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New Lochinvar Knight Questions / Concerns

2001_2001_ Member Posts: 8
Second time typing this so it's going to be shorter than the original which was lost somehow...

We had a new Knight KBN 211 installed two weeks ago. The house is staying warm at 68, however I have two concerns with the system and its installation.

Heres some quick info about the house and system first. ~4100 sq ft. 1920's Brick / block / plaster / concrete floors. No insulation at all and the original windows. Original 27 radiators and piping over three floors as a single zone. Original system in the house was coal, the Knight is replacing a 50's cast iron boiler, BTUs were 266k I believe, may have been 290k.

#1. My dad and I are concerned that the boiler is piped incorrectly. I will add pictures below but first will try to diagram and explain. The system return line dumps into the primary loop prior to the system supply line. Very roughly, without any valves, gauges, checks etc. it looks like this

Boiler Outlet ---> Capped DHW ----> Capped DHW ---> System return --- > System Supply ---> Boiler Circ pump ---> Boiler Inlet

In our opinion, this is cooling the boiler output water with the system return water before it even has a chance to get out to the system supply. So instead of 160 degree water going out into the system, that 160 water is mixing with the the system return which is cooling it to whatever temp. before it even gets to the radiators.

Boiler circ pump is a grundfos super brute set to high and system pump which is on the return is the grundfos equivalent of the Taco 0011, also set to high.

#2. The system cycles a lot. At 97 run hours, there have been 595 system cycles. It seems like the boiler will run for 15 minutes, rest for 10, and then repeat that. Now they have not been back out to program the boiler yet, but this still doesn't seem right. The thermostat calls for heat even though its already 68 degrees. My uneducated theory is that this relates to issue #1 in the radiators aren't getting that 160 degree water to begin with so they are cooling off much quicker and the temperature in the rooms drops much quicker.

Those are my basic concerns, I am going to add the pictures below, but if there are any details left out or pictures needed I will be happy to provide what I can. The house is warm and comfortable, but I am just concerned that the Knight isn't running efficiently and/or as it is designed to run.

Edit: The pictures are coming up way way too big on the message board, let me provide links instead

shows primary loop piping

system and expansion tank piping


  • ZmanZman Member Posts: 3,517

    Can you post a picture from a bit farther back?

    If you don't have the space a drawing would help.

    What are the copper pipe sizes?

    This is a converted gravity? How big are those pipes?

    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • 2001_2001_ Member Posts: 8
    edited January 2014
    picture attempt

    Ill get the picture up in a bit..

    Copper is 1 1/4 in.

    Supply pipe and return both get up to 4 in. in the boiler room but get smaller in the rest of the basement. Definitely down to 3, don't think any get down to 2. I can do a full check if thats important.

    My dad and I are pretty positive its converted gravity as we know there was originally a coal burner in there when the house was built in the 20's
  • Steve WhitbeckSteve Whitbeck Member Posts: 669

    If it is piped as you say it is not piped right.

    It should be house return, boiler return, boiler outlet supply, air separator, pump and then house supply. The domestic indirect tees should come off of the boiler as a separate loop.
  • paulpaul Member Posts: 91

    is that ball valve on the closely spaced tees suppose to be off and are those same pipes that rise first from the close space tees have the black grundfos pump on it?
  • 2001_2001_ Member Posts: 8
    new pictures


    Here is the new picture, I edited one to add color because I think it is difficult to see some of the piping from the angle

    Yellow is the boiler loop

    Green is the house supply

    Red is the house return

    Black is the DHW loop, currently capped, was piped for possible future unit

    ( , non colored)

    Steve Whitebeck

    I believe you are correct, could you look at my new picture to confirm ? Thanks


    That ball valve is on one of the capped DHW lines which I believe are the close tees you are mentioning; in which case no, the black pump is on the house return
  • 2001_2001_ Member Posts: 8

    I'll add a few observations (that may not matter anyways if the system is plumbed incorrectly)

    When the system cycles it gets up to the set point 160 degrees and begins to turn itself back from 100%, it gets down to the low 90%'s before switching off. I believe when it switches off it is the theromstat ending the call for heat rather than the boiler switching itself off. The difference in temp (delta T ?) between inlet and outlet, when at 160 is typically 34 or 35 degrees.
  • seabee570seabee570 Member Posts: 89
    edited January 2014

