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Condensing Boiler cycle times

spacoli
spacoli Member Posts: 61
Hi to all.



What kind of cycling should I typically have with a condensing boiler (Bobcat)?



I'm still tweaking my system, but at around 30* outside temp my boiler cycling on 15 minutes off and 15 minutes on.



I have dropped the weather compensation temp. from 86 to 76 and still maintaining comfort.



I'm still using the old circulator from the old boiler so I'm not getting the a good return drop for good condensing. I'm still making renovations and need to change out all the piping (2 zones) and get new circulator sized for all the new piping.



I'm sure once I have anew cirulator size, I will have to tweak everything again.



Any info or opinions are welcome. Thanks

Comments

  • Jean-David Beyer
    Jean-David Beyer Member Posts: 2,666
    What kind of cycling should I typically have with a condensing boiler

    It depends on everything.



    I have two heating zones on my mod-con boiler with outdoor reset. Although this boiler is the smallest in the product line, it is about twice the necessary size. One of the heating zones requires much less heat than the other. It would cycle on and off rather rapidly (10 times an hour, perhaps) when it is relatively warm outside. Even though this was less than my old oil boiler without outdoor reset, I considered it too rapid. The trouble is that the boiler would not modulate down low enough.



    The other zone is a radiant slab at grade that takes four times as much heat as the small zone (that is fin tube baseboard). Except when it is quite warm out, it just turns on until the thermostat is satisfied, and then turns off. This can take up to 18 hours straight because I have the outdoor reset adjusted very closely to the actual heat loss.



    I try to heat my house to 69F. And my boiler can easily do this (as I say, it is somewhat oversized), and my heat emitters are large enough. What I did to decreace the cycle rate in the small zone was to raise the reset curve to heat faster when it is warm out. I.e., instead of running 80F water in the baseboard, which is about all that is needed, I raised the minimum temperature to 110F. Thus, the boiler sees a greater heat load and this lengthens the cycles and decreases the rate. I also increased the differential between turn-on and turn-off from the default of 10F to 15F for that zone. The servo in the controller has the wrong time constants, so it has overshoot that makes it swing for the fences too hard. Since those constants are not adjustable, I reduced the firing rate for the small zone from the default 94% down to 55% so it would not rush up to where it shut off on high temperature. Combining these tricks, I now get about 5 cycles per hour from the boiler instead of about 10. I figure that is good enough. As it gets colder outside, the number of cycles per hour goes down.



    If my boiler had a large enough modulation range, I would set the reset curves so the boiler would run about 75% of the time. In very cold weather, I can get this for the large radiant slab zone, where once it ran 18 hours straight. Most of the time I am lucky to get 12 hours straight. That way I would be supplying the minimum possible heat that just does not satisfy the thermostat, but does satisfy me. It took a long time to get the controls adjusted this closely, like two entire winters. It takes a long time because with that slab, you adjust something, wait 24 hours for things to stabilize, rince and repeat. And then you wait for days or weeks until the outdoor temperature changes significantly for another test at the other end of the temperature range. Rinse and repeat again. It would be a lot quicker if I could adjust the outdoor temperature. ;-)
    smithfan
  • spacoli
    spacoli Member Posts: 61
    Allot of variables

    Thanks for your very informative reply.  I understand there is allot of variables.



    Correct me if I'm wrong. From what I understand the fewest cycles and lowest water temperature to maintain a desired comfort level is best?



    Since I lowered my weather compensation set point, I have noticed it seems more comfortable with no temperature swings. I just don't know how low I can go?







     
  • Jean-David Beyer
    Jean-David Beyer Member Posts: 2,666
    I just don't know how low I can go?

    1.) Realize that I am not a heating professional. I am really interested in this stuff and do a lot of reading. But my only practical experience is with one boiler in one house.



    2.) If your boiler is designed to condense (I think it is), you can go as low as you want. If you go too low, you will not get enough heat. If your boiler is not designed to condense, you probably want to keep it at 140F or higher return water temperature. My boiler has thermometers that tell supply and return temperatures to an precision of 1F. I do not know how accurate they are. If your boiler does not indicate that, you may wish to have a supply and return thermometer installed. The bigger they are, the easier they are to read.



