Direct Piping

Alan (California Radiant) Forbes

This photo is from an Eichler home in the Bay Area. You can see one manifold under the boiler and there's at least one other manifold in a closet inside the house.

The installer is using the boiler pump as the system pump when the manufacturer's instructions say to pipe the system with two pumps and a primary-secondary piping layout; either with a low-loss header or closely spaced tees.

I'll be going to the job next week to find out how the system has been working, but my guess is that it works fine. Some Eichler's have 3/8" tubing and you have to use a bigger pump to overcome the pressure drop, but the one manifold look to have at least ½" loops.

But, however tempting, common practice is to uncouple boiler and system.

The company that installed this boiler sold out to a larger plumbing company. When the owner called to have it serviced, they said they don't have anyone trained to do that work.

hot_rod

Some if the Viessmanns allow direct piping if you can assure the minimum flow

I suspect the boiler will error out if it is under pumped?

HydronicMike

Also can you check flow thru the boiler with an ultrasonic flow sensor?

Alan (California Radiant) Forbes

https://forum.heatinghelp.com/discussion/comment/1862048#Comment_1862048

You’re absolutely right.