    It is hard to tell from the pictures about the piping,but the return as you sid may not have to be piped as it is as this is a condensing boiler? was a heat loss calc done? one thing looking at the super brute specs is that it seems to be a little for your application. lochinvar specs;T/HD Minimum Pipe



    Grundfos TACO B & G Armstrong

    81 7.5 24 1" UPS26-99F 0011 NRF-36 E7

    106 9.8 27 1" UPS26-99F* 0013 NRF-36 E11

    151 14.0 20 1" UPS26-99F 0011 NRF-36 E7

    211 19.6 29 1" UPS32-160 1400-50 PL-55 E9*

    286 26.5 15 1-1/4" UPS32-80 1400-20 PL-36 E11

    look at 211 line-it calls for a taco-ups32-160, which is larger than the super brute.

    the super brute specs are for a 20 degree delta t,and you are seeing 35 degree delta t. also on the lochinvar specs,the pump specs are for 1 inch pipe. if it is 1 and 1/4 pipe,you may have to go with the next size up pump.

    the install looks nice,but with a gravity conversion,the larger old pipe sizes can cause lots of flow problems. is the boiler set up for out door reset?
  • M LaneM Lane Member Posts: 123

    That on Dan Holohan's site no one has mentioned the pump being on the return. It is always most optimal to 'Pump Away'. I would have have the house pump just downstream of the expansion tank, and fed the make-up water into a tee between the air eliminator and expansion tank. The closely spaced tees from the primary loop would be upstream from the tank, 1st stop on the return. Make sure the flow of the primary loop flows opposite of the direction of the secondary loop. Then with multiple branches going out supply and coming back in branches on return to pipe them 'first in, last out'.
  • 2001_2001_ Member Posts: 8


    The super brute is just for the primary loop, the other pump is the UPS26-99F I believe. Do you still think this would be an issue ?

    It is set up with the outdoor reset, however it has not been programmed yet.


    I don't quite follow your whole post, but you would have the system pump on the house supply after the expansion tank, right ?

    Could an easy fix to this be cutting the current house supply at the primary loop and capping in. Then use that first capped DHW tee that is currently very short and pipe that to the expansion tank / air eliminator. That way the house supply would be right after the boiler outlet on the primary loop, as opposed to after the house return. I suppose the pump could then be put after the tank, right before the house supply splits into two.

  • seabee570seabee570 Member Posts: 89

    the info i posted came from lochinvar.

    if you have the ups26-99f,it is listed for use on the two smaller sized boilers.

    06 9.8 27 1" UPS26-99F*

    151-14.0 gallons per minute at 20ft/hd and 1" pipe UPS26-99F

    the 211 calls for a ups32-160

    211-19.6-gallons per minute at 29ft/hd and 1" pipe- UPS32-160

    you look at the ft/head and gpm,and i think you need the one lochinvar specs,and if you have 1 1/4 pipe with those smaller pumps,this could be a problem.
  • RobGRobG Member Posts: 1,850

    2001, you are correct, from the closely spaced tees, the system supply water should be piped before the system return water. As well, the system pump should be on the system supply, after the air separator and expansion tank. there should also be a wye strainer in system loop (there may be, but I can't see it in the pix). your indirect water heater stub outs should be on boiler side as well. It looks like your installer did not look at the piping diagram in the installation manual. A shame, it is very easy to do correctly the first time, but a pain in the butt to do over. Show him the instalation manual piping diagrams. Don't let him get away with saying "that's how we always do it".

    Good luck,

  • Wethead7Wethead7 Member Posts: 170

    I would have the flow check at the boiler removed with the recipe. It may cause enough head pressure to worsen your current problems. I would also recommend the pump for the house piping be moved near the expansion tank( The point of no pressure change). The preferred arrangement it point of no pressure change in to the pump. Your piping could be a bit small for 221,000 btu's I would like 1.5" or larger.

    You could limit the maximum firing rate. This would cut down on the cycle times. Also those old coal gravity systems tended to only need 140f at the most. Your problem could be oversized boiler as well. Good luck I hope things turn out well.
  • M LaneM Lane Member Posts: 123
    edited January 2014
    2001_ Wrote:


    I don't quite follow your whole post, but you would have the system pump on the house supply after the expansion tank, right ?

    Could an easy fix to this be cutting the current house supply at the primary loop and capping in. Then use that first capped DHW tee that is currently very short and pipe that to the expansion tank / air eliminator. That way the house supply would be right after the boiler outlet on the primary loop, as opposed to after the house return. I suppose the pump could then be put after the tank, right before the house supply splits into two.


