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

EdTheHeaterMan

Here is a picture of the control after the red and White wires have been connected together with a small wire nut. you can hardly see a difference

DStreet

Thanks Ed. Would you educate me on the advantages of cold start when using in-direct water heating? Would the changes you’re suggesting still be good without the water heater? I say this because the tank is showing signs of leakage so I will need to replace it soon. I’m only keeping the house 3 or 4 more years and don’t want to spend a bunch of money I’ll never recoup.

DStreet

I have wired the Taco 504-4 as the instructions say and the boiler doesn’t fire and circulators pumps don’t work. I ran the low volt wire from XX to Tw T and 120v to the L and N connections. I don’t get how the boiler aquastat is powered without a 120v feed.

HVACNUT

https://forum.heatinghelp.com/discussion/comment/1902906#Comment_1902906

Is the green power light lit on the Taco zone panel?

If you're using X-X to Tw-T, then its a cold start aquastat? What model aquastat?

If you jump R-W at any zone on the Taco panel, does anything happen?

Is anything wired to C1 in the aquastat?

DStreet

DStreet

The green power light lights as do the red lights when t-stats are active.

PEr your previous suggestion I bugged R and W together to make a cold start.

Nothing when jumping R and W. As a matter of fact that whole low voltage strip shows no power at all. When I turn on the switch to power up the green and red indicator lights come on and the circulators start but no signal to the boiler to come on.

DStreet

I also tested the transformer and it has power in and out.

HVACNUT

So you changed the wiring in the aquastat to try and make it cold start? If the boiler is cold and you jump Tv-T in the aquastat, there should be 120 vac at B1 and the burner should start. The burner isn't in safety? If you jump any R-W in the zone panel, there should be 120 vac on the circulator side for that zone regardless if the burner fires.

Getting conflicting info if I'm reading it right. You say, "Nothing when jumping R and W. As a matter of fact that whole low voltage strip shows no power at all." Then you write, "When I turn on the switch to power up(,?) the green and red indicator lights come on and the circulators start but no signal to the boiler to come on."

So jumping Tv-T should start the burner if cold. If not, maybe think about an actual cold start aquastat.

DStreet

I do have indicator lights and power to the circulators but I have no power to the boiler.

Jumping Tv-T didn’t do anything. For some reason no power is getting to the boiler circuit.
I even held the contact in the aquastat closed and nothing happened.

I checked for continuity on the wire from X to Tv-T and it’s good. How do I check if the boiler isin safety?

HVACNUT

https://forum.heatinghelp.com/discussion/comment/1902917#Comment_1902917

Assuming its oil fired, the primary on the burner should have a reset button. First check to make sure there's 120 vac across B1 and B2.

DStreet

I have no power to he aquastat. That’s the problem. The boiler doesn’t fire because the aquastat isn’t getting power from the relay.

JMWHVAC

Yes, the aquastat needs power to the 120v terminals.

HVACNUT

https://forum.heatinghelp.com/discussion/comment/1902919#Comment_1902919

You need to connect to "120 v line" in the aquastat.

DStreet

I thought of that but was afraid it would back feed. I considered a branch off the service switch. Attach it to L1L2 of the aquastat to power just the boiler?

Jamie Hall

First things first. I notice that for some reason the ground leads on the 120 volts side are not connected.

They are there for a reason. Connect them.

Now. I've looked through these various notes up here, and I am trying with some desperation to figure out what ix going on. As I understand it, you have a boiler. Yo have an aquastat. You also have three or four circulators and associated thermostats —perhaps including one on the indirect water heater, which you might also be calling an aquastat (it is, but for a different purpose).

The thermostats should all turn on their respective circulators. Thermostat on? Circulator on. Including the indirect. The boiler aquastat should control the boiler and primary circulator. Circulating water too cool? Boiler on. Circulating water too hot? Boiler off.

Now another way to do it is cold start. In which case, the thermostats should turn on the boiler unless the boiler aquastat says it's too hot. When the boiler aquastat says it has warm water, the ciirculator — or circulators — associated with the calling thermostat turn on. If the boiler water gets too hot, the boiler aquastat turns off the boiler — but not the circulators. An alternative is to have the thermostats turn on the circulatorsm which in turn turn on the boiler if the boiler aquastat is in the calling range. A little less complicated (in fact, a lot — in manyc ases you can do the whole thing with no intermediate relays or cotnrol boards are anything fancy like that).

