Questionable delta-T

Jimbo_5

I have a TT-solo-110 and with the factory setting on the circ I was pretty steady with a DT of 20, then switched to the middle setting and went to a DT of 26-ish.  Now that I switched to the lowest setting, my DT is 30 to 34 as the boiler ramps up.  I cannot help but wonder if 34 is too much, too close to hitting the lock-down set point.  What do you think?

eluv8

Delta T

Typically,  high delta T (25-40) help increase condensing efficiencies but can lead to less comfort, Since Delta T  is relative to zones calling (Provided your not using Variable speed pumps or a bypass valve). You may have a high delta T with all zones calling however it could come down to 10-12 or less when only one or two zones are calling.



 If you are unsure what to set the pump speed at, you will be less likely to get a " I am to cold or it responds to slow" complaint with a Delta T in the 10-20 range.



Its been a while since I installed a TT and am not sure what their Delta T limit is however, If you are checking your Delta T at its worst with all zones fully open and cold at high fire, I would not be concerned with hitting the limit.



My primary concern would be a cold or slow response complaint with those Delta T's in low on a residential home in the middle of winter. I had a customer complain about feeling the cold pipes in the floor with only a 15 degree difference on a 12" spaced loop on tile. " You missed a whole section over here, feel here and feel here, its cold". Luckily the pump was on medium, bumped it to high and he was fine. Ever since I have paid attention to my layout and designs very carefully.

Jimbo_5

Thank you

I have but one zone, CI rads.  The TT cut off is, I believe, 44 degs.  I guess I will just have to see how it plays out this winter.  I've got to admit, it is condensing much more than before.  Granted it has only fluctuated between 119 and 30 degrees for the lows lately,  We shall see.  I am just afraid of hitting the lock out while away for the day.

cattledog

Delta T lockout

Jimbo--



In the older TT Prestige Solo 110 with the original MCBA controller the manuals say there is a standby mode soft error code (b 30) for delta T more than 72F which cycles the burner off for longer and longer times before going into a lockout. after 22 cycles. It's unclear if it then displays an E series error code (None of which appear to apply to this condition.) or goes dead with the b 30 display.



I don't know about the newer MCBA.



Where are you getting your delta T lockout information from?

Jimbo_5

Thanks

I do have the 1st board, series-3.  As odd as it sounds, I bought the boiler last years when there were none to be found, this one was in storage at a large distributor with multiple locations.  I called all over the place, only Solo-60s to be found.  Brand new, but the previous series.

Unknown

Curious???

What do you mean "lockout"?,,,,,, are you speaking of your "tailored curve"?

As eluv8 says,,,, the cooler the return water, the better, provided comfort does not suffer.



You can have 160 going-out, and 70 coming-back,,,,, if there is no-problem with your comfort level,,,, just sit-back and enjoy the efficiency!  ;-)

CMadatMe

Flow rate, Flow rate, Flow rate

There is absoutely nothing wrong with having an increased delta-t as long as you can maintain your design heat loss. If you are concered about the boiler, don't be. Worse case is it locks out due to low flow rate. What's the worst thing you have to do flip a switch? If you want to eliminate a possible boiler flow problem,  pipe in a low loss header and use a grundfos alpha for your system pump to maintain your desired system delta-t and let the boiler pump do it's thing.