# 2 pipe steam questions



## RealLivePlumber (Jun 22, 2008)

I've got a commercial customer that has a 2 pipe steam system. In the auditorium, there is an air handler, with a steam coil in it. This room was remodeled about a year ago, and there was some repipng/rewiring done on this air handler. It has, however, been working fine up untill now. There is what appears to be a regular Honeywell zone valve on the upper (supply) pipe, the lower (return) pipe travels 12" horizontal, then comes to a tee, with a 6" riser looking up. The pipe continues another foot, to a steam trap. I am told that there is another steam trap further down the line. 

On the top of the 6" riser, there is a coupling, with what appears to be a bushing inside of it. There are no threads in the inside of this supposed bushing. It is open, and spewing water. 

The air handler runs continuously, even with the t'stat removed. I am assuming that there is an aquastat somewhere that is calling the fan to run. 

They started having problems with the fan running continuously on Tuesday, and the maintenance guy changed the t'stat, played with the zone valve, and Lord knows what else, He is pretty knowledgeable with the bldg, though. The open ended tee started spewing water today. 

I gotta go back tomorrow to look at this mess. Any ideas?

Especially as to why that open ended riser would be there?

And why it would be spewing water?


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## Airgap (Dec 18, 2008)

Sounds like it could be a vacuum breaker gone bad. they can spew water and steam if they aren't reseating well. That would be an odd place for it to be though. There should be one above the highest point of the steam coil.

Weird, it would help to see it....


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## ZL700 (Dec 8, 2009)

First, H/W hydronic zone valves are not approved for steam, and cant be used.

Risers usually are for steam vents or steam system vacuum breakers depending on type of system however neither one will last long if they see water. Condensate is supposed to drain back.

Couple thoughts

1. System pressure is too high. Except for vacuum or vapor systems, recommended pressure is no more than 1 PSI for every 18" from water line to bottom of header, too much and pressure backs up the return line affecting condensate return.
2. Trap downstream in combination with another is allowing live steam to blow back-wards.
3. Improper piping during remodel (lack of experience is evident by using hydronic zone valve).


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## Lifer (Nov 23, 2010)

ZL700 said:


> First, H/W hydronic zone valves are not approved for steam, and cant be used.
> 
> Risers usually are for steam vents or steam system vacuum breakers depending on type of system however neither one will last long if they see water. Condensate is supposed to drain back.
> 
> ...


 
So how to fix it ? remove second steam trap , and use proper zone valve?

I'm just askin , never seen a steam system , just interested



Lifer...


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## ZL700 (Dec 8, 2009)

Proper advice requires a visit, or good pictures with a diagram

HW zone valve $65, proper steam $200, and special order for most, now you know why they used it.


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## Airgap (Dec 18, 2008)

ZL700 said:


> First, H/W hydronic zone valves are not approved for steam, and cant be used.
> 
> Risers usually are for steam vents or steam system vacuum breakers depending on type of system however neither one will last long if they see water. Condensate is supposed to drain back.
> 
> ...


He could be looking at a pneumatic steam control valve. Which would be very common. If this is the case and the condensate has any lift on it, it will leave condesate in the coil or return. This could be part of the problem. 

Every time the valve opens up it will hammer like crazy.


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## ZL700 (Dec 8, 2009)

Airgap said:


> He could be looking at a pneumatic steam control valve. Which would be very common. If this is the case and the condensate has any lift on it, it will leave condesate in the coil or return. This could be part of the problem.
> 
> Every time the valve opens up it will hammer like crazy.


Yea, but when someone states regular Honeywell zone valve, I picture V8000 or V5000 series hydronic.


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## Airgap (Dec 18, 2008)

ZL700 said:


> Yea, but when someone states regular Honeywell zone valve, I picture V8000 or V5000 series hydronic.


you're right, it needs to be seen. Could be many things.


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## OldSchool (Jan 30, 2010)

RealLivePlumber said:


> I've got a commercial customer that has a 2 pipe steam system. In the auditorium, there is an air handler, with a steam coil in it. This room was remodeled about a year ago, and there was some repipng/rewiring done on this air handler. It has, however, been working fine up untill now. There is what appears to be a regular Honeywell zone valve on the upper (supply) pipe, the lower (return) pipe travels 12" horizontal, then comes to a tee, with a 6" riser looking up. The pipe continues another foot, to a steam trap. I am told that there is another steam trap further down the line.
> 
> On the top of the 6" riser, there is a coupling, with what appears to be a bushing inside of it. There are no threads in the inside of this supposed bushing. It is open, and spewing water.
> 
> ...


The top of the tee could be a well for a temp senor or aquastat.... it could be rotten

made a pic is this what you are discribing?


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## OldSchool (Jan 30, 2010)

Furthermore the sensor or aquastat could have been used to turn on the fan of the heater or air handler


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## Airgap (Dec 18, 2008)

I don't think there would be an aquastat on a steam condensate return.


