DHW draws water whenever main circ is running...

Steve Jacques

I have a 2 circ system, one main circ on the return manifold, with ZV for 4 zones on the supply side. Second circ is on the DHW loop, this circ is installed on the return side with a flow chek installed 24" after circ prior to joining the main manifold. Both circs controlled by a Taco 6 zone controller w/priority...

All seems to be set up properly, i.e. main circ runs when zones call for heat, DHW circ only runs when priority zone (zone 6) calls for heat.
Problem is, whenever a zone calls for heat the main circ turns on, and seems to draw water through the DHW loop as well, so my DHW is now up to 135 deg F!
Supply side has 4 zones then at the end is a tee for the DHW loop supply. The DHW return goes to a Taco 007 circ, then a Flo-Chek valve, then to a tee on the return manifold.

Basically the setup is the same as I've seen in a few pipe diagrams, with the exception that my circs are on the return side and not the supply...

I was thinking maybe I need to tee the DHW circ AFTER the main circ (downstream) instead of in the main return manifold, would this fix my problem?

Thanks.

Steve

Unknown

Steve

Any chance you can take a digital picture and post it here ? Are you saying the DHW circ is pumping to the return of the boiler and it's teed in upstream of the heating zone circ ?

Meaning the piping goes ( from the boiler ) - boiler return - heating zones circulator , then the heating return pipes tee in with the DHW circ ? That would definitely heat up the indirect alot more than the aquastat setting .

Weezbo

that should not be a real problem...

with an anti scald valve on the potable....

Rodney Summers

check valve

> I have a 2 circ system, one main circ on the

> return manifold, with ZV for 4 zones on the

> supply side. Second circ is on the DHW loop, this

> circ is installed on the return side with a flow

> chek installed 24" after circ prior to joining

> the main manifold. Both circs controlled by a

> Taco 6 zone controller w/priority...

>

> All seems

> to be set up properly, i.e. main circ runs when

> zones call for heat, DHW circ only runs when

> priority zone (zone 6) calls for heat. Problem

> is, whenever a zone calls for heat the main circ

> turns on, and seems to draw water through the DHW

> loop as well, so my DHW is now up to 135 deg

> F! Supply side has 4 zones then at the end is a

> tee for the DHW loop supply. The DHW return goes

> to a Taco 007 circ, then a Flo-Chek valve, then

> to a tee on the return manifold.

>

> Basically the

> setup is the same as I've seen in a few pipe

> diagrams, with the exception that my circs are on

> the return side and not the supply...

>

> I was

> thinking maybe I need to tee the DHW circ AFTER

> the main circ (downstream) instead of in the main

> return manifold, would this fix my

> problem?

>

> Thanks.

>

> Steve



If a zone valve is open, what stops the flow through the heating loop when the DHW pump is running? Do you have any check valves on the heating loop to prevent this from happening? You might need a check valve on the heating pump.

brucewo1b

Yes you need to put DHW pump after system pump

evry time the stystem pump comes on it will pull through the DHW tank also might be ok in mild weather but when it gets cold you might be superheating the DHW tank.

Danimal

Your check valve is located in wrong place. should be located on supply side to prevent thermal siphoning.

brucewo1b

Check Valve location OK

but as long as his DHW Circ feeds into the inlet of his system circ that DHW zone will flow when the system circ is on.

Steve Jacques

Picture of system

I have attached a picture of the DHW circ setup... my thoughts after consulting a few people and a few e-mails from helpful members of this forum (thanks to Ron Jr) is that the current setup has the main circ drawing water through the DHW loop. In a circ system, the circs are on each zone loop, so they tend to draw less from the primary manifold, and the IFCs prevent backflow out of the individual loops, as well as the gravity effect of hot vs cold water.

In my current setup, the circs are actually in series, no amount of flow check will prevent the draw through because flow checks only prevent backflow, not draw through... A little lesson I just learned.

The solution is simple, tee the DHW circ after the main circ. When the main circ is running, any flow that wants to go down the DHW loop will be stopped by the IFC, and no draw through will occur.

This is how I understand it now, if I'm incorrect please let me know, and thanks again to all who responded!

Steve

brucewo1b

Right on Target Steve