Boiler Zone 2 won't ignite boiler

Dean60068

This is a new problem, and I've had 2 companies come and look at the boiler and neither were able to fix it.

The boiler has 2 zones and there are no zone valves, only separate circulators. If zone one is on and zone 2 calls for heat the zone 2 pump will turn on and circulate the hot water and the boiler will stop igniting and the pump will stay on, eventually just circulating cold water. If only zone 2 calls for heat, the pump turns on, but the boiler does not ignite.

I have replaced both pumps, thermostats, and the RA832As with a Taco SR502 switching relay.

109A_5

Hello Dean60068,

So when the system had the RA832As the behavior was exactly the same as it is now with the Taco SR502 switching relay ?

Can you take off the cover of the SR502 and take a picture of everything inside ?

What thermostats do you have ?

The zone 2 LED does come on with a zone 2 call ? I don't see it on in the picture.

Red arrows, Priority off and jumper installed ?

Dean60068

Thank you for your response!

Yes, it is acting the same way it did when I had the RA832As .

I have one Honeywell thermostats pictured below. The heat only is the main.

Zone 2 does light when it calls for heat. Right now, I have it off.

Priority is off and the jumper is connecting ZC/ZR.

109A_5

" Yes, it is acting the same way it did when I had the RA832As . "

This makes it very puzzling that so much was replaced and yet a strange problem persists. By the symptoms it seems like it was a relay issue or now a SR502 issue. With the Isolated End switch controlling the boiler the boiler should not be sensitive to which zone is calling.

I guess if I were there I would verify all the power supply voltages when it acts up, 120 VAC and the 24 VAC in the SR502 and the boiler.

I also would verify the voltage across the thermostat zone terminals, that they (both zones) go close to zero volts and the voltage across the Isolated End switch terminals also goes to zero with either zone calling.

When either or both zones calling the Isolated End switch terminals should have 0 voltage across them, and 24 VAC with no call. The voltage across the non active Isolated End switch terminals comes from the boiler (or an aquastat).

I would also use jumper wires as a test instead of the thermostats.

With zone 1 off and zone 2 calling (if the boiler does not start) I would jumper the Isolated End switch terminals and see if the boiler starts.

Dean60068

Thanks, I will test the above and let you know what I find. Thanks for your help.

HVACNUT

XX in the Zone panel doesn't know if Zone 1 or Zone 2 is calling. The contacts just close to complete the circuit to R-G on the control relay in the boiler. In the control relay, one set of Normally Open contacts powers the circulator. Another set of Normally open contacts starts the burner circuit. But it also doesn't know if Zone 1 or Zone 2 is calling. So it's hard to accept what you're saying is really happening.

Does the vent damper open when Zone 2 calls and the Red light is on?

Dean60068

You are right it doesn't know what zone it is. But I have never wired zone 2 into the zone 1 position. All I know for sure is, when both zones are calling for heat, the system will stop igniting and the pumps will continue to run. I checked the temperature thinking it may be causing the boiler to overheat or the pressure to be too high and neither are the case. I will shut off zone 1 and only have zone 2 on then see what happens.

Something I've noticed today is the main thermostat is reading the wrong temp almost by 2 degrees lower. I plan to buy a new thermostat today. Other than that, I did the checks on the voltage when calling for heat and it all appears good.

I think it's time to call my local boiler company.

Thank you all for your help. If they fix it, I'll do an update.

109A_5

Try to switch thermostats here, see what it does. Does the issue follow the zone input or the thermostat and its wiring ?

When this all started was anything else happening remodeling, hanging a picture with a nail into the wall, etc.?

The symptoms don't make logical sense with the RA832As or with a Taco SR502 switching relay. The boiler wiring is very simple, no electronics to do strange stuff.

Some voltage somewhere must be abnormal if the boiler does not fire.

Dean60068

It started at the beginning of the colder months, when I first started using the boiler for the season. I've been limping it along and throwing parts at it, hoping to get lucky and fix it.

Here is where it is at; no matter the zone when the thermostat initially calls for heat, the boiler ignites, and the pump circulates the hot water. But, then the pump doesn't stop, and the zones are still calling for heat. The pumps are just circulating cold water at this point, and the boiler is not starting. The flue closes after the initial run and the pumps never shut off until, I shut them off by turning off the call for heat at the thermostat. I can then turn the thermostat back on and the cycle starts all over.

HVACNUT

That makes sense. Shut off the power. Check all electrical connections, grounds. Make sure the relay on the left side of the boiler is in tight.

There's a little switch on the vent damper motor. The next time the burners are on and the damper is open, switch it from auto to manual. The damper will always be open and the end switch closed in this position. Leave it like that and see if the problem goes away. If it goes away, then you need a new vent damper motor. Or you can leave it and lose a little efficiency.

Dean60068

Holy Crap!!!

