Is there a "standard" way to indicate tstat call for heat at boiler?

Hipape

When my thermostat is calling for heat, it indicate that on the tstat display. That's nice. What would be convenient is if I had some sort of indicator at the boiler - did the burners stop because tstat stopped calling for heat? ptrol? lwco? Is there a standard way to provide an indicator at the boiler? Could I use a 24 VAC LED tied across the 2-wires that go to tstat? Spec sheet on 24 VAC LED says that they draw about 18mA - is Is that too much load?
Thanks you!

Jamie Hall

The 24 volt LED would go out -- not light -- if the thermostat was calling. Remember what T-T at the boiler is looking for is a closed circuit from one terminal to the other. That's all.

Same thing for the pressure control(s) and low water cutout(s). Normal is a closed circuit. Those controls, however, are not always wired into the thermostat and T-T lines. They aren't even all at control voltage...

I agree -- a nice status board would come in handy, now and then. It would almost have to be custom designed, though, as not all boilers are wired in the same way.

Hipape

D'oh! good point... Of course I should be able to do the conversion in my head: "light off" = "call for heat" Question 1: Will 0.45V (19mA across 24V) instead of 0V confuse or damage the boiler ? Question 2: what is "T-T" as in T-T at the boiler and T-T lines? Thanks!

Jamie Hall

Now that first question is a good one. I think it would depend -- a lot -- on the specific control being used. It wouldn't be noticed by a relay -- 19 mA isn't going to trip a relay, or at least not an ordinary one! -- but I'm not sure what it would do to a solid state control. Sorry...

And I don't know the origin of the T-T -- I'd always just sort of understood it to be the two terminals which, when shorted by the thermostat closing, indicated a call for heat -- hence "T" for thermostat. Good question!

mattmia2

You can use an LED and a resistor, need to put a second diode across the led biased the other way so the reverse half of the cycle doesn't exceed the reverse voltage of the led. Connect it to the coil side of the t-stat and to the side of the xfmr the coils connect to.

mattmia2

The solid state control would have to be designed to stay off at 20 ma or things like power stealing thermostats would trip them.

Hap_Hazzard

Funny you should ask. I just finished wiring up a LED display on the wall outside my boiler room so I can see what's up at a glance. I used three big AC LEDS. They're about ¾" in diameter, and there's a red one, a green one and a yellow one. (I think they might have been used in a miniature traffic signal or something.) The red one's connected to the "hot" side of the 24v transformer and indicates that the power is on. The yellow one is connected to the thermostat terminal and indicates that the thermostat is calling for heat. The green one is connected to the gas valve and indicates that the burner is (or should be) firing. So the red light is on all the time, then the yellow one comes on when the thermostat calls for heat, and I can hear the automatic vent start to open, then the gas valve goes "click" and the green light comes on and I hear the burner lighting up.

I made all the connections inside my probe-type LWCO, because all the connections I needed were right there in one place. I don't think those LEDS are available anymore, but if you're interested I can try to find the specs for them, but it's not critical. Any 24v LED should work. And if you happen to have a Hydrolevel LWCO I can tell you which terminals to wire them to.

Hap_Hazzard

mattmia2 said:

You can use an LED and a resistor, need to put a second diode across the led biased the other way so the reverse half of the cycle doesn't exceed the reverse voltage of the led. Connect it to the coil side of the t-stat and to the side of the xfmr the coils connect to.

You'd want to put the rectifier diode in series with the LED, not in parallel. Otherwise you'll let all the smoke out of the transformer.

Hap_Hazzard

I found some LEDs that are very similar to the ones I used, only they give you ten for less than I paid for my three!

https://www.amazon.com/Gasher-Energy-Saving-Indicator-Mounting/dp/B088JZMQH1/ref=asc_df_B081FCFLVT/

jad3675

I just finished something up with an opto-coupler and raspberry pi, tied into the 24V feed to my zone valves. 

JUGHNE

I am finishing up a boiler room project that has 3 boilers in it.
Also a feeder pump that cycles a lot, so I can barely hear a boiler light off.

