
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Thanks for the tips and advice! A few answers:

Yes, this is before cleaning- it looks a lot nicer after I clean

sorry I didn't make it clear - I'm not on LP, it's on natural gas. I suppose the fact that I calibrate it led you to believe that, since from the factory I guess the settings should have never needed changing for natural gas (at least in theory) ... I originally installed it myself though, and then had a boilder repairman check it and he did a calibration, and so I've been checking/tweaking a little every year...

I calibrate to 8.7 and 8.4% CO2 at the flue for the max and min thermal output respectively. This is at a 5400 rpm fan speed, which was the default used (I never changed). I never check any other parameters though. Sometimes I really have to go back and forth between the min and the max before I can get it right though, because changed the min or max screw still impacts the other (even though one is suppose to be for setting the max and the other the min...). I've never checked my inlet gas pressure though (I assume it's standard through the US though?), although I think at one point years ago I verified that it was at least suppose to match for the first table.

Anyway, Ford and poorplmbr make this sound like this would be low buildup for an LP system, but a natural gas should be cleaner? rbeck - any thoughts on how much less buildup would you expect from a natural gas system? If it depends on cycling mostly, I do have a bit of a problem with short-cycling during the heating season - (this is rambling, but the boilder even on low is overpowered for the Seattle area where I am for many months of the year when temps are moderate... I added a 50 gallon buffer tank to try and reduce/eliminate the short cycling, but it only helped moderately...I ran various numbers, and came to the conclusion that my primary loop, which has 2 zones off of it, doesn't circulate enough volume because of the 3/4 piping and connections on inlet/outlet to boiler and on the buffer tank. I can't do much about the boiler inlet/outlet connections but should really enlarge the rest of the primary loop to be 1" minimum. Just a big project I haven't gotten around to. Right now I programed the boiler to have a 9 minute boiler idle time between fires to try and have the system utilize as much heat capacitance stored in from the buffer tank and reduce short cycles).

Well anyway, I'm put a little at ease at least by knowing LP systems have even worse buildup then this. Even if I'm above average for NG, maybe it's within a "normal" range and explained largely by the amount of cycles this on-demand hot water and heating.

THANKS AGAIN! Any further thoughts I always appreciated though.\
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Old 11-28-12, 06:47 PM
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I have a Baxi Luna HT380 that was installed back in 2008. It's running on NG. I decided it was time to clean out the boiler last season and it looked clean as a whistle except for a few insects & such. Nothing like your picture.

I'm very impresed with the Baxi. Nice boiler. It's been pretty much problem free. Only issues I'm having is with a Watts B1156F pressure regulator but that's another post.

Robert McHenry
Concord NH
Old 12-04-12, 12:17 AM
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Thanks McHero, that makes me more concerned - clean as a whistle after 4 years? wow.

If you don't a few questions, are you using the on-demand hot water functionality? Did you have it install or install it yourself? Ever play with the calibration on it, or just all settings straight from the factory?

Thanks, Joe
Old 12-05-12, 05:30 AM
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Prior owner of the house installed the system. I do indeed use both domestic & forced hot water. Setting are standard, both dials pointing to center of comfort lable. I have not done any modifications yet. I do have an external temp sensor I'd like to wire up this winter.

I just didi not recall seeing such a buildup like yours. I'll be happy to clean her out this weekend. I'll take some PICS and post for you. Early AM here & I'm off to work shortly.

Oh, What size gas line you running to that Baxi? Can you provide some PICS?


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