Steam job's got me stumped

Ken C.

I need to get one or two of Dan's book on steam heat, but in the meantime, I'm hoping some of you can help me out here. A customer who just had a new steam boiler put in called us because a radiator air vent literally blew off the radiator (the vent broke off at the threads). I checked the pressuretrol setting on the boiler, the installer (one of our subcontractors) set the cut-in at 9.0 psi, with a 1.5 additive differential. I reduced the cut-in setting to 0.5 psi and replaced the radiator vent. When the system got up to pressure, the vent began spitting water. There was severe water hammer in the radiator (steel-fin on steel pipe convector) and also in the uninsulated steam main. The radiator was pitched properly (single-pipe system). I opened the union in the basement for the pipe serving that radiator, and no water came out. I then removed the radiator vent and used compressed air to blow the radiator out, but no crud came out of the broken union connection. Since there is another radiator in the customer's living room, I ended up capping off the problem radiator pipe in the basement for now, until I can figure out the problem. I also noticed the boiler sight glass had a blob of rusty crud floating at water level. I also noticed that the low water cutoff would shut the boiler down, but as the system cooled, the water level would come up again. What's going on here? Does this system have multiple problems?

Unknown

Gotta start with

the size of the boiler . Was the sq. ft. of radiation sized to the new boiler ? Oversizing a system with steel convectors will give you lots of hammering - I had one last year with similar symptoms . Also , was the near boiler piping done to the manufacturer's specs ? Both are extremely critical to starting off a new system in the right direction .

And was the boiler skimmed and the returns flushed ? I know when you replace an old steamer with a new one you'e gonna generate more steam much faster , stirring up all the crud that was in there over the years .

Did the vent explode off the radiator when the pressuretrol was set at 9 ?

Mark Eatherton1

Turnem Down Syndrome...

Try installing a vaporstat as the primary control and set it for 1.5 pounds wiyh a 1/2 pound differential and let it run that way for a while and see what happens. It's simply amazing what a screw driver can do TO and or FOR, a system.

I turned down a ladys system the other day, and told her I'd get back to her with some needed fixes. She called me back two days later and thanked me for letting her get 2 nights restful sleep in a row and told me to take my time putting the bid together. Her system quieted down:-)

The previous owner sold the house because they couldn't take the noise any more. Couldn't get any sleep! "All our plumbers could do is stand there and shake their heads..."

Poor guys:-)

Guess I "screwed" my way out of that job!

ME

Dave Yates (PAH)

had that once too

check the rad's inlet vlv for a broken (or partially closed off) stem. Lets steam in & traps condensate till she spits like a mad cat. Also hammers like a crazed smithie beatin on an anvil. Keeps the dust of'n the curtains though - unless they're sewn into the carpet(G).



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Ken C.

Dave, there is no shutoff valve to that radiator. The only way I was able to stop steam from going to the radiator was to remove a union in the basement and put a black cap in place of the union.

Ken C.

To answer your last question, yes, the pressuretrol was on 9.0 psi when the vent blew apart.

George_10

Mark

Excellent tongue and cheek. Brought a smile to my face.

Dale

Pipe pitch

I think you have a pipe pitch or plug problem. Sounds like the condensate is returning much too slowly. I would check the pitch back to the returns and just replace all the wet return and then flush. One thing to try is to remove the main vent after a call for heat and see if the condensate comes back faster.

Dave Yates (PAH)

missed info

I missed seeing your note that this is a baseboard unit. How long and what diameter steel piping? How much pitch? What size riser & supply? How does this supply leave the main - straight up - to the side - or on a 45?

Sounds like velocity, pitch, long run of BB or restricted size is holding the condensate from free return.

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Ken C.

Dave, it's steel fin-tube, about 12 feet long, 1-1/4" diameter. Pitch is approx. 1/4 inch per foot. Supply pipe is 1-1/2" diameter (although I noticed that the takeoff from the main is 1-1/4", then there is an 1-1/4" x 1-1/2" coupling shortly thereafter). I believe the branch leaves the main at a 45-degree angle.

Ken C.

Dave, it's steel fin-tube, about 12 feet long, 1-1/4" diameter. Pitch is approx. 1/4 inch per foot. Supply pipe is 1-1/2" diameter (although I noticed that the takeoff from the main is 1-1/4", then there is an 1-1/4" x 1-1/2" coupling shortly thereafter). I believe the branch leaves the main at a 45-degree angle.

Steamhead

I think you may have a velocity problem

in that fin-tube. There just isn't enough space in there for the steam and the water to get out of each other's way.

I'd add a return line and pitch the fin-tube down towards it. Run the return from the fin-tube into a wet return, or install a loop seal if you have to go back to the steam main or a dry return.

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