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Moving from series loop finned baseboard to parallel cast iron - how to pipe?

124

Comments

  • weekendguy
    weekendguy Member Posts: 181
    @NY_Rob Thanks for your comment. I had not thought of that possible issue. This clearly needs some more research on my part.
  • Brewbeer
    Brewbeer Member Posts: 616
    edited December 2016

    @brewbeer We sure can spend alot of time thinking about our heat, huh? :) The guy yesterday asked me why I built a controller and why I log several points of data to the cloud every minute. I really didn't have a rational answer (if you have to ask...). Data junkie pretty well captures it. I guess you just have to be slightly obsessed with your boiler. :/

    I've spent many early weekend mornings in front of the boiler display with a cup of coffee before the rest of the family gets out of bed. Automatically uploading data to the cloud seems like a great idea.

    I started this thread thinking about possibly changing out the finned tubing for cast iron but the cost is just a non-starter. Hatterasguy has been helping me analyze this data to try to make the best of the situation. As you probably noted, we now can see the impact of reducing the input from about 200K to about 150K. The cycles seem much better and FINALLY I am seeing a respectable DeltaT when several zones are calling. It's only been a day but It seems like a good move. The boiler was built to be 245K and is now running at 150K. Yes, this was oversized...

    I tend to think delta T is too overemphasized, especially if you don't need a large delta to get a boiler into the condensing range. If the emitters can put out as many BTUs as are needed and you don't need to condense, does it really matter if your delta T is 5 degrees of 15 degrees? My boiler runs on a delta T of about 4 degrees 80+% of the time.

    The way we use the house (our 4 kids are gone mostly) is that we heat the first floor primarily - that's the one long zone that tries to put out 65mbh if the flow will enable it. Clearly the length of the zone and the amount of baseboard has been an issue over the years. The main problem now is that when this zone is calling alone, which is probably 80% of the time, the boiler wants to make way more btus than the zone can emit. This makes for serious short cycling. The bigger circ definitely helped but not enough. I'm thinking of adding 20% more BB and splitting the zone to help with this issue - looking for opinions on that.

    More baseboard is always better, but be aware of disproportionately putting BTUs into the various spaces in your home. Probably not a problem if your house is a completely open concept, but could be an issue if not. Again, the accurate room-by-room heatloss and emitter survey will tell you what you need to know about adding baseboard. Take a look at the heat loss analysis I did in the thread about my system. If you are game for taking on that kind of analysis, I'm happy to send you the spreadsheet I used to perform it.

    I was actually thinking of adding a storage tank to store heating zone water - this would act as a buffer and allow the zones to draw what they need and also provide the boiler a place to put a bunch of btus on a 15 min running cycle. There may be dozens of reasons why this won't help but I haven't completely ruled it out. I don't think the tank would need a heat exchanger -it could just be in/out storage. I'm curious what @Hatterasguy thinks since he seems to have a direct line to the Roman God of Boilers (is that Lochinvarius?, Buderius?). :wink: No, wait - it's Uticas!

    Adding a buffer tank would definitely help. There is a buffer on my system (BoilerBuddy 30) because anytime it's above ~40F outside, or if only one zone is calling, the boiler puts out more heat than the emitters can shed. Given how oversized your boiler appears to be, for my money I'd first look at a seriously smaller boiler. It wouldn't surprise me at all if your boiler is 2x larger than you need on the coldest day of the year, even after you've downfired it to 150. Again, a room-by-room heatloss analysis and emitter survey performed really carefully, will answer this question for you.

    Do the analysis and survey and post the results here, that will help us figure out how much (if any) a mod-con would condense in your application.

