2 year old carrier Boiler will not fire.

Alex4700

I have a 2 year old carrier comfort 80 gas fired steam boiler that is acting strange and not working. The automatic vent damper is in the open position (switch is in the automatic position), and the Ignition module will click every 5 seconds. This is happening when the thermostat is not calling for heat. When I call for heat nothing happens.The transformer has 24V, I have replaced the vent damper, and cleaned the low water sensor.

Ironman

I would suggest calling a qualified tech. We're reluctant to give out DIY advice about gas components due to the liability.

JUGHNE

It seems that a 2 year old boiler should have some parts warranty available.
You should contact the installer of the new boiler.
BTY, what prompted the changing of the vent damper?

Alex4700

The boiler was installed just before I bought the house. Since I am not the one that purchased the boiler the warranty doesn't extend to me.

The vent damper had 24 volts going into it, and 21 volts coming out to the ignition module. It led me to believe there was an issue with the vent damper circuit board.

JUGHNE

Did you change the batteries in the T-stat, if any?
Then if you disconnect the T-stat wires at the boiler, the vent damper might close and nothing should click.
The 24 VAC (a nominal number) system usually reads 27-28 VAC.

Alex4700

The voltage at the transformer is about 27.5. I said 24 volts just because it is a 24 volt transformer.

I have over 10 years experience as an automotive technician. I am trying to diagnose this the same way I would with a car, but I know HVAC is a different world.

The thermostat is an Ecobee3 it is hardwired into the house.The damper closed on its own when I drained the water in order to clean the water level sensor. Once I filled the water to the correct level the vent damper will go to the open position. This is all happening when the thermostat is not calling for heat.

It seems to me like it is one of the sensors but I don't know the correct way to test them I have checked the continuity on all of the sensors to verify they are closed . After replacing the vent damper the only thing that stood out is the 24V ground to the ignition module. When I unplug the wire and check it (transformer to wire) ,it has 27.5 volts. When I plug the wire back into the module and check it, it has no voltage.

JUGHNE

Some how your T-stat is still calling for heat. You need to isolate the t-stat from the boiler system and see what happens.

Alex4700

If the thermostat is calling for heat wouldn't the heat turn on? I have been using the thermostat to control the A/C all summer. When I get home I will disconnect the thermostat wires and see what happens.

JUGHNE

When I call my auto tech with this many issues and questions he tells me to bring it into the shop.
Perhaps you need to do the equivalent with your boiler.....have a HVAC tech who knows steam boilers come fix it.

Steam and hot water systems are as different from each other as a gas and diesel engine might be. You want some one who knows steam systems.
Where are you located.....there is a Find a Contractor section above.

ChrisJ

The problem is, if you know how to troubleshoot you would've checked for 24VAC at the gas valve and worked your way backwards to see where it disappeared.

If you've got it at the valve, you'd then question other things.

Jamie Hall

Seems to me that you may have at least two different problems here. First, if the automatic vent damper is open all the time -- but closes when you drained the water to clean the LWCO - it would seem to me that power is available to the system, and that something (shorted wires?) is calling for the unit to fire when the thermostat is off. You need to track that one down.

Then, you say you hear the ignition module clicking. That indicates that it is trying to fire, but nothing is happening. No fuel or no spark... but it's not the same problem as the vent damper.

HVACNUT

Do you have the I&O manual?
Shut off the gas.

When you say you have 24v into the damper, and 21v to the ICM, where are you measuring?

There will always be 24v at 4 and 1 on the molex plug at the damper. (4 is common, 1 is power)

2 and 3 on the molex is an end switch.

There should ONLY be 24v between 4 and 2 if there is a call for heat.

There should ONLY be 24v between 4 and 3 if the end switch in the damper closes (damper open).

It seems like a back feed. Does the thermostat have seperate RC and R terminals? If so, is the jumper removed? No, it's not. Remove the jumper.
RC for cooling
R for heating

Your getting a back feed through the thermostat from the A/C power, sending 24v to #2 on the damper, and opening it.

PERFORM ALL YOUR TESTS WITH THE GAS OFF.

Alex4700

I figured out the problem. There was in internal issue with the ecobee3 thermostat. It was completing the circuit (RH to W1) with high resistance at all times. It had a constant 2 volt signal going to the W1 wire. It was enough to open the vent damper, and make the ignition module click, but not enough to fire the boiler. When I connected the RC, and W1 wires at the thermostat the boiler fired right up, I also moved the W1 wire to the W2 port, tricked the thermostat into thinking I had a 2 stage boiler, commanded the second stage to turn on, and it worked. I called Ecobee customer service, and they are sending me a replacement unit. Thank you everyone for the input.

