Wiring questions

HeatingHelp

This discussion was created from comments split from: ZR ZC and cold start.

DStreet

Hi, I’m new here and would like help with an issue. First, can you tell me what Honeywell aqua-stat is in the pic above? I have the same model but no label to indicate which variation. Also, I picked up a Taco sr504-4 to control 3 circ pumps and an indirect water heater pump but am not sure how to wire it up. Do I run everything to the Taco or leave the boiler circ pump wired to the aquastat and run the other pumps off of the Taco? Thanks for any help I can get.

HVACNUT

This aquastat

is an L8124E. You might have the A instead of the E.

All circulators will go to the Taco zone panel with the water heater being the priority zone. Since you have an indirect, you can run a 2 conductor thermostat from TV-T ( If you have the "A" aquastat, it's T-T or R-W) on the aquastat to X-X on the Taco panel and turn the Low side down to 135° if its a cast iron boiler. If its a low mass CI or a steel boiler you can turn the Low all the way down. No need to use ZR/ZC since there's no longer a tankless coil to maintain temperature.

DStreet

Thanks HVACNUT. My aquastat is the ”E”. It’s identical to the one in the picture. I was curious about the low side temp because of the indirect water heater. I bought my house a year and a half ago and it’s ago and the water heater tanks is showing signs of leakage. I need to figure out what to replace it with. I’m only staying in the house for a few years and don’t want to spend a lot of money.

EdTheHeaterMan

That control is easy to make it into a cold start control

HeatingHelp.com

@DStreet, welcome to Heating Help! We've created a new discussion for you here to prevent confusion within that older conversation. Thanks.

EdTheHeaterMan

Here is the easy way to make that L8124E into a cold start control.

Remove the Red wire from the R terminal on the LO side of the control block and remove the White from the W terminal on the LO side of the block. Now connect both Red and White wires together with a wire nut. Now you have a cold start control. See the illustration on the right.

After you do that, and you find that you are getting return water to be below 135° for more than 10 minutes (or for the entire call for heat) then you need to have boiler protection to reduce the chance of flue gas condensation. This is easily done without a separate control. just put the red and orange wires back in the control in the original location and remove the blue wire from the B terminal of the LO side That will prevent the burner from running to maintain temperature but hold the circulator pump off until the boiler reaches the temperature setting of the LO limit. I would try 140° with a 5° Diff for starters just to see how that works out.

There is a more detailed description of this topic here:

https://forum.heatinghelp.com/discussion/comment/1798670#Comment_1798670