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KHN startup first report.

keyote
keyote Member Posts: 659
edited October 2016 in Radiant Heating
flipped on power thinking it would wait for some setup manual said i was to use a paperclip to get it into service mode, but instead it just seemed to do its thing i decided to let it have its head although I was not really prepared.Anyway it took it time and hummed into dhw heating, noticed the 3 speed wilo was on lowest setting so i played with that a bit and it would widen and narrow the delta t. fumbled around and found the setpoint which only seemed to be able to go to 140, assumed i needed to know a trick to exceed that so settled for 140. next i noticed the system pressure on the caleffi makeup/checkvalve/ gauge was up to 29 psi from the cold setting of 19 psi, tried adjustuing pump speed again to see if it would bring it down didnt help only temp disruption, pressure eventually climbed to 131 as boiler supply got to 180, blow off didnt open though maybe i heard it squeak a sec. tank got to 132 by the time system supply got to 180, delta t varied between 20 and 9 depending pump speed boiler locked out at 182 so tank never got to 140, boiler seemed to reset itself and try again but barely got started when i heard a weird sound or vibration first thought it was pressure releif but wasnt put hear to boiler seemed internal so i shut it off.it was really whisper quiet during operation so sound was kind of scary. when i switched pump speeds while running [is that ok] i got some hammering type sounds but those were clearly from piping and possibly pressure relief valve not boiler this was almost certainly inside boiler of course i shut it down almost immediately rather than keep listening to identify. flue temp was about same as supply temp until boiler got supply about 150 then flue got up to about 10 degrees hotter boiler operated at 100% until i slowed

PS so i gave them a call and regarding the Hl issue i drew a blank on all the stuff we tried with boon but his take ewas set all the high limits at max because the boiler will continue to raise temp and fire 100% until tank gets close to satisfied. Im skeptical cause tamk was 132 of 140 and it wasnt modulating yet but whatever we shall see.
he says the modulation with heat calls is different and modulation is prompted by return water sensor.
as far as the noise he says it was either pump too fast or slow water rushing or flashing that med speed usual and delta t 20 is what to aim for again we shall see. Ill restudy books and video before trying again. boon if you have worked out an ideal setup for the dhw let me know for a strting point.
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Comments

  • keyote
    keyote Member Posts: 659
    So does that pressure rise seem right going from 19 to 30 psi ?
    i set the expansion tank and make up at 19 psi while water was about 70 degrees. top floor is 27' above tank x .5 = 14 plus 5= 19psi or was i suppose to do that with hot water but dhw and heating water 100 degrees apart?
  • Gordy
    Gordy Member Posts: 9,514
    How did you size the X tank? That would be the first thing to checK. How did you set the tank pressure to 19 psi? Needs to be done at ambient, and isolated from the system.


    Then system fill pressure is set at ambient.
  • Gordy
    Gordy Member Posts: 9,514
    Did you do a combustion test on commission? If you don't test you don't know.....
  • Gordy
    Gordy Member Posts: 9,514
    I would suggest being fully acclimated with the install, and other manuals before commissioning the boiler. GIGO means a lot.
  • keyote
    keyote Member Posts: 659
    I filled the ex tank with air compressor out of the box and checked with dial gauge.did it at about 70 degrees room temp.Then set the caleffi auto fill at same and it worked, it filled until it hit 19psi while water temp was room temp 70 degrees. if i let water out pressure drops back to zero on caleffi gauge.so i think good to go, fill back to 19psi and start boiler, i expect pressure should rise as temp increases, just did not expect it to come so close tomax pressure relief valve on boile,r but dont really know what the formula is.
    i sized tank using a calculator on web. its a 4.5 gal tank and loop cad i believe told me i had about 40 gallons in the system, i wonder if i used a radiant heat temp for expected rise rather than the dhw temp. still pretty sure the calculator pre plugs start temp at 50 not 70
    Ok found another calculator [watts] redid it 70- 130 on heating loop works fine[ .54 acceptance 3 gal total]. but at 180 - 195 im out of tanks range-BUT the DHW loop is not the full 40 gallons its eight gallons in the triangle smart plus my boiler trim of about 20 feet at most is only a couple more gallons so plugging in 15 gallons 70-195 rise im still good on the dhw loop
    I dont need to count them both simultaneously? - well sure, maybe a bit since neither side is likely to cool all the way down to 70 during heating season, but then again the differential will also be less so i could probably reduce starting room temp pressure below 19, this is differential calculus way above my grade level. the worst case is when the heat call just ended and the 40 gallons is still at 127 design day and dhw calls and the 15 gallons heats up to 195, i know its less than a 8 gallon tank because the entire 50 gallons at 180 is only that, and its more than 2.2 gallons which is the dhw only %$#^&*
    what crazy is only running the dhw it was getting 30 psi which seems to high if the calculator says it well well within bounds, seems to me i might get away with a reduced starting pressure and if that keeps it lower during dhw call i could try to do a heat call as well. its not simply the cost it was hell squeezing that tank in but i get its a serious explosive deal just now i think about what temp the water will likely settle at between dhw calls 19 psi @ 70 degrees seem high anyway
  • keyote
    keyote Member Posts: 659
    yes Im hitting the books and training vids tonight wont continue till up to speed
    i know combustion analysis is important but seems tool is like 2 grand so will have to outsource once thing will at least function.
  • keyote
    keyote Member Posts: 659
    inspectopedia article said under heat call [180 typically?] typical sytem [12 psi cold?] should rise 5% pressure. is something else wrong or is this due to undersize tank, that pressure increased 50%? hmmmm - yeah it is, isnt it. damn! you'd think indirect tanks would be common enough tank vendors calculators would ask the question. I suppose i could add a second 4.5 gal tank
  • keyote
    keyote Member Posts: 659
    added a second expansion tank, gong to try again in a bit.realized i never got a previous question answered but had a thought that might be the answer need confirmation.

