Taco ZVC with L8124A Aquastat

ms570

I’m in the process of cleaning up the wiring on my boiler (WGO-5) using a Taco Zone Valve Control - ZVC406. I have an indirect water heater (Boilermate CH-80Z). I noticed that the Honeywell R845A relay wired to the circulator for the indirect water heater is not wired to ZC or ZR on the triple aquastat, and neither is it wired to TT on the triple aquastat. So when the indirect circulator runs, unless heating zone valves have recently called for heat or it’s the summer, the indirect water heater is basically operating at the low set point. My understanding is that from an energy perspective this wouldn’t be any less efficient for the boiler, however the recovery time of the indirect will be longer.

The circulator for the zone valves is on the return side immediately after the zone valves but before the return line for the indirect. The circulator for the hydronic heat should only run when a zone valve is opened otherwise can dead heat. In the current setup it’s wired to C1 on the triple aquastat.

I’m guessing that calling for heat and getting a faster recovery time is preferable? If so, what’s the best way to approach adjusting this. I’ve considered:

1. Putting the indirect circulator on a SR501, letting it start without calling for heat. Leave the zone valve circulator on C1. No change in functional setup.
2. Putting the indirect circulator on a SR501 and wiring to TT on the aquastat, moving the zone valve circulator to the pump end switch on the ZVC along with ZC (or C1) from the aquastat in order that the circulator only becomes active when demand can be met. Could also use line voltage for the other leg of the pump end switch but I think it’s probably best to make temperature first before activating the circulator.
3. Putting the indirect circulator on a SR501 and wiring to ZC/ZR. Given that the indirect should already be warm, I don’t think this is necessary, easiest to cold start.

Looking for any suggestions or ideas to improve on the setup.

HVACNUT

4. Just do it like it says in the manual. 

ms570

Thanks for the reply @HVACNUT. Sorry I forgot to mention I considered the Taco documented options. However, in that documented setup when the DHW calls for heat, both the system circulator and DHW circulator would be powered. In my case, I just want the DHW to power the DHW circulator. They have a setup documented for a secondary circulator which I could use to handle the circulator for the zone valves, however when there is a call for DHW, then the secondary wouldn't receive power (verified with a meter). In my current setup, I don't have a need for priority though, I've never had an issue with heating the house simultaneously.



To your point though, I could use the ZVC just for the zone valves and wire the zone valve circulator to the pump end switch on the ZVC. Separately wire the DHW to a SR501. And then tie both of them to the TT on the Aquastat using each's end switch contacts.

To my original questions, and what you're suggesting I'm assuming that it is preferred that the DHW always does call for heat? As opposed to my current setup, where the DHW relay isn't calling the aquastat for heat.

HVACNUT

I don't run into zone valves and panels very often in this setup.
A domestic demand on zone 6 shouldn't close TT on the aquastat. 
Reps from Taco usually visit this site so maybe we'll here from them for clarification. 

ms570

I checked that with priority turned off, zone 6 did close TT on the aquastat. @HVACNUT - are you saying it's not necessary for domestic demand to call for heat from the aquastat? If so, then my current setup (1) is ok - but my recovery would be slower.

ms570

I spoke with Taco tech support. Basically given that I have a low set point and the boiler always maintains the low temperature - that the DHW isn’t calling for heat isn’t an issue. If I want a faster recovery time, then DHW could be wired to call for heat/high set point and/or priority if necessary.

HVACNUT

I don't know why I wrote a domestic call shouldn't close TT on the aquastat. Of course it should. 
You need to take the circulator wiring out of the triple aquastat and wire it into the zone panel. 

ms570

Ok that's exactly what I was thinking. I've reviewed a few other posts where you've provided significant feedback also and based on findings in https://forum.heatinghelp.com/discussion/160282/how-does-an-aquastat-circuit-work, I have a bit more clarity now. I have a Honeywell L8124A, and with a relay it will support multiple zones. I can have the ZVC operate just the heating zones, and connect the end switch from the ZVC to TT on the aquastat. This will drive the 1K contacts to provide voltage to C1 for operating the zone valve circulator. Another option would be to move the zone valve circulator to the ZVC end switch using line voltage, or similar to the way the SR501 is documented, use ZC to power the zone valve circulator - in which case I would be getting the same functionality as just keeping it on the aquastat C1 - so for simplicity just keep it on C1 at the aquastat.

Separately, put the DHW on a SR501 wired to ZR/ZC which will operate the circulator for DHW only. From what I'm understanding the 1K contact is only closed by TT on the aquastat. The ZR call will not close those contacts which should allow to run the circulators independently.

I lose the ability to toggle a priority switch which isn't a big deal as I don't want to use priority anyway. But this should solve the initial problem where I connected the DHW to the ZVC and now allow to operate the circulators independently but now DHW will call for heat and run to high limit.

Does this check out @HVACNUT?