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Lochinvar and Microzoning

We've installed a few of the KHN (now KHB) and WHN (now WHB) boilers with the promise of being able to microzone without 1°-2° piping or having to add a LLH. Promise may be too strong of a word, but there were words spoken, written or otherwise communicated that a fire tube boiler is better able to handle low flow through the HX. This has not been my experience as one or two of the ones we installed would lock out with a red screen, manual reset. This happens with properly sized boilers and zones that aren't really that small. We've had to go back to change the piping. Fire tube boiler with a 10:1 turndown ratio does not necessarily allow microzoning.

The last one was a KHN055 on a 3-zone system; the smallest manifold is 6 loops of 3/8" PB. The boiler spec's. say the minimum firing rate is 8,300 BTU's (.83 GPM) and a 6-loop manifold will flow at around 1.5 GPM which should keep the boiler happy, no?

I still like their boilers, but we are piping them the way we pipe other boilers. Any comments?
Often wrong, never in doubt.

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Comments

  • Jamie HallJamie Hall Posts: 10,293Member
    Only thing I'd wonder, @Alan (California Radiant) Forbes , is is the zone actually soaking up that 8300 BTUh (delta T at least 12 for a 1.5 gpm flow). I realise that sounds like an obvious question, and I'm sure you've thought of it, but if it can't that could give you a steady rise in return temperature, which -- eventually -- could cause the thing to lock out?
    Jamie



    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.



    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • IronmanIronman Posts: 4,970Member
    What was the lockout code? If the boiler was underloaded, it should simply cycle off and back on once the minimum off time is met.
    Bob Boan


    You can choose to do what you want, but you cannot choose the consequences.
  • GordyGordy Posts: 9,264Member
    edited March 11
    What's the load of the zone that causes lock out.?

    What is the boiler in and out delta?

    The KHB 55 is 1 gpm low fire, and 2.1 gpm high fire minimum flow rates.

    Minimum "output" is a little over 7.5k the 55 is not 10:1 tdr.

  • GordyGordy Posts: 9,264Member
    You need a delta of a little over 16.5 @ 1 gpm to get the math to work for the 8.3k input. However there is no getting around the minimum of 1 gpm at low fire.

    Question is as @ironman asked what's the lock out code?

    It's a fine line to walk when you get down in the weeds with the gpm, and proper delta to keep the boiler happy which seems to be 20. Possibly some tweaking certain boiler control inputs.
  • EBEBRATT-EdEBEBRATT-Ed Posts: 5,634Member
    You have to take everything a manufacturer tells you with a grain of salt
  • GordyGordy Posts: 9,264Member
    edited March 11
    I’m sure it’s doable. The question becomes how long the minimum load is steady state?

    A zone may start at full load, but as it closes on set point the load decreases. “Emitters are in charge” a very wise man said.

    That being said I’m sure lab testing was a constant load at minimum modulation to get the 1 gpm minimum flow rate.
  • hot_rodhot_rod Posts: 11,269Member
    In your climate Alan, I think a lot has to do with the % of time at design. This is especially true with micro zones.

    This is one of my favorite graphs to get a visual on how that load can vary across the season. This is a 0° design climate in Boston It would be interesting to develop a graph like this for a climate like yours.

    At some point a buffer or high mass heat generator is the only option once you have leveraged all the control and turn down options.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • rick in Alaskarick in Alaska Posts: 819Member
    I also had this happen. The lockout code will tell you if it is because of the temperature sensor, or something else. I can't remember the wording, but it was something like the inlet and outlet are too close together. It turns out they have some bad sensors that are giving bad readings. It is the one up top with a four wire molex plug on it. It also seems like when I had this problem that my rep had me disable the supply sensor. Again, I can't remember why, but it seems like it fights the system depending on how it is piped.
    Rick
  • Yes, Jamie and others: The zone is probably not soaking up all the BTU's and I probably should increase the anti-cycling time and/or anti-cycling ΔT which is a very nice feature on these boilers.

    "At some point a buffer or high mass heat generator is the only option once you have leveraged all the control and turn down options."

