2 pipe steam system lacking venting

Wvega123

Hi, i live in 6 story 60 unit co-op building. It has a 2 pipe steam system. The boiler runs on 5 PSI and our gas bill is pretty high.The boiler is controlled with a heat-timer platinum. Im confident none of the radiator steam traps work as i have never seen one changed in 20 years. I looked at the steam mains and only one main has a groton D but all have F&T traps where they connect to the dry return. Do you think this system would benefit from more air vents? I attach photos of the steam main diagram, three of the mains with F&T traps, and the one with the gorton air vent. The other mains not shown are pretty much the same as those in the pictures.Thank you for your advice.

Jamie Hall

Interesting. Well, I don't think I'd have done it that way, but I'm not a pro. and lately the pros have decided that those of us who aren't should shut up.

Mad Dog_2

Wvega..where you located?   Mad Dog 🐕 

Wvega123

Im in kew gardens in queens nyc. The building was built in 1932 and i believe it was a coal fired system then oil then upgraded to gas maybe 10 years ago. 

Steamhead

Definitely not enough venting. @Mad Dog_2 , that should be right near you..............

EBEBRATT-Ed

@Wvega123

Does this system have a boiler feed tank or condensate tank or does the condensate return to the boiler by gravity?

Wvega123

The system has a boiler feed tank i assume its a gravity condensate return system

EBEBRATT-Ed

Then you do not need venting if it has a boiler feed system.

Unless you have some return lines with water traps in them.

The steam traps do the venting and the air vents out the vent pipe on the boiler feed tank.

If the traps have never been serviced that is probably contributing to some of your problems.

Steamhead

@EBEBRATT-Ed 's point would apply to the dry returns when a boiler-feed or condensate tank is used. But those F&T traps' throughput are often not enough for good venting of steam mains. @Wvega123 , measure the length and diameter of your steam mains and post the results here. We can tell you what you need.

Wvega123

Ok will do on Monday when i can get access to the pipes in the basement. Thanks 

Charlie from wmass

Also check if returns are double trapped. Poorly maintained traps are often "fixed" by some mook putting traps on the pipes entering the boiler feed tank. Photos of tank also please. Other "geniuses " can't tell the difference between a boiler feed tank and a condensate receiver and use them interchangeably.

Mad Dog_2

Sir, You have the Steam Doctor RIGHT under your nose in Kew-Forest.  I'm 15 minutes out.  We are here to help....Find a Contractor!!  You found them...Mad Dog 🐕 

Wvega123

Here is a picture of the boiler feed tank. I don't see any double trapping

Wvega123

Here are the piping measurements to help determine the right venting. 99 feet of 5 inch, 54 ft of 4 inch, and 432 feet of 3 inch pipe. I also attach a new diagram of the system for what its worth. Thanks

EBEBRATT-Ed

That is a condensate tank not a boiler feed tank.

That open pipe that connects to the top of the condensate tank and goes up the wall and turns down with an open elbow is your main vent.

You should get air out of that when the boiler steams. No water and no steam should come out.

Jamie Hall

On a slightly different area, you mentioned drips into the wet return. While two drips from the same steam main or same dry return won't be much of a problem, you will have trouble if there are also drips from a dry return and a steam main, of from a different dry return, or from a different steam main. Those must be below the water line.

Wvega123

I don't think i asked about drip legs but thanks for the info. 

The super told me the boiler has a boiler feed tank but now i see that the system has a condensate tank which feeds the boiler and a low water cutoff feed in case of water leakage.

Back to the original question of venting. So what im hearing is that the system should vent thru all the F&T traps at the intersection of the steam main ends and dry return lines (see pictures) and thru the steam traps at the end of each radiator. 

However, the facts are the boiler is operating at 5PSI and probably all the radiator steam straps are stuck open. I guess it could be there is still a need for more venting, the setpoint on the heat-timer is too high (keeping boiler firing longer then necessary), maybe some of the F&T traps are not working properly, or something else? 

Any thoughts appreciated 

EBEBRATT-Ed

If the steam traps are stuck open you will see steam and water vapor coming out of the condensate tank vent.

The stains on the wall prove you have/had that problem.

If this happens the condensate will run hotter than normal and it will or has ruined the condensation pumps

The boiler will use a lot of cold make up water which will decrease efficiency, and really shorten the boilers life.

I am curious as to why you think you need more venting?

I will repeat what I said above on a job with a condensate or boiler feed tank the air is vented through the traps and comes out the condensate tank vent. You don't usually use air vents on these jobs unless there is some unusual piping configuration.

If you get steam out of the vent on your condensate tank your traps need rebuilding

pedmec

i find it complete nonsense that your trying to vent a 60 unit building thru a 3/4" vent. look at the back side on the condensate tank where the return enters. you should have multiple tappings on the back side of the condensate tank that would allow you to install a larger vent line. if your looking to get rid of air i would start there. not saying thats your only problem but a 3/4" vent is not helping

Wvega123

I think i need more venting because i keep hearing that a steam system running at 5 PSI is too high and the problem is usually related to venting. 

