firing 2 pipe steam for low pressure

Jamie Hall

that's a serious boiler. Can you give us all more specs on the heating system? And what else, if anything is hooked up to that boiler?

That much pressure doesn't look like your average steam heat system to me...

Malcolm

firing 2 pipe steam at low pressure

I've read Dan's book "The Lost Art.." and see lots of sins in my 2 pipe steam system but I still am missing something important. When I bought this mill the practice was to run the system at about 10-12 psi. After some reading I cut it back to about 9 psi but I really love what Dan says about running it at 1 or 2 psi. Problem is that the burner has a purge time of 90 seconds and it will knock the heat out of the boiler and right up the pipe. The boiler will then run for 2 -3 minutes and shut off and 2 minutes later the blower will be on again.

From a fuel use point of view it seems more efficient to run the boiler up to 15psi and set the spread to 14psi which would seem to minimize the purge time as a % of run time.

The boiler is a 3 year old Boilersmith 29HP welded (or real) type. It is only used for heating and replaces a 40 HP unit from the 1950's

Any clarity out there on a low cost strategy in this type of system?

Brad White

Modulating Fire?

The pre and post purge cycle is common and I believe required by code and insurers to vent the system of any stray fuel before ignition at each cycle, nothing one can do about that.

My best suggestion is to replace the burner with a full-modulating fire version if available and low-high-low if not. This way you will run longer and better balance output pressure without shutting down the burner and getting hit with another cycle.

Not sure what kind of burners are available for yours though. Others I am sure will have more targeted ideas.

Christian Egli_2

A bulimic boiler

Before spending anything on converted controls make sure your whole plant system can run at any minimum pressure. Look for condensate lifts hiding anywhere.

With such lifts, you'll still have to raise the pressure in cycles exactly like you suggest doing now. It doesn't necessarily matter that pressure is not up all the way up all the time.

Otherwise, Brad is right on with getting a burner that modulates. In the crudest, simply going from high to low is often enough sophistication. Perhaps your current burner is even ready for that. Now you won't be pre purging and post purging every 90 seconds.

You're thinking straight, Good for you.

[Deleted User]

Oil or Gas?

Burner Make & Model Number?

Many oil burners operating in your 8+ gph range will do lo-hi-lo modulation. Few power gas burners @ that input are configured for anything other than lo-hi-off.

W/ more info, we may be able to help.

Steamhead (in transit)

We have a customer

where we hooked up the unused lo-hi-lo feature on his boiler, and he saved 40% on his gas consumption. This is on a large Broomell Vapor system. A Vaporstat set at 2 ounces controls the firing rate.

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Boilerpro_5

Say steamhead

Where did you get the modulating vapor control, I've only seen them at higher pressures. A modulating burner does wonders for fuel efficiency.
And for my next trick, I'll be rebuilding a steam system that had a traffic accident( just put the boiler in two years ago). This should be interesting, details may follow later once I get a chance to look at it.

Boilerpro

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Steamhead (in transit)

Not a modulator on this one

just a Honeywell L408A or L608 Vaporstat- the one that maxes out at 16 ounces. The boiler is a large Weil-McLain LGB that's considerably oversized. All LGB boilers come with lo-hi-lo gas trains, 95% of installers never hook them up.

A steam system that had a traffic accident? Did a vehicle hit the boiler room?

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Boilerpro_5

Yep! NM



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Malcolm

Waterlogging in low press 2 pipe steam

Sorry guys, got diverted by life and just got back to reading the string. What I have been trying to do is set the Hi Lo so it only cuts in if the pressure is just above 0 and the Operator has been set at 3 psi with a 2 psi differential. It has been humming along most of the winter in this range. The burner lo fire rate is adjustable downwards - it came set at the highest rate and the Honeywell control can be converted to a modulating head if we want to get the next step.