    control issue.controls wired thus
    DHW tank semsor and pump wired direct to boiler control as priority
    CH Tstats into taco zone panels tstat terminal bar,
    Zvalves out of taco zone panels zone valve terminal bar,
    theres an 'end switch' that seems to be part of the taco zone panels tstat terminal bar that I assumed was to transfer the heat call to the boile so i wired that into one of the boiler panels heat call terminals
    but system pump i wired not into zone panel but into boiler panel. I am pretty sure either way would have worked.swei suggested the boiler to get the post purge fuctions actually think taco panel will do that but there are even more options with boiler.
    However then the thought occcured that it take a litle time for zvalves to completely open and will the boiler start the pumps simultaneously when the tstats call?
    I have a vauge memory that these taco zone sentry valve with four wires purpose is to delay signal by other wires until valve is completely open. so it may be fine except i donr understand how that panel works and sine the end switches seemed like part of the tsytat terminal bar not the zv terminal bar i worry i may have bypassed the zvalves safety and the pumps will pump against a closed valve
  • rick in Alaska
    rick in Alaska Member Posts: 1,362
    Sounds like you wired it like it should be. The Sentry does have an end switch on it, and if you have all four wires from the zone valve wired in to the bottom of the Taco box, the tt contacts on the Taco box will not send a signal to the boiler until the zone valve opens up all the way. So, you should be fine with the pumps not dead heading.
    Rick
  • keyote
    keyote Member Posts: 659
    thanks rick. you did a KHN install recently i think you even piped it non P/S any tips?
  • rick in Alaska
    rick in Alaska Member Posts: 1,362
    I have actually done three now that way. Still trying to get all the different control strategies figured out and dialed in, but so for everyone is happy. Have had a couple issues with the first one such as a broken gas inlet piece, but they have fixed it by shipping the black iron piece loose now. Apparently, the boilers were getting banged around a little too much in transit and causing the cast aluminum piece to crack.
    Also, the first one I put in the display was off center on the control panel, so you had to kind of look under the printed overlay to see some of it. With my VERY anal customer, I am surprised he let it go.
    I have been working with a very good rep who has been fantastic at helping me out. I would love to have some control training on these things, but it cost me a bloody fortune to fly down there to get it. There are so many things this control can do, I am overwhelmed by it, but learning more every day.
    Tip: Get an analyzer to set up the gas valve. I have had two that were off on there specs and causing ignition problems. In fact I have one right now that shut down because of ignition problems in a house that is un-occupied at the moment. Found it because he has the Lyric thermostats and I noticed the temperature was dropping. I need to get with the rep on Monday as I am still not sure why it happened. Analyzer readings looked good after I set it up, but it seems to me like the rep told me not to use the numbers in the book to set it with.
    I will let you know what I find.
    Rick
  • keyote
    keyote Member Posts: 659
    i cant recall where i was reading this but recall it seemed quite reliable very likely on here , techs were finding the ideal combustion numbers if i recall were at the low end of the recommend. argh cant remember shite except that after quite a lot of experience by smart guys they had found the mid point of range was not actually ideal. Ill have to find that myself soon yeah the abilities are overwhelming suppose you know about the lochivar university videos on the boiler and the free software for registrants
    rick in Alaska
  • Boon
    Boon Member Posts: 255
    I have had two that were off on there specs and causing ignition problems... Analyzer readings looked good after I set it up, but it seems to me like the rep told me not to use the numbers in the book to set it with.

