System 2000-DHW Priority on or off?

WalnutFarmer

HI all- We had an EK System 2000/Resolute system (boiler and DHW tank) installed a couple weeks back. Love the system so far. System is for my home in Central CT, with 5 heating zones + DHW (15 zone energy mgr). Due to a minor mix-up, the installer had to send a tech out to do some additional work a couple weeks after the main install.

The tech who came out mentioned that he noticed the system was set with DHW Priority OFF, and he switched it to ON. He did not explain why and I didn't think to ask.

I've read through old threads here and can't find much discussion of this other than one discussion that said it probably didn't matter much either way.

Any thoughts on pluses/minuses of DHW Priority on vs. off? Should I care? (Glad to add more details as needed)
THANKS

Robert O'Brien

DHW priority disables heating during a call for DHW, decreasing the recovery time by devoting the boiler output just to DHW production.

Chips203

Shouldn't make a huge difference either way. I'm not familiar with that zone control but I would just make sure that it allows the other zones to run if the call on the priority zone isn't satisfied in a certain amount of time. You don't want a bad circ, zone valve, air in the zone, etc. to cause a no heat condition in the whole house.

Roger

Thank you for your question @WalnutFarmer .

It is very rare that any of our systems with a storage tank need to have hot water priority on.

Our plate heat exchanger can take the full output of a boiler and heat the tank very quickly.  The heated water also flows into the top of the tank, right where the supply to your fixtures is, so the response is also very quick and consistent.  The location of the tank thermostat also signals well before the tank is short in supply. 

It won’t hurt to have hot water priority on, although if you never had issues with adequate hot water, you can be confident in leaving it off. It also times out, so you will not have to worry about any extended interruption from heating. 

Best,
Roger

WalnutFarmer

Thanks you all very much for your thoughts.

Sounds like it is not a huge deal, although based on the little more I know now, I think I'd lean toward turning HW Priority off.

Roger, is that something I could do myself through the energy manager? Could someone in your shop talk me through it by phone?

If you'd rather I leave this for a trained tech, I can wait until next year's PM service visit.

HVACNUT

You can certainly do it yourself. You should have the manuals.

Roger

Thank you for your answer, @HVACNUT - you beat me to it. It should be quite simple to change the hot water priority setting through the Display Manager menu.

 Roger