Right setup for DHW priority with IWH and TT Prestige Solo

Vad

Hello Experts,
I have a setup with a TT Prestige Solo 110 and Smart indirect water heater. It was installed 5 years ago. Finally it was found that there is no DHW Priority setup.
I have Argo 3 expandable zone control (arm3p) to where all my 3 CH zones are connected (but not DHW). Priority zone is not utilized
In particularly, when DHW is heating and the thermostat in any of the 3 zones is calling for heat, CH circulators start working and not only DHW is heated but also CH zones.
It was recommended to me to add an extra module to the Argo arm3p control to allow for 4 zones. Next to connect Indirect water heater to Priority zone of Argo arm3p control. Finally to connect Argos 3 control to IR882 Isolation relay and Isolation control relay to boiler low voltage terminals.

Is this the simplest setup available? I was under impression that DHW priority is built into the Boiler and I do not need additional modules in my setup.

Please help

Thank you,
Regards,
Vad

Bob Bona_4

Assuming there's a dedicated circ for the DHW? Yes, there should be a priority function on the boiler control. The Argo just needs to make the end switch on CH1. Trimax control or version 1?

Vad

Sorry, Bob,
I missed your reply. I do not quite get your question. Boiler indeed has a dedicated circuit for DHW and it is wired by manufacturer to allow priority. I attach a diagram of my near boiler piping. This may make a more clear picture of my current setup. I also attach a proposed solution (slightly different Argo model but the same idea)
When I DHW cycle is on (CH is turn off until later in the fall), both Return and CH supply pipes near the boiler up to connection to the loop, are very hot although pipes in the loop a cool. Not sure whether it supposed to be like this.
My main question is why should I use extra configuration having DHW priority built into the Boiler?
I will appreciate your input.

Regards,
Vad

P.S. Correction to my original post. Isolation relay model is Argo AR822

Bob Bona_4

You're missing a 1" flocheck on the return by the DHW/heat junction.

Vad

Thank you so much, Bob.
I attached a corrected diagram with your proposed flow check valve. Please check if this is the right location and direction. Is there a particular valve model that you can recommend that is better than others (longer life)?
Do you think check valve will solve this problem and I do not need to go with the original propose?

Bob Bona_4

Perfect. You need this to keep heat migration into the secondary loop when the DHW calls. I use weighted checks such as Taco or B and G iron IPS. I'll put a 1x1/2 bush with a drain in the bottom unused port for convenience.

Vad

Thank you, Bob. Is this the right valve?
http://www.supplyhouse.com/Bell-Gossett-107018-1-Threaded-Straight-Angle-Flow-Control-5596000-p#prPaContainerBG_107FC
My pipes are 1 inch and I need 1 '' flow check valve. Do I need NPT mail adapters to install it? Do you think an end cup is included. I do not need to install a drain at the bottom.

Thank you,
Regards,
Vad

Bob Bona_4

Yep, that or the Taco equivalent. Get 2 1" male copper adapters, and plug off the bottom port if you don't want to use a drain as a plug and a place to drain.

Vad

Thank you a lot, Bob,
I appreciate your time
Putting a flow check valve on Return prevent hot water from Return entering the loop. That is perfect. Now, as I mentioned, the CH supply line from the boiler up to the beginning of the loop is very hot too. Do you think that the water from Return enter the loop junction, goes up and enters CH supply line making it Hot? It is kind of strange for me that the water choose such route. More logically if the water from return would go down to the bottom of the loop.
Sorry for my unprofessional questions. I am just trying to understand whether something else is missing as well.

margsuarez

Hello there, I am a homeowner with the same boiler. Is the internal boiler pump firing when the DHW pump kicks on? There is a setting for "System Pump" explained on p. 10 of the Control Supplement Manual to select which circulators come on when there is a call for heat or DHW.

I believe you may want this setting for System Pump:

"CH1/CH2 – The system pump will only be enabled for a CH1 or
CH2 central heating call. Figure 3, page 12 illustrates a system
zoned with zone valves requiring this setting."

Otherwise on a call for DHW the internal pump may also come on and circulate hot water through the closely spaced tees, which sounds like what you are describing.

marg

Vad

Marg,
Thank you for comment. My boiler is an older version that you have. It does not have these options. It only have an internal circulator for CH.
I now have a valve related question. the flow check valve I choose on Bob advise is a cast iron valve. Will it create a corrosion when attached to a copper pipe? http://www.supplyhouse.com/Bell-Gossett-107018-1-Threaded-Straight-Angle-Flow-Control-5596000-p#prPaContainerBG_107FC
Should I use this Hydrotrol valve instead isince it is in bronze http://www.supplyhouse.com/Bell-Gossett-107037-1-NPT-Bronze-HydroTrol-Flow-Control-Valve-8620000-p

Thank you
Vad

Zman

Vad,
Bob has you on the right path with the check valve. Don't worry about the cast iron unless you have non O2 barrier tubing.
I did notice that the supply and return from the boiler to the secondary loop is backwards in your drawing. I also don't think the differential bipass valve should be there. If you drawing is correct there is some other work to be done.
All the circs in your system should have check valves not just the CH loop.
Carl