The problem that has shown up in the past few days is that one circuit which deadends at a trap on the first floor so it can feed a heater on the second floor, has become waterlogged so no steam to the second floor. I replaced the guts of the downstairs trap yesterday and it didn't solve the problem so I rebuilt the trap on the heater above it - still no luck.

I just got it working but I had to crank the system pressure up to 7.5 psi to push the water out of the circuit. I don't like this solution, it is expensive and is masking the real problem. What the's going on? Why is this circuit loading up with water when the rest of the system is clear?

MB

Steamhead (in transit)

What comes after the trap?

Follow the discharge line from the trap and see if there is a water pocket in it. The line should slope downward from the trap to the boiler (or condensate receiver if there is one).

If there is a strainer in the line to the trap, it may be blocked.

If you were the water, how would you flow out of the pipe and thru the trap?

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Malcolm

it's not as though this circuit never works,it was working more or less up to a few days ago when it became very intermittent then wouldn't go at all.

It also may be that problems are more obvious now. I was fed up with the noise of the unit heater fan in my office so I installed a (salvaged) Honeywell Pressuretrol in the steam pipe just before the heater. I turned the bulb around to make it NO instead of NC so now the heater only comes on when there is steam!

When I opened the plug in the filter before the trap, it was pushing water out - as though the trap wasn't working.

None of the piping from this trap to the boiler has moved for about 100 years - it's hard for me to see what could change there - but I'll look at it to see if there is a sag in the line that shouldn't be there.

Thanks for the feedback.

Malcolm

Malcolm

dead circuit solved!

SOLVED! thanks to Steamhead. I went and looked and about 50' away I found a water loop in the return pipe. I'm still surprised that it affect a trap 10' above it and 50' of pipe away from it but...

The heater is now coming on at the slightest whiff of steam.

By the way if anybody has any old Honeywell Pressuretrol units gathering dust, I have a few more unit heater fans I would like to control to run on "steam only".

Now what will this system think of next...

Malcolm

Steamhead (in transit)

Glad to help

now as to those Pressuretrols, they would need to "make on rise" that is, close the circuit and turn the fan on when the pressure rises. The usual unit found on boilers is "break on rise" which opens the circuit when the pressure rises. So the usual non-mercury ones we take off when we install Vaporstats wouldn't work for you.

We've had good results using "strap-on" aquastats for this. Again, these must "make on rise"- an SPDT unit would work too, properly wired. Strap the unit on the condensate outlet pipe after the heater but before the steam trap. Set it to 140 degrees or so, and the fan will run when steam fills the heater but stop when it cools down, regardless of the system pressure.

Honeywell's strap-on is the L6006C1018. White-Rodgers has two that would work, the 11B09-2 and the 1127-2.

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Malcolm

re-using old Pressuretrols

The three Pressuretrols I have were salvaged off the old boiler when I put the new one in a few years ago - who can throw out such nifty bits as tilt switches. You are right of course, they are break on rise - I removed the bulbs and turned them around so they are now make on rise. Works like a charm. I adjusted them with enough resistance to eliminate most of the cutting in and out as the steam is first coming up.

Malcolm

Aquastats?

I just got thinking about the Aquastats you described, are they accurate enough that if you put one on either side of the trap you could identify a bad trap by the differential in temperature? How expensive are they?

I've been wondering about installing a digital steam guage to make it easier to run at low pressure. There's quite a bit of guesswork with the direct reading unit on there now. Some of the units I looked at on line give analog output signals suitable for automation connections such as creating a closed loop control of the burner if I change the head to a modulating one. Do you see any surprise problems in this direction?

Steamhead (in transit)

You could use

an infrared thermometer to check for bad traps. Remember, an F&T trap has little or no delta-T across it. You'd have to check further down the pipe.

As for digital gauges, I've never used one and don't know anyone who has. Let us know how it works for you!

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Phil_17

digital gauge

http://www.pewastore.com/index.asp?PageAction=VIEWPROD&ProdID=23

this link came from the wall i think about 6 mos ago [or the boiler room.com]nbc