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How smart is the Knight?

Kevin O. Pulver
Kevin O. Pulver Member Posts: 380
and the Gyp-crete might have to go away from the second floor of the new home. )It's basically 2000ft.sq. on main floor and will have basement and 2nd story as well)
We are planning radiant in Gyp on the main, and radiant also in the basement. Amazingly, our Gyp numbers came in better budget-wise than extruded plates. Labor would be a little less that way too. Still, the homeowners are a little pinched.
QUESTION: If we go to baseboards or panel radiators in the second floor bedrooms/bath (recommendations welcome here) is there any way that the Knight could fire low for the Gyp zones, and high for the Baseboard? It seems impossible to me, but you guys specialize in that, so here I am again. I know I could do VSIM, but that would require higher boiler temps all the time only to mix it down. A waste of energy it seems to me. What is the best way to preserve efficiency and save a little on the budget? We've already combined zones, so that isn't an option. Thanks guys, Kevin


  • Weezbo
    Weezbo Member Posts: 6,232
    here is a thought...

    the house is slab on grade SOG that is medium type heat...

    think of the panel rads with medium heat..think about it...

    I would like you to hang in here until Mike Swampeast drops in...hear him out....

    Andrew said something that i think is right too, radiant walls in the bath is a great idea.
  • ALH_4
    ALH_4 Member Posts: 1,790
    2 temps

    The simplest, most integrated way to do this that I know of is to use a Vitodens boiler and motorized mixing valve on Circuit B connected to the internal Vitodens Comfortrol. However, I still see no way of avoiding running the boiler at the highest temperature required and mixing for the lower temp zones.

    I would go with panel radiators, or even radiant walls. The nice thing about radiant walls is that you can run them warmer which reduces the area required. Also, the R-value of the sheetrock is much less than the subfloor and flooring. The drawback is the possibility of a headboard or dresser being placed in front of the radiant wall. Personally, I am a big fan of panel radiators with TRV's. In my opinion, panel rads start getting pretty large for design temps below 140°F. Luckily, design loads have a relatively infrequent occurrance.

  • Tekmar 422 doing VSIM or a mixing valve for the radiant. You'll need a 337 in there, or a dedicated zone controller for the high temp vs the low temp depending on your zone counts. All zones get 54x tekmar thermostats. The knight will require some sort of interface card I think...

    That's not the cheapest, but will run a mod/con at the lowest possible temps at all times, syncronize zone firing, managing cycling, give indoor feedback... excellent stuff.

  • on the other hand, size the baseboard so that the high temp curve isn't too high, mix down for the larger radiant loads, and you'll probably find the larger volume of cooler return water will help out.. just keep your high temp curve down as low as you can. It's usually pretty easy to hit 140 if you try, and often 120 can be had.
  • Kevin O. Pulver
    Kevin O. Pulver Member Posts: 380
    I love to try a Viessmann sometime Andrew

    but that's not going to help me with the budget problem no matter how I slice it I'm afraid. Those things are a little scary. They can do anything but toast bread.
    From everything I read about them, they might actually be WATCHING us. Maybe the humans are on reset?
  • Tombig_2
    Tombig_2 Member Posts: 231
    Trick the ModCon

    Kevin, I feel your pain. 6000sf of low temp radiant with indirect DHW. Plug and play with an Ultra, Knight, Prestige, etc.. with all low temp on boiler curve. "Sure I can add a small sidewalk snowmelt" I say. In retrospect, not so easy while maintaining the low temp efficiency for the other zones.

    I don't have all the details worked out but here goes. Thanks to Peter at Able distributors for planting the seed. Program the Knight reset curve for your low temp radiation. Through simple relay logic and some well placed check valves and pumps trick the boiler into thinking it's making DHW whether it's calling for hot water or the high temp zone.

    A three way mixing valve and it's own outdoor reset will control the high temp zone. If your second floor might be copper baseboard just run 180* through it till it's satisfied without reset or mixing, like the old days. At least the boiler will be at condensing temps when the low temp zones are the only ones calling for heat.

    I, like you Kevin, feel I'm doing my customer a disservice installing a modcon while programming for higher temp zones and mixing down to larger low temp zones. Weezbo was right about adding enough radiation to cover the heat loss but there goes the installation cost savings. I've got whole house overpours that I didn't have to adjust the design setpoint over 110* until we had two weeks straight below 10*. That's some condensing efficiency!!

    This is creative thinking and I know there are hydronicians out there who are way more creative than me. Tricking a modcon into thinking it's into DHW production and sending the 180* water elsewhere besides the indirect is relatively simple. Sending it to the the indirect on priority is a little more difficult. Making sure the low temp zones don't suffer is more difficult, not impossible. Until the mfgrs come out with a plug and play two temp controller we're on our own.