    And clean the dust and dirt out of all your fin tube. I bet that makes a difference that will show up in your data. Hmmm, sounds like a weekend project! :D
    Hydronics inspired homeowner with self-designed high efficiency low temperature baseboard system and professionally installed mod-con boiler with indirect DHW. My system design thread: http://forum.heatinghelp.com/discussion/154385
    System Photo: https://us.v-cdn.net/5021738/uploads/FileUpload/79/451e1f19a1e5b345e0951fbe1ff6ca.jpg
    hot_rod
  • hot_rod
    hot_rod Member Posts: 14,784
    I tend to think delta T is too overemphasized, especially if you don't need a large delta to get a boiler into the condensing range. If the emitters can put out as many BTUs as are needed and you don't need to condense, does it really matter if your delta T is 5 degrees of 15 degrees? My boiler runs on a delta T of about 4 degrees 80+% of the time.

    Hear, here :)
    Heating loads are dynamic, always moving. allowing boiler input to modulate around thermal equilibrium, within reasonable ∆°Ts is not a problem, nor is it necessarily less efficient then forced ∆ operation
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • weekendguy
    weekendguy Member Posts: 181
    @Brewbeer @hot rod Thank you both.
    Brewbeer said:

    I've spent many early weekend mornings in front of the boiler display with a cup of coffee before the rest of the family gets out of bed. Automatically uploading data to the cloud seems like a great idea.

    I know exactly how this goes, this morning was no exception.
    Brewbeer said:

    I'm happy to send you the spreadsheet I used to perform it.

    Would love to see the spreadsheet. On the flip side, if you want to send data to the cloud I can advise...
    Brewbeer said:

    It wouldn't surprise me at all if your boiler is 2x larger than you need on the coldest day of the year, even after you've downfired it to 150.

    Maybe, but it ran a solid 65 minutes this morning to recover the whole house (graphs a few posts back) and only took one 4 minute break (only reached HL once). It's hard to imagine a much smaller unit handling that. House is 7400 sq ft (very open concept on 3 of the 4 floors).

    I have been hearing about this study and could not find it last time I looked - I am really game to understand the findings regarding finned low temp baseboard - some reading tonight...

    https://www.bnl.gov/isd/documents/28709.pdf

    Thanks again.
  • weekendguy
    weekendguy Member Posts: 181

    What is interesting about this result is the dramatic change in duty cycle. The boiler changed from 50% to over 90% on this test. The question begs as to why? The 30F ambient is not a factor. The radiation does not know the outdoor temperature.

    Yes, it's clear to me that the ODT is not a factor. Since I had a bad zone valve which was not opening (it literally went up in smoke tonight - very exciting), it's possible that the longish 2nd floor zone was never involved in the prior recovery. I'm also not sure of the SWT setting before - so bad scientist here. And - this morning there were three zones that started out very cold so the RWT impact was profound. Also, it's possible that the prior recovery test had one zone satisfy before the test finished (I had not yet balanced the zones). Also, because of the lack of balancing I was probably not getting full flow in the long zone(s) where most of the radiation is. And finally, the last test was with the 0011 circ I think - the 0013 only went in last Saturday.

    So not a very good set of control variables for the boiler science I admit. But in any case, I will set all the zones to a 4 degree setback and then retry the recovery on Saturday with all zones open the full time. There may not be a valid comparison available with before the downfiring, but I hope I can get some help assessing the current boiler as it is now. I genuinely feel that thanks to Hatterasguy and others, it's overall a better system today than a few weeks ago, and not done yet.

    I'm planning to take the @Brewbeer spreadsheet midterm exam so perhaps some true loss numbers will emerge (if I pass).

    Hoping for a design day soon! But not until the backordered globe valves get here...

    Many thanks, all. WEG



  • weekendguy
    weekendguy Member Posts: 181
    edited December 2016
    @Hatterasguy -

    Sat AM will run 6 zone recovery again. You mentioned a possible wider diff - I had it at 185/165 (20) for the last run. What would you suggest?

    Next week will do a "typical" 2-zone recovery as a reference point as well.

    I will absolutely monitor boiler on/off during a 12 hour period. I can maybe add that to my current cloud controller (tight on space in that box) but can also do it with a laptop and a few cables pretty easily. Will have that working tomorrow.

