Need help wiring aquastat

LongIslandSteamer

My plumber just finished setting up a hot water loop today off my Weil McLain steam boiler (with a heat exchanger and 2 circulators) and all seemed to be working OK until a few hours after the plumber left and we noticed that even though the hot water zone reached the set point in the hot water loop thermostat and the steam thermostat the boiler was still firing. So basically even though both thermostats are set to 68 the house is now 75 degrees because the boiler keeps firing. I suspect this is because the aquastat (a strap on aquastat strapped to the supply line feeding into the circulator feeding the heat exchanger) is checking for water temp and in turn firing the burner even though the hot water zone thermostat isn’t calling for heat. I suspect the aquastat isn’t wired properly in the Taco Sr 501 relay the plumber installed. Any ideas? If I can just move a wire in the relay and fix this that would be great. We are roasting here.

EBEBRATT-Ed

Just turn the aqustat down for now.

I can't tell you how to wire the system without a lot more information. Apparently you plumber needs to call in someone that knows controls

LongIslandSteamer

> @EBEBRATT-Ed said:
> Just turn the aqustat down for now.
>
> I can't tell you how to wire the system without a lot more information. Apparently you plumber needs to call in someone that knows controls

Thanks, Ed. Good idea. I will do that. This guy it totally clueless. I will try and get a photo of how it’s wired now to see if that helps.

LongIslandSteamer

> @EBEBRATT-Ed said:
> Just turn the aqustat down for now.
>
> I can't tell you how to wire the system without a lot more information. Apparently you plumber needs to call in someone that knows controls

Ed - just to be clear, the aquastat shouldn’t be checking to see if the boiler is at temp unless the hot water loop is calling for heat, right? Just need a sanity check.

Jamie Hall

LongIslandSteamer said:

> @EBEBRATT-Ed said:

> Just turn the aqustat down for now.

>

> I can't tell you how to wire the system without a lot more information. Apparently you plumber needs to call in someone that knows controls



Ed - just to be clear, the aquastat shouldn’t be checking to see if the boiler is at temp unless the hot water loop is calling for heat, right? Just need a sanity check.

That's correct. The problem may be in the actual placement o the aquastat -- as well as its wiring. If it is in the hot water loop or heat exchanger loop with the pump off, it won't be able to sense the boiler water temperature. It has to be located to sense the boiler water temperature, not the loop temperatures.

LongIslandSteamer

Jamie Hall said:

LongIslandSteamer said:

> @EBEBRATT-Ed said:

> Just turn the aqustat down for now.

>

> I can't tell you how to wire the system without a lot more information. Apparently you plumber needs to call in someone that knows controls



Ed - just to be clear, the aquastat shouldn’t be checking to see if the boiler is at temp unless the hot water loop is calling for heat, right? Just need a sanity check.

That's correct. The problem may be in the actual placement o the aquastat -- as well as its wiring. If it is in the hot water loop or heat exchanger loop with the pump off, it won't be able to sense the boiler water temperature. It has to be located to sense the boiler water temperature, not the loop temperatures.

Thanks Jamie. I am not home to take a picture but the aquastat is a strap on type and it's strapped to the pipe going to the circulator which goes to the heat exchanger. I noticed that the piece of pipe it's strapped to is a small length of iron pipe as opposed to the copper pipe between the circulator and the heat exchanger. Do you think it makes sense to move the aquastat to the length of copper pipe between the circulator and the heat exchanger? I would think copper would be a better medium for conductivity than black iron pipe.

Jamie Hall

Problem is that that pipe won't be at boiler temperature unless that circulator is running.

LongIslandSteamer

Good point. So i guess the black iron pipe is where it will stay for now. I seemed like it was seated properly when i last looked at it but I wouldnt be surprised if it needs adjustment. Ideally the plumber shouldve installed an aquastat in a well. Having said all that, i think the wiring is the main issue right now.

LongIslandSteamer

Jamie - actually now that I thought about it again, the circulator will always be running when the hot water loop zone is calling for heat. that's what should then trigger the aquastat to check the temp on the copper pipe - so i'm thinking the copper is a better place, no?

STEAM DOCTOR

Somewhat common to use strap on aquastat in such a setup. The kicker is that they are almost never accurate. Might take some trial and error. Turn down to the point where boiler won't produce steam but there will be hot water in the loop. Obviously, there may be other factors at play

EBEBRATT-Ed

@LongIslandSteamer

not knowing what you have for controls makes it a guessing game.

I would use a two pole relay with NO contacts.

When the thermostat calls for heat (hot water zone) 1 pole starts the HW circulating pump, the other pole goes in series with the aquastat and starts the boiler.

When the stat is satisfied the boiler and pump shut off. When the stat calls the pump and boiler run. The aqustat shuts off the boiler if it gets too hot but will allow the pummp to run to disipate heat as long as the stat is calling

You would be much better off with an imersion aqustat in the boiler and skip the strap on. You don't need an aqustat on the hx or zone piping

LongIslandSteamer

Finally got home from work and was able to take a look at my plumber's handiwork. As expected, the aquastat is definitely not wired up correctly. As you can see in the photos, the aquastat is only wired directly to the boiler and has ZERO wires going into the relay.

Is this a simple wiring fix?

HVACNUT

Why is there a jumper between R and W on the SR501?

Edit: disregard. I'm the meatball.

Jamie Hall

Ah. You do have a relay. @EBEBRATT-Ed 's wiring description is how you want it to go.

LongIslandSteamer

HVACNUT said:

Why is there a jumper between R and W on the SR501? If you didn't put it there to test something temporarily, then remove it ya meatball.

I didn't put anything there. I'll tell my plumber to remove it.

LongIslandSteamer

HVACNUT said:

Why is there a jumper between R and W on the SR501? If you didn't put it there to test something temporarily, then remove it ya meatball.

I just zoomed in and i dont see a jumper. I think it's just the way the wire is laying in the photo.

HVACNUT

> @LongIslandSteamer said:
> (Quote)
> I just zoomed in and i dont see a jumper. I think it's just the way the wire is laying in the photo.

You're right. Apologies. Maybe it's time to see the optometrist.

HVACNUT

@LongIslandSteamer
Discuss with your plumber but this should be acceptable. The L4006A aquastat is a Hi Limit only with an adjustable differential. It will basically act as a cold start.