Click here to Find a Contractor in your area.
Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit

Lochinvar WHN keeps tripping Relief

Colin47 Member Posts: 1
Hi everyone, this is my first post to this website, been reading it for a while.

My company installed a Lochinvar WHN 155 about a month ago and it seems like air is getting trapped in the system. I have gotten 2 call backs because the boiler made "a grumbling noise" and the pressure relief tripped and dumped water on the floor. I am assuming that the main boiler loop (primary loop) is getting air bound causing it to flash steam inside the boiler tripping the relief, but Im not sure because I am never there when it happens.

System info:



2 zones on secondary

1 zone is a converted gravity system

second zone is a regular copper fin baseboard loop

superstor is run off of the primary loop

extrol 60 exp tank

15PSI in gauge

There is a 1-1/4" spirovent on the supply side before the circulators, it is about 3 inches from an elbow. We have bled the system out for days and bled the radiators out, but can still hear air moving through the system. Any ideas? is the spirovent to close to an elbow?

Would extra air elimination devices help? Any input would be greatly appreciated.


  • Timco
    Timco Member Posts: 3,026

    Any piping that would trap air?

    Does your Spiro have some flux keeping it closed?

    Did you purge? I always purge each loop / zone.

    Air trapped in boiler? After fill, try letting air out through relief or gauge?

    You must purge.
    Just a guy running some pipes.
  • kcopp
    kcopp Member Posts: 3,819
    I would pull.....

    the spirovent apart. Do you have some pix? What size are the circs? and what size in the boiler? Purging out the old gravity part will be a bit of a challenge as you cant "purge" out each rad. Gotta rely on the bleeder vents... How well did you clean the old gravity piping? There is a lot of old ferrous stuff that can gum up a system especially if a gianonni HX is involved.
  • Zman
    Zman Member Posts: 6,975

    A picture of the boiler piping would help.Where is the exp tank?

    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • hot_rod
    hot_rod Member Posts: 15,019
    vent on the HX

    does it have a manual, or float air vent on the header inside the boiler? Often that needs to be checked.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
This discussion has been closed.