TT Solo 60 seems to cut out on low fire

smp74

I have a newly installed TT Solo 60 that is doing some short cycling. I know this is to be expected to a certain extent in the warm weather. However, I made some further observations that I would like to run by the wall here.

What I saw happening was once a zone was getting near the target boiler temp, the burner would of course modulate down into low fire. Then it would shut off, immediately re-light, modulate down again, shut off....repeat this every 30 seconds or so over and over. Still does this.

Now, what I noticed is that when this rapid cycling happens is that the "Flame ionization current" will drop to 0 microamps when the burner reaches low fire and within a second or two it shuts off, relights, modulates back down, flame ionization current goes down to 0 microamps again, shuts off....etc...etc

So, turn on manual mode operation. Engage the DHW zone so there is no way the load is too small. Fire the burner to 100%, of course it runs fine. Turn down to 1%, it runs for about 15 seconds, gas valve clicks closed, burner relights, modulates down to 1% for 15 seconds, gas valve closes, repeat on and on. Set modulation at 5%, runs fine, does not shut itself off at all.

So.....what gives? Gas valve not adjusted in low fire correctly? Ignitor / sensor bad? Planetary alignment? I'm crazy?

Thanks for any suggestions.

unclejohn

You need a combustion test done.

smp74

The combustion test was done at install. How do I convince the installer that there is something wrong and it needs to be done again?

Zman

They should be more than willing to retest. It is not working correctly. Make sure they test it on high and low fire per manufactures instruction.

RobG

And get a printout of the readings and post them here.

smp74

Will do. I was there at the initial test. They only tested on high fire. Manual clearly states to check high fire then low fire. I will call the installer today.

Zman

smp74 said:

Will do. I was there at the initial test. They only tested on high fire. Manual clearly states to check high fire then low fire. I will call the installer today.

Yes, They should test both. There is another adjustment screw that is used if they are out of range.

I think technically, you are only supposed to make that adjustment under direction from tech support.

It's not rocket science, they just don't want everyone fiddling with it.

Carl

smp74

Waiting for a call back now. In the meantime I called TT just to get their take on it as well. They basically said the same as the comments here "need combustion test numbers". It was also suggested that the flame sensor could be having issues. In either case, it looks like the analyzer needs to be put on it before anything further can be done. Get to burn up another vacation day now (I work 2 hours from home, not possible to schedule service outside of my work hours).

smp74

Well, no call back yet. I emailed and called the installer last Wed. This thing hasn't run correctly since it was installed 5+ weeks ago. How long would you all give an installer to make things right before searching elsewhere? I called TriangleTube this morning and a rep is going to get back to me with some factory recommendations for a different service company.

Also, I watched the installer when he was testing and adjusting at the commissioning of the boiler. After further reading of the manual, based on the suggestions above, I know exactly what the problem is and I'm really not happy.

smp74

Tech just finished up.
Results:

Initial test on low fire confirmed the suspicion that it was out of adjustment. It didn't run long enough for readings to stabilize but the oxygen reading went as high as 11% O2 before it kicked off. So, yep, waayyyy too lean. That would explain the flame current going to zero.

It had to be adjusted back and forth a couple of times between high fire to low fire as it was so out of whack. New readings are:

High fire:
3.2% O2
80ppm CO
16.4% ex air
11.69% CO2
94ppm undil CO

Low fire:
3.3% O2
3ppm CO
16.4% ex air
11.69% CO2
4ppm undil CO

Running as it should now. Stays in low fire until the built in 6F differential is reached. Flame current is minimum 6 microamps. Today that was about a 6 minute or so burn to maintain the 120F call on the baseboard zone. Much better than a 15 second burn previously. Setting the call blocking to 5min now gives <= 6 cycles per hour.


How's that all look?

Zman

That looks good, real good!
Nice work!

smp74

It was a different tech that came out this time. He said no problem that I wanted to watch and take notes on the readings etc. I did request a printout on high and low fire though. We'll see how it's running next fall at annual service.