As Ed says I should focus on fixing the clear steam trap issues. Im not sure how the steam trap failures impact the system pressure except maybe it doesn't allow pressure differential which forces the supply side pressure to increase? 

Pedmec also states that the condensate tank vent is too small so instead of adding venting iit seems better to improve existing venting.

I guess my next steps are to increase the vent capacity at the condensate tank and determine how to replace the many radiator steam traps. Is there a link to the threads which would help? 

Thanks everyone I have learned much. I appreciate your feedback 

Jamie Hall

The fact that the system is running at 5 psi has nothing to do with venting (well, within reason). The pressure is controlled by whatever pressure control you have, and the boiler can't raise the pressure above that setting.

Wvega123

Fair point. However, there is no pressure controls. The system is run by a Heat-Timer which is controlled by the outside temp to start the system and return line temp (setpoint) to cycle off. 

EBEBRATT-Ed

@Wvega123

You cannot have a steam boiler without pressure controls.

The heat timer operates the boiler with two different sensors.

1 sensor senses outdoor air temperature

second sensor is the "heat established sensor. This could be a pressure control or a temperature sensor. located usually at the farthest point from the boiler. It tells the heat timer tistart timing when heat is established.

Jamie Hall

Perhaps more to the point -- you have to have at least one pressure control functioning as a safety cutoff. At least, I've never heard of a code or building inspector or insurance company which would let you get away without one..

Wvega123

To clarify yes the system has a temp sensor to tell it when heat is established. I didn't think of that as a pressure control but technically i guess that's right.

Charlie from wmass

Reduce the pressure. See how system works. Have a trap survey to confirm functionality of traps. Low hanging fruit first before changing mechanical parts. 

Charlie from wmass

Wvega123 said:

To clarify yes the system has a temp sensor to tell it when heat is established. I didn't think of that as a pressure control but technically i guess that's right.

You have a pressuretrol on your boiler. This is fact not guess work. If you post a photo of the boiler someone here will point it out.

Wvega123

We have a pressuretrol but it doesn't function. My guess is when they added the heat-timer 10 years ago they disabled the pressuretrol and put all the control in the hands of the heat-timer. 

Charlie from wmass

That's not how it works. Pressuretrol is a safety and is independent of the heat timer. I have worked on hundreds of heat timer systems. 

KC_Jones

Wvega123 said:

We have a pressuretrol but it doesn't function. My guess is when they added the heat-timer 10 years ago they disabled the pressuretrol and put all the control in the hands of the heat-timer. 

If that's true, someone made and extremely poor decision. The pressurtrol is a literal safety device. The only pressure protection you currently have is the pressure relief valve.

5 psi is ridiculously too high, you probably don't even need 1. The rest is waste.

Wvega123

Yes i agree. I realized the super has little knowledge of how a heating system works so Im trying to piece together as much as i can. 

You say 5psi is too high others say 5psi is within limits you can see how that is confusing. 

If the pressuretrol is replaced and nothing else changes the cutoff would have to be set higher than the current 5 PSI otherwise i don't understand how it works together with the heat-timer.

JUGHNE

Pictures of the boiler including the controls and piping, floor to ceiling, from 4 sides if possible will help everyone out.

ChrisJ

Wvega123 said:

Yes i agree. I realized the super has little knowledge of how a heating system works so Im trying to piece together as much as i can. 

You say 5psi is too high others say 5psi is within limits you can see how that is confusing. 

If the pressuretrol is replaced and nothing else changes the cutoff would have to be set higher than the current 5 PSI otherwise i don't understand how it works together with the heat-timer.

It can be confusing, absolutely and understandable.

But 5 PSIG is too high.

Charlie from wmass

There is a wall or a barrier here in translating what we are saying to what you are understanding us to be saying.

I am going to start with the basics. The pressure on a steam system for residential heating was designed in enough of a majority of heating systems that are in existence for us to say all heating systems two PSI or less. The pressure control at the boiler. A heat time simply control the number of minutes a system is supplying heat to the building. It determines that he is being supplied by a set temperature on the return piping or the supply piping at the last radiator. Is that uses a logarithmic equation to determine based on outdoor temperature or feedback from indoor thermostats how long that time has to be during shoulder season heating.

Wvega123

Ok all that makes sense. Let see if i got it straight. I set the heat-timer to winter mode. Outside sensor set at 50© when outside drops to 49© boiler kicks on. Return line setpoint is 145© when return condensate rises to 145© the boiler looks at the algorithm which tells it how much longer to stay on (colder means longer) before it turns off. Here is where i stumble A working pressuretrol is set to say 1.5 cut in and 2.5 cut off. If the pressure goes to 2.75 the boiler will shutoff regardless if the return line setpoint is below 145? And when pressure drops to 1.5 it will turn on regardless of outside temp? In short its confusing how heat-timer and pressuretrol work together since they don't talk to each other. 