I added a red LED pilot light in the side of each cabinet, it is connected to the main gas valve of each. 1/2" hole and they pop in.
Got them from Grainger for maybe 8 bucks each.

That tells me when the fire is on (well hopefully lite, the gas valve is energized).
The led's on the LWCO tell if there is power to the unit.
Also added LED to the W and C of one unit to see that the stat was calling.

The other two units use a double pole RIB relay that has LEDs whenever each pole is activated by the 2 stage tstat.

All direct connections to tstat wires, so far the smoke has stayed inside the devices.

As far as why the boiler might shut down when tstat is still calling;
The Cyclegard, (major PIA) will throw a green light and shut down all 120 VAC.
The pressuretrol might open at about 2 PSI by the gauge.
The high limit manual reset ptrol will pop out the button.
The secondary LWCO will throw a red low water light and must be manually reset.

Hap_Hazzard

JUGHNE said:

All direct connections to tstat wires, so far the smoke has stayed inside the devices.

That's important.

JUGHNE said:

As far as why the boiler might shut down when tstat is still calling;
The Cyclegard, (major PIA) will throw a green light and shut down all 120 VAC.

I've noticed that about the 120v CycleGards. My 24v CycleGard just opens the control circuit, same as the LWCO, Pressuretrol and the automatic vent. Is it possible to put the 120v ones in series with the other controls so it doesn't shut down the whole party?

Hipape

@Hap_Hazzard - that's the ticket! Why yes, I do have a hydrolevel CG-400A LCWO - some hints would be much appreciated! And thanks for the LED link.

Hap_Hazzard

Hipape said:

@Hap_Hazzard - that's the ticket! Why yes, I do have a hydrolevel CG-400A LCWO - some hints would be much appreciated! And thanks for the LED link.

If you're using the AC LEDs, like the Gasher LEDs from Amazon, the wiring is pretty easy, because polarity doesn't matter, and you don't need any resistors if you get the 24v ones. If you have an automatic vent damper wired into your control circuit, it makes it a little more complicated, because the thermostat really controls the damper, and the damper controls the gas valve (through the limit controls), but if you can follow how the damper is connected, you shouldn't have any trouble getting it right.

I'll refer to the terminals as they're labeled in the CG-400 installation instructions. (See below.) So terminal 1 is the second terminal from the left, not the first terminal, as you might expect.

1. Start by connecting a common wire to one terminal of each of the three LEDs. Connect this wire to terminal 2 of the CG-400.
   
2. Connect the free terminal of the "power indicator" light to terminal 1.
   
3. Connect the free terminal of the "call for heat indicator" light to terminal P2.
   If you have an automatic vent damper, and your limit controls are connected to it instead of terminal P2, you need to connect this wire to the vent damper wire that your limit controls are connected to.
   
4. Connect the free terminal of the "burner on" indicator to the "burner" terminal on the CG-400.
   If you have not connected the "hot leg" of the burner to the "burner" terminal of the CG-400 to enable the "smart cycle" feature, you'll need to connect this wire to the "hot leg" terminal of the burner instead. (You might as well enable "smart cycle" while you're at it.)
   

Zman

Um,
They already solved this problem.
https://www.supplyhouse.com/Switching-Relays-443000
https://www.supplyhouse.com/Taco-Zone-Valve-Controls-326000

Hap_Hazzard

Zman said:

Um,
They already solved this problem.
https://www.supplyhouse.com/Switching-Relays-443000
https://www.supplyhouse.com/Taco-Zone-Valve-Controls-326000

That's a solution to a whole different problem. We're just talking about how to see when the thermostat is calling for heat at a steam boiler. Zone controls are a whole different subject. Most residential steam systems don't even have zones.

Hipape

Thanks @Hap_Hazzard - I printed out my wiring diagram and the hydrolevel install doc and am tracing things through on paper...Looks pretty straight forward.

Of course, next I'm going to want to dangle a raspberry pi server on it like @jad3675 did...and while I'm at it, why not look at...

