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Thread: Too much cycling

  1. #16
    In the trades Dana's Avatar
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    It's definitely boiler input temp that determines efficiency, but if the delta-T on the radiation is too small you can't make it any lower by adjusting only the boiler flow. If the radiation is already returning 125F water with 150F output you can leave the radiation loop flows alone and concentrate on what it takes to optimize it on the boiler loop.

    (This is the problem of design-by-hackery rather than doing all of the math up front, eh? :-) )

  2. #17
    Retired Defense Industry Engineer jadnashua's Avatar
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    Most economy IR thermometers cannot be adjusted to account for the IR emissivity of various materials. Because of that, you won't get accurate readings when comparing different surfaces, even if they are the same temperature. Black, hockey tape provides a better surface to monitor (and would be consistent across most materials) than metal that may have various levels of paint, corrosion, etc. on it which can affect IR emissivity. FWIW, the relative readings from the thing would be pretty reliable, but if you want it closer to reality, you want to account for the emissivity, either by adjusting the tool, or normalizing the reading surface material's properties. This might shed some light on the subject: http://www.eutechinst.com/techtips/tech-tips34.htm
    Jim DeBruycker
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  3. #18
    DIY Member Handymaner's Avatar
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    Yeah, I've been trying to get some consistent readings, but they are all over the map. I tried on the copper piping near the boiler, and on the baseboard itself. I need to pick up some hockey tape, I guess. I'm not familiar with it, is a sporting goods store the place to find it (I'm assuming it actually has something to do with hockey)? Black electrical tape wouldn't work as well? Thanks.

  4. #19
    DIY Member Handymaner's Avatar
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    Quote Originally Posted by Dana View Post
    (This is the problem of design-by-hackery rather than doing all of the math up front, eh? :-) )
    I'm not sure what would have been designed? The house is 35 years old and all the radiation loops were already in place and it's not in the cards to change that now. I dream of warm board or something similar on the upper floor (1000 sq ft), but I think that stuff must be quite expensive, as they don't seem to list any prices. At that time some engineering could be done, but I'm pretty much stuck with what radiation I have for now. I did re-use the old system pump, perhaps that's what you are referring to?

  5. #20
    In the trades Dana's Avatar
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    I don't expect homeowners to instantly become hydronic designers given that half the folks in the heating & plumbing biz don't have a clue! All retrofits involve some amount of re-design and reconfiguration, and some of the architectural & pumping issues might have been forseeable by a competent pro (emphasis on "competent".) Blame the original installer/designer if you like- it's would probably well deserved, but there doesn't appear to be any un-resolvable issues here.

  6. #21
    DIY Member Handymaner's Avatar
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    Default Tweaking Delta T's

    OK, I’m back. Work has been crazy; I’ve been forced to be away from home literally since the end of December. The boiler has been working GREAT, the reset curve seems to be really close as it just barely keeps up-which is the goal I guess? The usage has continued to be around 50-70% of last year, so I’m really happy with that.

    The only trouble I’ve had is one of the baseboard radiators started leaking. I came home from work at about 2AM. I’ve been very in tune with what the boiler is doing since the install and after parking in the garage I instantly realized something was up, as the boiler sounded like it was at 100%-which it never is except for DHW and a 2AM that seemed odd. I went over and looked at the screen, and sure enough it was at 100%, the set point was calling for 130*, but the system temp was only at 80* and I realized I could hear make up water flowing! In the hazed thinking of panic (worried about a flood in the house) I noticed that only the upstairs loop was on. You can imagine the sleeping wife’s surprise as I ran the perimeter of the house turning on all the lights checking the baseboards looking for the flowing water! The upstairs was dry-so to the basement I went, thinking it may be from a portion of piping within the walls. No sign of leakage there either. Only then did it hit me that all the loops are pressurized through the return even if the zone valve is closed. So my dash continued through the sunroom and finally I found the leak in a semi-heated storage area off the sunroom. Thankfully I had the foresight to plumb in ball valves on both the return and supply side of the loops, so I could isolate the loop easily (without completely shutting down the boiler) for later repair. My wife said that she had heard water running prior to going to bed, so I know it had been leaking for 2 or 3 hours. I was later able to just bypass the bad baseboard.

    I still need to tweak the delta t. I discovered that squeezing down the radiation loops actually lowered the delta t spread as read on the diagnostic screen. I guess that the pump on the primary loop must be recirculating more heated fluid when the radiation loops are slowed. I did squeeze down the valve in the primary loop as per Dana’s suggestion, and that method is able to raise the delta t considerably. With me being away I did not want to risk it being unmonitored, so I opened it back up.

