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TriangleTube Prestige Excellence-minimum Heat-supply H20 max 132F

SALBuild1
SALBuild1 Member Posts: 11
Need help in diagnosing TT Prestige Excellence 110 "low" heat issue.
Full system installed ~ 6 years ago, no issues until now. Two boilers installed for identical apartments, so I can also compare to what the "OK" boiler is doing for outputs.

Installation: Propane fuel, 4 cast iron radiators plus 1 kickspace heater, each on own loop. Pex supply/return lines. 1 internal and 1 external circ pump. 2 expansion tanks (1 heat (on return), 1 DHW).

Thermostat set at 74F, actual room temp 62. Set it to 80, and still doesn't get up to temp (got up to 70, but the CH target still 132).
Here's the "INFO" (these are avg/range, I tracked for awhile):
1 (measured supply H20) 128-134
2 (Mea RTN H20) 124-130
3 (Mea DHW) 160(mostly), 154,152
4 (Outdoor) 30-26
5 (Flue temp) 126 (max)
6 (Target supply temp) 132 (never changed except during Hi Fire Test Mode)

The other boiler fires off and circulates 174F water for heat. This is what I would expect.
I've replaced the Honeywell R845A switching relay with a Taco SRT501 (originally thought that was the issue- but not).

I shut off the DHW, to eliminate the priority of hot water, to see if the DHW temp probe was the issue, but it still didn't come up to temp.

I can tell the external circ pump is running, as I can feel a slight vibration with hand on top, and the manifolds get hot.

Ran it in Hi Fire Test Mode (stat at 80), it cycled through, the same as the "OK" boiler (stat at 65). It put the CH target to 150F, and the CH water would get to 158F. After running the Hi Fire Test Mode, with the thermostat set to 64, the switching relay no longer indicated a call for heat. - But it seems to be calling for heat otherwise.

I checked the thermostat resistance (honeywell classic round with mercury), and it works.

Cleaned out the condensate traps on both boilers while I was at it. No red herrings there, and no improvement.

The Parameter settings are the same as the "OK" boiler. I have it set to max target supply temp of 150F. I sized the radiators for the lower supply temps, so larger than "typical" rads.

Any suggestions as to what it may be, or what I should check next? The issue seems to be the Target Supply Temp setting doesn't match the heat call.

Thanks for any and all help. HeatingHelp has improved my knowledge depth in Mod/Cons, hydronic and steam heat tremendously over the last 6 years.

Comments

  • HomerJSmith
    HomerJSmith Member Posts: 1,344
    Is the boiler short cycling?
  • DZoro
    DZoro Member Posts: 1,048
    How is your outdoor reset set up? Is it set up ? Sounds like it's set too low for your outdoor temperatures. Is your outdoor sensor out of the suns path? Does it read close to actual temp? Check which curve you are on, possible go to the 130-180. Not sure which model TT you have. Just for starters.......
  • HomerJSmith
    HomerJSmith Member Posts: 1,344
    Is there an outdoor reset?
  • SALBuild1
    SALBuild1 Member Posts: 11
    Hard to tell if it's short cycling, as these are So quiet. It may be, as in the two times I've been there, ~ 2 hours each time, and tracking the readings, the flue stack temp has been anywhere from 100 to 132F.
    Yes, the outdoor reset is set up, on North wall- no sun, next to the other boiler's. Reading right-on with actual temp(18-30F).
  • SALBuild1
    SALBuild1 Member Posts: 11
    It may not be short cycling, as it may just be "ON" constantly, until after I ran the Hi Fire Test Mode, that then brought the room temp up high enough that the zone wasn't calling.
  • SALBuild1
    SALBuild1 Member Posts: 11
    I'll get installation pix and post.
  • HomerJSmith
    HomerJSmith Member Posts: 1,344
    I would off hand suspect a faulty thermistor in the outdoor reset and would want to check the resistance with a meter against the manufacturers chart of resistance to temperature. You can go thru the trouble of switching the two reset modules and see if that makes a difference. I assume the reset curve is set properly.

    If the ohm reading on the chart goes up as the outdoor temperature goes down, disconnect the leads from the outdoor reset module from the boiler controller. The boiler should run at full fire.

    If the ohm reading on the chart goes up as the outdoor temperature goes up, suspect an open on the thermistor circuit.
  • NY_Rob
    NY_Rob Member Posts: 1,370
    edited January 2018
    Check the installer menu- see if some has dialed down the heating capacity or fan speed to under 100%.

    I can limit my mod-con down to 50% of full fire rate, it will never make 170F SWT at that reduced output with the radiation I have.
  • DZoro
    DZoro Member Posts: 1,048
    Sounds like the good boilers current target temp is 174* and this one is asking and your getting 134*. You said your max temp is set at 150*

    "The Parameter settings are the same as the "OK" boiler. I have it set to max target supply temp of 150F. I sized the radiators for the lower supply temps, so larger than "typical" rads. "

    The bad boiler should also have the max temp at 180*
  • SALBuild1
    SALBuild1 Member Posts: 11




    It's the boiler on the left. Both have had issues with air vents failing/leaking, and I've changed a bunch out over the last 5 years. This one "currently" had the DHW air vent leaking around the seam at the top (but only when the boiler was not running), so yesterday I changed it out. Hadn't gotten to it, because I didn't think it was related.

    Low and behold, now the boiler runs correctly- heats the CH supply to 178F with the thermostat set to 66F, bringing the room temp up quickly, just like designed.

    The failing air vent issue is another story. Supply house suggested it was because of restored cast iron radiators in the system, but that wouldn't explain the failures on the DHW side.
    Any suggestions for air vent failures?

    At this point, I have happy customers with heat.
  • SALBuild1
    SALBuild1 Member Posts: 11
    Thanks HomerJSmith, I checked the outdoor reset ohm resistance, and both boilers read the same. Good idea as I hadn't thought of that. Thanks.
  • DZoro
    DZoro Member Posts: 1,048
    Yes have too experienced air vent leaking issues. Which in turn cause water in the cabinet, and those board hate moisture. When they do dry out they usually do come back to life....
  • HomerJSmith
    HomerJSmith Member Posts: 1,344
    Boy, you learn something new every day. What make and model of air vent and where on the vent is the leak coming from?
  • SALBuild1
    SALBuild1 Member Posts: 11
    I've tried a number of mfgrs/models. This is the first I've seen leak like this. I think it was a Taco. I can get the model # later today. The replacement was Watts 1/2" FV-4-M1.
  • SALBuild1
    SALBuild1 Member Posts: 11
    Thanks Dennis, you may be right on the water issue (makes more sense than just the vent). When I replaced the air vent, I also dried out the cabinet, since there was a bit of water overflow during the change-out.
  • kcopp
    kcopp Member Posts: 3,784
    Poor water quality.
    The heating system should be cleaned w/ a good cleaner and then flushed and have an inhibitor added.
    Fernox, Sentinel and Rhomar are three brands.
    That will help the vents last longer as well and protect the boiler and other components. Helps w/ overall efficiency too.
  • HomerJSmith
    HomerJSmith Member Posts: 1,344
    Take the air vent apart and examine the inside, float and valve mechanism. If it is filled with crud, determine what kind of crud. Use a magnate especially if it is black crud. If it is black crud and magnetic, it could be magnetite, in which case you would need to install a Caleffi Dirt Mag.

    I would probably choke it down from 1/2" to 1/8".
    It would certainly be cheaper.

    Replacing a part doesn't solve the problem, you gotta come to some determination of what cause the problem in the first place or you will be constantly, over time, replacing the same part when it again fails.