Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

pensotti install hints? (asking not giving, I'll give on another thread)

archibald tuttle
archibald tuttle Member Posts: 1,078
edited December 2020 in THE MAIN WALL
so after pursuing the elusive pensotti I have got a new one from sid's for a project that is my intro to this boiler. while i have a list of questions to call granby about, a few of them probably can get weekend answers here from those with experience and the kindness to share it.

My biggest question marks on seeing this thing up close is that feed and return connections line right up with the stack which doesn't seem like a superior approach. Not to mention that the length of the manifolds provided is actually longer than a couple of smoke 90s to turn up and then into chimney so that I would actually have to move the boiler further from the chimney than i have set it to fit that manifold in.

Seems like these are standard size flanges so maybe I can make my own manifold that turn more quickly (and reduce the leverage of any weight, e.g. circulator) placed on the manifold.

Then on the feed the manifold runs right into the stack. I guess they anticipate a longer horizontal although I didn't read their minimum flu pipe requirement as being horizontally oriented out of the boiler and somewhere in all this, maybe discussions here, had come to the conclusion that the closer i got the barometric damper to the firebox, the better. So i turned up out of the breach and into a tee for the damper.

This leads me to consider using the front flange which was shipped capped instead of the back flange as the feed. There doesn't appear to be any discussion of this in the manual. I would have to drill a hole in the front cover and throw in a union so it would come off for cleaning. or I could use a flange with a street el and cut a U into the top of the front panel, or for ultimate convenience, combine those ideas and extend the U down the front of the panel and then bolt a piece of steel angle below the U to retain the integrity of the panel across the upper front of the boiler that would be challenged a bit by the removal of material at the folds that provide its rigidity across the front of the boiler. (obviously I looked at how the manifold I created wouldn't have anything mounted so as to interfere with the door swing for cleaning/service access.

If I can use standard flanges, which appear to match to construct my own headers the other question is material. nice stainless ones are available and or brass and brass piping. The amount needed wouldn't be ridiculous but I'm wondering if putting too much galvanically-less-active pipe material adjacent to the boiler is just making the boiler sacrificial so how much attention to this rather than just using steel flanges and block pipe would anyone recommend.

And sideways to that question @Hotrod , are the swivel flanges on the grundfos shutoffs for the circulators stainless as they appear. this would be a little further from the boiler, maybe a foot and a half up accounting for the elbow and tees for the pressure temp gauge and for the PONPC just before the pump. (or it did occur to me that this is not going to be a high pressure drop boiler (on the water side vs. the flu that is) so I might bring the PONPC to the return entry just upstream of an 1 1/4 inch ball valve to allow boiler isolation when working on that equipment. This offers a more out of the way placement for expansion tank and I pipe separate bleeding fill off the backflow preventer to a spot forward of the circulator isolation valve so I don't subject the boiler to higher pressures during bleeding with full on domestic water pressure. (i've taken to running pex to a drain tub with air gap piped to tees with ball valve just upstream of zone isolation ball valve for each zone rather than garden house outlets–of course, when I do this I never have to bleed the system a second time so it might be overkill but it sure is nice even for first fill or refill after working on a zone.)

Finally, as if that weren't enough questions, the return flange mount on the back of the boiler has a 45 degree pattern such that the provided return manifold has a 3/4" tapping pointing straight down and one straight up. So i'm assuming, although it doesn't really match the ergonomics of boiler drains that this would typically be where the boiler drain valve would go? I could put a close nipple out of a flange to a 1 and 1/4 by 3/4 branch tee for a drain and still be tigher than the factory manifold. I could face that down which would be similar to the factory bit, but my tendency would be to make it horizontalm or slightly down from horizontal. This would leave a small bit of water in the pipe and the bottom of the boiler although i notice the boiler geometry is such that some water actually sits below the flange exit itself, maybe 1/2". Just wondering on the approach there. Don't think i'm setting this up for a lot of sedimentation but wondering on best practice ideas. It still would be tighter than the factory manifold meaning I don't have to move the boiler out (more work and slight loss of room space in a not exactly copious area) and to avoid the the stack i'm planning on offsetting the elbow after the drain tee at 45 degrees to a 45 placing the return rise some 6 to 8 inches to one side of the stack.

Any other hints about what folks have done piping these boilers greatly appreciated as I often find the best ideas here. There blowing some smoke up your smoke pipe, so to speak.

happy thanksgiving or advent or whatever floats your boat.



  • archibald tuttle
    archibald tuttle Member Posts: 1,078
    and now more targetted. Granby says the flange spec is pretty close to a regular circulator flange, not exact but its been done before. they prefer graphite gaskets to flat rubber although haven't tested like elastomeric rings.

    as far as front mounting the feed manifolds or whatever flange their engineer says you need to move them both because i guess the water passages are such the the water misses a pass if they are not on the same end of the boiler. so that there are pass arrangement for the water as well as the flu.

    and if i'm obsessing about flange and near boiler piping materials vis-a-vis not making the boiler sacrificial, is there any reason I can't pick a 12 inch stretch in the near boiler boiler piping and as i turn out of it replace the elbow with a 1 and 1/4 x 3/4 x 1 and 1/4 tee and thread a sacrficial annode for a water tank setup in?

    can't really figure why that wouldn't be a good idea. if so best location? feed, return, high, low in piping?