Noisy, bubbling exhaust on Burnham Freedom Boiler.

[sharkytm]

I got my Burnham Freedom 120 installed a few months back, and everything about it is great, except for the noise from the exhaust. My heating bills have been cut in HALF, I have reliable hot water, and I've regained about 10% of my basement thanks to the removal of my old oil furnace.

However, the noise from the Burnham is getting annoying. Its piped up from the basement with their special concentric venting kit, and goes out the side of the house near the corner of my living room. When the boiler fires, it starts out very quiet. After about 5 minutes of firing, the exhaust starts to burble and bubble. It gets progressively louder for about 3 minutes, then abruptly quiets down. No more bubbling, no more burbles... just the expected exhaust noise. After another 5 minutes, it starts again. Repeat until the boiler is shut down by one of the zone valves. The contractor, who I've been extremely pleased with, says he's never heard one like this, and has contacted Burnham, but they don't have any ideas.

So... is it possible that condensate is pooling somewhere in the piping (which is only about 6' long), or is this just something I'm going to have to live with?
Thanks.

[tfkol]

Take a good look at the exhaust line from boiler.
Make sure it is graded at 1/4 inch to the foot back to the boiler and there are no sags in it. If that is ok, check out the drain on the boiler to make sure it drains properly and not air locking. If you are not sure drain it into a bucket for a while to see if it makes a difference.

[sharkytm]

I just checked the exhaust line. Its pitched properly, as it drops about an inch over the 2' horizontal span.

I checked the condensate cup on the bottom of the drain, and it had about 1/4" of black grit and some small aluminum shavings in it. I'm not sure, but I'd bet that those are from the boiler and it was never drained when it was first installed. I drained the condensate line and the emptied the cup. I'm running the boiler now to re-fill the condensate trap and see if that fixes it. Its possible that some of that crud got into the pump, and either clogged it or damaged it. We'll have to see. With it drained, its not getting noisy, so I'm betting that its not pumping correctly.

[sharkytm]

Well, here's an odd update.

The noise happens when the boiler is NOT firing. It hits its set point (190*F), and turns off, but the circulators keep going, like they should. This is when the noise starts, and the abrupt stop is the boiler re-firing after the water temp drops below the low point.

It sounds like there's air in the lines from the basement, and it sounds like the burbling/bubbling up in the house.

I've got a good air/water separator in the system, so I'm confused as to why there's air in the lines. We've also heard it a few times upstairs in our bedroom.

So, any thoughts?

[beenthere]

Time to call your installer back, and have him check it out.

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[local553]

it will make that noise if trap is empty trap should always have water in it. do you have an auto air vent on top of your air seperator?.

[mgs2253]

It is important with this type of low mass boiler to have correct flow rate. Is it possible pump is undersized and noises you hear is from boiler over firing. I would definitely check with contractor and make sure system is piped correctly. ( should be primary/secondary with dedicated pump for boiler side)