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## RealLivePlumber (Jun 22, 2008)

OldSchool said:


> The top of the tee could be a well for a temp senor or aquastat.... it could be rotten
> 
> made a pic is this what you are discribing?


Pretty close. The supply and return come dirctly from the boiler, and feed only this air handler. 1 1/4" supply, 1" return. The supply reduces to 1" within 2' of the coil. They enter the coil in the same side. The riser is exactly as you have drawn it. 

The bushing in the coupling is all new. I was wondering last night if there was supposed to be something in it. It doesn't look like it though. 

Thanks, OS. you da man.

FYI, I looked at Honeywell's site last night. They DO make zone valves rated for steam, that look exactly like a hydronic valve. I will check today to see if that is indeed what is installed, and try to get some pics.


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## OldSchool (Jan 30, 2010)

Airgap said:


> I don't think there would be an aquastat on a steam condensate return.


Look at the drawing.... the tee is prior to the steam trap ...... condensate is after the steam trap 

as the steam condensates at the bottom any water moves into the steam trap

The well at top was more than likely for sensor bulb activating the blower on air handler

This way the fan has some type of control

Once the zone valve opens and the coil reaches it temperature it activates the fan motor.

And yes there is zone valves rated for steam


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## OldSchool (Jan 30, 2010)

RealLivePlumber said:


> I've got a commercial customer that has a 2 pipe steam system. In the auditorium, there is an air handler, with a steam coil in it. This room was remodeled about a year ago, and there was some repipng/rewiring done on this air handler. It has, however, been working fine up untill now. There is what appears to be a regular Honeywell zone valve on the upper (supply) pipe, the lower (return) pipe travels 12" horizontal, then comes to a tee, with a 6" riser looking up. The pipe continues another foot, to a steam trap. I am told that there is another steam trap further down the line.
> 
> On the top of the 6" riser, there is a coupling, with what appears to be a bushing inside of it. There are no threads in the inside of this supposed bushing. It is open, and spewing water.
> 
> ...


Also the more than likely reason that it has been working fine prior since the renovation is that the Fan is more than likely now operated by a line voltage thermostat or relay

I would also check the steam trap..... if you got water flying out of that tee other than steam then the steam trap is not working.

I suggest changing steam trap and capping off 6" riser as the fan seems to be activated differently than it was originally intended to do..


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## wundumguy (Apr 3, 2010)

RealLivePlumber said:


> The air handler runs continuously, even with the t'stat removed..


The tstat heat/cool signal often does not control the blower fan of an air handler or unit ventilator. Regardless of the call for heat/cool the conditioned space requires ventilation during occupancy to filter, deodorize, de/humidfy, and oxygenate air. The tstat heat/cool signal controls the heat/cool valves, and usually in conjunction with outside and return air controllers, determines the ratio of mixed air.


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## OldSchool (Jan 30, 2010)

I missed the part where he says the fan run continously...

So for sure somebody didn't know what they were doing during the renovation.....

The fan was like I said controlled through the aquastat or sensor in the well at outlet of air handler....

Suggest putting in aquastat and well at top of 6" riser to control fan

and changing the steam trap.... could also be the condensate line after steam trap blocked with rust... this happens if the system has been taken out of service for any extended period of time.... rust develops eventually blocking condensate line

Now the zone valve would be controlled by thermostat and fan would be controlled through aquastat .... this way fan only runs when coil gets hot....and a call for heat


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## RealLivePlumber (Jun 22, 2008)

Well, got a better look at it today. After we set up 3) six foot high sections of scaffolding. The unit is above a stage in a ballroom, above a t-bar ceiling.

They had a couple of issues. 

What appeared to be a bushing in a coupling was indeed a vacuum breaker. Odd looking unit, though. Non adjustable, and never saw one like it. It was mounted like old schools picture, in the lower return.

Let me preface by saying that the fan started to run continuously last Tuesday. ( I found this out this morning) So, yesterday, this vacuum breaker starts spitting water. That's when they called me. (The room was booked for both days this weekend). It was pure coincidence that both problems occurred together. We pulled the vac breaker, and could not locate one today. We disassembeled it, cleaned the scale out of it, lapped the seat, and reinstalled it in the upper supply. The fan was controlled by a general purpose relay, in the air handler. We swapped that out, and repaired a few loose stake-on terminals. The new 8000 series t'stat was connected to a remote sensor, and they never programmed the stat for the sensor. So, we did. Still not sure about what fires the boiler, it could be the end switch on the zone valve. It is indeed a steam rated unit. 

Anyway, the unit is now functioning as it did last Monday. 3 hours after we got there. (4 days after the maintenance man messed with it:laughing 

Thanks for the tips.


