Oxygen Diffusion

CMadatMe

I recevied a phone call yesterday from a good customer who was at his Uncles house and couldn't figure out the problem. His Uncle called him because the relief vlv on the indirect would continue to blow, the boiler according to the tridicator couldn't get above 165 and he was stomped as stumped could be. When the indirect called and the boiler fired the tridicator temp would actually head left instead of right.  The job is just a simple two zone heating and a zone for the indirect. No priority. Piping is the standard antler nothing wrong with any piping. Zoned with zone valves. Boiler is  a Weil WGO-3 w/Reillo F5 burner.



When I got there we fired up the boiler and opened the indirect zone. Couldn't get a 20 degree delta-t. The boiler circ was running (you could hear it and feel it) and the tridicator temp was heading left.  As we shut down the boiler and started to ponder. I saw that one zone was  zoned with PEX tubing. This was down about 7 years ago and this run is well over 100'. I coudn't read the tubing as the writing was not visible. I grabbed small stool and climbed up to to read the backside of the tubing and low and behold it was plumbing pex.



After I explained to my customer the possible effects of oxygen diffusion so we decided to take out the circ. Oh my god! What a stink, smell coming out of that boiler,. like dead fish baking on a summers day at the dock. The circ was covered inside with a film of black as was the nipple coming out of the boiler. Took apart the zone valve and the same film. I also noticed on the side of the boiler that the stack temps since day one have been only 300 degrees. Took at the stack pipe and could see the right side of the masonary chimmney eating away and the pins on the iron covered in a hard white. Boiler was cleaned in July this year.



Question? What is the best way to clean out the boiler? Is it worth it? Same goes for the indirect. Do you think the reading on the tridicator are false do to covering of film?

Any suggestions would be appreciated. Customers uncle has very little dough. He is by himself. My suggestion was to put in a 50 electric htr for now and clean up the boiler and change the pex.

Mark Eatherton

We don't need no stinkin' oxygen barrier...

Chris, What kind of delta were you seeing on the IDHWH? More than or less than 20. If less than 20, and not under a load, that sounds normal. These things struggle to get to set point the closer they get to set point. Lack of delta T between boiler H20 and potable H2o.



The stink is normal. If it is associated with a red color, it is bacteria farts from iron consuming bacteria, hence the red color.



Gauge sounds bad.



Lack of expansion tnak on the potable side may be the issue for the IDHW heater. That, or temps approaching 210, and you would know that as soon as you opened a tap.



As for the residue in the flue, sounds like it has been condensing, or there is a leak in the casting, neither of which are good. If the boiler rumbles and jumps on the water side while firing, the boiler may be limed up on the bottom, but if that were the case, you should be seeing higher flue gas temps due to lack of transfer.



As for the lack of barrier, they will need annual fluid/chemical maintenance to insure pH stays between 7.6 and 8.5.



Put a recording pressure gauge on the potable side of the water heater to eliminate thermal expansion as the culprit on the weeping relief valve, replace the gauge, and get some chemicals in the boiler ASAP to cease any further damage.



If the HXer on the IDHW had failed, the pressure relief valve on the BOILER would be leaking, but that's not what I read... unless I misread it, which I have been known to do.



ME

CMadatMe

Mark

Once I changed out the circ and put in a new relief vlv on the indirect we had a 20 between indirect supply/return and boiler supply/return and it stopped relieving itself. I traced back the potable feed to the indirect. No backflows, checks or pressure red vlv at the meter. Water pres coming into the house was 75PSI.

Flue has been condensing since day 1. Caved in on the bottom right hand side. Oil company did a cleaning in July and you can see the brush marks still in the residue left in the flue. They should have atleast notified the homeowner. Funny thing is that this has been an issue with the indirect since original install. Seems like the burner isn't very hot. Flame was like a campfire yellow, very wide and stringy. Nozzle was .75 x 60B as per the Reillo Spec for the boiler. Air set up for 3.1 as per the spec. Since day one this boiler has been running a 300 degree stack.