Hot water zone off steam boiler; advice on which tapping to use

njphil

Hi everyone,

Long time reader, first time poster. Sorry in advance for the long post.

I bought a house a couple of years ago with a Pennco 1606 boiler. When I first got it, it was a sight, with a soldered copper "header" about 30° from vertical. The old owners didn't say there were any problems with it when asked, but then again all the radiators were pitched wrong, every other valve leaked at the stem, and the thermostat was set to 64 °F, so I'm pretty sure they weren't paying too close attention to much but their gas bill. Anyway, I've taken care of all that by replumbing the thing with a (sort of ridiculous-looking) drop header, adding some main venting, putting TRVs and new air vents on the rads, adding a vaporstat, fixing the leaks, insulating pipes, etc.. Dan's books and the help you all offer to the other posters has been invaluable to me; the thing hums pretty well now.

Last fall, we had our basement floor broken up, dug down a couple of inches and repoured (the boiler didn't move; so it sits on a little platform now), and in the process, we changed the main sewer drain, and insulated the slab and ran three radiant loops in it. The total load is ~21,000 BTU. This summer's project is to hook up the radiant to a heat source.

The boiler was a bit oversized to begin with, so I figure it can't hurt too much to steal the heat from there. I was planning on an Everhot RH-8 heating a conventional-looking (with the exception of the beefy pump I'm going to be forced to use because I could've done better designing the circuits) loop . My question is which tapping I should use on the steam boiler.

For available tappings, I have:
- a 1-1/2" tee I can reuse that's now the water supply feed on the return line (on the boiler side of the hartford loop).
- an unused 2-1/2" return tapping on the other side of the boiler.
- a 1/2" tapping about 3-1/2" above what's now the lower 1/2" tapping for the sight glass, also on the other side from the 1-1/2" tee.

I've read this: https://heatinghelp.com/systems-help-center/how-to-run-a-hot-water-zone-off-a-steam-boiler/
I can see a couple of options:
1. I can run across the mud leg, pumping from what's now the fresh water supply, through the heat exchanger and back into the boiler (I was also going to put a bypass on just to be on the safe side), but I understand that won't get me enough heat. Can I get away with it for 20,000 BTU out of the 153,000 the boiler can make? Getting the plug out notwithstanding, this seems easiest and cleanest, but if it won't work... I was planning on using a bronze B&G 100 for durability, so without having done the calculation, I suspect I'd be pushing a heck of a lot more flow than is needed through the Everhot to get the BTUs I need for the radiant with 180 °F boiler water.
2. I can still take from the water supply tee, but return by moving the lower sight glass fitting up to the 1/2" tapping 3.5" higher, buy a shorter sight glass, and return into the lowest 1/2" tapping. (The water level would be about halfway on the new shorter sight glass, which seems fine to me. Now, the bronze B&G 100 as recommended in the page above would generate a lot of flow to push through this 1/2" pipe. Is that going to cause problems? Noise? Also, I know from the link above that it will mess with the sight glass level if I tee right in, but does it make it ok by just going directly downward as little as 3.5"?
3. I can do the injection-through-a-bushing thing as described in the link above through the unused 2-1/2" tapping. I'm not enthusiastic about this option, as space on that side of the boiler starts to become an issue (that's where my electrical panel is).
4. I can do the injection-through-a-bushing thing from the other side, but this would have me undoing some unions on the Hartford loop and rejigging stuff. I'm also not so enthusiastic about this, but it wouldn't be THAT bad.

The Pennco's not the greatest boiler in the world, but it works, and since it's oversized for the steam radiation, taking the heat from it seems to make sense. As another option, I've also got a gas water heater that makes 38,000 BTU, which I guess I can crank up, put a mixing valve on, and run the radiant loop off a braised plate heat exchanger. Then I start to get worried about hot water in the dead of winter...

If I can pull this off without another heat source with another gas line, another vent, etc., I'd be a happy camper.

Any advice?

kcopp

depending on how old the boiler install is, pulling plugs out may be a real challenge. Got any pix? They help us see better. I would use the boiler.....Its made to heat as the water heater is not.

njphil

Here are some pics. The jacket is all unscrewed so I could get a good look at whether there were any tappings to be had, so don't mind the mess...

The first one shows the water feed; you can't see it very well, but it goes into that 1-1/2" tee which goes into the return tapping. (I'll scavenge the unnecessary pressure reducer for the hydronic loop.)

The second one shows the other side of the boiler. You can see the unused 2-1/2" return tapping on the other side of the mud leg, and current sight glass, which is 11" tall. You can also see the knockout in the cover for the 1/2" tapping over the lower sight glass tapping; I guess this was for a float type LWCO?

The third one is from the back of the boiler, peeking inside the unscrewed cover. Here you can see the two 1/2" tappings, one used for the lower sight glass fitting and the other plugged.

Having fought with one of the 2-1/2" plugs before, right now I'm leaning toward the easier and more reversible thing: return the water from the heat exchanger through the 1/2" tapping. If it sends my water level all crazy or makes a lot of velocity noise, I figure I'll know as soon as I turn the circulator on for the first time and can rethink...

Thoughts?

Steamhead

That's actually a Dunkirk boiler which was re-branded with the Pennco name.

Your best bet will be to get that 2-1/2" plug out of there. Yes, I know this won't be easy but at least you now have some time before the heating season starts. Use the newly opened 2-1/2" tapping as your supply, and tie the return in on the other side.

Steamhead

????????

N.H. Yates is a manufacturers' rep- ECR owns Dunkirk, which AFAIK makes those boilers. Look on the rating plate, it says "Certified by Dunkirk Radiator Corporation". You see that on all of these boilers.

njphil

Steamhead,

Thanks for the advice. I'll let you know how it goes.

