Pulsating Burnham

Tony Viz

I have this oil fired, Steel Burnham with a coil. The pressure gauge starts pulsing and the pipes start shaking. this happens only when the burner is firing for a couple of minutes and is the most bizare thing I have ever seen. I was called out for a dripping relief. I changed the water logged expansion tank and relief valve. i thought the system was running fine when I left. Could the boiler be clogged up with minerals due to the leaking relief?

Paul Fredricks_3

seen it

We ran into a similar problem with a Burnham steel boiler a couple of years ago. We had the rep out to look it over. The basic problem is a lack of flow through the boiler. We tried increasing the size of the supply header since it was small, but that didn't help. The ultimate solution was the installation of a circulator, I think we used a Taco 005, piped between the supply and return that runs 24-7. That keeps the flow up and solved the problem.



It makes sense that since the boiler didn't do it when it was new that there must be a build up inside the boiler. It may not be much, but just enough to cause a problem. I suppose you could use something like a muriatic acid solution to try and clean things out, but I don't like to touch acid. The circulator solution worked fine, and the energy usage is minute.

Mark Eatherton

The vicious circle...

Here is a common scenario. Possibly not exactly yours, but I have seen it numerous times.



Customer calls and complains of noise issues in their heating system. 1st year service technician shows up and diagnoses problem as air in suspension. They install numerous automatic air vents throughout system in effort to quell noise problem. Expansion tank is old, non captive tank, hung from the ceiling.



Compressible air cushion is expelled by the automatic air vents that were wrongly installed (should have moved the pump from the return to the supply and made sure pump was pumping away from the PONPC.)



With no cushion, when boiler fires pressure rises to relief valve threshold (typically 30 PSI in residential applications). Relief valve does its job, releasing extra pressure, dumping water down the drain, undetected.



Make up valve sees a drop in pressure, and does its job of replenishing the water pressure, typically back up to 12 PSI. When boiler starts back up for either space heat or DHW call, pressure again rises due to lack of compressible cushion, and the vicious cycle starts all over again...



In the process of introducing significant amounts of fresh water, it introduces high quantities of solids (lime scale) into the water, and coats the surfaces directly above the radiant heat transfer process. As the heat is trying to transfer from the fire side to the water side, it's movement is retarded by the lime scale accumulation, and the energy JUMPS into the water, in the form of steam bubbles, and causes what you are seeing.



This can be confirmed by doing a combustion analysis and if the flue gas temperatures are higher than normal, it may indicate scale accumulation and lack of thermal transfer into the water.



This scenario can also be promulgated by a failed DHW coil, causing a cross connect between the potable and non potable water, and subsequent pressure releases. Under this scenario, water loss is constant regardless of boiler operation.



Sound familiar?



ME

billtwocase

diaphram tank

I have seen this quite a few times. Change the tank, and it goes away. I think the bladder is glued or stuck to the side of the tank internally and won't compress. Just my guess, Air pressure, etc can be spot on