Thanks everyone!

JUGHNE

Hap, if one has a 120 VAC Cyclegard what would the "burner connection" go to?

jad3675

Hipape said:

Of course, next I'm going to want to dangle a raspberry pi server on it like @jad3675 did...and while I'm at it, why not look at...

Thanks everyone!

Here's the optical relay I picked up (mine is a 4 channel though):
https://www.amazon.com/Voltage-Level-Converter-24V-3-3V/dp/B06XKYS8VC/ref=sr_1_1?keywords=8+channel+voltage+level+translator&qid=1638892465&sr=8-1

Here's the code I use to scrape the GPIO signal and send the status to my monitoring.
https://github.com/jad3675/Triangle-Tube-Boiler/blob/main/zone_status.py

And with a clear case, you can look at the lights!


Or lights on a screen:

Hap_Hazzard

JUGHNE said:

Hap, if one has a 120 VAC Cyclegard what would the "burner connection" go to?

Do you have a 120v gas valve too? If so, the hot leg is probably going to be 120v, so you'll either need to get a 120v AC LED or calculate the resistance you need to drop it down to 24v at 20 mA.

JUGHNE

Not worried about the LED's, as mentioned above everything is lite up as needed.

The problem is short cycling.

This CG450 1560 came OEM on my 3 steamers. The other 2 were converted to use M&M 150 LWCO/feeder pump control.

I requested anything but CG's, but when ordering this early summer you are lucky to get the actual boilers.

The CG's are 120 VAC and they use a 120 V VXT water feeder.
When they test they shut off all 120 V power to the boiler including transformer.
All other components are 24 volt.
So vent damper remains open until power returns, then closes, then opens, then fires.

Also the 15 minute cycle runs constantly, heat call or not.
So your heat call may start at the 14 minute mark....short fire then shut down.
The tstat loses power, reverts to batteries and when re-energized goes to a several minute "wait" cycle.
So it is down for 4 minutes.
Bad if you are just starting up.

Not bad if you have slow cond water return, I do not believe I do.
Also added an accumulator/reservoir pipe on this boiler.

There is more, boiler also cycles on pressure at 1.5 PSI.

Considering a Hydrogard might be a trade off versus changing damper motor that fails from possible over use.

Hap_Hazzard

Supply House has a Hydrolevel Safgard for $93, but it's 24v. The VXT itself can be converted to 24v IIRC with one resistor, BUT you also need a 24v Dema valve, and those aren't cheap.

JUGHNE

This is a commercial setting of a schoolhouse.
One does not want to tinker with OEM safety controls for liability reasons, IMO.

mattmia2

Hap_Hazzard said:

BUT you also need a 24v Dema valve, and those aren't cheap.

Couldn't you just use a relay or is there more to it than just a solenoid?

Hap_Hazzard

mattmia2 said:

Hap_Hazzard said:

BUT you also need a 24v Dema valve, and those aren't cheap.

Couldn't you just use a relay or is there more to it than just a solenoid?

You could use a relay, or a transformer, but that would get a little messy.

BTW, you don't have to pay heating supply company prices for the valves. It's a popular valve used in a lot of different applications. They make a lot of similar valves, so you have to be careful to get the right one. It's a 24v diaphragm valve, 3/8", normally closed.
https://www.kleen-ritecorp.com/p-4427-dema-443p-3-nc-3-8-diaphragm-valve-with-epdm-seal-and-24-vac-spade-coil.aspx

JUGHNE

VXT has a programmable fill timer with LED read out showing the gallons added.
In addition to the solenoid coil.
Again OEM controls.

Chris_L

jad3675 said:

Here's the optical relay I picked up (mine is a 4 channel though):
https://www.amazon.com/Voltage-Level-Converter-24V-3-3V/dp/B06XKYS8VC/ref=sr_1_1?keywords=8+channel+voltage+level+translator&qid=1638892465&sr=8-1

@jad3675, will that level converter work with 24V AC? Or just 24v DC?