    3.) As far as cycling rate is concerned, it depends on a bunch of things. If the boiler controls are exactly right, the cycling rate will be determined entirely by the thermostat in each zone. These generally have adjustable cycling rate. Older ones have an adjustable resister that adjust anticipation. The theory is different for each of these, but the results can be pretty much equivalent. For a radiant slab, a cycling rate on the thermostat of one cycle per hour is a good first step (and you may never need to change it). At the other extreme, for a copper tube aluminum finned basebard setup running high temperatures, a cycling rate of 3 cycles per hour might be appropriate. I run my baseboard at a very low temperature, so I use one cycle per hour on my baseboards too. I have way more baseboard that usual, so my maximum water temperature in there is 134F, where the usual temperature used is 180F. I put in excess baseboard so I could use lower temperatures and get more condensing. I should be able to condense provided the outdoor temperatures are above 6F; since design temperature here is 14F, getting 6F or less is a very rare occurrance. I have been monitoring the outdoor temperature for almost three years and I have never seen it below 9F. This winter, the lowest it has gone so far is 23.9F, but February is the cold month.



    3A.) If the thermostat cycling rate is too high, the boiler and its controls will wear out more quickly. If it is too low, the temperature will vary more than you might like, so you will want to make sure you get it about right. New thermostats usually come with an installation manual that suggests appropriate cycling rates to set for the heat emitters you have. But if you do as I do with severe reset adjustments, these cycling rates may be too high. They are probably a good place to start.



    4.) If the cycling rate of the thermostat is set to a suitably low value, the boiler can still cycle, and you will wish to minimize that. The way you do that is to adjust the outdoor reset curve so that the heat delivered to the house is very very close to equal the heat loss. Even if you could do this exactly in theory, in practice you would have problems because, at least for my boiler, the reset curve is a broken straight line. When the outdoor temperature is over 50F, the temperature is a constant 110F into my baseboard zone. Between 52F and 6F outside, it is a straight line that goes from 110F up to 134F. If it is colder than 6F outside, it is a constant 134F. But in reality, the heat loss is not really a straight line. For one thing, if the wind speed changes, the air leakage through the house changes as well. My reset curve is set assuming no wind, so if I did it "exactly" I would not get enough heat in windy weather. So I have it set slightly higher. In the baseboard zone, I use 4F setback at night. It takes two to 4 hours to recover from that because the heat delivered is set to maintain the desired temperature, but not really designed to recover from setback. My recommendation is to not use much setback at all. I do not use any setback for the radiant slab zone, because it takes about 24 hours to recover from setback in that zone.



    5.) You want the cycles per hour caused by the boiler controls to be as low as possible. This implies that you are supplying just enough heat for the building. Any more and you are wasting energy. Incidently, if you supply just enough heat, you will not get much overshoot, or undershoot, which implies more comfort. This is much less an issue with quick-acting emitters like baseboard, than it is with a slow-acting emitter, like radiant slab at grade, where it is a major problem.



    I seem to be starting on the Great American Novel here, so I better stop. I hope you get the idea. I found setting the reset curves for my boiler to take seveal years. Most of it was done in the first year, and a lot of fine tuning in the second year. I think I may make one change this year. It depends on how obsessive you are. I thinlk it should be possible in theory to set the reset curve(s) by examining your heat loss calculations. I used the old Slant/Fin heat loss program, and I imagine that the program itself was pretty accurate. But you have to input a lot of data, data I just did not have. I knew the length, width, and height of all the walls. The length and width of the windows. I knew the house was pretty well insulated, that High Price Marvin gas-filled windows, and stuff like that. But the house was built almost 30 years before I bought it. The heat loss enabled me to specify the smallest boiler in the contractor's product line, which was right. But when I set up the reset curve from that, I found the calculations were much too far off to set the reset curves. I did not know the exact construction of the walls (especially the corners), I did not know if the slab was insulated underneath or around the edge, I did not know how much wind leaked through the walls. And since I could not adjust the outdoor temperature, I had to wait until nature set the outside temperature to the test I needed to run to set a point on the reset curve.



    So you will have quite an opportunity to tune your system. Read the installation manual where it describes how to adjust the reset curve(s) and be sure you understand it. And then you can start a program of increasing your patience.



