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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.

Comments

  • ced48ced48 Posts: 453Member
    Have you thought of combining zones?
  • masterofnonemasterofnone Posts: 25Member
    Yes. The short cycling zone predominantly heats our basement. I had it combined with the first floor living room/kitchen zone of our Ranch home and short cycling was not an issue. Living room/kitchen were comfortable and basement was adequately warm for laundry and workshop. However, we took my mother in and we had to begin sleeping in the basement and it was too chilly; thus I put a stat near the bed and created it's own zone so as not to overheat the living room/kitchen. Each zone has adjustable flow-metered manifolds but finding a happy medium may be tricky if I recombine the upper and lower zones. I have been and will add more emitters in the basement zone. That should help but I still would like to know more about what specific changes to the reset curve might help, if any. Most likely, reset curve changes can only do so much for one short cycling zone. If anyone can address my concern over running the internal circulator on low speed I would appreciate that also. I'd rather have short term short cycling than compromise the boiler. Hopefully no one will suggest putting my mother in the basement :-)
  • IronmanIronman Posts: 5,309Member
    Reset curve adjustments are gonna help much, if any.

    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.
    Bob Boan


    You can choose to do what you want, but you cannot choose the consequences.
  • masterofnonemasterofnone Posts: 25Member
    Thank you CED48 and Ironman: you answered most of my questions. There's lots of info here on Buffer tank options. Not sure if it can be as simple as adding the buffer tank in-line between the boiler and zone circulators? The Prestige also supplies a Smart 40 as priority.
    Should I be concerned about running the boiler pump on low speed if the boiler sounds normal under low or high fire? Thanks again
  • masterofnonemasterofnone Posts: 25Member
    Thank you Carl for the response and searching out that pic from a few years ago. I've attached a new pic of the Smart hook up. Something like the Boiler Buddy is beyond my current budget so I will look into the simple electric(less) tank as you suggested.image
  • ced48ced48 Posts: 453Member

    Thank you CED48 and Ironman: you answered most of my questions. There's lots of info here on Buffer tank options. Not sure if it can be as simple as adding the buffer tank in-line between the boiler and zone circulators? The Prestige also supplies a Smart 40 as priority.
    Should I be concerned about running the boiler pump on low speed if the boiler sounds normal under low or high fire? Thanks again

    What kind of delta t are you getting at the different speeds?
  • masterofnonemasterofnone Posts: 25Member
    With only the small zone calling, the delta t from cold start averages about 16 degrees now. As it approaches the hi limit, the delta t is about 6 degrees. The numbers are slightly better after slowing the internal pump to low, and the boiler runs perhaps five minutes longer before reaching hi limit. The most short cycling occurs when either or both larger zones end a call for heat and the small zone is still calling. I am temporarily turning the basement stat down during the day which helps (during the day).
  • IronmanIronman Posts: 5,309Member
    What's the btu load of the small zone? What type of emitters?

    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".
    Bob Boan


    You can choose to do what you want, but you cannot choose the consequences.
  • DanscrewDanscrew Posts: 117Member
    Master
    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
  • IronmanIronman Posts: 5,309Member
    Danscrew said:

    Master
    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

    TT doesn't offer an 085, though others do using the fire tube HX. I don't know why they don't, but changing the firing rate of the gas train on any boiler is universally frowned upon by manufacturers, even though what you did accomplished the same as if it was done at the factory. It has to do with the certification of the appliance.

    Bob Boan


    You can choose to do what you want, but you cannot choose the consequences.
  • DanscrewDanscrew Posts: 117Member
    Weil Mclain said no problem spoke to Tech deparment and others they more or less took as no big deal Dan
  • masterofnonemasterofnone Posts: 25Member
    Thanks again. That is a very neat install and I see the similar application. I wish I had gotten in to hydronics when I was much younger. I have a lot to learn and appreciate the ability to access and learn some here. I try to keep things simple and rather not get involved with the software (at least not yet).
    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*.
  • SWEISWEI Posts: 7,356Member
    TT uses different heat exchangers for each model, but they all share the same controller and (other than the 399) the same fan assembly. This makes it easy for the wholesalers and installers to keep a simple spares kit on hand.

    Their PTS60 could probably fire up to 80k, but that would require changing the fan and using different controls for each model.
  • masterofnonemasterofnone Posts: 25Member
    unclejohn said:

    The parallel shift won't help you since that is for a constant boiler temp set up. The call blocking will but you might give up some level of comfort. You didn't adjust the "boost " feature did you. That will increase your target set point. I believe that's parameter 18. set that to off or zero.