HVACNUT you have solved the puzzle! I flipped the switch to the damper and now it appears the system is working.

Why did flipping that switch work? It was opening on the first cycle.

Alan (California Radiant) Forbes

Kudos to HVACNUT! He does it again!

Now, why does it only happen when a second zone calls for heat?
Is there something weird going on with the Taco end switch?

Is something in the flue damper circuitry preventing enough power to close the boiler relays?

109A_5

" no matter the zone when the thermostat initially calls for heat, the boiler ignites, and the pump circulates the hot water. "

This makes more sense, than zone 2 stops the boiler from working.

" But, then the pump doesn't stop, and the zones are still calling for heat. "

Since the Taco SR502 switching relay (and the previous RA832As) controls the circulators and when there is a call for heat the circulators will run, regardless of what the boiler is doing.

Why " 2 companies " missed that the damper may have an intermittent issue is beyond me.

The Taco SR502 switching relay's Isolated End switch closes, this should tell the boiler to fire and remain firing until the Isolated End switch opens.

The Isolated End switch closing commands the boiler circuitry to activate. This activation should open the damper completely first, then when the damper is completely open the damper's end switch closes actually firing the boiler. If the damper does not remain completely open or the damper's end switch is intermittent the boiler will not work consistently as it should.

Why " 2 companies " missed that the damper may have an intermittent issue is beyond me. I suspect they just like to change parts unit it hopefully starts to work correctly.

Alan (California Radiant) Forbes

Why2 companiesmissed that the damper may have an intermittent issue is beyond me. I suspect they just like to change parts unit it hopefully starts to work correctly.

This problem was not an easy one and it took us some banter before one of us came up with an answer. If I was one of the technicians that showed up, I really doubt that I could have figured it out on the first try. We're all sitting at our office desk, nice and quiet with no distractions; our phones are quiet and there no deadlines, except maybe dinner.

109A_5

https://forum.heatinghelp.com/discussion/comment/1837255#Comment_1837255

Well, logically IMO the OP's complaint made no sense. That was clue #1. Listen to the customer, then do your own due diligence to find the actual problem.

And in my mind using someone else's eyes, mind, hands and tools and test equipment by remote control, if that, is way more difficult than being there in person, regardless of my personal comfort at the moment.

Clue #2 the thermostat (zone 2) is calling and the boiler is not working, find out what is actually causing that, that should be rather simple. Start at either end (your choice) or sometimes much more efficient start in the middle and divide and conquer. For the most part ignore what is proven to be working correctly, and move on. There really is not that much there, a service Pro that is skilled in control electrical should have figured this out in under an hour IMO. Not skilled in control electrical, maybe they should not have been there.

Clue #3 " I have replaced both pumps, thermostats, and the RA832As with a Taco SR502 switching relay. " Not sure who all replace what, had they kept going and replaced the boiler and the damper it would have probably fixed the problem. This type of troubleshooting seems to happen way too often. Frustration is not a good troubleshooting strategy. Also changing a lot of parts can become problematic, since you can unknowingly introduce other new defects, now you may have multiple issues to find. More issues = more time.

Not that I really want to know, but how much time and money was spent replacing both pumps, thermostats, and the RA832As with a Taco SR502 switching relay and paying for two service calls, to basically end up with zero results.

I don't know who changed what and in what order, but the homeowner (?) really should not have to take matters into their own hands. Or maybe they (the homeowner (?)) changed everything and then out of frustration called the service companies. I don't know.

In my mind (in a perfect world) the first service call, spend an hour (or less, if the problem is repeatable) with a multimeter and some jumpers, then change the damper, done, happy customer. BTW its not like dampers and micro-switches never fail.

HVACNUT

@109A_5 , yes, when I go on call backs from other techs, I don't always want to know the history. Even if it's my call back, I'll start from square one. It's good to see for yourself what's actually happening, if you can get it to happen. But listening to the client is something that even if their description doesn't make sense, you can usually get a clue or two. Besides, they're unloading their frustration, and we're the heavy bag. If we were on site, we would've been out of there in half an hour. That's true of most of these threads though.

I went on an emergency service call Sunday night. System 2K boiler. Only the power light on at the Manager. One heat zone, and the water heater. On the phone I ask is the thermostat raised above room temperature? YES. Do you have hot water? NO. Weird. I go there, walk down to the basement. The burner is idle, circulator is running, lights are lit on the Manager up to 150. I jump the heat zone at the Manager, everything cycles fine. "Can I see your thermostat?" We go upstairs. 2 thermostats in the hall. Old line voltage Honeywell T451A for the heat. Digital thermostat for the AC. Heat thermostat set to 66°. AC thermostat reading 64°. "I have no heat." They have a service agreement so they didn't get hit with weekend rates, but they still had to pay for me to raise a thermostat. And they'll think about replacing the bi-metal thermostat.