    Open up this link for the installation .pdf. Scroll down to page 32 (35 on the Adobe scroll button). it shows what I was saying. This is how these systems should be piped.
  • 2001_2001_ Member Posts: 8

    Thanks for the replies everyone

    Based on the responses, I made another colored overlay of the easiest way they could repipe it to make it per the installation diagram.

    I think similar to what I mentioned before, the unused/capped DHW closest to the boiler outlet would become the system supply. The current system supply would be capped for a future DHW return. The house supply pump would be moved to after the expansion tank.

    Going by that on the primary loop it should be... boiler outlet --> house supply --> capped DHW supply --> house return --> capped DHW return --> boiler circ pump --> boiler inlet

    I think I will worry about the cycling and outdoor reset programming once the system is piped as it should be

    thanks again
  • SlimpickinsSlimpickins Member Posts: 314
    installation manual

    Both pumps should be moved. The primary needs to be pumping into the boiler, move it to the other side. The secondary needs to pump away from the exp tank as you have it it green. Moving the primary pump to pump into the boilerwill ensure the primary loop and secondary loop will flow against each other at the closely placed tee's. Make sure the make up water is tied into a tee below the exp tank. The DWH tee,s need to be on the primary, one in the supply, one on the return. Really, all the contractor needs to do is read and look at the pictures in the installation manual. The pump selection info is there too. You just need to do a bit of math to figure out the secondary pump size.
  • 2001_2001_ Member Posts: 8
    edited January 2014
    more questions

    Hey all, the system has been repipes and the system pump moved to the correct location. I'm now going to observe the boiler for a few days to try to figure out the best settings for the outdoor reset. If anyone has any input on that now , it would be great to hear.

    Anyhow, the question I have right now is: is there a max delta t you don't want to go over with these boilers. While the boiler is reachong its setpoint currently, the delta t is typically 35 with both pumps on high. With pumps on medium the delta t reaches 40. From my reseach Im assing the delta at boiler is so high because my 27 radiators draw so much heat from the circulating water. Is there an ideal temperature that cast iron radiators should reach ?

    I still have a lot of reading and research to do...


    Also, setting the honeywell thermostat menu option 5 to value 1 fixed the short cycling, it typically fires up once, no more than twice an hour
  • Steve WhitbeckSteve Whitbeck Member Posts: 669
    Boiler temp

    With cast iron baseboard or stand up radiators the max boiler temp USUALLY only needs to be 160* F.

    I would set the minimum boiler temp at 120* at 68* outdoor temperature, 160* max boiler temp at 5* ODT, And 68* warm weather shut down.
  • gennadygennady Member Posts: 680
    edited January 2014
    design day water temperature

    Radiators and baseboards are rated based on average water temperature. With delta T 20F, entering water temperature 160F, we have 150F AWT. with 180F entering WT we have 170F AWT. Looking at Governale gov-free radiator we see that btu per square foot of EDR will be 150 for 170F AWT and 110 for 150F. Now, there is a question if existing radiators will emit enough BTUs to cover heat loss at 160F entering water temperature. Also we have to consider that piping is not insulated and probably there never will be 160F at radiator.
    Gennady Tsakh

    Absolute Mechanical Co. Inc.
  • 2001_2001_ Member Posts: 8

    thanks for the replies.

    Steve, with those settings /  that curve, the boiler will run at 100% until the call for heat ends at the thermostat. It will not reach the high setpoint (140's for high 30's I believe last night) that is being calculated by the boiler prior to the heat call ending.

    With the system pump on high and boiler circ pump to medium I am seeing a 35-39 deg delta T. Setting both pumps to medium will get me to 40 deg delta t. Both pumps to high will give about 28 deg delta t. These begin to drop once the boiler reaches setpoint and begins to scale down.

    Comments ?

  • Steve WhitbeckSteve Whitbeck Member Posts: 669

    Sounds about perfect to me. I would put the pumps on high and the settings I posted. The ideal system would turn on and run constant to maintain your desired temperature until it warmed up outside.

    I have always run those settings with cast iron without a problem. If everything is right it should do the trick.

    I would rather have a lower delta T AND lower boiler supply temperature.

    Having a low return temp is only good if you can have a low supply temp also.

    It is the supply temp that is relative to the overall efficiency.

    Low return temp but 180* discharge temp will net about 87 to 89% efficiency.

    Slightly higher return temp but 160* supply temp will net you 92 to 93 % efff.
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