Indirect Tank - Primary or Second Loop Preferred?

grant_andrew

I will be relocating my Burnham Alpine boiler and HTP indiret water tank as part of a basement renovation. I'll be converting from my old gravity fed cast iron pipes to a homerun manifold with pex al pex tubing to each cast iron radiator, so I can tuck the plumbing in the joist bays, and I'll also be adding a second heating zone to the system for the new basement space.

Currently the indirect tank is piped off of the primary loop of the boiler. I plan to use a header to distribute the secondary loops to the radiators and their circulators, so I was thinking I could use this opportunity to move the water tank circulator to this header as well, as it would make the relocation easier.

The boiler circulator is currently configured to only run when the radiators call for heat. If I made this change, I would reprogram the control so the boiler pump would also run for a call for DHW, but other than that, are there any other decisions I should weigh? Is there any reason not to move the DHW circulator to the secondary loop? It would make it easier to replumb when I move the system, but if there another consequence I'm not thinking of, I can make it work the way it's currently set up.

Thanks,
Andrew

EBEBRATT-Ed

I would keep the dhw circ piped to the boiler directly. You want the hottest water available for the dhw. Keep it separated from the heating

HVACNUT

If you bring the domestic to the secondary loop how can you utilize ODR? Can it be programmed for the primary circ to power up on a domestic call without wiring it to the zone board?
I believe if you address a zone as DHW then the primary pump drops out automatically when the DHW zone sensor closes and brings the burner to high fire to meet demand.

grant_andrew

I really appreciate the responses. I've been a long time lurker. To clarify, this would be zoned with circs, not valves

With regard to the ODR question, my boiler has the ability to command the primary pump on and off based on where the domestic hot water loop is located. Meaning, I have the ability to set my primary pump to turn on when there is a call for DWH. Currently it ignores a DWH call and only turns on for central heat.

I can also configure the system so that DWH has priority and the central heat circ doesn't run if there is a DWH call. In this setup, wouldn't this water be the same temperature as the water from the primary loop? The ODR would be ignored and the water would be at 170, and unmixed with the radiator loop.

Solid_Fuel_Man

The only consequence I see is if there us a simultaneous heat and DHW call. After the DHW is satisfied the header will still have 170 degree water which would make it's way the the P-Al-P going to radiators. This small inconsequential hot water could make some noise, but I doubt it!

Most boilers (I'm not familiar with your Alpine) can be setup either way as you indicated by changing the program of the boiler pump to run on heat only or bothering heat and DHW.

As a benefit, you do get better air elimination action by putting indirect on secondary as the boiler water always goes through the airsep no matter the call.