    Of course, you might find a contractor to do this for you, but you want to be sure you find one who understands all this, and I fear they are very rare. Also, if the contractor is like mine, they will have to charge you an hour of labor each time they come out to do 5 to 10 minutes work. (And I do not think this would be unreasonable.)  And if they do that 10 times the first year, and 5 times the second year and once the third year, it will be a question of whether they run out of patience or you run out of money first.
  • furnacefigher15
    furnacefigher15 Member Posts: 514
    mod cons

    Im not familiar with the particulars of the bobcat.



    I am how ever familiar with mod cons, and it may be as simple as changing a setting that may only be available in advanced setup, or you may have too much boiler for the load.



    If it is a setting, it would be along the lines of max firing rate for a particular function. If you use the boiler for heating domestic hot water, that firing rate could be as much as the boiler can give. But, the space heating may only need 50% of the firing rate even at very cold conditions.



    This is very common with the boilers I come across, that were never set up properly.



    If your boiler does not have a max firing rate limit setting, then you may need to provide the boiler with a false load.



    I find in commercial application of condensing boilers if the turn down on the boiler is not low enough, then many times I'll have to incorporate the use of storage tank that all boiler water goes into before going to the supply header.



    The tank acts as a time delay, till the load comes back naturally, and prevents excessive cycling of the boiler.



    In an ideal situation, the boiler will turn on and run continuously and modulate in response to load variation.
  • gennady
    gennady Member Posts: 836
    edited December 2011
    cycling

    You need no cycling. Boiler should work non stop . you get reset curve from heat load calculation. flow must be constant, temperature must follow reset curve. the lowest temperature you get, the better.every time boiler cycles, you lose efficiency. get rid of your thermostat and zoning. Also, do not change water temperature reference point, unless you running baseboard or cast iron radiators,  change reset curve number  , page 33 of the manual, parameter os. and look at page 34 for reset curve setting.
  • spacoli
    spacoli Member Posts: 61
    Thanks

    Thanks for your reply. I am using mostly cast iron rads in all rooms and some baseboard, toe space heat in kitchen and bath areas.
  • gennady
    gennady Member Posts: 836
    edited December 2011
    settings

    then set reference water point to 110F and pick reset curve to 1.8 ( it depends on locality design temperature, i gave you general curve number for NYC, it might differ in your location) for beginning, and set your thermostats to 88F, this will disable them. do not use night setbacks, make sure outdoor sensor activated and installed on north side , away of heating sources. You will be amazed.  
  • spacoli
    spacoli Member Posts: 61
    Please explain

    Could you explain this more?



    The outdoor sensor is on the north side away from sunlight, but it is next to a window. I have noticed a little temp difference from the actual sensor temp and the temp outside. I'm guessing I should more away from the window. 
  • gennady
    gennady Member Posts: 836
    outdoor sensor

    outdoor sensor location is extremely important, as this sensor becomes your thermostat, you want it not to be affected by heat sources and wires must be run at least 12" away from any other wires. as electromagnetic fields will affect its reading. do not forget to activate sensor in menu. In address c-t pick option 1
  • spacoli
    spacoli Member Posts: 61
    Thanks

    Thanks you for your time. If possible can you explain the settings you described in more details?
  • gennady
    gennady Member Posts: 836
    edited December 2011
    details

    water reference point establishes minimum water temperature.

    curve # is picked based on design outdoor and design water  temperature.

    you pick one from diagram on page 34 in manual. you want to pick one, that shows 180F water temperature (design water themperature) at design outdoor temperature, design outdoor temperature  you can get from google search in various publications.
  • spacoli
    spacoli Member Posts: 61
    My problem

    I think my biggest problem is that I retro fit the new boiler to the old piping and used the old circulator until I get  the new piping installed (split zones) and home renovations done to the house. Then I will get a properly size circulator(s) to get the right temp drop on the return side.
  • gennady
    gennady Member Posts: 836
    circulator

    As long as you used primary/secondary piping arrangement, you will be fine, you do not need to change anything. Just do water treatment and cleaning, use x400 centinel for initial cleaning, combined with water filter installed at boiler inlet, then after filter will be clean add x100 once a year. read instruction on the tube. You can leave your existing system as is. no problem
  • gennady
    gennady Member Posts: 836
    edited December 2011
    zoning

