2-Pipe System on City Steam NYC - Help

SuperRM

I'm the Super of a Coop on city steam. I am having the issue of "too much/not enough heat". My lower units have windows wide open and are cooking, and my upper units aren't getting any heat. The building isn't giving me the funding to change all the traps throughout the building (approx. $300K). We have two vacuums and they should be pulling the steam through the system, but unless I open the steam valve more than 10% my return lines stay cold and I get calls from cold residents. My vacuum is showing a psi of about -10. My questions are: is this only the result of failed f&t traps that need to be replaced or is something else amiss? Can I install thermostatic valves in my lower units to help control the heat entering their units and force more steam to the higher floors without totally jacking up my system? Can anyone recommend a really good company that knows City Steam to help EVALUATE my system and offer innovative ways to raise the efficiency of my system?

mattmia2

if you have traps failed open, you will have to find and fix those. the steam in the return will keep the air from being able to get out of other radiators. You don't have to replace all of them, but you do have to test and replace the ones that are bad.

neilc

your valve at 10% is volume,
what's controlling building pressure feeding the rads?

Jamie Hall

If you can get the funds to do it, see if you can get John Cataneo, @JohnNY , to come look at it. He doesn't come cheap, but he's one of the best in town.

EBEBRATT-Ed

@SuperRM

Unfortunately you can't make a vacuum system work without working traps and there is no work around.

@JohnNY is your guy

nicholas bonham-carter

Maybe an infrared camera would pay for itself in locating any stuck open traps.—NBC

SuperRM

Thank you all for your comments! I am truly humbled by your timely replies. It looks like my first step is an infra-red camera to locate open traps and a replacement.  This will take a long time since residents don't always like to give access, but it has to be done. 

Any suggestions on installing thermostatic valves that will individually shut down the radiators in rooms when the room temp is met?

jumper

Bad traps breed more bad traps. Some vacuum pumps don't like bad traps either.

retiredguy

You can't fix a steam system with an infrared camera. You need help so get the OK make the call. A good working steam system will save the building owners a lot of money but first they need to get the system working properly. A valve open 10% is not a zone valve or temperature controller.

ScottSecor

It's been a while since we worked on system with a vacuum pump that was actually still capable of pulling a decent vacuum. That being said, the ones that were capable of "sucking" would typically overheat and give us problems due to numerous - failed in the open position steam traps. In other words, on many of these jobs we found the vacuum / return pumps would have issues when trying to pump live steam that was blowing through the stuck wide open traps and ultimately entering the station. In my experience, it would be odd to have all cold return lines at the vacuum pump station with old (often original) steam traps. Any chance there are manual shut off valves on the steam mains that are closed?

I think giving John NY a call may be your best bet.

Pumpguy

What is your system operating steam pressure? Is there a way you can check the steam pressure and return line vacuum at various locations out in the system?

Typically on a district steam system, the pressure is reduced at the building to very low, even down to 1 PSI.

So long as you have steam at 1 PSI at the radiation, you have a temperature to provide 100% of the heat output of that radiation.

To me, your idea about reducing steam flow to the lower unit's rads has merit. Getting access to these rads could be a problem for you though.

The attached file shows how condensate temperature affects achievable vacuum. Hope this file is found useful.

mattmia2

Note that any steam you remove with the vacuum pump is wasted energy that you paid for.

JohnNY

Thanks a million for the referrals, gentlemen. I'm fortunate to be able to get my hands (kind of) dirty on numerous systems of this type year after year. The problems repeat themselves but every one is unique in some way. I welcome the opportunity to evaluate the the system @SuperRM is dealing with and am confident I can bring the condition to resolution.

9 days away from shot number 2, btw. Looking forward to putting this pandemic crud behind us all.

dopey27177

To Super M

I am retired 21 years from my consulting company, I spent 20 years working for the NYCHA maintaining the Steam Systems and Dunham Varivac systems. I was the plumbing section supervisor and the HA Licensed Master Plumber before the HA went to hell.

Before you do anything you need to be sure that your temperature controls are in proper working order.
You stated that you set the steam control at 10%. that tells me that your temperature control is not working on automatic.

Your temperature control is supposed to open the zone valve in proportion to the outdoor temperature. Additionally, the zone valve should have a micro switch that starts the vacuum pump.

The first test is to do a dead end test on the vacuum pump. This done by closing the inlet valve to the vacuum pump and running the pump cold to see if it is capable of producing a vacuum up to at lest 20".
At that juncture shut down the vacuum pump to see if it holds vacuum. If it holds vacuum the vacuum pump is O.K. If it don't not hold vacuum find the leaks and repair.

The next item is to identify what kind of vacuum system you have.
1. Dunham
2. National pump and control
3. Heat timer
4. warren Webster system ect.

Has your heating system been changed from Dunham to something else.

To pull a sustained vacuum in the heating mode the condensate has to be 160 degrees or less.
Steam pressure for the system depending on the size of the zone valve (EDR) should not ever exceed 10 psig.
Example: if you have a full sized zone valve inlet pressure may be set as low as 5 psig.
If you have a reduced size zone valve the steam pressure could be set as high as 10 psig inlet.
Down stream of the zone valve there should be a pressure control set at at no more than 2 psig.
The pressure control will maintain a steady steam pressure without over pressurizing the low pressure steam heating system.

Once you are able to provide no more than 2 psig you then can try to determine wheres team traps are defective.

The temperature controls are supposed to modulate the zone valve according to the the outdoor temperatures.
The zone valve will float based on the temperature in the building, never staying at one setting. Rarely will zone reach 100% open, this may occur when the outdoor temperature drop below 20 degrees and the zone valve will cycle down to as low as 40% and rise upward toward 100%.

During this operation vacuum in the system can drop down to as low as 4" Hg. This because the system is seeing the full measure of steam and the condensate temperatures may have reached 180+.

Higher vacuum cannot be reached until the zone valve is at 50% or less,
The lower the zone valve opening the higher the vacuum.

For a better understanding of what your heating system is see attachment.

The 12 pages I sent you are from my book on steam.
If you need to contact me I am at dopey27177@aol.com title you email steam heating problems.

Jake

dopey27177

Why has no one read or tried to help SuperRm with my post'
Jake

dopey27177

To JohnN.Y.

Since you will run to steam systems similar to this one I hope you will read the enclosure.
It may be helpful to you when you meet with future clients when you can explain what the problems are and how to approach the job in phases where some of the costs can be deferred by fuel savings on each heating seasons.

Jake

jumper

dopey27177 said:

Why has no one read or tried to help SuperRm with my post'
Jake

I think your post is helpful. Now SuperRm has to study it. City steam is expensive so proper control of two pipe pays for itself fairly quickly. The too much heat radiators benefit from inlet restriction.

dopey27177

I,know how expensive Con Ed steam is. back in the day 30 years ago it was $18.00 per thousand pounds of steam plus all the crap and dirt you got for free along the west side of Manhattan. Plugged pilot valves scoured valve seats etc.

Jake