    Now that I will be home for a time I want to start tweaking again. I did have a chance to do some experiments but I haven’t found a reliable way to measure the temp of the pipes to find the delta t’s of my radiation loops. My IR gun is all over the map. I tried the tape suggestion, but it didn’t seem to help. I then grabbed my little desktop digital thermometer, the kind with the 5’wire with a probe on the end that you stick out the window to get indoor/outdoor temps. I tried to place the probe inside the pipe insulation but still can’t seem to get consistent results. My next attempt will be with the wife’s candy thermometer stuck inside the foam insulation. Any suggestions for an easy reliable way to measure the pipe temps?

  7. #22
    Retired Defense Industry Engineer jadnashua's Avatar
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    A curved surface is tuff to get a consistent reading of, especially if it doesn't have an accurately aligned laser pointer.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  8. #23
    Master Hot Water Mpls,MN BadgerBoilerMN's Avatar
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    Hold on. I can't watch anymore.

    First, the Alpine boiler will suffer a 40 delta T (not for beginners) so slow the pump down as Dana suggests.
    Second, by limiting the max operating temperature you are also limiting the potential output of the boiler and the radiation connected thereto. Raise it to 180F.
    Finally, setback thermostats are all the rage and perfectly acceptable for forced-air furnaces and the people who own them, as they don't know real comfort anyway. As Dana suggests, a ModCon boiler such as the Alpine will modulate supply water temperature based on a properly programmed--built-in--outdoor reset. No special radiant thermostat needed. Many of our retrofit condensing boilers are still "controlled" by a Honeywell mercury switch (I know, I am going to burn) providing perfect comfort while regularly cutting fuel bill in half.

    The Alpine, and many other ModCons, may also let you set back the design water temperature while asleep or away. This will save fuel without sacrificing comfort.

  9. #24
    In the trades Dana's Avatar
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    Thank you Morgan!

    BTW: One mercury-loaded Honeywell contains as much mercury as 1000 compact fluorescent light bulbs that some folks get all tweaked about- maybe you really WILL burn for leaving any of those in place! :-)

  10. #25
    Retired Defense Industry Engineer jadnashua's Avatar
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    Quote Originally Posted by Dana View Post
    BTW: One mercury-loaded Honeywell contains as much mercury as 1000 compact fluorescent light bulbs that some folks get all tweaked about- maybe you really WILL burn for leaving any of those in place! :-)
    Much better than throwing it in the trash (which is illegal!).
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  11. #26
    DIY Member Handymaner's Avatar
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    Quote Originally Posted by BadgerBoilerMN View Post
    Hold on. I can't watch anymore.

    First, the Alpine boiler will suffer a 40 delta T (not for beginners) so slow the pump down as Dana suggests.
    Second, by limiting the max operating temperature you are also limiting the potential output of the boiler and the radiation connected thereto. Raise it to 180F.
    Finally, setback thermostats are all the rage and perfectly acceptable for forced-air furnaces and the people who own them, as they don't know real comfort anyway. As Dana suggests, a ModCon boiler such as the Alpine will modulate supply water temperature based on a properly programmed--built-in--outdoor reset. No special radiant thermostat needed. Many of our retrofit condensing boilers are still "controlled" by a Honeywell mercury switch (I know, I am going to burn) providing perfect comfort while regularly cutting fuel bill in half.

    The Alpine, and many other ModCons, may also let you set back the design water temperature while asleep or away. This will save fuel without sacrificing comfort.
    OK Badger....evidently I'm not making myself clear enough. I'm not using any set back on the thermostat. My issue with the thermostat was that it was only calling for heat for a couple of minutes and then off. I found no way to adjust the hysteresis (even calling Honeywell tech), it must only allow a half a degree or some very small amount. I would rather it had a larger spread (maybe 1.75 deg) to promote longer cycles. Does anyone know of an electronic thermostat that allows this adjustment, or is that relegated to the older dial type units?

    I've got the design temp (-6 deg) system temp on the outdoor reset curve at 160, but that doesn't limit the max operating temp if it gets colder.