    Abandon idea of zoning. in high efficiency zoning and setbacks are bad habit, leftovers from old heating ideas
  • spacoli
    spacoli Member Posts: 61
    Circulator

    How do I get lower return water  temp drop for condensing without the right sized circulator? . Right now at the end of the cycle the flue/return temps are the same.
  • gennady
    gennady Member Posts: 836
    edited December 2011
    delta T

    you have to have 20F temperature difference between water temparture  to radiators and from radiators. if you have it, you are OK. system circulator must run continiously, exept when boiler is on DHW call.
  • spacoli
    spacoli Member Posts: 61
    Tempuature drop

    I have around 10 degree temp drop from supply and return. So I'm guessing I need more radiation and a slower circulator.



    I'm planning on moving a larger left over radiator from the renovations up to my bedroom. For some reason it has a small radiator and is the coldest bedroom. That should help some.
  • furnacefigher15
    furnacefigher15 Member Posts: 514
    Abandon zoning?

    I see that picture there, and that looks a lot like zoning to me.



    Zone abandonment question. Is this a strategy you incorporate on all building types and sizes?
  • gennady
    gennady Member Posts: 836
    edited December 2011
    zoning

    Yes, you are right. I had made my share of mistakes and learning as I go. The job in the picture was the last one I did with zoning , but I like how it feels and looks. The other one has no zoning, as well as many others. This is Viessmann Vitodens 200W. No zoning.No thermostat. Happy customer.

    i abandon zoning for all types of installation. I picked this old strategy from times I had worked at district heating power plant with outdoor reset.  It is very old idea, and works very well with all types of installations
  • furnacefigher15
    furnacefigher15 Member Posts: 514
    Building size?

    What size of buildings do you typically work on?



    I understand the concept you are using, but have never done it. I often deal with buildings and homes that have widely variant loads.



    Meaning one side of building needs heat, and the other does not want or need any
  • gennady
    gennady Member Posts: 836
    edited December 2011
    building type

    The last job we did was a 18 apartment building. and it worked pretty well. As per different loads, i would use VFD pumps coupled with mixing valves with outdoor reset. (or VFD pumps with outdoor reset),  it allows to set different curves for different parts of the building. but the concept is the same, working only on outdoor reset, and loading  boiler all the time, assuring continuous operation at low water temperatures.
  • gennady
    gennady Member Posts: 836
    circulator

    you have to increase radiation as much as possible . do not install smaller circulator, you can either install circuit setter or VFD pump.

    let me know what you decide to do and how it works i n regards boiler settings
  • spacoli
    spacoli Member Posts: 61
    Delta T circulator??

    How about a variable speed Delta T circulator? This seems like it would take care of my high return water temp. problem.



    I really want to get rid of the old circulator. It's noisy and I don't know it's history, how old it is or how long it will last.
  • Jean-David Beyer
    Jean-David Beyer Member Posts: 2,666
    I do not understand abandoning zoning.

    My house has two zones at the moment and they have very different heating characteristics. It used to be one zone and the smaller zone had very unacceptable heating.



    The house downstairs is radiant slab at grade, At 0F outside, it requires 24,000 BTU/hr. The upstairs is baseboard (now oversized) that requires 6,500 BTU/hour when it is 0F outside. The current boiler is the smallest in the product line: a mod-con with outdoor reset that can burn 80,000 BTU/hour and modulate down to 16,000 BTU/hour.



    The radiant zone could probably be run with constant circulation except that when it is over 50F outside, it cannot absorb over 16,000 BTU/hr, so the boiler cycles on and off.with a supply temperature of 75F. I used to let the reset go down to 70F, but the boiler was rapid cycling.



    The baseboard zone is worse. Until I fiddled the reset curve, the maximum firing rate for that zone, and the differential, it rapid cycled all the time. I raised the minimum temperature up there from 80F to 110F to make it sink heat faster, dropped the maximum firing rate from the default 94% to 55% to get around the fact that the time constant of the controller was too slow, so it was underdamped and unstable. And I increased the differential from the default of 10F to 15F. But there was no way I could run that with constant circulation, because there would be nowhere to dump the excess heat.