    Uncle John,
    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.
  • unclejohnunclejohn Posts: 1,420Member
    You can run the boiler pump at low speed with no problem and that will give you the widest DT. The bottom line is until you have all zones above which ever it is that the lowest firing rate you will short cycle with out a buffer tank. What did you do with your old water heater, that's what I used for my buffer tank. I piped the TT directly into the old electric heat element fittings and used the hot and the drain for supply and return to the system.
  • masterofnonemasterofnone Posts: 25Member
    Our old N.G. hot water tank corroded out a few years ago, so I then added the Smart tank to the radiant system. I'm thinking I should correct some of the basement zone piping. It's currently piped in series with most of the fin tube and the C.I. radiator after the pex manifold. I plan to add a Buderus panel rad (rated about 5000 BTU @180*) and another section of fin tube to the basement this week. The basement needs more BTU's to satisfy it's stat when it gets below about 15 degrees outside.
    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.






  • clammyclammy Posts: 2,356Member
    Short cycling does truely stink ,you should just bite the bullet and get a small boiler buddy,re pipe the boiler to it as a hydronic seperator with your indirect off the boiler .I have used them a few times on jobs using both panel raditors and baseboard with excellent results .I also had the boiler differianal set for 30 degrees which helped slow down the short cycling issues on mirco zones . It seems that alot of times with short cycling it is the firing rate at which the boiler lights off and the time in which it finally regonizes the flame and starts to down fire .On some mod cons its 50 % of max fire ,so when a mirco zone is running alot of times the boiler is unable to even estabish flame current before it cycles on limit ,widen that boiler diff is the best you can do or combine zones .When i look at a job w a mod con and short cycling thats where i start to look and i usually end up thinking and using buffer tanks and there usually boiler buudies 30 gal .I re pipe the boiler using it as a hydro seperator and your done .They work very well .On another note have you have your boilers pumps programed to run post call for heat or domestic ,it s a good pratice to get that excess heat out of that exchanger .With a taco exp sr model circ relay you can set them for post run of the system circ side just some thoughts .Hope this helps out ,peace and good luck clammy
    R.A. Calmbacher L.L.C. HVAC
    NJ Master HVAC Lic.
    Mahwah, NJ
    Specializing in steam and hydronic heating
  • clammyclammy Posts: 2,356Member
    Not to be cirtical but do you have the miniun of straight pipe before your set of tees on your ps piping .Just wondering .peace and good luck clammy
    R.A. Calmbacher L.L.C. HVAC
    NJ Master HVAC Lic.
    Mahwah, NJ
    Specializing in steam and hydronic heating
  • IronmanIronman Posts: 5,309Member
    The mixing valve in the TT drawing is because there's a radiant floor connected. You don't want one with high temp emitters like BBs or panel rads.

    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.
    Bob Boan


    You can choose to do what you want, but you cannot choose the consequences.
  • masterofnonemasterofnone Posts: 25Member
    clammy said:

    ,widen that boiler diff is the best you can do or combine zones .
    Thanks Clammy:
    The only differential parameters on the control I see are for the domestic. I have done several changes of the CH reset curve and min./max. operating setpoint as mentioned earlier in the thread to get the longest runs. I'll listen to advice on this.

    On another note have you have your boilers pumps programed to run post call for heat or domestic ,it s a good practice to get that excess heat out of that exchanger .
    Yes, I have bumped up parameter 32 for CH post pump and will add some time to the domestic also (para 33).

    clammy said:

    Not to be cirtical but do you have the miniun of straight pipe before your set of tees on your ps piping clammy

    Just took a few pics of the piping and attached. Measured about 11" from the 90 to first tee.
    Ironman said:


    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".
    I recently added one of these to another 1st floor zone using a monoflow tee on the return since the panel radiator had the TRV installed. I'll do the same with this panel radiator but understand I may need two monoflow tees facing each other since it will be at a low point in the system.

    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.

    The Smart has a tempering valve in place now. Despite heat transfer plates and decent insulation, the CH water temps need to run pretty high (140* near design temperatures) due to our thick floors and generally poor windows and exterior wall insulation (working on that a little at a time). The floor surfaces are not overheating though IMO.

    The price point of the Boiler Buddy is deterring me from that option right now. Will try adding the additional emitters with better piping practice and if needed, zone off the indirect.
    Thanks again.

    imageimageimage
  • masterofnonemasterofnone Posts: 25Member
    unclejohn said:

    The bottom line is until you have all zones above which ever it is that the lowest firing rate you will short cycle with out a buffer tank


    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.


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