Zone valves and circulator pump on return line

timm08

We have a boiler with a single circulator and two zone valves - one for the majority of the house with radiators and another for an addition that has baseboards. Is it a problem if the zone valves and the circulator pump are on the return line? Do they need to be on separate lines? A contractor installed a new boiler and circulator and it's not working as well in one room - I wondered if this could be part of the reason as it is different than our last set up.

jad3675

timm08 said:

We have a boiler with a single circulator and two zone valves - one for the majority of the house with radiators and another for an addition that has baseboards. Is it a problem if the zone valves and the circulator pump are on the return line? Do they need to be on separate lines? A contractor installed a new boiler and circulator and it's not working as well in one room - I wondered if this could be part of the reason as it is different than our last set up.

Circulator on the return isn't bad as long as you're pumping away from the PONPC - but the zone valves on the return line seems like a bold choice.

Also, pictures if possible.

timm08

Thanks @jad3675 for responding! I don't have pictures handy but can give more info on the issue we are seeing. I'm curious if this could potentially be related to the zone valves on the return line.

The entire system heats well with the exception of one room in one of the zones (the zone with baseboards). In that zone, the upstairs rooms heats up very well, but the main level does not get above 65 on a cold day. There is no air in the lines and the pipes are hot to the touch throughout. With the previous boiler/pump everything was heating properly including this room. One of the main differences in that set up was the zone valves on the supply line - which led to this question.

hot_rod

One though about zone valve location is thermal migration. The hottest water, from boiler supply can go up a vertical riser, colder fluid fall down the same pipe. This is especially a concern when the piping all goes straight up above a boiler.

Zone valves on the supply after the circulator give you 100% shutoff for potential ghost flow or thermal migration.

The same reasoning for putting flow checks after zone circs.

A schematic to help visualize the concept.

Imagine the valves on the return, and notice a clean path for migration.