    It seems to me that having two zones, two reset curves, and a little creative adjustments is the only practical way to do this house. I suppose I could get a buffer tank and run it like a huge hydraulic separator to drive that zone. It would need about an hour of capacity (I did not figure how many gallons that would be). But it would need super insulation and 4 ports instead of the usual two. And a place to put it. And it would still be two zones.
  • furnacefigher15
    furnacefigher15 Member Posts: 514
    Control Stradegy

    In order to have longer run times with your boiler, you need more load.



    Maybe try lowering the max firing rate farther.
  • gennady
    gennady Member Posts: 836
    edited December 2011
    zoning

    did you pipe your boiler in primary / secondary loops?

    did you install mixing valve for low temp zone?

    there is no reason to derate boiler, as what matters in your case is boiler stability on low load.
  • furnacefigher15
    furnacefigher15 Member Posts: 514
    boiler load

    His load at 0 is barely more than the lowest firing rate of the boiler.



    Im guessing its warmer than 0 where he lives most of the winter.



    At 45 degrees the load on the system may only be 5000 btu, but the minimum on the boiler is 16,000



    There's not enough load.
  • Jean-David Beyer
    Jean-David Beyer Member Posts: 2,666
    primary / secondary loops?

    1.) did you pipe your boiler in primary / secondary loops?



    One primary loop, one secondary loop. Secondary loop is two parallel zones.



    2.) did you install mixing valve for low temp zone?



    No. The boiler can use two reset curves, one for each zone. So the low temperature (slab) zone goes between 75F and 120F. It gets up to 120F only if it gets down to 6F outside, and design temperature around here is 14F. At the other end, it does not start sloping up until it gets down to 50F outside.



    The high temperature (fin-tube baseboard) goes from 110F up to 134F. It starts sloping up when it gets down to 52F outside and hits 134F when it gets down to 6F outside.



    The slab zone has more priority than the baseboard zone. If slab zone calls for heat, it usually gets it. If the baseboard zone calls for heat at the same time, it gets it too, but only following the slab reset curve, so it is some, but not enough heat. If the baseboard only wants heat, it gets it at the temperature it wants. This works because the baseboard zone requires very little heat. No one priority (there is also indirect hot water heater at highest priority) can hog the boiler over 30 minutes. At that point the lower priority zones get a chance for a while.



    3.) there is no reason to derate boiler, as what matters in your case is boiler stability on low load.



    I do not know what you are talking about. This is a mod-con, and it is too big for the load, but was the smallest boiler available in that product line. The contractor even wanted to supply the next larger size "to be safe", but I refused. It is clear I could use one half the size if they made one.
  • Jean-David Beyer
    Jean-David Beyer Member Posts: 2,666
    Did you ever guess right!

    I have an indoor-outdoor thermometer that records the highest and lowest temperatures I got since I last reset the thing. I reset it September 1 each year when I replace the batteries. Design temperature around here is 14F, and in three years I do not remember ever seeing it below 9F, and that was probably for only an hour or so on a cold night. 21.4F is the coldest so far this heating season.
  • Jean-David Beyer
    Jean-David Beyer Member Posts: 2,666
    lowering the max firing rate farther.

    I cannot. The reason for lowering the max firing rate is to get around a slight design error in the control board. It is not exactly an error that the manufacturer needs to fix. It is that the damping ratio is too low for my undersized load. (I used to design electronic feedback control systems, so I know about that stuff.) Any adjusting I can make in the firing rate, the boiler can do automatically and better. I cannot lower it to less than 20%. The minimum is 16K BTU/hr,  and I would like it to go down to perhaps 600 BTU/hr, and it just will not do that.
  • gennady
    gennady Member Posts: 836
    boiler load

    If you do heat load calculation, and sized boiler to the load , then you should not have these conditions. If boiler is too big for the load , then you absolutely need buffer tank to decouple boiler from the system. end then you should separate high and low temperature zones.

    regarding lowering boiler firing rate to 55%, did you also lowered boiler firing rate at low fire, or only cap high fire?

    could you post photo of your hydrolic separator or 2 tee arrangement?