I've wrestled out (with some help!) one plug before, along with two copper NPT-to-sweat adapters that were good and stuck (those had to be cut out very carefully...), so I think I can do it. The first time I attacked this boiler I was blissfully ignorant of just how stuck a plug or fitting could be. There's lots of advice already on here about how to do it, so I'll run with that. What I lack in strength I can make up for in patience.

njphil

Soooo....it's been many months, but I'm happy to report that the radiant system is in its second week of operation and working well (when it's still cold enough to need to work!).

I went a little crazy and went with primary-secondary piping off the heat exchanger, and left a couple of pairs of stub-outs to run lines up to our unfinished attic for when we want to finish it. It seemed easier to provide for bringing hot water up vs. finding a way to get a couple of steam risers up there or hacking the hot water loop apart later.

Both the mixing valve and the "aquastat" (an SR501-OR-4, with the sensor in the heat exchanger shell, and the thermostat for making steam on the DHW contacts) are on outdoor resets, so the heat going into the floor in what's now the shoulder season is mostly what's left over from the last time the boiler was asked to make steam.

The Taco 0013-VDTF3 I'm using to push through the 300' loops of 1/2" PEX is a little louder (60 Hz hum) than I'd like (it seems from searching on these boards that I'm not the first to complain...next time, less head loss in the loops!!), even with the DIP switch set for the lower minimum speed, but it's nothing I (or more importantly, my wife) can't live with. The plan is to eventually close the boiler off in a little room and bring make-up air in, so there will be ways to deaden the sound.

Anyway, I'd be happy to post pics if there's interest. It's been a PITA for me to execute as a homeowner, but I'm pretty happy with the result. After applying a little more pipe insulation I can leave the boiler alone for a couple of years...I definitely wouldn't do it again, though.

Paul S_3

Yes please post some pics love too see

njphil

OK, here we go. Be gentle!

The first pic shows the zone valve control and the mixing valve. I probably should have used a smaller mixing valve, but it seems to be working pretty well. Also, I could have planned the location for where the radiant tubing came out a little better.

The end switch for the zone valve control switches the relay in the second pic. The associated pump pumps the primary loop off the heat exchanger.

The third pic is of the expansion tank and air separator. There will be a wall there, and it's tucked so far behind the water heater that I'll likely end up leaving an access door to the three-way ball valve so the system can be serviced.

The fourth pic shows the heat exchanger, bronze-body pump, and the last relay, which functions more or less as an aquastat (with the sensor in a thermowell in the heat exchanger shell) on outdoor reset. The upstairs thermostat is wired into the DHW priority contacts to make steam, the relay in pic 2 into the regular t-stat contacts, and the pump set up to run whenever either system is calling for heat. I tried to get the pump as low as I could, but didn't bother with a bypass. I can hear a noise that I'm guessing is cavitation during and right after a call for steam; time will tell whether I'll have durability issues and I'll regret not putting in the bypass.

Funny story: while filling the system, I did something dumb with the purge valves and got the motor on the B&G 100 all wet, and so kept blowing fuses in the relay. It took a while to figure out, but after a couple of hours for the motor in the oven at 170 °F it was as good as new.

Pics 5 and 6 show the sides of the boiler, with the low-pressure gauge, and vaporstat on the right, and the heat exchanger return tied into the steam return on the left.

There's piping of the backflow preventer to 6" from the floor, some pipe insulation, and tidying up of some of the low-voltage wiring left to do, but otherwise it's a done job from this homeowner's perspective. I know this much: I'm never hiring that sloppy plumber (me! har har) for such a big job again!

Mannu

Can you post pictures past the everhot heater?

Mannu

Also why is a indirect water heat preferred for this application over a heat exchanger?

njphil

A braised plate heat exchanger would clog from boiler water debris. The indirect hot water heater is basically a shell and tube heat exchanger, with the boiler water in the shell (less prone to fouling) and the hydronic loop in the tube. These everhots have finned tubes, to get a bit more thermal contact.

Reliability in service with steam boiler water is the same reason the bronze body circulator is chosen.

Mannu

So i've done wiring with a taco relay before, but i'm puzzled as to how to get both pumps to work when the call for heat comes in from the t-stat? Do you just piggy back them on the same # in the taco relay?

Also can you show a picture of the return to the boiler of the everhot? Did you put it into the hartford loop?

great job, it looks like a work of art.

SteveSan

If you are looking to use 1 t-stat to bring on two zones you would just wire r-w to first zone then jump w on first to w on second zone. That will bring on both zones with a call for heat.

Mannu

Thanks for the relay information.

njphil

So the return from the water heater went into a tee between the Hartford loop and the boiler. It guess this defeats the Hartford loop with respect to leaks on the water heater loop, but I'm not sure there's a way around that, since you have to come down from the boiler to supply the water heater anyway. I think it works either way, but I'm no pro.

As far as the running the pumps went, I had thermostats in the basement heated with the in-floor radiant controlling the valve control module to run the pump (and open the zone valves) on the secondary loop for the in-floor radiant. I needed a pretty high-head pump to push through 300' loops of 1/2" pex, which I regret, as it's kind of loud.

This valve control module controlled a switching relay that turned on the primary loop pump, and that switching relay controlled an aquastat (I used a Taco FuelMizer) that turned on the circulator for the water heater loop, and fired the boiler. I wired the house thermostat (heated by the steam from the boiler) to the DHW terminals of the FuelMizer so that I could just make steam when needed for the rest of the house. The circulator on this loop was set up to be on any time the boiler was firing, to avoid any risk of thermal shock from stagnant cold water in the water heater getting pumped into the boiler.

This is all maybe overkill, but the system has performed well over time, and will flexibly accept expansion. These daisy chains of control were set up using the switching outputs (com, n/c or n/o as appropriate) on the relays.