Thermostatic Valves on Steam system>

jasonnyc14

We have a building with 40 units on a steam radiator system and were interested in replacing all the valves with TRV's in each unit. Our contractor shot it down saying it was impossible

"While individual thermostatic controls work well on hot water systems, they do not on steam systems. In essence – either a steam radiator is on and fills with steam, or it isn’t and doesn’t. Closing the valve partway apparently has little or no effect. Whether an individual radiator, or even a group of radiators fill with steam or not has little or no effect on the cost of running the system. Basically the entire branching system fills with steam and the system only shuts off once sufficient back pressure is built up in the entire network."



Is there any validity to this or is he making stuff up?

Anyone have any comments on that?

thanks

- j

Rod

TRVs for 1 Pipe & 2 Pipe Steam Systems

Hi- You didn't say whether you have a one pipe or a two pipe steam system so I will explain both types of TRV though since it sounds like you system is one pipe I'll put more emphasis on that. T   he best general answer is:: “well, that depends”.



There are basically two basic types of steam system.



1.  The One Pipe System - can be identified as it has one pipe leading to each radiator.



2. The Two Pipe System - -can be identified as it had two pipes leading to each radiator.



There are TRVS made for each type system though each system needs a particular model TRV that is designed for specifically for that type of system.  A two pipe  model TRV won’t work on a one pipe system and a one pipe model TRV won’t work on a two pipe system.



Each model TRV works on a different principle. The two pipe TRV works on the inlet pipe and the one pipe TRV works on the radiator vent  port.  



If your system is one pipe steam then your contractor is correct. The TRV on the one pipe system is attached to the radiator vent port. If it is a two pipe system then your contractor is wrong as the TRV on a two pipe system is installed on the inlet pipe.



TRVs control the amount of steam getting into the radiator. If the temperature of the room is below the temperature setting on the TRV when the TRV valve is open which allows steam to get into the radiator. When the room heat matches or is greater than the temperature setting on the TRV, the TRV valve closes which prevents steam entering the radiator.



The two pipe TRV works on the intake pipe of the radiator and works like a regular valve in that it controls the supply of steam coming into the radiator.



The one pipe TRV works on a different principle.  As mentioned above it works on the vent port of the radiator and is installed between the radiator and the radiator vent. The one pipe TRV also has a vacuum breaker which can be either internal or external on the unit.



How it works: When the room is cooler than the temperature  setting on the TRV, the TRV is open and air and steam pass through the TRV and out the radiator vent. When steam reaches the radiator vent, the vent closes trapping steam in the radiator. Just like it does without the TRV.   When the temperature setting on the TRV is reached the TRV closes and prevents air or steam passing through the TRV to the radiator vent. There is still steam in the radiator however when the steam system shuts off,  air re enters the radiator through the one way vacuum vent and when the system comes on again, steam is prevented entering the radiator because of the trapped air in the radiator and won’t be able to enter the radiator again until the room temperature cools below the temperature setting on the TRV and the TRV opens which lest the air out of the radiator.



With each type of TRV you are limiting the use of steam. If less steam is used,  the pressure builds up quicker and shuts off the system resulting in short interval where the burner is on which results in saving fuel so TRVs do save fuel.   The temperature setting is from 42 F to about 85 F.

I’ve attached a tech sheet on a Danfoss 1 Pipe TRV and here is a link to info on Macon TRVs

http://www.maconcontrol.com/opsk1204.html

You might also want to take a look in the shop section of this website as there are some great books on steam heating. The best introductory book is "We Got Steam Heat!"

http://www.heatinghelp.com/products/Steam-Heating-Books/25/61/We-Got-Steam-Heat-A-Homeowners-Guide-to-Peaceful-Coexistence

If you have any questions let us know and we'll do our best to answer them.

- Rod

nicholas bonham-carter

Trv's on steam

Before you install the trv's you should make sure the system as a whole is functioning properly, which includes:

Massive air venting, so the air can escape rather than being forced out by excess fuel consumption.

Checking the operating pressure which should be as low as possible (possibly 8 ounces with a vaporstat)

A control system which is accurately responsive to the building heat-loss, and heat-gain.--nbc

Henry

TRV

We do install many TRV on steam systems. One client had us do one floor first. The savings were so great the first month, that he had us do all the other 7! We have done many large apartment buildings but also many more commercial buildings.

Of course, one needs to keep pressure down and make sure that all the steam traps work properly!