    @Rick in Alaska I'm so glad to see you report this. My readings were within the book's range and my KHN would only hold fire 1 out of 10 times. The other 9 times you could see it ignite in the window but fire wouldn't hold. I was told not to use the numbers in the book, too.
    ...barely got started when i heard a weird sound or vibration...

    This might be the same as what my boiler is doing now: Fire starts at 53% and then races toward 10% before going north again. On cold starts and when fire hits 10% the fan will cavitate and can even snuff out the flame. [My vent does not exceed lengths]. Have you seen this, too, @rick in Alaska? I'm wondering if the gas valve still needs more adjusting. Here is a short video of what I'm seeing and hearing: https://drive.google.com/open?id=0B9RHDu3JwkMqUjRDdWJ0LWRjeHM
    DIY'er ... ripped out a perfectly good forced-air furnace and replaced it with hot water & radiators.
  • Gordy
    Gordy Member Posts: 9,514
    If you don't test you don't know........
  • keyote
    keyote Member Posts: 659
    the 2-3 times ive started it it fires and holds fire ok.it could probably use a tuning anyway what number did manufacturer say to use now?
    cheapest analyzer i see is about 350 dont know if theres an alternative or rental, boon did you buy one or have someone come analyze?
  • keyote
    keyote Member Posts: 659
    reading through the two manuals really doesnt give you an idea at just how many settings there really are its really daunting. went through some settings and decided to try another run at dhw but this time the system pump fired with the dhw pump dont know what i did, i mean im aware if you select dhw as a zone that should happen but i didnt select that.
  • rick in Alaska
    rick in Alaska Member Posts: 1,362
    Pretty much same issues I had with the rumbling startup. I just left the last job because it went in to lockout again, and reset the numbers so C02 was around 9.3 instead of the 10.2 I had it at. Need to get with the rep tomorrow to see what it is they like, but seems like low end of specs.
    You MUST have an analyzer to set it up. The adjustments are a little sensitive.
    I also had it go into lockout when I was testing as I forgot to open up the zones to dump heat and it ran up to high limit lockout. Problem is when it does it it shuts off pumps, so then it can't dump the heat to cool down. Need to find out how to overcome that. I had to manually hook the pump up to power to cool the system down.
    Will keep you informed as to what I find.
    Rick
  • rick in Alaska
    rick in Alaska Member Posts: 1,362
    Keyote:
    There is a setting on the DHW screen where you can tell it what pumps to run on DHW call. Can't remember, but seems like it says " force system pump on DHW call". You can turn it off there if needed, depending on how things are piped. Still trying to play with these settings myself.
    Rick
  • Boon
    Boon Member Posts: 255
    If you don't test you don't know.....

    Me? Agree. I bought an analyzer. I've already tested and adjusted the gas valve to the numbers they wanted to see [while I was on the phone with them]. This flame fail thing is new with the colder weather. Could be the fan, I guess. I don't have the fan test tool, though it seems to be meeting its target RPM

    Keyote, if you can't get your hands on one I can ship you mine but you'll need to promise to ... use punctuation and full sentences on future posts. I've seen you do it before so I know you have it in you.

    I tried to get someone to bring an analyzer but either the companies I called didn't have one or they didn't want to touch a newly installed boiler that they didn't install. After explicitly asking for someone to bring an analyzer, one guy showed up without an analyzer and admitted to never adjusting a gas valve in his 20 years. I bought my own analyzer as soon as he left.
    DIY'er ... ripped out a perfectly good forced-air furnace and replaced it with hot water & radiators.
    keyoteChrisJGordySteve Minnich
  • Brewbeer
    Brewbeer Member Posts: 616
    Boon said:


    Keyote, if you can't get your hands on one I can ship you mine but you'll need to promise to ... use punctuation and full sentences on future posts. I've seen you do it before so I know you have it in you.

