Aquastat / circulator function

Oilfool

Since I've lived in my house the last 4 years, I always noticed it has taken a while for the radiators to heat equally. I've recently rebalanced and rebled any air out, which was none. However I noticed recently that I could hear the aquastat relay clicking on and off during the course of a call for heat , so it was turning the circulator off and on constantly. The controls are set 160 high and 140 low. It seems like it shouldn't be doing that while still needing to satisfy the thermostat. Also it always puzzled me why the main house circulator and thermostat is wired directly to the aquastat and the second zone is wired to the SR503 relay. I'll attach pictures.

Oilfool

Other pic

STEVEusaPA

Well it's doing its job and keeping your boiler from condensing, which is a good thing.
It's wired conventionally, using ZC & ZR terminals. It could be wired another way, but it's not going to help your situation.
So...what to do
Assuming that your settings match the boiler temp, and that you must be using this for domestic hot water heating, you could bump your high limit up to 170°-just to make sure you don't have an issue with the High and Low limits. Honeywell recommends a min of 20° difference between the 2.
Second would be to add a boiler by-pass or system bypass to avoid that cold water coming back to the boiler, dropping the boiler temp, and cycling the circulators.
Another cause is coming out of deep setbacks.

Is this just a 2 zone system, with an internal coil, and only 2 circulators? Or do you have primary/secondary and 3 circulators (probably just the 2)?

EBEBRATT-Ed

In addition to what @STEVEusaPA asked I would think the HIGH LIMIT setting is too low at 160 degrees.

First thing to do when the boiler shuts off on limit at 160 see what the boiler water actual temperature is by checking the thermometer. If the temperatures are within 5 degrees of each other set the high control at 190 deg and see if you have better operation.

If your boiler is oversized compared to your radiation you will build temperature and shut off the burner but your circulators should continue to run if the heat is calling.

Also with your present high limit setting of only 160 when a bunch of circulators come on or if you have a heavy DHW demand your boiler water may drop too low in temp and shut down the circulators.

I would leave the low at 140 and raise the high to 190 and try it. It will do no damage

Oilfool

Ok. It's a two zone system; one zone for most of the house another zone for what was a spare kinda office room. I was watching the temp gauge as the circulator was running. It does drop lower and then eventually kick back on, but I thought as long as it's being called for heat the lo control shouldn't have any affect on it. The bypass loop seems like a good idea. How would that be plumbed in?

Oilfool

The temp gauge and aquastat settings are pretty close maybe a few degrees difference but with in spec. The only wires going to the ZR terminal is the green wire from the 503 relay. Circulator is on C1 and C2

Oilfool

I don't understand why both thermostats aren't going to the 503 and circulator wiring going there as well. Why wire anything direct to the aquastat? And to clarify it's two zones, return side circulators, and indirect water heater with my priority

Paul48

On a call for heat the lo-limit controls the circulator to make sure that cold water does not return to the boiler, and cause flue gases to condense. That would rot the boiler out. A bypass loop does the same thing.

Oilfool

How does it do that?

Paul48

By bleeding some of the supply into the return to keep the temperature above a point that would cause the flue gases to condense.

HVACNUT

First, using green on H and ZR is a no no for line voltage. Green is only to be used as a ground wire.
Second, you don't have domestic priority if a space heat zone is connected to the triple.
You can certainly bring the main zone wiring into the 503. Rewire ZR,ZC (I always used red for ZR and blue for ZC).
You'll have you move or remove jumpers in the 503. Check inside the 503 cover.
For domestic priority it might be jumper placement or a switch.

Instead of using ZR,ZC, you can also wire low volt from TT on the aquastat to XX on the zone board. The boiler will maintain low limit and cycle to high limit only on a heat demand. Circ(s) will run continuously until demand is met.
With the TT to XX setup, you can also turn the low all the way down. As I mentioned in another post, I don't believe condensing of the flue gasses in a CI boiler with an indirect is an issue anymore since the introduction of ULSD

Oilfool

Ok. So on the aquastat the only wire going to ZR is coming from the 503 and it's a green wire. My indirect is set as a zone in the 503 along with the second home zone. For the main zone I do notice the temp gauge drop when the aquastat has kicked off the main circulator. I should mention I use a wood burning insert so the home radiators cool down while in use and just the boiler itself stays warm. I'd like to use the bypass loop if that would allow the aquastat to keep the circulator to continually run to heat up the house quicker. The second zone temp drops and it's circulator never kicks off. It's from the 503. Is there a explicit schematic for how how should move the main circulator to the 503 and plumbing schematic to put a bypass loop in.

Oilfool

503 pic.

Paul48

You have neither of those diagrams.

HVACNUT

> @Paul48 said:
> You have neither of those diagrams.

Put he can wire it to either of the diagrams.

Paul48

I don't necessarily think that having a bypass would heat the house faster. It would allow the circulator to keep running, but stop and start, or run continuously, you have to apply the same btus to the water.

Paul48

@HVACNUT

Sure.......Just making sure he realized that his was not wired to the instructions.

Oilfool

So from what you guys see in the pics of my aquastat,you can see it should be wired different?

Paul48

If everything is working, I'd leave it alone until the spring.