    I see that Lochinvar makes a 2-level firing gas boiler - any reason to consider that to help mitigate the over supply of btus?
  • weekendguy
    weekendguy Member Posts: 181
    @Hatterasguy I do not need to heat all zones. Let's see how the 6 zone recovery does and then I will do the 2-zone recovery (however irrelevant) :) because they together provide the "bookends" for the ultimate size decision. I'll post graphs in the morning (and I'll start working on adapting Brewbeer's spreadsheet for loss analysis).
  • weekendguy
    weekendguy Member Posts: 181
    @Hatterasguy

    Hi-

    Here is some new data. All zones were set to 64F overnight and then pushed up to 72 at 6:15 this morning. The boiler ran 100% with minimal temp diff for 1:15. Average SWT was about 170F.

    Based on the BB this is theoretically 175K heating demand and the boiler is putting out 130K. I then selected only the 3 primary zones (typical use) which should total 115K. The boiler went to a 65% duty cycle. 65% of 130K is 85K so BB can only accept 25% fewer btus than the zones are spec'ed for. What does this say? Not getting 500 btuh/ft from the baseboard @ 170F?

    Assuming the 130K is correct, the ES25 that provides 115K should shift from 65% to about 72% duty cycle on the 3 primary zones. I'm thinking this is a good size with the big remaining issue being the single zone short cycling problem.

    I'm not sure where to start with considering a mod/con or the Lochinvar Solution. I'm concerned about durability of the Lochinvar based on comments. But I'm skeptical that a mod/con can work properly above 130F and doubtful that my current amount of BB will work effectively below 150F.

    Regardless of choice, is there an argument for having a separate HWH? The boiler runs all summer to make DHW although it is cold start and typically runs > 10 min on a cycle. I'm feel the standby loss just standing near it. Although I suspect that the Weil has more SBL than a newer Burhnam.

    I attached the graphs. I went to 3 zones about 7:30. The supply temp is interesting - it was set at 185F HL. I watched it climb to 184F and then the DT caused the VDT to speed up and it dropped back down. So the VDT really does work in a system running with a supply/demand balance. But thinking that it solves the problem of a single zone is wrong. And, I should add that Taco sold me on it for that very reason and then underspec'ed the pump size. I'm generally a Taco fan but the data speaks for itself. Expensive lesson.




  • weekendguy
    weekendguy Member Posts: 181
    @Hatterasguy thanks again. Considering that the 3 typical zones ran 8min on 4min off giving the 65% duty cycle, I would guess the large zone would probably hit HL in 4 min or less.

    I thought about combining the two large zones but their use is different. It would result in more unneeded heated areas and I would guess that would not be worth the efficiency improvement.

    We're going to be darn close to design temp in a few days. I'll try the 160F AVG SWT and see if we hold temp. Then we can pick up the mod con discussion.

    Thanks.
  • weekendguy
    weekendguy Member Posts: 181
    I have no place to bring a vent pipe outside near the boiler which is one reason I was thinking atmospheric boiler. Can the modcon use a 45 ft chimney flue? I already have an outside air kit for intake.
  • weekendguy
    weekendguy Member Posts: 181
    Can that be flexible to get past the fireplace?
  • weekendguy
    weekendguy Member Posts: 181
    So in that case the SS tube would be in place of the full chimney liner? Would the chimney guy install the SS tubing?
  • weekendguy
    weekendguy Member Posts: 181
    Ok thanks. That leaves the modcon an option for now. I was planning to calculate the heat loss but I think once we determine how low the SWT can be on a design day we already have the answer we need. You may like this - it shows the boiler run state and also shows the duty cycle over 24 hours. Left is off time, right is on time.

    Boiler Run State
  • weekendguy
    weekendguy Member Posts: 181
    I'm at work so can't be sure of zones but I suspect this may be 1-3 zones reflected in the graph changing from time to time.

    Ignore any single "1 minute" state changes (like at 8:30) - that's a data error in my logger which I need to correct. It sometimes reads the state wrong. So there's one good 10 minute run there.

    The left side of the duty cycle shows the minutes "OFF", the right side is "ON". So right now it's like 720 off, 320 on. So "on" times are 320 out of 1040 (total) or about 30%.

