One zone works but another doesn't

JibbahJabba

Bought our first home and had a high-efficiency tankless combi system installed since the boiler was sketchy.

I thought the installer was experienced with these systems but I'm doubting that more and more. As it is, when Zone 2 is on and Zone 1 is off, the loop in the utility closet gets piping hot but not on the other side of the Z2 solenoid.

Photo w/ markups labeling zones and returns.


I included red markings to show the continuation of the pipe behind the compression tank. Also note that the two returns from Z2 and Z1 tee into this loop.

After looking at the diagram included in the manual it seems that this "short circuit" that exists is causing Zone 2 to not get any heat. Zone 1 still seems to get heat, but I'm not sure why. Shouldn't both zones be short-circuited by this loop?

Any reason why this would be put in this way that I'm not understanding? I was a bit confused by the primary loop when I first saw it but then I learned that the Navien has a dedicated circulator pump that keeps flow direction going in the right way. Is this a similar thing?

It seems to me that the pipe section in orange should not be there. Is this a correct assumption? Or is it more likely that the solenoid for Z2 is the problem?

Also, the installer did not set up the outdoor thermometer. I live in a cold and snowy part of the country and tend to like the cool nights during the summer (i.e. heater is turned off for 4 months). Are there significant savings associated with using the outdoor sensor?

PS: Found these boards through "AdamEater"s youtube page, very thankful for the recommendation.

clammy

From the looks of it your correct in assumption the pipe is not necessary and that it short circuiting thru that pipe . By any chance there is a valve on it behind the expansion tank the installer may have installed a throttling valve there to prevent the pump from dead heading when a zone valve shuts being the valves are on the supply . Outdoor reset should be used w any mod con wall hung . Read the i and o manual and program the controller also I would think possible a professional who is familiar w your brand boiler should give it a good look over and proper start up ie checking boiler is programed properly for it application and that gas pressure is correct and that combustion number are with in manufactures specs .also that it has been installed according to the manufactures specs and that all local plumbing and electrical codes have been followed . Don’t assume that every plumber or hvac contractor is equal make sure they have a combustion analyzer and digital manometer and are familiar w your unit even some who are registered installer of said equipment still may not have test equipment for a proper installation ,unfortunately, if they don’t have the proper testing tools find some one who does . Peace and good luck clammy

HVACNUT

Can you post some pics without drawings from different angles?
Also make and model of boiler. 
Zone valve 2 is definitely open and has been purged?
Not sure about the placement of the air eliminator in relation to the circulator. 

STEVEusaPA

Sounds like the installer gave YOU some JibberJabber.
Outdoor reset should be hooked up. But it may not work as well with deep setbacks.