Another Twin System - 6" Drop Header

JStar

We seem to be doing a lot of twin steam systems lately. Possibly one more in the near future...



Here's a few photos of the old National Radiator Co. boiler, and poor piping.

JStar

Photos

Here's an old TACO heat exchanger. Keeping this in the museum-piece collection.

JStar

New system

We'll be installing 2 SMITH series 8 boilers with CARLIN gas burners. New 6" drop header. Controlling the boilers with a 2-stage tstat and High/Low Vaporstats. The system has 4 steam unit heaters and 2 small radiators. There's also a small circulated hot water loop.



Pictures of the new system coming tomorrow or Friday.

Boiler wrestler

Nice

It always amazes me to see a real old boiler piped improperly, they all weren't on top of it back then. But still it worked for all these years. It looks like you are on 1st floor and won't have to take those sections up stairs, lucky you.



Can't wait to see the new install.

JStar

Demo

The boiler room is through one door, about 5 feet from our trucks. Can't ask for a better work environment than that!



The original header was only 4", which is what we use for single 5 section boilers. Being piped wrong, they probably spent 2x on fuel than they should have. Add to that, a major lack of main venting, and our fuel savings are going be easily predictable.

Steamhead

We still have a couple of those National 3-pass boilers

one of them has a Sunray burner mounted in the firing door and a full set of what appear to be factory-spec baffles. I got surprisingly good combustion test numbers out of that one once it was cleaned and tuned, but it still has a lot more thermal mass than a current model so it takes longer to heat up.



Was that a Wayne burner on the one you removed?

JStar

New

Here's the new system.



Steamhead, it was a Becket. I'll check what model number tomorrow.

ChrisJ

6 inch

Beautiful work Joe.

Now my 3" header really looks inadequate.

JStar

Header

The 6" fittings really kicked our butts. Embarassingly, we had a few leaks from being too conservtive with our teflon/dope. We remade the fittings by using dope, teflon, and more dope. The big threads of the 6" pipe digs deep and tears up all of the teflon tape. Lesson learned!



The system still needs some fine tuning and plenty of skimming. I'm debating whether or not to remove the Vaporstats on the unit heaters and install temperature controllers.

Boiler wrestler

header

That looks great. Did you consider welding the 6" header instead of screw fitting? Turning 6" isn't my favorite and those tees weren't cheap I'll bet. Bushings seem to give me the biggest trouble and I won't put them in without expando.

JStar

Header

I refuse to weld a header. I'd much rather struggle with threaded fittings than have a rigid header that's going to stress out and bust open in the future. We have 36" chain wrenches that just barely fit 6" fittings. A 5ft pipe wrench is on our wish list.

JStar

System

So, I spent the afternoon skimming and testing. Here's what I'm seeing...



The staging and unit heater controls are very fickle and hard to fine tune. I'm going to scrap the Vaporstats for pipe-thermostats to control the heaters. I will also set up another relay to turn off 2 of the 4 units heaters when the 2nd stage boiler reaches pressure and shuts down. The idea is that when 2nd stage isn't needed, neither is the full capacity of 4 unit heaters. In a sense, I will be modulating the heat emitters as well as the heat source.



More to come as I play around with this system.

SWEI

Unit heaters

what about slowing down the fans?  Ping me -- I might have something that will help.

Paul S_3

jstar

That 3/4" copper pipe with the two ball valves that are connected to the two boiler in the front....is that there to keep the water lines the same???or is that the supply or return for the condensate loop?..thanks Paul S

JStar

Copper lines

Those are for the circulated zone. The water level in the boilers equalizes because the returns are connected.

gerry gill

That, Joe

is one beautiful looking installation!!

gcp13

looks great

we had issues with the 5 in.drop header also

when it built pressure we had a few leaks on the bushings

reset fittings with wicking, how did you pipe the equalizer to

the return ? an how do you deal with carryover

from left boiler to right?

JStar

Header

We were out of wicking, or else we would have used it. The last 6" 90 faces down at a 45 degree angle, and reduces down, going to the equalizer in the back left. There is surprisingly little steam carryover between boilers.

ChrisJ

Laying

Won't water laying in that 90 be a problem with a reducer in it at an angle?  Even if you use a 6" to 2" coupler instead of a bushing its still going to cause water to puddle in it.

JStar

Water

You're right that it will. However, we needed to keep the Gifford Loop high enough to keep all of the wet returns wet. There is also about 2 cups of water that lays inside of each tee. In fact, every header, no matter what size, has water trapped in the fittings.

ChrisJ

True

Very good point.

vaporvac

Mother of all headers!

I think that one wins the prize, for biggest at least! Amazing! The control mounting on the header is an impressive arrangement. Is that your own design? I'm also wondering if you could share what two-stage Tstat you used. I see it's Honeywell, but they seem to make so many. I'm also a little confused how the vstats and Tstat work in tandem. Maybe i'll just search that.

nicholas bonham-carter

Twin system pressure

What pressure can you use as the cutout for the lag boiler?