I don't know much about normal controls (my boiler works on millivolts so I can monitor the switches directly with a microcontroller) but I thought most normal systems were 24 AC.

jad3675

Chris_L said:

jad3675 said:

Here's the optical relay I picked up (mine is a 4 channel though):
https://www.amazon.com/Voltage-Level-Converter-24V-3-3V/dp/B06XKYS8VC/ref=sr_1_1?keywords=8+channel+voltage+level+translator&qid=1638892465&sr=8-1

@jad3675, will that level converter work with 24V AC? Or just 24v DC?

I don't know much about normal controls (my boiler works on millivolts so I can monitor the switches directly with a microcontroller) but I thought most normal systems were 24 AC.

Yes. Works with both AC and DC. Your output on the DC side will be square wave though if the input is AC, which means you need to monitor the GPIO voltage change on the pi side on the rise/fall.

Hap_Hazzard

JUGHNE said:

VXT has a programmable fill timer with LED read out showing the gallons added.
In addition to the solenoid coil.
Again OEM controls.

It's actually a diaphragm valve. I think the CycleGard instructions even say not to use it with a water feeder that has a solenoid valve.

mattmia2

A diaphragm valve is controlled by a solenoid, right?

mattmia2

An LED is a diode. An LED isn't AC or DC, whatever you are calling an "AC LED" must be something like an led, a back biased diode, a zener diode to regulate voltage, and a current limiting resistor.

Here is the $.30 way to do it. Depending on where the safety chain is and where you tap in you will see if the safety chain is closed or not too. Note that the LED only sees half of the ac cycle, the other half flows through the reverse biased diode to keep the inverse voltage across the LED to the junction voltage of the other LED. If you had a maybe 100 v piv LED you could skip the reverse biased diode.

Hap_Hazzard

mattmia2 said:

A diaphragm valve is controlled by a solenoid, right?

Right. But solenoid valves don't have diaphragms. Besides, Hydrolevel wouldn't use a solenoid valve in the VXT if it meant you couldn't use it with their LWCOs.

Hap_Hazzard

mattmia2 said:

An LED is a diode. An LED isn't AC or DC, whatever you are calling an "AC LED" must be something like an led, a back biased diode, a zener diode to regulate voltage, and a current limiting resistor.

Okay, it's an AC LED Indicator Light. These are LED devices intended for AC applications. I was calling them AC LEDs for short. I didn't mean to confuse you. Sometimes the manufacturers provide the rectification for you, like the people who make those LED light bulbs you can screw into your light sockets—without having to convert your household current to DC!

HomerJSmith

mattmia2 said: Couldn't you just use a relay or is there more to it than just a solenoid?

I haven't worked this out, but why not use a reed relay in series with the common wire from the thermostat. They use very little current. Wire it like a regular relay with the points connected to a LED that operates at 24 V AC. The points would be connected from the transformer 24V thru the reed relay points to the LED back to the common on the transformer.

The current would flow from the transformer to the thermostat back down to the reed relay coil to the common on the transformer. Hmmm

Chris_L

jad3675 said:

Chris_L said:

jad3675 said:

Here's the optical relay I picked up (mine is a 4 channel though):
https://www.amazon.com/Voltage-Level-Converter-24V-3-3V/dp/B06XKYS8VC/ref=sr_1_1?keywords=8+channel+voltage+level+translator&qid=1638892465&sr=8-1

@jad3675, will that level converter work with 24V AC? Or just 24v DC?

I don't know much about normal controls (my boiler works on millivolts so I can monitor the switches directly with a microcontroller) but I thought most normal systems were 24 AC.

Yes. Works with both AC and DC. Your output on the DC side will be square wave though if the input is AC, which means you need to monitor the GPIO voltage change on the pi side on the rise/fall.

Got it. Thanks. I've never worked with the pi, but maybe one of these days...

Arduino-type boards have worked for me, especially the ESP8266. Not only can you monitor your boiler, you can get it to send you messages when there are problems.