    OMG I cracked up when I read this. +1.
    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
    BoonGordy
  • Steve Minnich
    Steve Minnich Member Posts: 2,758
    Run on sentences are the rule with keyote : ). I never know where to begin or end?
    Steve Minnich
    Minnich Hydronic Consulting & Design, LLC
    [email protected]
    keyote
  • keyote
    keyote Member Posts: 659
    Been getting complaints since sister Irene in the third grade.Ill try harder.I type with two fingers so I correct sparingly kek.I should also apologize for cursing i noticed today a couple of you gents flagged me.
    So i have a report. Tried another run at the DHW side.Ran perfectly.I took their advice and set the automatic and manual resets at 200 and 210; but it came nowhere close. Tank setpoint was 140, think I had the boiler supply at 185 with a 10 differential and a... I forget I think there's a second fudge factor above the supply temp but with the lockouts at 200 I had room to play.Again it didn't matter.
    I could figure out why the system pump symbol lit up with DHW pump for DHW call, couldn't find a way to lock it out but realized I have my only CH pump wired to the boiler 'boiler' not 'system' terminals so I decided to ignore and proceed. during the run I noted the system pump speed read 0. So whatever.
    It fired up to about 30% and took a little dip [think I read its does this for a reason] then ran up to 100%. The flue temp was a steady 10 degrees hotter than supply temp.the S/R DT held 15% really steady, the wilo pump was on medium speed the whole run as they suggested.The suppl;y seemed to hold a steady 50 degrees higher than tank temp until just before the end. and the return was about 20 degree's difference from tank.It hovered at 165 for A bit it seemed. It got up to 184/185 just as the tank hit 140 it modulated down to 95% just then before meeting the call. the pump ran a minute more and the tank overshot to 142.


    Rich_49
  • keyote
    keyote Member Posts: 659
    edited October 2016
    Took my first shower after that successful run.Checked it right afterwards and was surprised to see it was running, seemed like it had just started. The 50 gal tank was down to 110 degrees, I thought that strange. I take decent showers but it was 148 degrees before I took my shower [seems like it had absorbed the heat from the last run that was still around the tank, because it finished at 142 with the supply water at 170 once the boiler shut down].
    This time it didn't seem to hover at 165, but got to 185 a bit earlier in cycle and modulated down to 95% which seemed to hold it at 185 fairly steadily for less than a minute, but it started rising again and so modulated further to finish the call at 90% at 185 with the tank at 140.seems to run really well.

    While it was running DHW I thought Instead of shutting it down for the night I might open up the S/R isolation valves on the heating zones and plug their zone valves back in just in case it got a heat call overnight the pump wouldn't dead head. I had filled purged the loops earlier and set up the heating parameters though i wasnt really confident I hadnt missed some heating controls.
    But as soon as i opened the isolation valves the hot water started heading up the return riser. The hot water coming back from the tank turned up the return header and into the riser.I had forgone a check valve at that connection for two reasons; one was the flow checks had them, but mainly because I couldn't see how any water could reverse flow with the zone valves normally closed.
    And because I was sure of that I ended up eliminating the spring checks in the flow checks in case they clogged.
    I dont know how the water could do that, I stopped it too quick to know how far it would have gone a few feet in a couple secs was enough for me, thinking that 185 water in my pex. Maybe the DHW pump was just stretching the pex enough to get a few feet and would have stopped in a second pretty thoroughly purged don think i have air in the loops. try it again tomorrow.
  • keyote
    keyote Member Posts: 659
    edited October 2016
    THIRD COLD START,had it off over night due to the hot water wanting to climb the return riser etc.So after failing to get the CONXUS to work pulled it out and ran it again stock.tank was again at about 110. This time it seemed to hold back from 185 towards the end and hold 180 which it would bob above now and then but held at 100% wasn't on a fan speed screen so maybe it was modulating the fan only. after a minute or two of this it slowly climbs as high as 185, again it seemed like it had learned what to expect, so every time it hit 185 it immediately would mod to 99% hit 184 and go back to 100%. This too went on for the last minute until on the very last bob it seemed to know 99% wouldn't cut it this time, [probably from return sensor which I wasn't concentrating on] and so the last time it modded down to 99, then 98 , then 97% holding 185,which BTW it never exceeded. And then the call ended successfully again this time.
    Also, the hot water never tried to climb the riser again, although I left them open in advance to see what that was about. My guess is last night the act of opening the valves while the DHW pump was running created a siphon last night.

    So CONXUS. Anyone have trouble? I ordered mine through supply house.com with the boiler. The instructions didn't include the KHNinstall, so I had to reinterpret, basically swapped the com cables to allow it it to reach proper plugs. It also was missing nuts to hold the board down to the rod coupling they use as spacers.