    This is not quite 24 hours of data yet.

    I'm glad you suggested logging this state data. It provides some good info.
  • weekendguy
    weekendguy Member Posts: 181
    I'm not opposed to a buffer tank. There are so many reports of problems with electronics in the modcons due to their complexity. I'd rather keep it simple if it can be doable. But I'm open for now...

    On the duty cycle page, left side it shows number of entries under "Channel Stats". Once it gets up to 1440 (24 hrs) it will always be 1440.
  • weekendguy
    weekendguy Member Posts: 181
    I found some threads about the Lochinvar Solution. I think I'll read up on them to see what I can learn as a possible half way point between the straight CI and the modcon.
  • weekendguy
    weekendguy Member Posts: 181
    I suppose I could install 2 small boilers and make my own two stage system....
  • weekendguy
    weekendguy Member Posts: 181
    If the duty cycle is 30%, does that mean the house only needs 30% of 130K (running all the time) to heat the house at 30F ambient? Maybe two 50K CI boilers is not such a bad idea. Can they share a flue?
  • weekendguy
    weekendguy Member Posts: 181
    Is it popular enough that it is well understood for installation and service? What criteria does it use to engage "high speed"?
  • weekendguy
    weekendguy Member Posts: 181
    Sounds like with my super variable DT due to long zones it would be switching back and forth every few minutes. I'd rather have a control that knows which zones are calling and use that criteria to control low/high.

    I'm still intrigued with two boilers. One could just be cold unless the demand required it. I'm sure there are controls out there to decide if and when to fire the 2nd boiler. Do you size these 60/40?

    Although they would have to share a chimney (if that's possible)
  • weekendguy
    weekendguy Member Posts: 181
    edited December 2016
    Can they share a stack? And are the plumbed P/S?
  • weekendguy
    weekendguy Member Posts: 181

    You'd need to design your own control to operate it depending on which zones call.

    Challenge accepted... :-)
  • weekendguy
    weekendguy Member Posts: 181
    I agree the algorithm would need to push the total zone demand through the reset curve to determine one or two boilers. I think I'll investigate the commercial dual boiler controls and see what I can learn.

    Would you use 2 equal size units or split them 70/30 or 60/40?

    Thank you for the help.
  • weekendguy
    weekendguy Member Posts: 181
    edited December 2016
    @Hatterasguy

    I looked at one control (I think it was tekmar) that evens out their use over time. Very cool. But now I realized that I don't think I can fit 2 of these in the space I have (once you add all the piping)

    I'm going to call Lochinvar tomorrow and ask some questions about the Solution. Evidently their builtin bypass does not work based on some postings I read on this site.

    Also I need to understand if their hi/low/hi will work correctly with my long zones.

    The CBN135 is input 135K which is just a hair smaller than the downfire I am running (150K). On low it will put out about 48K net which will suffice for much of my single zone needs.

    I'm just nervous about it being so complicated - some real horror stories out there. I'd have to find someone very experienced in the area I think.

    And it will work with CPVC (3") which will allow me to avoid $2,500 to line my 50 ft chimney. That's like a free boiler...

    Do all these low mass units need yearly maintenance and clean-out, etc.? That's a cost to consider if so.
  • weekendguy
    weekendguy Member Posts: 181
    @Hatterasguy I'm still waiting for globe valves to ship out. A friend was trying to understand why I needed them and he claims the differential bypass on his boiler evens out the pressure/flow by bypassing back to the return. Is he confusing head loss with flow rate? In any case would a DPV be a good thing to have?
  • weekendguy
    weekendguy Member Posts: 181
    @Hatterasguy That's what I suspected. So given that I am stuck with my piping/pumping environment, and non-linear DT, I assume that having the DT higher rather than lower is a good thing because it gets more BTUs out there, but a bad thing because it contributes to short cycling (is that right?). So it seems like a 2-stage boiler like the Solution is a decent way to split the difference. Any other ones out there in CI that have two firing levels? These low mass things make me nervous but I suppose I could get over that.