DStreet

First, let me say thanks for the input. Second, the grounds aren’t connected because I’m not done.

I didn’t know a boiler needed circulator to monitor itself. I thought that was the aquastats probe that did that.

You don’t mention the Taco 504 circulator relay which is where I put all of the circulators. As a novice at boilers and relays I could not find an explanation of how they worked together, only as individual units.

Your last paragraph is what I am striving for. It was suggested to me to bug the R and W wires from the aquastat to create a cold start.
The biggest problem I’m having is power to start the boiler when a t-stat calls for heat. The directions from the Taco say 120v to the circulator connections and a wire from X X on the relay to the T Tv on the aquastat. Well I did that but when I turn on the power I get a green light and 4 red ones. The circs run but the boiler won’t fire.

Originally the boiler was tied to a circ pump but I moved it to the relay thinking that was the right thing to do. How would you establish power to the boiler?

Jamie Hall

Quick question. When one or more of the circulators calls for heat, does the relay close? Check to see if X-X is a closed circuit.

Now… I notice that X-X is on the low voltage side of the Taco board. Further, X-X is for an isolated contact set on the Taco board — among other things, that means it can't supply power to anything — just open and close a circuit.

In this instance, I expect it is closing a 24 VAC circuit from the aquastat, which includes the power transformer on the aquastat and the coil of the aquastat's relay (which, in turn will send a closed circuit to the burner control.

BUT. to have 24 VAC for that relay, the aquastat has to have a 120 VAC power input, as @HVACNUT mentioned. That 120 VAC input only powers the transformer on the aquastat — it's not connected (or shouldn't be!) to anything else. I'd take it off the same circuit which powers the Taco and the burner. That way if you flip the breaker for the system, or open the service or emergency switch, everything will be dead.

So what will happen is this: the Taco board senses that one or more zones needs heat, and does two things: closes a relay to power the appropriate zone or zones, and also closes a relay which closes the circuit between X-X on the Taco board. Now on the aquastat side, there is a 24 VAC power source (which you just hooked up!) and there is a relay; if X-X on the Taco is closed, and the temperature sensed by the aquastat is between its limits, that relay will close and send create a closed circuit with the control terminals on the boiler, and the boiler will fire.

I'm honestly not sure which pair of terminals on the aquatstat are the burner control termnals. I THINK they are B1 and B2.

DStreet

When I turn on the power to the Taco the green light shows there is power. Also, the zone lights turn red when I turn up the individual t-stats and the circulators run. I still have one question though. I put the boiler circulator on zone one of the Taco. It was controlling that zone when it was on the aquastat. Should I move it back to the aquastat?

Thanks for the help guys. I do appreciate it.

HVACNUT

@DStreet , leave all circulators in the zone panel.

If you were to put one circulator back in the aquastat, where would you connect the thermostat wire? Tv-T is already being used for the zone panel.

If you had 5 zones and needed to add a circulator to the aquastat, you would not wire X-X to Tv-T. You would wire a 120 volt circuit ZR/ZC in the aquastat to ZR/ZC in the zone panel.

Jamie Hall

Wait. What? The boiler circulator — if you are referring to some sort of primary/secondary arrangement — has to be on an aquastat on the boiler circuit. Last thing you want is the boiler thundering away with no circulation…

DStreet

That’s what I wanted to know.

DStreet

I got rid of the indirect water heater so the priority zone is vacant. Would it be appropriate to use that as the boiler zone/ circulator?

Jamie Hall

https://forum.heatinghelp.com/discussion/comment/1903031#Comment_1903031

No — the priority zone is just that, and if it's set to "on" it shuts down all the other circulators when it is activated. Not really what you want… just give the primary loop its own aquastat and let it go. Send power to that aquastat and hence the boiler when any of the other zones are calling.

HVACNUT

https://forum.heatinghelp.com/discussion/comment/1903031#Comment_1903031

Sure. Just shut off the priority switch or what @Jamie Hall said will happen will happen.

pedmec

You need to feed 120 volts to the triple aquastat. It will power up the tv-t circ. The tv-t circuit will land on the x-x of the switching relay. The x-x on the taco switching relay are dry contacts and when any zone calls the x-x circuit will close causing the triple aquastat to function.

DStreet

Thanks. FYI I bugged together the R and W to make it a cold start.