    The app scanned the boiler barcode OK, but a dozen attempts to scan the CONXUS failed, as did manually typing in DNS. I figured perhaps it had to be live to register So decided to install it. Anyway once it was all wired and i flipped the switch nothing, no power to boiler control board,checked harness still nothing. Took it out and reconnected boiler without and boiler was fine.
  • Gordy
    Gordy Member Posts: 9,514
    You, and Boon have to realize the goal for DHW is to satisfy the tank as quickly as possible. Also to keep up with running demand. So this thinking that the boiler is suppose to be modulating down passed 95% is a fairy tale. You can curb it some.
    Cycling for DHW is not the end of the world. The KHN 85 is a pretty small boiler to meet the peak output hot water production of an indirect. Read your indirect ratings to see how their recoveries are compared to btu input of the boiler.
    njtommy
  • Gordy
    Gordy Member Posts: 9,514
    Sounds more like a flow issue to me. The indirect should easily except the output of that boiler. Think if it were a CI boiler.
    njtommy
  • Gordy
    Gordy Member Posts: 9,514
    Why would you not want full output out of the boiler especially if it is under rated for the max recovery rating of the indirect.
  • Gordy
    Gordy Member Posts: 9,514
    edited October 2016
    The smart 50 performance rating is based on 140k output boiler with 200 degree supply with 90 degree temp rise.

    The smart 40 is based on 112k boiler output.

    The KHN has an output of 79k. So tell me why is it the boilers control strategies fault that the indirect can not except 79 k with out short cycling.

    Is the piping to the indirect from the boiler 1"? Is the pump correctly sized for the flow rate needed? We can not always accuse the boilers controls as the cause. When the short fall of proper piping, and pump sizing could be suspect. People are looking more ,and more at technology as the band aid for the lack of proper practices.

  • keyote
    keyote Member Posts: 659
    whoa guys Im not complaining where do you get that Im ectatic its operating flawlessly as i describe in detail it gives it 100% all the way to 185 degrees then hold that first by modulating fan then by modulating flame one degree at a time back and forth to hold 185. for the very last few seconds it might mod down a bit more once to one 95% the last time 97% still holding the temp i programmed for it to supply and bringing them tank to the temp i set. It actually looks from the phenomenal performance that I could trust it with an even higher supply temp closer to the lock out since its never exceeded it or had to use its wiggle temp.

    as to weather its should mod to tank temp, Ok I talked to them before I set it up and they said it mods on heating calls according to supply temp which is the setpoint. but on water calls its mods according to tank temp, what this seems to mean in practice since as gordy points out faster is better on water, its going to hold as close to the max supply temp until the last minute even then modulating only enough to hold that number steady. whereas on a heat call you might put in a much lower number and it might have to mod way down,
  • keyote
    keyote Member Posts: 659
    Hat I get, I think, what youre saying, that it shouldn't lock out on a DHW call like boon experienced, and you're right. He is having combustion issues that might be the cause. Maybe its something else, we are both just getting up to speed. One thing they mentioned is the auto and manual High Limits max out at 200 and 210, they suggested I keep them at max and thats what was pre set, then theres the supply temp, the supply temp diff, and i think another i gave them all about 5-10 degrees space but turned out wasn't needed, so i wonder if boons problem is even setting related. Pump speed used was recommended medium, Ill see if i can go high speed tomorrow.Boon is running 1" pipe and i ran all 1-1/4" maybe thats having an effect his is I believe a 055 so its I think a derated 084 that might be problematic?
  • Gordy
    Gordy Member Posts: 9,514


  • keyote
    keyote Member Posts: 659
    Gordy wrote
    Sounds more like a flow issue to me. The indirect should easily except the output of that boiler. Think if it were a CI boiler