    My problem with the delta t is that I need a consistent way to measure the individual radiation loops. I discovered that the readout on the (Lochinvar Knight) screen gives you the delta t between the system temp and the return water. The trouble is that the return water has (potentially) already been mixed with the heated supply water via the primary boiler loop. I think this is what is limiting my delta t now, as when I slow the flow in the radiation loops, the delta t on the display screen is reduced NOT increased. My theory is that there is not enough return water flow causing the primary loop to make up the difference by drawing hot water from the supply along with the return water coming from the radiation loops, thereby preheating the return water. Obviously if the goal is lower return water temp to increase condensing efficiency of the boiler, this is to be avoided. But to confirm this I need a way to measure the return water via the copper pipe. The pump on the primary loop came with the boiler with instructions to run it on medium-I've already got it set on low. Before I start further restricting it with a ball valve, I want to get reliable measurements of the delta t from the radiation loops. Perhaps I even need a larger pump for the loops, anything is possible but I won't know until I find a consistent way to measure the temp of the copper tube on the supply and return ends of the radiation loops. Any suggestions for that?

    With my (Quite possibly inaccurate) understanding of the outdoor reset you want the system temp as low as possible while still keeping up with the heat load. If it is set like that then you could not set back the design water temp while asleep or away or it wouldn't keep up and the house would get cold, right?

    Thanks for your insight.

  12. #27
    Master Hot Water Mpls,MN BadgerBoilerMN's Avatar
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    Stretching the differential (Dana likes 'hysteresis') will effect comfort more than system efficiency. We don't do it. Many of the ModCon boiler manufacturers, in their mania to sell boilers to anyone, anywhere, have not only encouraged, but often mandated the seldom needed and always costly P/S pumping system. It took me a year to get rid of the UP2699s that Lochinvar was sending with a 3gpm 50mBtuh boilers--most went to snow/ice melting duty. We don't use P/S unless it makes sense and yours is a prime example of our argument against the practice. If you can't widen the delta T at the boiler, your secondary pump is too big. If you had one pump, and it wasn't over-sized, it would be a simple matter of slowing it down--choking ball valves is not recommended.

    By the way, the nice folks at Burnham will let a professional use one pump if he can do the math. I appreciate that and don't ever have to disqualify them for some of our simple, one-zone gravity conversions.

    It is a complicated matter and best done on paper, leaving field adjustments to the installer.

    When does fishing start?
    Last edited by BadgerBoilerMN; 03-14-2013 at 03:03 PM.

  13. #28
    DIY Member Handymaner's Avatar
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    It's still pretty frozen over. Just went through a 2 day blizzard last week. But since we've sprung forward it's not dark until 9PM!

    Maybe in this case it's not optimum to follow manufacturer's instructions and dealer's guidance regarding P/S-but that's all I had to go with. I'd sure like to optimize what I got. Slowing the secondary loop reduces delta t at the boiler so a smaller pump won't help in this case unless something is changed in the primary loop. Secondary pump is a Grundfos UPS 15-42 F. It's flowing through two 75' main loops of baseboard and a third of about 50', with I'm sure many elbows in each. My dealer thought it was too small for my system, but it's what was there so I thought I'd try it. Is it lower flow than the primary pump that Lochinvar sends out? If so could that mismatch be contributing to my issue? Because it seems to me the primary pump is flowing more than the secondary causing recirculation, although I'm far from a hydronics expert. If that does turn out to be the case then that's probably why the manufacturer wants P/S. There must be a Grundfos flow chart I can find somewhere.

    I still need a reliable way to measure pipe temps so I know what the delta t of the radiation loops are and go from there.
    Last edited by Handymaner; 03-14-2013 at 11:42 PM.

  14. #29
    Master Hot Water Mpls,MN BadgerBoilerMN's Avatar
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    In a residential, single boiler hydronic heating system, the circulator serving the boiler is consider "primary" and the circulator or circulators serving the distribution system "terminals" are considered "secondary" or tertiary.

    Yet another reason to hire a professional designer before you start. But hey, keep plugging away.

  15. #30
    DIY Member Handymaner's Avatar
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    Quote Originally Posted by BadgerBoilerMN View Post
    In a residential, single boiler hydronic heating system, the circulator serving the boiler is consider "primary" and the circulator or circulators serving the distribution system "terminals" are considered "secondary" or tertiary.

    Yet another reason to hire a professional designer before you start. But hey, keep plugging away.
    Yes I am totally aware of that. Absolutely no confusion there on my part. I'm calling the primary pump the one that came with the boiler that's in the primary loop. The secondary pump listed above (Grundfos UPS 15-42 F) is the one that's always been serving the baseboard loops, and if I SLOW that one my delta t as read on the boiler screen DECREASES. That's how I came to my hypotheses that the secondary pump flows too little causing the primary loop to back feed a portion of the heated water coming from the boiler directly back into the boiler without going through the radiation loops, thus lowering delta t.

    To avoid this happening, the secondary (radiation) loops would have to flow at least as much as the primary loop, correct??
    Last edited by Handymaner; 03-14-2013 at 04:37 PM.

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