  • weekendguy
    weekendguy Member Posts: 181
    edited December 2016
    @Hatterasguy By "low mass" I mean the Solution. Is that not a low mass unit? It's actually pretty reasonable in price -- less expensive than the ES25. Also if I can use the CPVC vent I can save a bundle on the liner. So I think cost to own should be ok unless I am missing some expense.

    https://forum.heatinghelp.com/discussion/160251/space-required-for-side-wall-venting-picture/p1?new=1

    Also, I spoke to Lochinvar about how the 2 stage firing worked. It was not a clear answer. You seemed to understand it. Basically I just want to know if the way it decides to be on low will help my oversized boiler problem on 1 or 2 zones. I don't get the up and down part. Thank you.

    Gonna be cold up there tomorrow and Thursday? --WEG
  • weekendguy
    weekendguy Member Posts: 181
    @Hatterasguy Well here we go. I called contractors today (recommended by the Lochinvar distributors) and none of them were excited about the Solution. The most knowledgable guy (who was rude) actually suggested the ES2 (!). Evidently the Sol is a finnicky unit and hard to get set up right with a bypass, etc. Especially with the big circ and the odd sized zones. He actually suggested going down ANOTHER size to an ES24 and just deal with the few days a year that are below design.

    So confused again. :# I talk to another chimney guy later this week. We'll see what he says. I'm shooting for the 5.5" liner.

    I'd like to be the engineer on the project but there seems to be some defensiveness when I tell them what I have done to research this and how I want to approach it.

    Many thanks. Would you like a job for a nice family in PA? :smile:
  • weekendguy
    weekendguy Member Posts: 181
    @Hatterasguy Thank you. I solved the circuit problem (I think) so I will get to work on the new VDT algorithm sometime soon. I bought enough parts to send you one assuming it does the job satisfactorily. Thank you for your continued help! Much appreciated.
  • weekendguy
    weekendguy Member Posts: 181
    @hatterasguy I had a thought about going down to an ES2-4. For $200 I can add an electric heat unit in the A/C air handler. This would give a backup 30K btuh in the rare case that we'd have a week of design temps. I already have a 60 watt subpanel in my shop which sits about 10 feet from the air handler. Fairly trivial electrical work. I could control the e-heat from the same thermostat using 2nd stage logic so it would come on with the boiler only if the 'stat sees the demand > 3F from the setpoint. Pretty simple. That gives me some confidence to "go low". What do you think?
  • weekendguy
    weekendguy Member Posts: 181

    I like it.
    The only time you'll need it is when the temp drops near design and you desire to maintain on all six zones. By your own admission, two of those zones are rarely heated so you may be in a situation where the auxiliary heat is never required.

    @hatterasguy
    I agree - I probably will scope out the elec heat but not get into it right away - I'll see how next winter goes with the ES2-4 (assuming).

    The cold night is tonight. They were forecasting 14F but now saying 18F. I have all 6 zones on now and will leave things alone until tomorrow mid-day since the coldest time is in the morning.

    I have been logging duty cycle at various temperatures so I can plot a curve - that should help extrapolate the sub-design days. Latest reading was 73% DC at 25F. So that means needing (130K * 73%) = 95K to sustain at 158F SWT. We'll see how that changes tomorrow morning.

    Thank you.
  • Paul48
    Paul48 Member Posts: 4,470
    The burning question........Will it make it to Mars and back? :wink:
  • weekendguy
    weekendguy Member Posts: 181
    @hatterasguy Actually I just did DC for 21F and got 57% which makes more sense. Possible DHW use earlier or it was still getting the frequently colder spaces up to temp. So using 74K now at 21F. Quite windy so that should increase ACH which will further stress the system tonight.
  • weekendguy
    weekendguy Member Posts: 181
    @Paul48 Of course - we're going to "science the sh*t out of it" as Matt Damon famously said...
  • weekendguy
    weekendguy Member Posts: 181
    @Hatterasguy While I'm all about metrics here, the DT over the last 100 samples is 16, but the standard deviation is 11, so it's all over the place. To be expected I think. The Honeywell control is supposed to do zone coordination and keep multiple zones on at once but I don't see that happening. My next sampling project will be to log all 6 zone open times each minute. I can add that to the device that logs boiler run time. That will be interesting...
  • weekendguy
    weekendguy Member Posts: 181
    @Hatterasguy Great comment. My honeywell control counts run hours. I'll check the count at 10pm tonight and check it at 6am. It will report boiler and primary circulator usage separately. This will confirm boiler DC as well as circulator DC over 8 hours.
  • weekendguy
    weekendguy Member Posts: 181
    @Hatterasguy It's 18F now. The boiler is at 65% DC. I finally took over the speed control of the VDT pump. You can see where I changed it and how much better the DT is... I think the circ has been running 100% simply because with 6 zones the odds of at least 1 calling is pretty high.