Henry

jasonnyc14

Reply on TRV on Steam

Thanks for the extensive helpful replies..

by the looks of this hallway radiator, its a 2 pipe system. (see photo)

Basically you are saying that they make TRV's for either type of steam system and can be installed if they know what they are doing



Thanks

jason

David Nadle

One pipe, I think

I don't know why you have two supply risers to one radiator, but that air vent indicates one-pipe steam. Which is good, because adding a TRV is as simple as replacing that air vent with a TRV assembly.



One thing that concerns me about adding TRVs to a large multi-unit building is that the building management has to be on board and keep the presure below 2 psi.

jasonnyc14

reply

ill look at some other radiatiors and grab some photos.. this might be a bad

representation thx

Rod

TRVs on One Pipe Steam Systems

Hi - LOL- Interesting photo- reminds me of the phrase: “There is always an exception to the rule!” though why it has two steam supply pipes is beyond me. As David pointed out the vent pretty well classifies it a one pipe system. Also most two pipe steam systems have what is called a “trap” on the outlet pipe and the inlet piping enters at the top of the radiator.

As others have mentioned these steam systems are designed to operate at very low pressures. The Empire State Building operates at close to 2 PSI! ( Wikipedia - Empire State Building -Architecture section)

Higher pressures ruin vents and TRVs. so it is important to make sure the system is operating at the proper low pressure first ( under 2PSI) before changing to new vents and TRVs.

Since the 1 pipe TRVS are so easy to install, you might want do a small group of apartments first as an experiment to see what the actual benefits are.

I might also mention that on a one pipe steam radiator the inlet valve should always operate either be fully open or fully closed. I’ve attached a diagram explaining why this is necessary.

- Rod

LeeB

Can I do a thermostatic radiator valve?

Hello!

I have recently purchased a home ( 2 story- built circa 1959)  with a steam heating system and it appears the radiators are "one pipe" As the second story is rarely used, I thought my only option to control the amount of heat on the second floor, would be to have a second zone installed.  However, I was told that a second zone was not possible- although I did not fully understand why.  Nonetheless, obviously it is not cost effective to heat the second floor.  

Could a thermostatic valve be an alternative as a means to reduce the amount of heat on the second floor? 

Although the process of installing a thermostatic valve appears to be rather simple I have great concern of the potential for breakage of the air vent upon removal and how serious of a problem that in itself would be.

Lastly, are all of these radiator thermostatic valves created equal, or  does one get what they pay for, so to speak.

With fingers crossed that this is an option, thank you in advance for any assistance/advice you have to offer

Steamhead

That's a 2-pipe, air-vent system!

you would use the same TRVs on this as on a 1-pipe system.

Steamhead

That should be as easy

as falling off the proverbial log. If a vent breaks off we simply drill out the remaining brass piece and clean the threads with a tap. 

David Nadle

Good option

TRVs are a good option for you. I have Danfoss TRVs upstairs and they work great. Other smart people on this board have recommended Macon Controls. The Danfoss TRVs go as low as 45°, so you should be able to keep the second floor as cool as you want.



Note that TRVs still require an air vent, typically with a straight configuration instead of a 90° configuration. Those are less common and with air vents you do get what you pay for.



Your air vents probably won't break but if they do shear off you might be able to use a properly-sized screw extractor to get out the threaded bit. Screw extractors look a little like drill bits; the sharp teeth grab the inside of a hole you've drilled in the screw (or in this case, the inside of the nipple) in a counter-clockwise direction so you can get good torque on it and back it out. 



The following link has some good information:

http://na.heating.danfoss.com/PCMPDF/Instructions%20RA2000%201PS.pdf

Rod

TRVs

I have an old 3 story house with a 1 pipe system and use TRVs on 3/4 of the radiators in the house. It's just my wife and I  now and using the TRVs, we can shut down those rooms we aren't using which saves on fuel.  In the winter we are away traveling a lot.and when we leave the  TRVS are set very low (42-  48 degrees) which really saves fuel but is just enough so the water pipes in the wall don't freeze. One thing we found was that it helps to open closet doors (if you suspect there are pipes in the walls of the closet)  and the doors under the sinks to allow the warmer air to circulate.   TRVs are also great to use in upstairs bedrooms if they get too hot or if you like to sleep cooler.

- Rod.

jasonnyc14

New photos - Radiator

I just snapped a radiator shot from front and back and this one is slighty different, but probably all the same in the other units



so... 1 pipe or 2?



and would the correct TRV work on either type?



thx