Dunkirk boiler repipe - thoughts?

Justin20

I've just finished repiping my boiler after seeking help on here for my one pipe steam system that took a long time to heat all the rads and was resulting in really high heating bills.

Here's the thread: https://forum.heatinghelp.com/discussion/186823/missing-main-vent-high-heating-bills/p1

After adding 2 B&J BM vents at the 'end' of the main and a few other tweaks to the boiler controls (replaced Cyclegard with Safegard & pressuretrol with vaporstat), i decided to go all in and do a repipe. Special thanks to @SteamingatMohawk for providing graphs and calculations showing i was definitely undersized and could benefit from an added supply riser.

Well i took a crack at it and here are the results. Please let me know what you experts out there think. I'm no plumber... just a DIY homeowner with way too much time on his hands 😁.

BEFORE:

AFTER:

One thing of note - while it was never terrible, there was some hammer as the boiler started to make steam at the beginning of the initial heating cycle. This is now gone.

I notice some of my vents spit a wee bit water but I'm told varivents are infamous for this so i can live with it.

I'll have to wait a month to see if my heating bill goes down any. The rads definitely get hotter faster.

I'm open to suggestions on vaporstat settings. It's currently set at .5 cut-in - 1.5 cut-out (ive verified with the gauge... the controls are not 100% accurate).

Thoughts on the amateur repipe job? I took the opportunity to add a tee at the new supply riser for skimming. I suppose I'll wait a few days before attempting to skim.

JUGHNE

That looks impressive, there should be other Dunkirk boiler owners here who are jealous of you.

Where the outlets 2" or 2 1/2"?
Is that a 3" header?

If you take out your skim plug and look inside the boiler, you may see reduced push nipples across the boiler. If so then I would recommend adding a reducing coupling down to 1 1/2" for your skim port.

This will make the skimming water rise up above the top of all the small push nipples and skim all top water.

Without the reducer to raise the water level in the boiler, then you will only get water from the section closest to the skim port.

ethicalpaul

Three years ago @JUGHNE gave me the same advice which I didn't quite understand at the time but I followed it, it's good advice!

You now have one of the best piped dunkirk boilers I've seen on this site (they seem to always attract "creative" piping--including my old one). Very nice job, done in the middle of winter no less!

After you skim it, it will be running great. If it still hammers after that you'll know you have a sag somewhere.

Justin20

@JUGHNE all piping is 2" with a 3" header and 1-1/4 equalizer.

The tappings are 2-1/2 but i left the risers @ 2" for two reasons:

1 - that original tapping's nipple and reducing elbow was really stuck on there. I would have needed to remove all boiler controls to get a 4-5' cheater to try to crack it and may have risked tipping the boiler over.

2 - based on @SteamingatMohawk calculations, adding a second 2' riser would have gotten me below the recommended steam velocity

3 - I've read multiple posts where people researched this boiler type (dunkirk, utica, etc) and found other manufacturer names based on the same boiler work fine with 2'

@ethicalpaul i took a look inside the tapping and there were multiple sections. I'm not sure what a push nipple looks like... Can you explain how simply reducing the 2" skim port i have now will help me get all the water?

ethicalpaul

You'll get all the water either way, but with skimming, you want to get all the "top water", that is the stuff floating on the top, so you want it to have a clear path to the exit.

The nipples are just the connectors between the sections that connect them (at the top are the ones we are talking about). Apparently the push nipples are smaller than 2" so in order to have a clear path of the high level when skimming from that side port, you want to reduce it which will raise the water level just a bit higher so it clears the higher level inside between the sections.

Did I describe it OK @JUGHNE ?

Hap_Hazzard

That's nice work. You're a quick study!

EBEBRATT-Ed

Looks good!! Nice job and the fact that it heats better tells the story

Steamhead

Justin20 said:

............3 - I've read multiple posts where people researched this boiler type (dunkirk, utica, etc) and found other manufacturer names based on the same boiler work fine with 2"

For the record, the Utica boiler is not the same. The cast-iron block is completely different, and the outlets are 2" instead of 2-1/2" on the Dunkirk block.

With that said, you're definitely light-years ahead of where you were. Please post fuel-savings figures.

mattmia2

ethicalpaul said:

You now have one of the best piped dunkirk boilers I've seen on this site (they seem to always attract "creative" piping--including my old one). Very nice job, done in the middle of winter no less!

i mean that piping is creative, it just also happens to have got everything in the header in the correct order.

I assume that there are returns at the other end of the mains.

You could even reduce your skim port to 3/4" or 1" and use an inexpensive ball valve with integral hose thread and attached cap.

Justin20

I assume that there are returns at the other end of the mains.

The main to the 'left' (looking at them dead on) is a parallel flow system. You can see the 'dry' return coming back against the wall

The one to the right is interesting. It only feeds 2 radiators at the back of the house –one on each floor– and i can't seem to find a return (much of it is in the ceiling in a finished basement). It appears to be a counter-flow main with no drip or any type of return. I guess condensate just flows against the steam back into the boiler??

Interestingly enough those 2 rads have never given me a problem... No banging, they heat up fine. go figure

SteamingatMohawk

Only one thing left to do...

mattmia2

Justin20 said:

The one to the right is interesting. It only feeds 2 radiators at the back of the house –one on each floor– and i can't seem to find a return (much of it is in the ceiling in a finished basement). It appears to be a counter-flow main with no drip or any type of return. I guess condensate just flows against the steam back into the boiler??

There should be a drip on that main which was probably removed on some previous boiler replacement although there is probably so little water in that drop header and not much coming back from those radiators such that it won't be a problem. It might slow the steam down to those radiators a little.

Justin20

SteamingatMohawk said:

Only one thing left to do...

A new gauge (5psi this time) is on order.

SteamingatMohawk

Valve?

Justin20

@SteamingatMohawk I've been away for the last few weeks.

My new 5psi gauge has arrived. I'm looking for advise on a good isolation valve for this gauge.

mattmia2

Just a 1/4" ball valve or whatever size the gauge is.

SteamingatMohawk

From NY state Labor law 27 4-5.5:

"...arranged that the gage cannot be shut off from the boiler except by a cock with tee or lever handle, placed in the pipe near the gage. The handle of the cock shall be parallel to the pipe in which it is located when the cock is open".

Just don't use a valve with a round handle.

https://dol.ny.gov/system/files/documents/2021/03/cr4.pdf