Pictures of boiler 

JUGHNE

Your pressure controls are the 3 gray boxes on the top of the boiler on either side of the pressure gauge.

I can't believe anyone would by pass those pressure switches.

Even at 1.5 PSI the steam will still heat the building and the return sensor temp will rise.

The heat timer control just asks for heat and doesn't know or care about boiler pressure.
The boiler would be told to run up to pressure setting and then cycle on the control settings.
It would do this as long as the heat timer called for heat.

If the domestic hot water is still produced by this boiler, then there then this beast has to be hot all summer long to heat the insert coil. This would explain high gas bills for the summer.

ChrisJ

Can you imagine a boiler that size with no pressure control?

Jamie Hall

Or to put it in a slightly different way from @JUGHNE . The pressuretrols-- and I see you have three of them -- on your system served three different functions, and they ALL must be opreational on a system that size, both for safety and reliability.

One of them must be set for a cutout not greater than 2 psi. That one controls the system pressure between the cutin -- which should be less than 1 psi and 2 psi. If the boiler is making more steam than the system can condense, the boiler will cycle on and off so long as the heat timer is calling for heat, and steam will be being provided to the radiation so long as the heat timer is calling for heat.

The second is the primary safety control for pressure. That one may be automatic, and usually is set around 5 psi. If something goes wrong with the control pressuretrol, that one will still let the system operate until the operator (you) can find out what is amiss with the primary control

The third pressuretrol is the backup safety, and should be (must be, by code, for a commercial or rental establishment) a manual reset It is set higher -- typically around 7 psi or so -- and is, as I say, is a manual reset. It will cut the system off if the something really goes west with the other two. Being a manual reset, the operator must determine what went wrong, fix it, and then manually reset it. Then the other two will take over again.

In brief, all the heat timer does is tell the system that heat is needed -- just like a thermostat in a single residence. The control pressuretrol maintains the system pressure at the level needed to provide that heat by cycling the boiler on and off as needed.

Wvega123

Now i think I'm clear on how the system should be setup.

Get a working pressuretrol. Set pressuretrol to 2 psi cut out and 1 psi cut in. Put boiler on manual and turn on. Go to furthest radiator and when full of steam note setpoint. Use setpoint for heat-timer. Set second pressuretrol to 5 psi and third one to 7 psi. Turn the system back to the heat-timer.

The issue of bad steam traps will mean it will take longer to reach the setpoint but that can be fixed by eventually repairing the necessary traps.

Of course observe the system to see if anymore adjustments are required. At worst I can go back to the inefficient setup except with a working pressuretrol.

JUGHNE

Could you zoom in on the 3 pressure controls that we might read the settings?

As Jamie pointed out one is for control, one for high limit with manual reset and one could be a high-low fire control or a form of modulation of burner flame.

I doubt if your super could have jumped the pressure controls without messing some other controls up.

There are about a dozen devices for safety and control on that boiler. Inside the burner control box is a great number of wires connected to terminal blocks.

He probably just jacked the pressure up on the operating control.

A boiler of this size has the potential to remove most of the building if things really go south.

You really need a pro in burner controls and steam to go over every thing.

EBEBRATT-Ed

@Wvega123

You have 3 pressure controls on the boiler.

#1 is the operating control that turns the boiler on and off.

#2 would be a high limit control. The high limit control is a "back up" for the operating control. It only comes into play if the operating control fails. It is set at a cut out pressure higher than the operating control say 10psi. Modern codes call for the high limit control to be a "manual reset" control. If a manual reset control trips and has to be reset (there is a button on it). By doing this you know the operating control has failed for some reason.

#3 control is for modulating the burner flame. A larger burner like you have can run on low or high fire or any size flame in-between. I know this because the burner has a Honeywell series 90 mod motor on it.

The pressure control on the left looks to be the #3 modulating control. I do not believe you have a manual reset but the picture is not close enough to tell.

The control on the left will be a L91A or L91B if it is for modulation

The control on the left will be a L404E (usually) if that is the manual reset.


In addition to all that there is a hot water control somewhere that fires the boiler for domestic hot water.



If the controls are set properly:

1. The boiler probably stays hot and fires for domestic hot water but does not make steam regardless of the pressure control settings unless the heat timer calls for heat.
2. When the heat timer calls for the boiler to fire the boiler starts up. It will continue to run until one of two things happen:

The heat timer is satisfied it will shut down until the next call for heat or

The boiler will shut off on the operating pressure control (with the heat timer still calling). As the boiler uses steam the pressure drops and the boiler refires. It will continue to do this until the heat timer is satisfied.