    I also realized that the H'well records hours for each zone calling. I recorded the numbers and I can compare them in the morning. Possibly adding some BB will help level that out.

    Full report in the morning. Should get down another 4 degrees or so (that's design temp).

  • weekendguy
    weekendguy Member Posts: 181
    edited December 2016
    @Hatterasguy This is not a control system - I just fudged the inputs so it stays at a steady speed slightly below full speed. I'm still waiting for the parts for the actual DT controller. I agree we're not going to see much higher DC. I also think the zones will all hold temp.

    The only somewhat cold area is in the long zone - a place where there is lots of glass, 14 ft ceilings and also kitchen counters so higher loss and less linear ft for BB. I was doing some math and if I replaced just this 40 ft of BB with Runtal the btu output at 180F goes up from 580/ft to 770/ft. That would dump an additional 5000btuh (at a lower reasonable temp) into that area which would be about the equivalent of a 1500w space heater.

    I think that would be a welcome improvement. Something to consider as I'm replacing the boiler. I have not yet thought through the limitations of the zone's delivery of btus - maybe that will impact my logic. Also, the Runtal would be in the middle of the zone and it may suck the heat out of the delivery and not pass enough to the 2nd half of the zone. I might end up splitting the zone to address this. Comments welcome.

    Also - check out the run state page. I added some other DC periods to see shorter term impact.
  • weekendguy
    weekendguy Member Posts: 181
    @Hatterasguy

    Drum roll....

    Results of last night's stress test:
    All zones held temperature down to 15F ODT
    Average SWT: 157F

    Boiler DC last 8 hours: 62%
    Worst case boiler DC (1 hr): 70%
    Circulator DC: 100%


    Zone run times last 8 hours:
    1st floor 69mbh: 7.5 hrs
    2nd MBR 29mbh: 1 hr
    primary 2nd 32 mbh: 7hrs
    3rd floor 15mbh: 3 hrs
    office 15mbh: 8 hrs (don't get this - possible error)
    Rec room 15mbh: 1 hr

    Worst case building load (current unit 150/130/110)
    110 * 70% = 77mbh

    ES2-4 is validated with net AHRI rating = 77mbh

    Absolute DESIGN case with all zones heated to comfort level would require near 100% of ES2-4 possibly 3-5 days/year.

    Typical DESIGN case (not all zones) at current size: 60% of 110 = 66

    66 mbh with ES24 is a DC of 85%

    Get me my checkbook.... I want to buy a Burnham... B)

    Comments?
  • weekendguy
    weekendguy Member Posts: 181
    @Hatterasguy Thank you. Something is odd about the office. It held temp fine - it's also very small (15mbh) and right next to the boiler - and below grade on 2 sides. I have the ball valve down to almost nothing to get the DT to match - it's possible I'm choking it too much. On that note, the globe valves arrived - I will start putting them in.

    The 1st floor zone has an area (see my post back a few) that drops 3-4 degrees from the 'stat. High ceilings, much glass, not enough radiation. I'm interested in your thoughts on that post about changing the radiators.

    Also, what about splitting off the long zones and having the 0013 handle those and use a smaller circ for the smaller, less used zones?

    Sorry about all the questions - now that I'm circling the runway I'm trying to get everything lined up.

    Thanks!
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