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## Airgap (Dec 18, 2008)

It sounded like a vacuum breaker. OS is right about changing the trap, but you don't want a sensor or aquastat in that return. Fan needs to be controlled by the space you're heating.


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## Airgap (Dec 18, 2008)

OldSchool said:


> Look at the drawing.... the tee is prior to the steam trap ...... condensate is after the steam trap
> 
> as the steam condensates at the bottom any water moves into the steam trap
> 
> ...


I know how a steam trap works...That's not where you want the fan control though. When is the fan going to cut out?


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## ZL700 (Dec 8, 2009)

A lot of times its just easier to use a stat with electric heat fan option that way R closes to W for zone valve, at same time R closes to G to start fan. If initial cold air discharge is a concern a $10 cube delay timer cam be put in series with fan R&G circuit.

That HW 8000 series visionpro can be programmed to do that, I thunk even the fan delay if I recall.


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## Protech (Sep 22, 2008)

disclaimer: I have very little experience on steam systems.

Doesn't seam like a logical place to put an aquastat for the function you are describing. I would think you would want the aquastat before the coil, not after. Your gonna get condensate on and around that sensor and will throw your readings off.




OldSchool said:


> Look at the drawing.... the tee is prior to the steam trap ...... condensate is after the steam trap
> 
> as the steam condensates at the bottom any water moves into the steam trap
> 
> ...


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## OldSchool (Jan 30, 2010)

Airgap said:


> It sounded like a vacuum breaker. OS is right about changing the trap, but you don't want a sensor or aquastat in that return. Fan needs to be controlled by the space you're heating.


Nope I disagree....

Most fans are controlled by the temp of the heat exchanger.....

It has been lately that the have been put on a timer..... it is not the space you are heating that controls the fan......

That been said ..... the heat exchanger reaches a certain temp then the fan turns on.....


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## OldSchool (Jan 30, 2010)

Airgap said:


> I know how a steam trap works...That's not where you want the fan control though. When is the fan going to cut out?


when the zone valve closes and temperature drops.... thus turning the fan off for what ever temperature you set it for


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## OldSchool (Jan 30, 2010)

Protech said:


> disclaimer: I have very little experience on steam systems.
> 
> Doesn't seam like a logical place to put an aquastat for the function you are describing. I would think you would want the aquastat before the coil, not after. Your gonna get condensate on and around that sensor and will throw your readings off.


like I said earlier.... once the zone valve opened and temp increased fan would turn on.... once zone valve closed temp would decrease turning fan off....

what reading you talking about....


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## Redwood (Sep 8, 2008)

Protech said:


> disclaimer: I have very little experience on steam systems.
> 
> Doesn't seam like a logical place to put an aquastat for the function you are describing. I would think you would want the aquastat before the coil, not after. Your gonna get condensate on and around that sensor and will throw your readings off.


The only reading you are looking for is that there is some hot stuff remaining after it passes through the coil. That says the coil is hot and its time for the fan to turn on without blowing cold air....

It's a simple old school method of doing the fan control but it does work quite well...:thumbup:


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## Airgap (Dec 18, 2008)

OldSchool said:


> Nope I disagree....
> 
> Most fans are controlled by the temp of the heat exchanger.....
> 
> ...


So you don't have any kind of stat in the space you are heating? You just have a steam control valve opening up and heating the coil, then when your aquastat heats up in the return the fan comes on? When is your zone valve going to shut? Where's it getting it's temp to close from? A steam coil heats so fast you will be reading the temp on the steam instead of the space...

It's really irrelevent to RLP's question, cause there's a vac breaker where the aquastat would be.


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## wundumguy (Apr 3, 2010)

I believe the control system described goes like this:

tstat energizes steam valve on call for heat.
aquastat energizes blower when steam (heat) is present.

tstat de-energizes steam valve on termination of call for heat.
aquastat de-energizes blower when steam (heat) subsides.

The control strategy is similar to an older furnace in a residential or light commercial application:

tstat energizes gas valve on call for heat.
fan limit energizes blower when heat reaches preset limit.

tstat de-energizes gas valve on termination of call for heat.
fan limit de-energizes blower when heat subsides to preset limit.


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## RealLivePlumber (Jun 22, 2008)

The wiring in this place is a jumbled mess. As best we could determine yesterday, (They were setting the place up for an event as we were finishing up), the t'stat calls for heat, energizes the zone valve, which allows steam into the coil. And it does heat up almost instantly. 

The t stat also turns on the blower in the air handler. The coil gets so hot so fast that a slug of cold air is almost not possible. This room has 25' ceiling, and the registers are up high, so it really does not matter anyway. 

We still are not sure what calls the boiler. could be the end switch, or through the tstat. Or, they could just be relying on another zone to be on for the boiler to produce steam. 

We believe that their is also make up air. Not sure though.

There is no aquastat. Not really a need for one. You could not use it to control the fan if it was on the return, as it is really pretty cool, in respect to the supply.


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