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O/S TT Prestige 110 specific questions
Been adding convectors to one zone (of three) which has helped, but still short cycles on high limit more than I like. What is acceptable seems to vary by opinion, but every 15 minutes has me concerned over wear and tear on the boiler components. If any of the other zones are calling, the system is fine. It's one of the typical oversized boiler scenarios. All near boiler piping is to TT spec and primary/ secondary confirmed correct by Wallies here. I don't have a great understanding of ODR but keep tweaking with parameters related to it. It seems that I get slightly less short cycling by adjusting parameters such that my ODR max temperature setpoint is higher ; the only parameter I leave at default is "coldest day" curve of 0* for upstate NY. Each zone has it's own 3-speed UPS-15-58 Grundfos circulator which are identical to the factory internal circulator. When the short cycling zone's pump is on high the run times are longer. I previously dropped the internal circ. to low speed and the sound of the heat exchanger changed slightly noisier (perhaps steam flash?) so changed back to medium speed. Boiler pressure then was only about 11 PSI and recently went to 14-15 PSI and now the exchanger sounds normal with internal circ. on low speed and, cycling is slightly better on the troublesome zone but still room for improvement. Questions: Will this boiler show an error if it senses too little flow through the exchanger from the internal circ. being on low? Can any other parameter adjustments on this TT improve the situation without causing other problems. I refer to "parallel shift value" and "CH call blocking time" and any relevance they may have. I cannot currently afford a buffer tank or too much expense. Thank you for any suggestions.
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Comments
Adjusting the blocking time should help between cycled.
A buffer tank may not be as expensive as you think if you just use an electric water (elements disconnected) for the buffer tank. We do this regularly when customers have this problem because someone over-sized the boiler or added too much zoning.
You can choose to do what you want, but you cannot choose the consequences.
Should I be concerned about running the boiler pump on low speed if the boiler sounds normal under low or high fire? Thanks again
http://forum.heatinghelp.com/discussion/133897/thanks-and-tt-prestige-solo-110-questions#latest
I assume you connected the supply to the smart to the connection on the boiler and the return on the pipe that is capped under the boiler just to the right?
The boiler circulator on low should be just fine with your arrangement.
Carl
Albert Einstein
A simple solution might be to connect that zone to the HYDRONIC side of your indirect as shown in the attached drawing. This way, you have the buffer capacity of the indirect, but it's connected on the hydronic side.
I also posted some pics of this which were included with an install we finished a few days ago. The thread is on the main wall titled "New Install - Putting 10 pounds in a 5 pound bag".
You can choose to do what you want, but you cannot choose the consequences.
Sorry to hear your Troubles I had the same problems with my Weil Mclain 97+ 110 The min firing is to large for your smallest zone. So i started looking into the differences in the next size smaller. Of the same boiler which was the 70 I had to replace the venturi on the gas valve and switch the softare setup for the boiler to run as a 70 it was already configured in the setup. The primary pump running at low is fine for my setup. So inturn i changed the min from 22.000 to 14.000 to run a smaller zone runs great. Not sure how TT sets up there boilers and if the softare is set up like that. And the HX is the same size as the smaller model mine was just giving you food for thought Dan
You can choose to do what you want, but you cannot choose the consequences.
I've been adding to the smaller zone the past couple years in somewhat unorthodox ways to help with short cycling. The goals were to better heat the basement and kitchen floor without too much cost, and still keeping the boiler condensing much of the time for efficiency. Having the kitchen tied in with the basement is unusual, no doubt, but my wife is happy with the kitchen temps so... The only mixing is our domestic water from the indirect. Small zone is: about 225' 1/2" pex loop in aluminum subfloor plates; 25' of 3/4" fin-tube around perimeter of basement: and since we had a large CI radiator (5' x2') in the old system, I flushed it and plumbed it in the return a couple years ago. Perhaps the 1/2" pex loop should be after the radiator. I understand that all but the Pex was designed to run about 180*.
Their PTS60 could probably fire up to 80k, but that would require changing the fan and using different controls for each model.
Not having a full understanding of Para#19 "boost feature" or #20 "parallel shift value", they are at original defaults of 00 minutes and 00* degrees respectively. Thanks for lending an explanation. Some minor lengthening of #40 "call blocking" time I have done, but don't see much benefit.
If the short cycling persists after making those changes, I may begin using the indirect as a buffer as Ironman suggested. Hopefully that is as simple as moving the pump and return to the hydronic sides of the indirect as in his setup. The TT diagram for that setup shows a mixing valve before the zone pump. I'm not sure what water temps would be entering that zone off the indirect. I've left the boiler temp setting at the factory 140* and the controls automatically add 46* for a domestic call on priority. No concerns with Legionella anyway.
Any advice is appreciated.
NJ Master HVAC Lic.
Mahwah, NJ
Specializing in steam and hydronic heating
NJ Master HVAC Lic.
Mahwah, NJ
Specializing in steam and hydronic heating
Make sure that you don't pipe that panel rad in series with the BBs. Buderus has a bypass valve that's an accessory, but it's still only 1/2".
If you're gonna use the indirect as a buffer, I'd do it now while you've got the system open.
Also, remember to size your emitters for 140* or raise the temp in the indirect and add a tempering valve to the domestic side to prevent scalding.
You can choose to do what you want, but you cannot choose the consequences.
Perhaps taking my elderly mother in, pushing us into the chilly basement bedroom has inadvertently resolved the short cycling. One previously unused manifold loop now supplies 12' of fin-tube mounted on the coldest end of the basement. That additional load appears to be putting that zone over the lowest modulating rate of the Prestige (and better meeting the heat loss of the basement.) Admittedly, we are at near design temps but it's encouraging to finally see a delta t near 20 degrees for a fairly long run of various zones...not before seen under the same conditions. I sure won't miss that 6XXX on the display!
Most of this was brought on by over-zoning and oversizing the boiler for the domestic tank.
Thanks again to those who take the time to share your knowledge here.