zoning single pipe steam

webskier

I have a customer with a single pipe steam system; they want zoning.  Looking at the honeywell V110 valve they recommend this valve for two pipe.  The current system has manual valves on it. What's the difference?

Greg Maxwell

Zoning

You cant really "zone" steam. You can regulate the output of rads, but you are still limited to the single thermostat. On both systems, you are controlling the heat output by only letting a certain amount of steam in. On a 2 pipe system, you do this at the inlet of the rad, because you can still condense the steam that did come in, and the condensate will be handled by the trap on the outlet. On one pipe however, you have to control the venting rate of the radiator. If air cant get out, steam cant get in. I believe that Honeywell makes 1/8" thermostatic steam vent valves to to this. Then, just adjust them to the comfort level of the room.

Charlie from wmass

You can Zone steam

It just does not work as well as it does zoning hot water. Drips need to be installed and near boiler piping needs to be better than the minimum recommended. As in large drop header and proper equalizer. The Best way to zone steam is with TRV's on the air vents. DO NOT USE TWO PIPE TRV'S FOR ONE PIPE STEAM SYSTEMS! On one pipe the trv goes where the vent is and gets a vertical vent installed.

webskier

zoning single pipe steam

Thanks for you quick response;  the radiators already have the vent controls and apparently have not been effective in the temperature regulation.  Of course this is based on accounts from very non-technical owners.  Could TRV's be used in combination with the vent valves?  I guess my question is how does the TRV vary from a manual valve in its effect on the steam flow? 

Rod

TRVs

Hi- Here is some information on TRVs

TRVs stand for Thermostatic Radiator Valves.  They are used on hot water and steam systems to regulate the heat output of the radiator.  On the models for  hot water and two pipe steam, the TRV is installed on the inlet pipe to the radiator. On a one pipe steam system, the TRV is installed between the radiator and the steam vent. A one pipe steam TRV also needs a vacuum breaker to allow air back into the radiator when the boiler shuts off. On the Macon TRV, the vacuum breaker is external and on the Danfoss TRV, it is internal (built in).

   Since you have a one pipe steam system it is important to get the model designed for one pipe steam. As mentioned above the one pipe TRV is mounted on the radiator vent hole, between the radiator and the radiator vent.  When steam enters the radiator, if the room temperature is below the setting on the TRV, the escaping air goes thru the TRV and out the air vent, when steam reached the air vent it closes just as it would without the TRV. When the boiler shuts off, the vacuum breaker allows air to re enter the radiator.  This cycle continues until the room temperature reaches the setting on the TRV. The TRV valve now closes and prevents air from escaping out the vent. With the air trapped in the radiator, steam is now prevented from entering  until the TRV drops below the set temperature and reopens, allowing air to escape and steam to now fill the radiator again.

I use TRVs  on about half of the radiators in the house. They are really handy in the bedrooms as I like the bedrooms cooler at night and they also allow me to shut the heat off in unused rooms to save fuel. (The minimum setting is 42 degrees so this makes sure the room/piping in the walls doesn’t freeze)



Here's some links to several different models.

 Macon - The Macon model for one pipe steam -   http://www.maconcontrol.com/opsk1204.html



Danfoss TRVs:

Danfoss 1 pipe steam model -  Danfoss keeps changing the web address of the page so I attached it bellow.



Danfoss Animation

Note: These animations show TRVs for hot water systems however the mechanism is basically the same on the one pipe steam model. - Click on the following link:

http://na.heating.danfoss.com/Content/161a8b0f-a195-42b2-9487-7ee4083398cf_MNU17483715_SIT209.html

This will take you to a Danfoss page which will say “The page can not be found” Go to the menu at the top of this page and click on “Knowledge Center”. On the Knowledge Center page, click on “Operation of the RA 2000- Thermostatic Operator ‘and that will take you to the animation page.  For some reason the direct link isn’t working at the moment.

 

You can install 1 pipe TRVs yourself.  You should be able to get these units from your local heating supply or on the internet. (Try Pex Supply - http://www.pexsupply.com/ Type in the word  “Danfoss”in the Search/Find window and that should get you to them.



Note: The Macon TRV comes with a radiator vent included. On the Danfoss your must supply the vent. It needs to be a straight vent rather than the normal angled radiator vent.  You can use a 1/8 inch 90 degree street elbow between the TRV and then use a regular angled vent,

    If you don’t have them already you might want to take a look in the SHOP area on the Heating Help website.  Dan has written some great books on steam heating . If you don’t have it already I’d start with “We Got Steam Heat!”.

http://www.heatinghelp.com/products/Books/5/61/We-Got-Steam-Heat-A-Homeowners-Guide-to-Peaceful-Coexistence

- Rod