    Thanks, Tom G
  • Uni R_3
    Uni R_3 Member Posts: 299
    They exist...

    "Until the mfgrs come out with a plug and play two temp controller we're on our own."

    The Vitodens does dual temps and Viessmann sells a complete solution for it. The MCBA based boilers could do it as well but for some reason just not in North America! I'm not sure why Honeywell and the manufacturers that are using MCBA controllers such as ECR, W-M, Burnham, T-T, etc. don't get it in place for over here.

    I'd try and keep the sizing of the higher temp emitters up and then dial the boiler curve down for those. Then for the infloor radiant use a Taco RMB. The Taco RMB is ideal for situations like this. It's another grand but everything's there in one little package.

    Attached is an ACV Prestige set up for dual temps (and can still do DHW as well). The hi and lo temp modules plug into something like a hydro separator that connects to the boiler.
  • Dave_4
    Dave_4 Member Posts: 1,405
    google John Siegenthaler and minitube

  • Mike T., Swampeast MO
    Mike T., Swampeast MO Member Posts: 6,928


    I have an idea but MUST have some numbers to work with to see if it's feasible.

    Am guessing this is what I call a "multi-gable monstrosity". 1 1/2 story home (with basement) with irregular footprint, steeply pitched roof with the upper floor area significantly smaller than the ground floor and ground floor heat loss the greatest of all the floors. If I'm completely off-base, please let me know.

    Need to know:

    Outdoor design temperature and general location. If any unusual site-specific considerations, please describe.

    Design heat loss in each temperature area (e.g. basement with tube-in-slab; ground floor with gypcrete; upper floor with panels and/or baseboard. No need to bother with individual room loss--if the idea works it will be up to you to size everything appropriately to each room.

    I also need to know the MAXIMUM design delta-t your experience makes you comfortable with for both the tube-in-slab and gyp floors.

    I've again studied the Knight literature and my initial (and simple but crude) ideas are impossible.


    My idea is for traditional primary-secondary with three sets of closely spaced tees. First set to the baseboard and/or panels; 2nd set to the gyp; 3rd set to the tube-in-slab. One motorized mixing valve for the gyp to be controlled via separate outdoor reset of what's now a relatively simple outboard controller. Everything designed to keep return temperature below 100F AT LEAST 85% of the time even though the reset curve in the Knight will be set to satisfy the panels and/or baseboards on the upper floor while minimizing their size. I will however say that significant daily setback of the panel and/or baseboard area will be an efficiency problem TO THE ENTIRE SYSTEM.
  • Mike T., Swampeast MO
    Mike T., Swampeast MO Member Posts: 6,928
    Multi-Temp Systems with a Mod-Con

    First a law:

    When you maintain space temperature via a hydronic system that is constantly providing energy, the temperature of the emitters--regardless of type--will be at the minimum possible.

    As a consequence of this law applied to the real world regarding a structure with individual spaces whose losses vary depending on the sun, occupancy level, ancilliary energy soures, comfort desires, etc. etc., you MUST have a supply temperature sufficient to meet the needs of the most temperature hungry area.

    You MUST supply sufficient temperature to at least meet the maintenance requirement of the space requiring the highest temperature. The LAW applies. But guess what? That LAW says that any spaces requiring lower temperature will be over-supplied.

    To complicate things further the mass, volume and construction of the emitters affects their output characteristics!

    If there is a significant difference among the emitters in ANY of these characteristics there is NO CHOICE other than to supply the emitters with different temperatures.

    To fulfill the LAW with a single source of energy there is NO CHOICE other than to provide the HIGHEST temperature required in the system at the MINIMUM possible temperature to maintain space temp.
  • Mike T., Swampeast MO
    Mike T., Swampeast MO Member Posts: 6,928

    I cannot find a way to "trick" the Knight in this case. DHW is the WORST way as it [appears] the the Knight will produce 180F supply regardless of load.

    Can the temp produced by the Knight be adjusted during a DHW call? I may be wrong, but it appears to be fixed at 180F.
  • Mike T., Swampeast MO
    Mike T., Swampeast MO Member Posts: 6,928


    The problem you asked me to try to solve is still in my head.

    Your radiant start-ups in North Pole, AK in structures that might not be complete could possibly exceed the energy required to maintain space temperature comfort for the entire season.
  • Weezbo
    Weezbo Member Posts: 6,232
    Howdy Mike. *~/:)

    i just finished my Final inspection a few days ago....

    so, i am home reading resting and eating food :) i sorta feel guilty as there is so much work to do...well, it is good to see you here. Let me ask you a question as i do not have the Knights operational manual in front of me at the momment...am i mistaken that it has more than one way it may function as a hydronoc boiler? what i mean by that is is it possible to use a "set Point" senario with the boiler that steps or is that only when one is using multiple boilers?

