Best Of

some gas utilities use a gas cock that can be turned off with a tool, aka Cresent wrench, but cannot be turned back on without a special tool. There is a pin on the backside that needs to depress. I think Michigan requires this type of valve at the meter.

Lye is "Kryptonite" to aluminum. I tried to store wood-ashes in an aluminum vat. They got wet—being outside, and uncovered—and the bottom 1/3 of the vat disappeared. An inadvertent experiment, but very instructive.

The damper probably covers the a high jet or high air passage so a low jet can handle the small flows sort of how you use 2 mixing valves in parallel for a wide range of flow rates.

Keep in mind Patterson Kelly boilers start at 300,000 BTU/hr. They play mostly in the 750,000 and up range.

A few points I would mention. He talks about the need for turbulent conditions in both the gas side and the water side. In residential sized systems, piping below 1-1/4" that would be a very low flow condition. Somewhere below .5 gpm in copper tube to go laminar.

He mentioned that modulating boilers are mainly used to correct a piping or design deficiency. I think in residential work they are more to address zoned and micro-zoned systems. Again PK deals with larger commercial systems, so that may be more of their market, solving problem jobs.

For years now we have been suggesting all hydronic systems should be designed to supply a design load at 120 SWT! So that keeps you in condensing range, 90+ fairly easily. In his example you may see flue gas a few degrees above return, now approaching 99% efficiencies!

Although when I suggested 120 max. SWT, Robert Bean asked me why not 110 or 120. Always a step ahead, that boy:) His crystal ball was already presenting A2WHP potentials.

I think the damper you see in mod cons is how they get above 10-1, the gas valve doesn't really modulate down so low, they start to chock off the air flow as he mention. That is why cleaning and keeping those dampers moving is an important part of mod con service.

As far as 20-1 and higher, that is often two 10-1 boilers inside the jacket, both running 10-1, not necessarily one HX modulating that range. Or a HX like the Sermeta DUO 260K and up.

I though he did a great job of making the presentation understandable.