Taco SR503 and Hydrolevel 3250

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shawn06260

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Hi All, was hoping someone might be able to help me out here. I'm replacing a 40yr old boiler which currently has 2 heating zones and an indirect tank. It currently has 3 old R845A relays which I'm hoping to replace with a new Taco SR503. The Aquastat that comes with my burner is a Hydrolevel 3250 Plus. https://hydrolevel.com/wp-content/uploads/2019/11/HydroStat-3250-Plus-Instructions-web-111919.pdf
My question is there seems to be a couple of different options to wire the indirect zone with priority and just wanted to make sure I'm doing it correctly. I originally planned to wire per diagram #5 in that manual, with the End Switch wired to the T/T on the aquastat. Then I planned on tying in the ZR of the aquastat to the hot of the indirect circulator.
The only thing that is causing me concern is the there's another diagram, #8 that's a little different and has a note "Taco’s SR503 combines ZR amd X2." Is this saying that I don't need to run that hot leg from the priority circulator circuit? Does the SR503 take care of prioritizing that Zone 3 on its own?
https://s3.amazonaws.com/s3.supplyhouse.com/manuals/1351150925280/85270_PROD_FILE.pdf

Thanks in advance for your help.
 

Fitter30

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Taco sr503 use Tankless Coil Boiler Application the right diagram zone 3 will prioritize dhw on its own. Read the notes under diagram.
Hydrolevel looks like diagram 8 is the one you use. Diagram 5 is for a end switch.
Never used hydrolevel control but it does have a lot package in one control.
 

shawn06260

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Ok, thank you for your feedback. Yea, the problem with Diagram 8 is that the SR503 board doesn't have an X1/ZR terminal like the Hydrovel shows, so I'm not sure what they're talking about there. As you can see in the 503 manual, that terminal doesn't exist. Maybe it's a typo. Thanks again for answering.
 

shawn06260

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I have an oil fired burner. I'm almost positive I can wire it up just like it shows in the Taco instructions, left diagram for cold start. I think that controller will take care of prioritizing my hot water zone automatically. I'm thinking that the Hydrostat has the same functionality in case you weren't using a "smart controller" that does prioritization. The TACO relay says that it will shut down the other 2 zones for zone 3 if needed, and that should take care of my indirect tank. I still have a little time, I'm waiting for my new boiler and burner to be delivered so still have a couple weeks to figure it out.

upload_2020-9-1_17-34-18.png
 

shawn06260

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Just wanted to follow up on this in case anyone else runs into this same setup with the Taco zone controllers and the HydroStat 3250. After talking with Hydrostat, who were very helpful, we determined I'll need to wire the End Switch of the Taco controller to the TT of the Hydrostat. Then I'll need to run another 120V wire from the ZR on the Hydrostat into the hot leg of the priority zone circulator pump. This will send a signal when that priority hot water zone comes on to shut down the economy mode on the Hydrostat and fire to high limit. If you didn't want to make that connection to the ZR of the aquastat, you just wouldn't be able to take advantage of the economy mode feature that the Hydrostat offers.
 
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