Another advantage of that big drop-header may be that it's oil will not go into the boiler, but into the equalizer, where a valve located at waterline height could drain away any accumulation.---NBC

JStar

Pressures

The lag boiler cuts out at 12. Lead boiler cuts out at 16. When both boilers run, it builds pressure steadily, and maintains system very well. When only the lead boiler runs, it doesn't maintain enough pressure to keep the unit heaters running.



I'm planning to go back soon to add modulating fan controls to the unit heaters (as recommended by SWEI). If the blowers run at 50% speed, they should more closely match the lead boiler's output.

Toymotorhead

wow.

That is pretty amazing looking. (On the other hand I don't want to know what happens when you knock  your head into a 6" tee when working on the burners.)



I will admit, I was a little confused as to how your control piping was arranged, the straight on camera angle makes it look just like it is magically floating in the air not connected to anything.



Richard.

vaporvac

No Pigtail?

Hi Jstar. I like this arrangement, but noticed the controls don't use a pigtail like you used on the Veco system and most others that I've seen. How is that? Is there some principle one should follow? Also, is the Honeywell control on the far left the 2-stage Tstat? Really beautiful install.

JStar

Controls

No pigtails. We had more room to work here so I made my own manifold pigtail. The control assembly comes out of the last boiler riser, and drops down to form a water seal. Easier to work with when you have a lot of controls/gauges..



That is indeed the 2-stage relay. The green one.

nicholas bonham-carter

Gifford loop on a twin system

Do you have any pictures of the way you ran the Gifford loops?

There is usually only 1 equalizer, and so I am wondering how the two Gifford loops were piped in.

I certainly appreciate all of your postings here, so many thanks!--NBC

AaronH

Amazing

Please keep us posted... this is super fascinating!



Great work as usual, where is this system located?

JStar

Update

No pictures specifically of the Gifford Loop. There is only one loop for the whole system. Think of the two boilers as just one boiler. The equalizer drops from the header and ties directly into both boilers.



In this case, the Gifford Loop acts as a false water line for one of the returns as well. Seems to work very well for this double-duty application.



CONTROLS UPDATE:

About two weeks ago, I added the modulating controls. It was a Sunday and I just threw them up onto the unit heaters quickly, to make them operational. I'll be going back to tidy up and finalize their installation. Initial response was very positive. The unit heaters turn on as soon as steam is established, and stay on until the coil temperature drops below 100F.



I also set up some data loggers on the supply pipe and air stream of one unit heater. Should have a little bit of data soon, as well as pictures of the modulating controls.

JStar

Location

In a contractor's shop in Colt's Neck, NJ. The owner is, hands down, the best slate roofer in the tri-state area. I'm sure he won't mind me dropping his name here.



http://shortslate.com

JStar

Short cycling

Not so much. But, the weather was mild while testing. The warehouse was up to 60+F at one point. The system cuts out on pressure when both boilers run, but still drops down to less than 5 oz. with only one running.



I think the controls were a worthy trial, but they may not have the range that I was expecting. You can barely notice the fans modulating, although there are signs that they do. Most likely, I'll add a time delay-on-break to the lag boiler to prevent rapid cycling. The system maintains temperature, but not pressure, which is not at all a bad thing.

JStar

Repost

....

nicholas bonham-carter

Twin boiler water level discrepancy?

When the lag boiler shuts down at a few ounces, do you notice any difference in the waterlines from lead to lag, since there is no Gifford loop to separate them? The pressure in the lead boiler could force return water into the lag boiler. It's only a few ounces, but at 1.75 in/ounce, there could be some water movement,, so is there anything to worry about with the return water stacking up a bit in the lag boiler, while the lead is firing?

In my 2-boiler situation, I had thought of isolating each boiler with a loop, rising up to the Gifford loop height, from wet return to the boiler return port. My equalizer would come down into the wet return, instead of the usual route.--NBC

JStar

Water

There is no noticeable difference in water levels when only on boiler is running. On the VECO job, if we shut down a riser valve, the water would back into the off boiler within a few seconds. So, my theory is that the supply pipes and header equalize the two boilers to each other and prevent that from happening.

Tinman

Joe

A thing of BEAUTY! Wow!!!

nicholas bonham-carter

Big brother-little sister

Have you ever tried a pair of boilers, one of which would be 1/3 of the load, and the other 2/3?

As you have noticed no waterline movement in the lag boiler, it seems that the lag boiler (1/3) would have to fire only at the beginning, except in very cold weather.--NBC

JStar

Lead/lag

Thought about it. I came to the conclusion that I would rather go 60%/60% for redundancy. If one boiler goes down, the other can keep up in most weather.

JStar

Update

Didn't get a chance to grab the data loggers, but the owner told me that the system is maintaining 8oz with both boilers running. I think the colder weather has finally allowed this system to level out.