    Also, what pumps is installed on primery loop?

    where point of no pressure change located , on what loop?
  • gennady
    gennady Member Posts: 836
    minimum load

    You are absolutely right. if boiler oversized, it will cycle no matter what.  He need buffer tank in this case. One thing surprise me, is where the hell is installer ? Why he is out of the picture?
  • gennady
    gennady Member Posts: 836
    delta T

    Sure these are right for the job. just when it will go to low RPM, you might have water distribution problem. I prefer keep flow at optimum, (auto adapt)on VFD pump like grundfos alpha, and control water temperature with mixing valve with outdoor reset, like taco mixing valve. http://www.taco-hvac.com/uploads/FileLibrary/100-19.pdf
  • spacoli
    spacoli Member Posts: 61
    Thanks

    Thank you for all your input. It sounds like it's more complicated for a experienced  DIY like my self.



    I installed my system (retrofit to get it up and running) and it's working but I need allot of fine tuning to get the efficiency the boiler can provide.



    Lucky for me I have an engineer friend that works and specializes in large building HVAC   systems. He has helped me so far and when I'm ready, he will do all calculations for me and get this system working right for me.



    One thing I remembered and might have a big affect on the system. The old boiler was centrally located and the main supply and return pipes T off (two directions) around the perimeter of the house. I installed the new boiler at the end of the line and capped off the T. So now I'm thinking all the rads are out of balance and the locksheild valves need adjusted. The rads all heat up and the house temp seems fine. I have been adjusting with the other wheel valve to get the rads working and balanced.



    Just a thought.
  • Jean-David Beyer
    Jean-David Beyer Member Posts: 2,666
    where the hell is installer ?

    Installer is out of the picture because I no longer trust his firm. It used to be a very good firm but is now suffering from success. They grew very much larger too quickly, and seem unable to manage. The techs I got seem to know the heating business of yesteryear, but do not understand this (W-M Ultra 3) boiler as well as I do. And it was their idea to use the Ultra 3. In my view, their techs should have been trained by W-M on how to service it. They should have already known how to do a heat loss calculation. And all I did was read the installation manual cover-to-cover a few times, and John Siegenthalers big book:



    http://www.heatinghelp.com/products/Hot-Water-Heating-Books/26/96/Modern-Hydronic-Heating-Third-Edition-br-by-John-Siegenthaler



    At the time, I read the second edition, but I now have the third. I get the impression that these techs had never read the installation manual. But I have bored the Wall with my complaints about this before and need not do it again.



    But even if he were in the picture, what would you have him do?

    I have not figured out the size of buffer tank I would need to smoothe out the load to the little baseboard zone. It would need to hold about an hour's worth at about 3 gallons per minute (estimated flow rate of circulator). 180 gallons? It would need to be a 4-port tank, I suppose, running as a very large hydraulic separator. And I guess I would need another circulator. I do not have room for a tank that size. 3 gpm is probably a little too fast, but that is what I have in there, and replacing it may not be cost effective.



    By the adjustments I have made, it does not cycle too much when only that zone is running, though the 15F differential up there causes a little more expansion noise than I prefer.  But I imagine if I were turning on and off 180F water would be much worse. When it cycles most now is when it is warmest out, and the water temperature is only 110F. The simplest way to fix this is to open the windows up there. For obvious reasons, that is not acceptable. I think it now works acceptably, but I need to keep the two zones I have, and cannot run the small zone continuously. I do not run the big zone continuously either, but in cold weather it does run 18 hours straight some days. That is about as close as I can get the reset to the actual need. On warm days, like today, it runs much less because I cannot modulate the boiler down far enough. 53F out at the moment and the thermostat has called for heat only 7 hours 25 minutes since midnight (that is more than I expected). It may have gone down to 45F overnight. Sometimes when it is this warm, it does not run at all. Cloudy and almost rainy today.
  • Jean-David Beyer
    Jean-David Beyer Member Posts: 2,666
    edited December 2011
    If you do heat load calculation ...

    I did a room-by-room heat load calculation. The installing contractor paced the length and width of the house and that was it. He thought I needed a 105,000 BTU/hour boiler. I said no, the smallest (80,000 BTU/hour) would be enough.



    "and sized boiler to the load , then you should not have these conditions."

    You cannot get a smaller Weil-McLain Ultra 3 boiler, and the installing contractor handled only W-M, and I wanted a mod-con. I should have gotten a W-M Ultra 3 32,000 BTU/hour model but they do not make one. That would not have solved everything, but would help a lot. This was almost three years ago. There may be smaller mod-cons now. Also, if I knew then what I know now, I would have picked a different contractor.