    Thanks, HR. Interesting to see high mass boilers becoming available ala Viessmann CU3A. I think we will start to see more.
    Often wrong, never in doubt.

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  • bob eckbob eck Posts: 849Member
    How is the boiler piped? Please show us some photos of the boiler piping. Did you zone with pumps or one pump with zone valves. If using pumps on all zones you could be over pump the zone.
  • hot_rodhot_rod Posts: 11,269Member
    This could make a nice 20 gallon "buffered' heat source. Built as a water heater, no listing if that bothers you. I used Voyagers and Phoenix tank heaters from HTP for radiant dedicated appliances.

    Seems to me these are as safe or safer than "boilers" for low temperature radiant appliances.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • bob eck said:

    How is the boiler piped? Please show us some photos of the boiler piping. Did you zone with pumps or one pump with zone valves. If using pumps on all zones you could be over pump the zone.

    It was originally piped straight and then 1°-2° when we had problems. It's zoned with zone valves.

    Hot Rod: I'm not a HTP guy, but the Crossover would be perfect for a small to medium size house with micro zoning going on.
    Often wrong, never in doubt.

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  • clammyclammy Posts: 2,211Member
    In my heart of hearts I knew it was to good to be true .I ps every mod con including the few fire tubes I ve installed . I just figured that the slowest wide open space is the heat exchange just where all the crud will end up without have enough velocity to keep it moving .i love the idea of a variable speed pump matched to boiler modulation but I would worry bout enough velocity to keep it moving .i know big v has it in there line for quite a while and I know loch has it as a opintion . I would gather if one where to be really anal they would install mag separator and use cleaner then power flush fill test and treat the water and test periodically that’s a lot of work$ I think most HO would just roll the dice and replace in 5 to 10 peace and good luck clammy
    R.A. Calmbacher L.L.C. HVAC
    NJ Master HVAC Lic.
    Mahwah, NJ
    Specializing in steam and hydronic heating
  • Clammy: You're a better installer than I am. I take chances and sometimes fail.

    Good luck and peace.
    Often wrong, never in doubt.

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  • rick in Alaskarick in Alaska Posts: 819Member
    Fyi. My new Lochinvar whb110 I just installed came with the new Grundfos 10vdc pump for the primary. I was surprised to see it in the box.Will see how it works out.
    Rick
  • bob eckbob eck Posts: 849Member
    All Lochinvar Knight boilers wall or floor come with a ECM primary pump.
    Please let me know how you like that boiler.
  • GordyGordy Posts: 9,264Member
    But not 10 vdc
  • hot_rodhot_rod Posts: 11,269Member
    here is the pump that Lochinvar had at their booth at the Keller Supply Expo last week. I'm not sure which models it is supplied with?
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • rick in Alaskarick in Alaska Posts: 819Member
    That's the one! Came with my new WHB110. The problem is that they do not tell anywhere which wire is positive and which is negative. Luckily my rep new. I just have to find my note to remember.
    Haven't had enough time to watch it after installation, but maybe next week after things slow down.
    Rick
  • SuperJSuperJ Posts: 478Member
    It's about time!
    Commercially we've been flow tracking the primary/secondary loop for years with VFDs, and proper temp and flow sensors everywhere. But residentially with constant speed boiler pumps it's been tougher to avoid diluting your return with hot supply water and ensure proper minimum flow, and still have enough flow at high fire to keep the delta reasonable (or avoid diluting the supply with cold return).

    With a variable speed primary pump the boiler flow should be able to be tuned to track the system better. I think lochinvar gives you a couple parameters to tune the boiler circulator speed.
  • BrewbeerBrewbeer Posts: 575Member
    I have a Loch WHN055 install in 3 years ago. The boiler pump is a Grundfos UPS15-58 set on low, and I recon it's moving about 7 or 8 GPM on it's lowest setting (60 watts). The system pump is a Taco 2218 set on low (9 watts), which flows about 2-3 GPM. I'd love to get a boiler pump that would work more harmoniously with the system side pump.


