Taco SR504 losing priority setting

Canucker

I have the SR504 for my house, 3 zones and a 30 gallon indirect. It normally runs flawlessly, I have had the odd time I've had to cycle power to the unit as I found the indirect running in addition to one or two of the zones. I chalked it up to possible short power loss to the house (it happens from time to time here), nothing to worry about as once the power was cycled, the priority reestablished and ran fine. Fast forward to the last couple of days, where I've had to reset it 4 separate times and there haven't been any issues with the power. I'm wondering if this happens as the unit ages and what I should look for to sort out the problem. Normally I don't run out of hot water but with extended family over and losing priority, the boiler can't keep up.

Thanks in advance,
Eric

Joe Mattiello

Good morning
Hope you had a great holiday!! The SR504 should be maintaining priority. I have not heard of any intermitting problems like you’re experiencing. I suggest giving me a call at Taco 401-942-8000 to try a few things before we condemn the control.
You mentioned resting control, however, there is no reset unless you’re referring to the normal/reset toggle switch synonymous with available add on controls for EXP models.

Canucker

Hi @Joe Mattiello , I'll have to give you a call when I get back home, out visiting family until the New year. Just for some additional information, I don't think the control is broken. When I say I reset it, I'm just cycling the power which shuts down the boiler and the zone controller. Once the power is turned back on, the priority setting runs like it's supposed to, I'm just not sure what seems to cause it to drop in the first place. I had a theory that I was having short power losses to the house but when it acted up a few times in the past weekend, the power was steady.

Canucker

Just thought I'd add an update to this as I believe I found the reason I was "losing" the priority setting. If I'm understanding the setting properly, the Taco maintains priority for 30 minutes before it resumes space heating. If the DHW takes longer than 30 minutes to satisfy, space heating resumes in addition to the indirect calling and it appears that the priority setting is lost until power to the unit is cycled, which restores the priority of zone 4(the indirect in my case)
In my scenario it was a combination of poor maintenance on my part (I hadn't cleaned out the indirect and decaled it since it was installed. Bad, bad, bad, we have very hard water) and my daughters and wife starting to have showers back to back to back which caused the 30 gallon indirect to call for longer than 30 minutes. Since I've cleaned up and descaled the tank, I haven't had any issues with the priority setting.
That said, I could be wrong but that's the only change I've made to the system and it appears to have worked.

Leon82

Isn't there switch that controls the behavior of the priority override?

Canucker

I'm not aware of another switch beside the one that turns the priority on or off for zone 4. Is that the one you mean?

HVACNUT

> @Canucker said:
> I'm not aware of another switch beside the one that turns the priority on or off for zone 4. Is that the one you mean?

Yes, that switch. What temp is the water heater set for?
Maybe think about a mixing valve to help prevent it from happening again.

Canucker

It's at 140, mixed down to 110 on the outlet. There's always plenty of hot water. I've never run out, even when the incoming water drops below 40F. The boiler is 86000 btu/hr output. It just seems to run longer than 30 minutes when there is a heavy load on the system, which seems to mess with the priority. Once it resumes space heating after an extended DHW call, it doesn't have a priority setting anymore, until I cycle the power. I have no idea if that is by design or not

Leon82

Priority protection was the one I was thinking of. Switch number 6

Canucker

It's the older model, not the EXP.

Canucker

I would like to know if losing the priority setting on long calls was an issue on the older controls. Any input from anyone familiar with them? @Joe Mattiello ?