HVACNUT

Keep figuring.
In no way will 2 volts power the damper motor open.
Either the jumper was never removed, or 24v from the A/C transformer was connected to Rh.
The module was just clicking because 24v from the A/C was essentially butting heads with the 24v from the boiler through the coil.
If the R and W wires were switched at the thermostat, you would've blown one, maybe both transformers.

P.S. Who clicked the Like icon from the OP reply?
Did 2v really power the damper open? I'd be very afraid if it did.

Alex4700

I have included a pic of the thermostat wiring, and the wiring diagram from the side of the boiler. There is no RH to RC jumper on the Ecobee thermostat (external, or internal). I didn't switch the RH, and W1 wire at the thermostat. I disconnected them and touched them together to complete the circuit. When I would disconnect the RH wire from the green wire on the LWCO the vent damper would close. The green wire from the LWCO has 24V.

Everything is wired exactly as the diagram shows.

ChrisJ

HVACNUT said:

Keep figuring.

In no way will 2 volts power the damper motor open.

Either the jumper was never removed, or 24v from the A/C transformer was connected to Rh.

The module was just clicking because 24v from the A/C was essentially butting heads with the 24v from the boiler through the coil.

If the R and W wires were switched at the thermostat, you would've blown one, maybe both transformers.



P.S. Who clicked the Like icon from the OP reply?

Did 2v really power the damper open? I'd be very afraid if it did.

I clicked it, because he figured out the problem.

I had a strange scenario where a rapid pulsing of the 24VAC slowly opened the damper, but never opened the gas valve.

I read his response as he had a 2 volt drop across the thermostat, but perhaps I misunderstood.

HVACNUT

> @Alex4700 said:
> When I would disconnect the RH wire from the green wire on the LWCO the vent damper would close. The green wire from the LWCO has 24V.
>
> Everything is wired exactly as the diagram shows.
>
>You will always have 24v at the B terminal (green wire) on the LWCO as long as it's not a low water condition.
Let's call the green wire "Line" and the black wire "Load". Black being the wire in series to the pressurtrol, then to the 2 terminal on the vent damper.
When you disconnect Rh from green, your opening the circuit from the Line side, and the damper closes?
Is the thermostat off, or turned down below room temp when you did this?
If so, then that blows my theory right out of the water. You sank my battleship.
If everything was the way you found it, my reasoning was 24v was being back fed from the thermostat to the Black, through the pressurtrol, energizing terminal 2 on the vent damper. Closing end switch to 3 and applying 24v to the ICM.
If there's no back feed, and RH is connected to green, and the damper opens, where is the 24v coming from?
And the White from the thermostat is spliced to the Black at the boiler, correct?
If you remove the White wire from the thermostat sub base, does the damper stay open?
If it does, something is wired wrong in the boiler.

Alex4700

When I disconnect the W1 wire from the thermostat the vent damper closes. I did misinform you yesterday. When I got home last night I rechecked the voltage coming from the W1 wire (black lead on 24V common side of transformer, Red lead on the W1 wire) and it was 15V not 2V. Everything has been happening no matter what setting the thermostat is on A/C, Heat, or off. When the new thermostat arrives I will hook it up and re check everything.

HVACNUT

I never worked with the Ecobee.
I've installed customer supplied Nest thermostats, and had many sub base shorts. Constant circulation though a hydro coil. Constant condenser only running. POS.

John Mills_5

Only Ecobee I did like that I had them use an isolation relay to bring on the boiler. Hooked the power from the air handler to RC & RH, W sent 24v to the relay and back to common. The relay closed calling for heat on the boiler. No issues. Otherwise, not sure how to run a common from both the cooling and the boiler to the stat.

JUGHNE

Don't some boilers come with an isolation relay for this very reason?

AMservices

John Mills said:

Only Ecobee I did like that I had them use an isolation relay to bring on the boiler. Hooked the power from the air handler to RC & RH, W sent 24v to the relay and back to common. The relay closed calling for heat on the boiler. No issues. Otherwise, not sure how to run a common from both the cooling and the boiler to the stat.

You only need one common to the thermostat. The common wire is only there so you can power to thermostat without using batteries.
If there are separate terminals for RH and RC, then there must be a way to separate them. Sometimes there's a factory-installed jumper wire, sometimes there's a dip switch on the back of the thermostat and sometimes it's in the installer set up. By separating the RH and RC terminals, you are isolating the two 24 volt input going to the thermostat from the boiler and the air handler.
I would use the common from the AC system, connect the 24 volt power from the AC to the RC terminal, then connect the two wires from the boiler to the RH and W.
With that thermostat you're most likely going to need to go into the installers programming and tell the thermostat that the heating and cooling systems are separate. If you don't it may try to run the fan during a call for heat.

Alex4700

Update: installed the new thermostat about a month ago and everything has been working as it should. Thank you everyone for helping me figure out the problem.

Harvey Ramer

I'm a bit late to the party. I could have helped. The ecobee3 has an internal setting to connect or disconnect rc and rh.