    I think the way it was conveyed is, while all radiant systems is what we basically are into...quite often the application of the boilers is in retrofit applications...so there is a means to still garner high efficentcies of the boiler itself rather than say on the combined system.

    the idea that crosess my thought is to utilise this function for mixed systems except with a change to some of the step (time dependent) off on features...maybe ?

    then having constant circ on the medium radiant one would have sort of a puseld injection constant circ on the pannels and constant circ slightly larger Delta T lagg on the medium temp radiant...that is still primary secondary and pulsed injection it just limits the higher temp by not allowing it to boost past the set point ..

    to me having the dollars to add larger pannel rads limits the high side of the reset curve... and that in turn allows the full rangeability of the modulating control...

  • Mike T., Swampeast MO
    Mike T., Swampeast MO Member Posts: 6,928

    The Knight is quite versatile when it comes to internal programming and outdoor reset is not required.

    So, YES, it can be used as "setpoint" boiler.

    I do NOT however see any way to use it as a multiple setpoint boiler without resorting to relays and resistors.

    Nor can I see a way to add a fixed setpoint that overrides the reset curve other than for DHW and even then it [appears] that output temperature during a DHW call is fixed at 180F.

    While it has a 0-10V input for control of modulation I see no "supported" way (either built-in or manufacturer accessory) to control a two temperature system.

    If I'm wrong in any of this please correct me--either publicly or privatel--and I will publicly correct!!!

    With what I understand about your area Weezbo, I would SERIOUSLY look into the new oil boiler offered by Slant Fin. It's the first North American integrated boiler control system I've seen that combines outdoor reset with variably influenced indoor modification. Granted it cannot modulate the burner, but it's going to do a damned fine job of producing a target temperature that has a decent chance of being maintained for at least a reasonable period of time in typical weather.
  • Steve Gates_3
    Steve Gates_3 Member Posts: 27
    try this

    Set the modcon for the highest temp. Set a Taco RMB for the lower temp and so on. Use odr on the boiler and the odr of the RMB. It works quite well and everything modulates.
  • Weezbo
    Weezbo Member Posts: 6,232
    i have been practising Gomoku the last few hours ....

    and lost track of the time of day....

    i like the idea of a RMB too.. Mike made a good point though...the panel rads do not behave quite the same as the slab on grade emmitter.
  • Nick S
    Nick S Member Posts: 62
    Vision 2

    Have any of you guys tried the Munchkin Vision 2 controls for an application like this? I've always wanted to try it, but the chance hasn't come up yet. Of course I think it only works with the Munchkins and probably not the Knight?
  • Steve Gates_3
    Steve Gates_3 Member Posts: 27
    done that

    Have used Vision 2 twice with a t-50. Works. Monday I'll fire up a t-50 with the RMB. Why? Priced it out. Installs faster. Wires easier.

  • Tekmar 423. Capable of sensing DHW tank temp and satisfying it without going into priority or high output unless its needed.
  • big willy
    big willy Member Posts: 92
    knight rep

    talk to the knight rep. The local rep told me with the right adaptor and software you can program the knight to do anything but wash your car. I know that all the knights have the HWT set at 180deg from the factory but with the software and adaptor you can change it to what ever you want. You can also change many other things about the way it runs but this really aplies here.
  • Kevin Pulver
    Kevin Pulver Member Posts: 67
    Mike, I'll get the info and be back tonight

    Yes, it's about as you described. I don't have all the info at my fingertips, but I'll get it and be back tonight.
    Thanks, Kevin
  • Mike @ Capco
    Mike @ Capco Member Posts: 4
    alternates for turning down temps for radiant without sparing

    cont'd energy effieciency.

    How about a Tekmar 360 mixing control running a Buderus mis station, all of this for about 1000 bucks your cost. Or, a more affordable alternative is a Taco I Radiant mixing valve. It is about 230.00 your cost for a Taco I Radiant Mixing valve and the cost of either a thermostat to operate it which will snap it off if you go to overheat or a permanent mix demand with outdoor Warm weather shut down. This will keep the knight running at it's lowest temps. Yes, the Knight has it's one design temp but it also has a thermostat contact. So, you would set your Knight for the high temp heating design temp at whatever your outdoor design temp is and then the Tk 360 or Irdaiant does the Low temp.

    What part of the world are you in? Mike@capcosupply.com
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