    Gordy Im not sure if youre understanding. Boons tank was taking the heat and had room to spare if his pipes and boiler are a bit small all the more reason it shouldnt have locked out. the problem he had was his boiler exceeded his boilers settings not the tanks settings his boiler tripped his boiler that shouldn't happen if you want to give your tanl 180 degrees or 190 degrees it should be able to not trip over its own settings- mine doest exceed its settings by even a degree.
  • Gordy
    Gordy Member Posts: 9,514
    Thats all there is. Like I said DHW is all about speed.
  • keyote
    keyote Member Posts: 659
    Gordy I would interpret that as when you have a much larger boiler than a tank, but boon and I have the opposite., how can you say a tank thats not satisfied is not able to accept what the boiler is giving.
    . He did mess with his fan mine stayed at 8500 give or take, however I describe above how once it got to 185 it kept bobbing down to 184 yet the mod was 100% i suspect it used fan speed to micro mod, a bit later just before it got satisfied it actually started to mod from 100-99-100-99 to hold the 185 and the very last ten seconds it modded down to 97% i think it saw its return water rising and knew it had to mod more than 1%.
  • Steve Minnich
    Steve Minnich Member Posts: 2,758
    I don't think it's so much micro-modding as you say from 85 to 84 or 100 to 99 as much as the sensor is just dialing in.
    Steve Minnich
    Minnich Hydronic Consulting & Design, LLC
    [email protected]
  • keyote
    keyote Member Posts: 659
    Maybe but all through the run up it never reverses temp below what its reached thus far [although it sometimes seems to pause at a temp a bit longer] and it never shows mod below 100%fire throughout the climb, until it reaches the 185 setting.
    Only then does it go 185 184 185 184 but still at 100% fire. So it seems to be modulating without lowering fire rate. Since fan speed is a parameter that can be used when you have an undersized indirect or an oversized boiler, and during the run up its rpm does fluctuate slightly [maybe 25 rpm out of 8500] I suspect thats what happening, but at the time I didnt think of it so didnt check fan speed during this phenomena only fire rate.
    It only lasts less than a minute before actual modulation starts and fire rate drops 99 98 97% while holding 185 supply temp steady.This too is less than a minute, so its also pretty good at pacing itself to not reach max temp until the very end.
  • keyote
    keyote Member Posts: 659
    Thanks Gordy
    I don't disagree and I didn't mess with it because as i said if anything Im an undersized boiler. I only mentioned it in my last comment to bolster my theory [and its only a theory] that the boiler can use both the fire modulator and the fan to hold a temp.I only postulated this theory because the boiler seemed to be "modulating" 185 184 185 184 while its modulation rate was steady at 100%.The next time it does this Ill see what the fan is doing.I get that fan modulating is also part of fire modulation as fuel decreases and flue gas decrease the fan must slow down as well, I just thought maybe at the micro level it can drop a degree with fan speed alone.
    Im a bit confused on how Im to set the heating up.I put in a maximum temp [which was the water temp on design day according to loop cad] and the low temp same way. I havnt done the outdoor reset curve yet. I get its got a ratio that can be adjusted to sort of amp its up or down all along the curve. If I recall thats to be left alone unless unsatisfactory then try very slow changes. Its more the basics Im unclear on, do I just say make one end 17 degrees outside and 127 degree water and the other 65 degrees outside and 90 degree water because that is what loop cad gave me and the ODR will adjust between those.
    I worry about too hot water in loops under hardwood floors.
  • njtommy
    njtommy Member Posts: 1,105
    Honestly I probably would of ran 1-1/4" piping to the indirect tanks to maximize flow.

    @Boon recheck your combustion numbers. They can change a bit with colder weather. And watch you CO ppm they must be under 150 as per Lochinvar. On the KHNs I've done they hang at 9.5-10 co2 and 3.5 o2 at full fire.
    Gordy
  • keyote
    keyote Member Posts: 659
    Tommy I did use 1 1/4" for all my near boiler only the zones reduce.
    On the fan question, I watched a DHW cycle again and it really does seem to first micro mod with fan only before starting to reduce modulation rate.
    all during the run up the fan only fluctuates about 19 rpm but once it hits max supply setpoint the fan starts dipping the rpm down as much as 40-100 rpm then back up and down and up,its very sleight. Of course once real modulation kicks in the fan definitely slows a few hundred rpm by 95% modulation.
  • Gordy
    Gordy Member Posts: 9,514

    Gordy said:



    I want to address the fan speed limit for DHW so that there is no confusion about it.

    In theory, this parameter is absolutely not required, If the indirect cannot accept the full output of the boiler, the boiler simply modulates down...............just like it does with CH.

    The only reason it is present is under the condition where the indirect can only accept a fraction of the capability of the boiler. Under this circumstance, the boiler might climb to HL before it has sufficient time to modulate down. With a fan speed limit, this problem is eliminated.

    Under any reasonable scenario where the boiler is not 200K with a small indirect, this parameter is most definitely not required.

    It is no different than the CH limit. A bandaid for the control system to prevent a HL trip. In theory, the boiler shouldn't require it.

    Then why is it a parameter to be used specifically for DHW?

    How does fan speed relate to the burner output?

    What is the goal of a DHW call in priority?