    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
  • IronmanIronman Posts: 4,970Member
    edited March 12
    One of the caveats with most , if not all, fire tube mod/cons is that the secondary must always have greater flow than the primary regardless of what the minimum flow requirement is for the boiler. So, if the boiler requires 1 gpm, the flow in the secondary must be more than 1 gpm.
    Bob Boan


    You can choose to do what you want, but you cannot choose the consequences.
  • GordyGordy Posts: 9,264Member
    you Still have to deal with that minimum output. It doesn’t magically go away.

    I suppose a steady state load at minimum flow rate is sustainable in the lab. Problem is the load is never that stable for very long in real life.
  • betweentheframebetweentheframe Posts: 97Member
    I eliminated PS piping cause was scavenging too kuch supply water into return water. Using about 40 percent less LP. I took one microzone (single rooms buderus) and added to zone that most often is cycling and put a TRV on that rad.

    Have smallest zone as staple up and rad and that TRV, so at least 2gpm with zone adjusted to 1gpm. I turned the percentage of max modulation down to make it slow and condensating to get up to temp and set the CH refire delay to 10 minutes.

    The only real issue i can see is when you use DHW on combi it resets the refire on my baxi 40ga so then may have been almost about to shut down cycle so return water is lretty hot, refires after DHW, and then reaches 176 quickly and shut down.

    Also without the PS, with the grundfos ecm downstairs pulling kn supply on middle constant pressure setting, if you use DHW the flow through zones stops because the combi 3 way bypass valve goes back over to DHW, ecm obvi does not dead head like many pumps might. Have been told can tun with just the internal 15-58 in the baxi, but that pulls return water and pushes through the boiler and the 15-55 in basement I think is helping pull from supply and keep flow good when all zones are open.

    PS on this set up was pretty much useless for heating house. Next Up I want to figure out how to run a 3 way mix valve so i can run the concrete radiant cooler than the rads, think 120 into cement and 150 into the rads would be ideal, but my return water would likely be too hot from rads so would have to figure out how to make that work
  • MikeT_Swampeast_MOMikeT_Swampeast_MO Posts: 27Member
    It's been a long time since I've been here--probably about a decade.

    Amazing how the equipment changes but not the problems :wink: Low circuit volume + low circuit flow + high efficiency, rapid head and [presumably] low boiler mass = potentially skyrocketing supply temperature almost irregardless of the mass of the emitters.

    Presuming you used primary/secondary Alan it sure sounds like the problem is low flow in the secondary circuit. If you're moving 4 gpm through the primary but only 1 gpm through the secondary you can only remove 1/4 of the net heat produced by the boiler! Combine that with a minimum boiler firing time and it's no wonder you get an overtemp lockout. Things may be fine from a dead cold start-up but once the system is up-and-running with the thermostat cycling delta-t in the secondary circuit will drop quickly as delta-t in the primary nosedives.

    If you can't set a shorter minimum firing time (perhaps you can select different times depending on which/how many zone(s) call?) I believe the only solution is a buffer tank installed for the zone and after the emitter(s). Why after? Because the emitters will get the hottest supply with the buffer the last to heat thus maximizing delta-t in the circuit as long as possible. In a perfect world there would be a simple and easy way to "post purge" the excess heat in the buffer into the emitter(s) at the end/just after the thermostat call with that circuit isolated from the primary :smile:
  • GordyGordy Posts: 9,264Member
    Welcome back! How’s the “Euro Cave” ?

    @Mike T., Swampeast MO A few of the new mod cons boast minimum flows of 1 gpm at low end modulation. So piping direct would be the only possible way to achieve this.

    In this case for this model it’s 1 gpm at low fire, and 2.1 gpm at high fire for the KHN 055.

    In a perfect world with a constant load equal to the minimum modulation of that boiler for a sustainable period of time it’s probably possible. In a Lab....

    But that load is not sustainable for a lengthy period of time in real life as a zone closes on setpoint.