    "If boiler is too big for the load , then you absolutely need buffer tank

    to decouple boiler from the system. end then you should separate high

    and low temperature zones."



    Well, as far as I can tell, I only need to decouple the little baseboard zone (second floor of Cape Cod type house) as the radiant downstairs zone works satisfactorally; much much better than with the non modulating 60 year old GE oil burner that came with the house. I cannot run it quite low enough until it gets down to about 55F outside, but in winter it is close enough. The high and low temperature zones are separated. They have their own circulators, thermostats, reset curves.



    "regarding lowering boiler firing rate to 55%, did you also lowered boiler firing rate at low fire, or only cap high fire?"



    I lowered the maximum firing rate in the small zone to 55%. I hesitated to lower it below that because the controller, at initial firing starts it out at 50% and I did not want to confuse it by saying the maximum is less than that. I never tried it, it may be ok. But basically, the firing rate is controlled by the modulating function in the controller, not the limits I set at either end. And the installation manual does not allow setting that below 20%. I would love to run it down to 2%.



    "could you post photo of your hydrolic separator or 2 tee arrangement?"





    "Also, what pumps is installed on primery loop?"



    Taco 007 as specified by W-M, and supplied by W-M. It is black instead of Taco green.



    "where point of no pressure change located , on what loop?"



    Point of no pressure change is the expansion tank (diaphragm type). It is connected to the bottom of the Taco 4900 series microbubble resorber that is in the secondary loop just before the boiler supply water temperature sensor. This is exactly where W-M specify it should be located. It is not clear if W-M are right or not. The water temperature up there never exceeds 140F, and normally is much less than that. I thought perhaps it would be better to put it in the primary loop because then hotter water would go through it when the indirect calls for heat. But that is only 20 to 30 minutes per day, so that would not be much use either.



    W-M recommend using at least 1 inch piping in the primary loop. My contractor used 1 1/4 inch because they said it worked better. I think they are right. This way the flow rate (feet per minute, I mean) is less so the microbubble resorber has more time to work.



    Picture on the right is the whole thing (except for the indirect that is way off to the right past the edge of the picture).
  • spacoli
    spacoli Member Posts: 61
    Radiator not getting hot enough

    So I had a cold bedroom with a small rad and could not understand why the largest bedroom had such a small rad. So I had a larger rad left over from the kitchen remodel I wasn't using and decided to install in the bedroom. The rad was almost twice the size as the one it was replacing. After changing it out, I was please with the results.



    Now the rad on the first floor right below the one that was replace was cold. They are T off right next to each other in the basement.  I got it working but it is not heating up as much as it did.



    I'm not getting any air out of the bleeders, so I'm guessing I need to go around and tweak down all the rads before that colder one?



    I noticed a the lock shield valves on every rad are fully open, so I'm guessing it was balanced with the piping layout or never balanced at all. The lock shield valves are only 1/4 turn on/off and from the inside, look like this     (II)     and have a lock nut and flat screw driver blade for adjustment.
  • spacoli
    spacoli Member Posts: 61
    edited December 2011
    Sorry

    Sorry for the duplicate post, I was getting an error when posting.
  • spacoli
    spacoli Member Posts: 61
    edited December 2011
    One radiator not getting hot enough

    I forgot to mention there are two rads after the problem rad that are heating fine. 
  • spacoli
    spacoli Member Posts: 61
    One radiator not getting hot enough

    So I had a cold bedroom with a small rad and could not understand why

    the largest bedroom had such a small rad. So I had a larger rad left

    over from the kitchen remodel I wasn't using and decided to install in

    the bedroom. The rad was almost twice the size as the one it was

    replacing. After changing it out, I was please with the results.







    Now the rad on the first floor right below the one that was replace was

    cold. They are T off right next to each other in the basement.  I got it

    working but it is not heating up as much as it did.







    I'm not getting any air out of the bleeders, so I'm guessing I need to go around and tweak down all the rads before that colder one?







    I noticed a the lock shield valves on every rad are fully open, so I'm

    guessing it was balanced with the piping layout or never balanced at

    all. The lock shield valves are only 1/4 turn on/off and from the

    inside, look like this     (II)     and have a lock nut and flat screw driver blade for adjustment.
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