Combi boiler rattling and gurgling

ensmingeraa

I have an Weil-McClain AquaBalance combi boiler. I am using it for both radiant heat and our domestic hot water. For some time now, I have noticed the boiler is making a fairly consistent rattling noise, but certainly not all the time. If it IS rattling, and I turn on a domestic hot water tap, there is some immediate gurgling from the boiler and the rattling stops for a time. It will come back later.

My first guess is that something is causing the boilers little domestic HW chamber to empty if nothing is run for awhile, and the boiler doesn't like running when that is empty, so its rattling. I don't even know if that makes sense though. Is a check-valve typical on the supply line feeding the boiler? I certainly don't have one. Could I be pulling water OUT of the boiler when other cold taps turn on? Wild guesses.

Of note - I designed/installed this whole system myself in a fairly ambitious DIY effort (after quite a bit of research), so it's likely I've done something incorrectly, but it HAS been working wonderfully for several years now, if a bit noisily. If its useful to have details on the install I will provide pictures and/or diagrams.

Thanks in advance. This place rocks.

hot_rod

Could be air trapped up high in the boiler. Does it have an auto, float style vent on top? Check that it is working.
What is the boiler pressure running?

warmAK

Noisy flow is almost always trapped air even with functioning air vents in a flow state they usually won’t scrub air until flow stops.