    I remember following your “documentary” of the viessman 200 in your home direct piped with trvs IIRC.
  • MikeT_Swampeast_MOMikeT_Swampeast_MO Posts: 27Member
    The "Euro Cave" continues to work to design with excellent comfort at very modest (say 65F) approximate setpoints on the TRVs with the "wild" (no thermostat/constant circulation) radiant floor baths comfy. The Danfoss TRVs perform perfectly.

    I had to replace the built-in circulator in the Vitodens (the only circulator in the entire system) about two years ago and was very pleased to find zero sign of any grunge either in the circulator or internal boiler piping.

    The Vitidens continues to operate in what I called "pulse" mode (VERY short firing less than 30 seconds) for much of the season made even more frequent when the exterior was replaced with EIFS to further reduce infiltration and increase insulation in an already nicely renovated 1903 3-story.

    The ignition system shows no sign of wear and the sound of the draft fan is unvaried. "Coffee grounds" accumulate in the HX and have to be removed during annual service.
  • EBEBRATT-EdEBEBRATT-Ed Posts: 5,634Member
  • MikeT_Swampeast_MOMikeT_Swampeast_MO Posts: 27Member
    Gordy said:

    Welcome back! How’s the “Euro Cave” ?

    @Mike T., Swampeast MO A few of the new mod cons boast minimum flows of 1 gpm at low end modulation. So piping direct would be the only possible way to achieve this.

    Understood. Then if not primary/secondary the obvious problem is still a zooming supply temperature due to low delta-t combined with a minimum firing time. If firing time can't be reduced then the only reasonable solution--with this zone operating alone--is a buffer.

    Any report on FHVs (the TRVs for floors)? Put this system on those, set a nice reset curve and the "microzoning" problem should disappear :smile:
  • GordyGordy Posts: 9,264Member
    The fhv a looks interesting. Pricey?
  • clammyclammy Posts: 2,211Member
    Alan just a observation on my half . On my own system I have a califee hydroseparator and I have noticed that my td across my boiler before reaching set point is usually anywhere from a minimum of about 15 to about 20 degrees on start up I’m looking at anywhere from 25 to 30 until I reach my ODR setpoint then I mod down to 15 to 20 td . I have noticed that on standard piped ps without the hydroseperator that the td across the boiler is less , I have also really noticed more temperature straticafaction w the hydro separator w less mixing as w standard tee s . I de have to really go out and look but most of that mod cons I do I try not to Mirco zone to much and I kind of pic my boiler based on the smallest zone and the boiler lowest modulation that the boiler will produce .i know I don’t have much to teach , you been around long enough to know much more than I just giving u my observation no criticism . I have also down as u suggested and ties zone together to help prevent short cycling . In one or two cases I have used a aquastat to enable low temp zones to help get longer cycles outta the burner .its worked out quite good most ho don’t even realize it .As long as the Dhw has priority and piped so it doesn’t effect that aquastat peace and good luck clammy
    R.A. Calmbacher L.L.C. HVAC
    NJ Master HVAC Lic.
    Mahwah, NJ
    Specializing in steam and hydronic heating
  • MikeT_Swampeast_MOMikeT_Swampeast_MO Posts: 27Member
    Gordy: The last time I checked FHVs (by Danfoss) the price seemed very reasonable.

    Like a TRV there are two components--the valve itself and the operator. Both cost somewhat more than their TRV counterparts in large part because they're designed for wall mounting. The operator replaces the wall thermostat while the valve replaces a zone valve or zone circulator. In my admittedly limited direct experience but high observation of systems both the valve bodies and operators can be expected to far outlast their "standard" counterparts.

    To install the FHV you bring a loop up into an interior wall--obviously make certain you can "power purge" the circuit! The location of the valve within a single circuit is immaterial. If the zone requires more than one circuit you get a larger/higher flow valve and install either ahead of the supply or behind the return manifold serving the zone.

    The standard FHV operator modulates on air temperature. You can also get a version that modulates on slab temperature (it uses a probe obviously) for special uses.
  • Leon82Leon82 Posts: 589Member
    > @hot_rod said:
    > here is the pump that Lochinvar had at their booth at the Keller Supply Expo last week. I'm not sure which models it is supplied with?

    Searching the part number only brought European results, about 195euros
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