LWCO Placement

Kestrel

I have another quandary with regard to my boiler install.



Per code, I need a low water cut off.  However, given the way I piped the system, most all of the components are below the level of the top of the boiler heat exchanger (Lochinvar wall hung fire tube, WHN-085).



I've attached a schematic that shows fairly accurately the lay-out of my system.  On it are two proposed sites for the LWCO.  One requires a significant (about 3') vertical loop between the boiler and the LLH.  This position is closer to the fire-tube, with fewer intervening components, and is within easy reach of the cable harness (Hydrolevel model 1100).  That is 'Position A' on the drawing, with the required vertical loop in dashed line.



The other possible position is labeled 'Position B', and is on a piece of pipe that already exists, given the position of one of the manifolds.  It, however, is farther away, and has multiple components between it and the boiler.



Is position A the better choice?  Any other thoughts?



Thanks!

Kestrel

Oops, schematic needed...

Looks like my drawing didn't post the first time - here goes again

Kestrel

HMMMM...

Not sure what's wrong - I have a saved PowerPoint file that won't see to attach.  I've posted these before - not sure what's wrong.



One more time...

Kestrel

HELP!

OK, picture posting not working it seems...not sure what to do next - can I email it to someone to post for me?

ChrisJ

resolution

Make sure the picture isn't too large.  I usually use 1280x960 with good results, you may be able to go larger.  If you go too large when you post it messes up.

Mark Eatherton

JPEG only...

JPEG or PNG graphics can be downloaded to the site, but not powerpoint.



As for an optional place for the LWCO, if this is a WHN, you can use the pressure relief valve connection by installing a cross. The relief valve come out of the top tapping, the LWCO goes in one side tapping, and an automatic air vent with elbow to set it vertical in the other side branch, and the boiler connection in the bottom.



This will keep the LWCO above the crown of the boiler, which is important. The air vent will act as a vacuum breaker in the event of a loss of water, thereby allowing air in, and a LWCO condition to halt hot water production.



I believe there is also a low pressure cut off as a part of the safety controls circuit, which SHOULD activate before the LWCO does. Belts with suspenders if you will....



ME

Kestrel

Brilliant!

OK, here it is in JPEG.  And a picture of the relief valve in question.



Mark - attaching to the air vent is excellent - saves lots of time and space and pipe!



To make the piping easier, can the present relief valve (which is vertical) be placed horizontally - with the new air vent on top, and the LWCO on the other horizontal?  Does a Taco Hy-Vent (I have one handy) suffice for the air vent/vacuum breaker?



Thanks!

Kestrel

Doh

Nevermind about my question - forgot about the long probe attached to the relief valve.



thanks!

Jean-David Beyer

the long probe attached to the relief valve.

Why would a pressure relief valve have a long probe? I though the probe was needed only for a pressure-temperature relief valve to measure the temperature. On my boiler, there is a pressure relief valve and the instructions say to hook it onto a street elbow to connect it to the supply pipe from the boiler at a T. I believe P-T relief valves are normally used for hot water heaters, not boilers.



I am not a professional, but I have been lead to believe that it is a bad idea to operate these valves other than vertically. Something to do with messing up the valve seat if it opens ever so slightly, but I forgot the details.

Mark Eatherton

Relief valve MUST be mounted upright...

Otherwise, is will malfunction.



Use a "cross" tee as described above. See attached photo.



Any automatic air vent will act as a vacuum breaker when it sees negative pressure.



Also, per JDB's comment, pressure relief valves don't have a thermal stem on them, but still must be mounted vertically. If you can't find a cross fitting, two tees stacked on top of each other will do the same thing, just taller.



ME