Primary Secondary with Reversed Secondary Flow

Kirchof1

I recently purchased a house and have been working on improving the efficiency of the hydronic heat system. It's a Munchkin 80M with 2 zones controlled by zone valves and a primary secondary piping configuration. The kicker is that the secondary flow is backwards. Both primary pump and secondary pumps are Grundfos UPS15-58. Based on a heat loss calc and the head loss of the secondary and primary I knew which setting I wanted to run each pump at until I realized that the secondary flow was reversed. I'm wondering what the implications of this are. It's not really a primary secondary system because the secondary return must mix with the boiler supply and flow through the common pipe. Is there a reason that the piping would be installed this way? It seems like the worst strategy for condensation. Any insight would be greatly appreciated. Thanks everyone. Chad

Gordy

Pics?

Kirchof1

The primary pump is pumping into the return side of the boiler and the secondary is pumping away from the expansion tank, toward the zone valves and out to the house.

CMadatMe

Dont' see a pressure differential by-pass...

You are still piped primary secondary in your pics. The 2 closely spaced tees dictate that..

Gordy

That is correct. You want to pump into the boiler with the high head loss of that HX this adds the pressure differential of the primary circ to the pressure in the HX.

The secondary should pump away from the x tank.

Gordy

Hmmm unless my eyes are crossed I think the piping to the closely spaced ts are reversed. The return from system is headed for the supply on the primary.

CMadatMe

Gordy said:

Hmmm unless my eyes are crossed I think the piping to the closely spaced ts are reversed. The return from system is headed for the supply on the primary.

Gordy said:

Hmmm unless my eyes are crossed I think the piping to the closely spaced ts are reversed. The return from system is headed for the supply on the primary.

Bingo!. Nice catch Gordy they are backwards.

Gordy

So primary flow return is mixing with boiler supply, and boiler return is taking in its own supply need to get that fixed. Per @chris posted schematic.

Kirchof1

Thanks for the confirmation guys. Guess I'll be finding a new HVAC contractor. Crazy.

Paul48

I can't see the volute of the secondary circ, but I think it's pumping at the x-tank.

Kirchof1

Arrow on the cast housing of the circ points away from the x-tank and towards the zone valves.

Paul48

OK....Let your new contractor straighten that mess out. It's amazing how many contractors can't read and follow directions.

Formerly

Aside from the reversal of the close T's, someone mentioned a differential bypass... But since those are Grundfos Alphas, they remove the need for the bypass, right?

delta T

They are not alpha's just regular 15-58 3 speed. If they were, then yes you would be correct.

Formerly

ah thanks for clearing that up. I don't know why I thought they were alphas.

Formerly

one thing I am super uncomfortable with is the unbonded CSST running next to elec and plumbing. One lightning strike nearby and you will need a pack of marshmallows.