Hydrostat 3250-Plus Circulator Hold Off

spd1980

Hi,

I have a Taco SR503 controlling 3 circulators with 2 of them used for heat and the other used for hot water with priority enabled.

Does the hydrostat circulator hold off feature work when wiring everything as per the picture below?

Note, the picture doesn’t show anything as connected to the C1/C2 contacts and I saw a post on here mentioning that a circulator should be wired to these contacts or you lose the thermal pre-purge and circulator hold off features. I don’t know if that post is applicable to my set up or not so I thought I would ask in case anyone knows.

Thanks!

DJD775

I don't see how those features could be activated as you have it wired. If I remember correctly you need 120v at ZC on the zone panel for the circs to run. Right now that power is provided by the ZR which is active on a call for heat. If I had to guess you would need to remove the ZR/ZC jumper and connect the ZC's together on the zone panel and aquastat.

Steamhead

Wire both your zone circulators through the C and NO contacts of an RIB2401D or similar relay:

https://www.functionaldevices.com/products/building-automation/details/RIB2401D/

and use the circulator output on the HydroStat to operate the relay's coil. Problem solved.

MikeAmann

That is brilliant Steamhead!

spd1980

Thanks all. I’m going to ask my installer to look at the wiring when they come back to fix another issue.

HVACNUT

ZR on the 3250 Plus is an input, as shown in the diagram. A call for domestic energizes 120v for the indirect circulator as well as sending 120v to ZR on the Hydrostat. This goes to the burner circuit through the high limit only, bypassing the economy settings. 

You don't need an additional relay for circulator hold off.

You'll need to power the SR503 constant to L1, L2.
Remove the jumper between ZR,ZC in the SR503.
Run a wire from C1 on the Hydrostat to ZC on the SR503. That will provide the circulator hold that you're looking for.

DJD775

HVACNUT said:

ZR on the 3250 Plus is an input, as shown in the diagram. A call for domestic energizes 120v for the indirect circulator as well as sending 120v to ZR on the Hydrostat. This goes to the burner circuit through the high limit only, bypassing the economy settings. 

You don't need an additional relay for circulator hold off.

You'll need to power the SR503 constant to L1, L2.
Remove the jumper between ZR,ZC in the SR503.
Run a wire from C1 on the Hydrostat to ZC on the SR503. That will provide the circulator hold that you're looking for.

For future reference is there any difference between connecting C1 or ZC on the aquastat to ZC on the Zone Panel?

offdutytech

Plus One on Steamheads suggestion. Coming from commercial DDC control world RIB relays are so common. Don't know why more supply houses don't carry them. Makes life so much easier

HVACNUT

DJD775 said:

ZR on the 3250 Plus is an input, as shown in the diagram. A call for domestic energizes 120v for the indirect circulator as well as sending 120v to ZR on the Hydrostat. This goes to the burner circuit through the high limit only, bypassing the economy settings. 

You don't need an additional relay for circulator hold off.

You'll need to power the SR503 constant to L1, L2.
Remove the jumper between ZR,ZC in the SR503.
Run a wire from C1 on the Hydrostat to ZC on the SR503. That will provide the circulator hold that you're looking for.

For future reference is there any difference between connecting C1 or ZC on the aquastat to ZC on the Zone Panel?

I'm not sure. I'm just going by what I remember from Hydrolevel tech support. It was a question I had when I still did installations. 
I never tried ZC to ZC in that application. 
They should update their manual though. 

MikeAmann

While it does not specifically say so, the C1 C2 contacts can power a circulator (5.8 FLA), but ZR ZC might not be rated for that much current.

DJD775

In the setup in this thread the ZR would not be powering the circulators. It would only be communicating to the zone panel that the pump is active.
I would stick with HVACNUTs suggestion anyway as there is no question that the desired features will work when connected to C1.

spd1980

Yeah hvacnut’s solution looks good since it doesn’t require extra equipment. The RIB relay is cool to know about for future reference though. In general it’s interesting how the manual doesn’t have the most up to date or complete information in it. The manual for the Aquasmart seems a lot more thorough and it even had a separate wiring guide with lots of equipment configurations. On a side note, I also need to ask my installer to wire things to turn my air handler off during the domestic priority call otherwise it’s just blowing cold air out the entire time someone is in the shower or using enough hot water to cause a priority call. 

Rickoo

HVACNUT said:

ZR on the 3250 Plus is an input, as shown in the diagram. A call for domestic energizes 120v for the indirect circulator as well as sending 120v to ZR on the Hydrostat. This goes to the burner circuit through the high limit only, bypassing the economy settings. 

You don't need an additional relay for circulator hold off.

You'll need to power the SR503 constant to L1, L2.
Remove the jumper between ZR,ZC in the SR503.
Run a wire from C1 on the Hydrostat to ZC on the SR503. That will provide the circulator hold that you're looking for.

Trying to understand this.

What exactly happens when you connect the Hydrolevel's C1 terminal to the Taco SR's ZC?

How does this enable circulator hold? Providing boiler temp is above 140 degrees, wouldn't C1 just provide 120v to the SR? The SR already has 120v via L1/L2.

HVACNUT

Rickoo said:

ZR on the 3250 Plus is an input, as shown in the diagram. A call for domestic energizes 120v for the indirect circulator as well as sending 120v to ZR on the Hydrostat. This goes to the burner circuit through the high limit only, bypassing the economy settings. 

You don't need an additional relay for circulator hold off.

You'll need to power the SR503 constant to L1, L2.
Remove the jumper between ZR,ZC in the SR503.
Run a wire from C1 on the Hydrostat to ZC on the SR503. That will provide the circulator hold that you're looking for.

Trying to understand this. What exactly happens when you connect the Hydrolevel's C1 terminal to the Taco SR's ZC? How does this enable circulator hold? Providing boiler temp is above 140 degrees, wouldn't C1 just provide 120v to the SR? The SR already has 120v via L1/L2.

Sorry for the slow response. I got lost.
Anyway, if you set it up as a cold start, then the circulator hold feature is not set to 140°. It's set 125°. At that temperature, C1 will be energized as long as there's a heat demand. If boiler temperature drops below 115°, power to C1 is interrupted. 

Simply wiring C1 on the Hydrostat to ZC (jumper removed) on the Zone panel does not enable the circulator hold off feature. It must be enabled by programming the Hydrostat as well.

If it's not wired for circulator hold off, then the circulators will just run on a heat demand regardless of boiler temperature. 

Rickoo

Thanks for the follow up. I understood the necessity of enabling circulator hold off in the 3250 settings. So, when the boiler temp reaches 125, C1 is energized and sends 120v to ZC on the SR504. (with ZC/ZR Jumper removed) I suspect that this then powers the bus in the SR504 and allows the calling circulator(s) to run?

Does removing the ZC/ZR jumper in the SR break the connection between L1/L2 line in on the SR and the bus that feeds the relays?