Lochinvar NKC150N - DHW High Temp Issue
Hi,
I have 2 Lochinvar Combi Boiler NKC150 N installed in my house, each of them with 2 zones.
I have issue with heating where the DHW in one boiler is going to high ( 170-175 degree when the DHW set temp is 125 and the DHW Max Temp is 130 ) and of course the house is not getting warm enough. More colder is outside more "cold the house is" !
In this boiler, that heat the 1st floor is biggest issue ( this part of house need more heating because is more expossed to cold). Here the water flow at pumps is always 3GPM ( and sometimes lower) in both zones.
To many times the boiler "Lockout" because is overheating.
When I open the shower/kitchen/sink hot water I can see that water temp is to high and in that moment the DHW on boiler go down, even 58-60 degrees.
The 2nd boiler, that heat the 2nd and 3rd floor (need little less heating because is less exposed from cold) the DHW is getting more higher than set temp but nothing crazy, max 145 degree. At both pumps of this boiler the GPM is going up and down from 4GPM to 3GPM.
The water line go first at 1st boiler that pumps show always 3GPM and has bigger issues with DHW and after connecting with the boiler that pumpw show 4GPM ( I don't think is water presure from system I mean).
I replaced diverter valve and the flow sensoe but the issue is the same.
I realized this issue only 2-3 weeks ago when it was extremely cold and not sure, when "it started".
I am trying to find a solution but not sure what is causing this.
Thank you,
Comments
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Have you called tech support? If the unit is still firing on constant DHW call when that far above DHW setpoint, there is most likely an issue with either the diverter, flow sensor, or the control board. If the flow is very low or is fluctuating, it may simply be unable to react fast enough. With that said, the factory HL is set much higher than that so it should not be kicking out on ARHL until 190*+. Looks like you have a multitude of issues here but finding out what the actual flow is while this is occurring might help narrow things down. If, for example, you have a shower and sink both running wide open hot at the same time, does this same thing still happen or only when the faucet is on by itself? Space heating will be turned off while there is a call for DHW, so that may be a part of your cold house problem too.
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I called Lochinvar support and they sugested to replace Diverter Valve and Flow Sensor. Just replaced those but same issue. Meantime I am waiting my contractor to come and check it.
My boilers have almost 2 years installed and this started only 3-4 weeks ago, when was really to cold, before I didn't realized anything and heating was fine. Maybe issue was but I was not feeling it.
One day before plumber replaced heating and water piper in basement, I am doing finish it and he replaced those and installed new ones inside walls and beams, boilers he only shut down and turned onn when he finished. Not sure if something happened that day "or was just casuality that was very cold next day and this happened". We followed all the pipes and they looks good, not mixed heating with dhw pipes.
Shower, sink, in same time? Didn't understood this. DHW is high all the time, more I set up the Heating Temperature more the DHW go up.
When I open 1 tab, doesn't matter, shower, kitchen or sink than the DHW temperature in boiler go down, I think because inside "pipes is heating water and when open the tap its goes out".
Thank you,
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which mode are you running for DHW?
I think in that model you can run cold start which takes longer to get hot water, or the always hot mode, where the boiler always maintains temperature
Could the dhw settings have been changed? Or reset was hit and they went back to factory default settings
I write down all the settings in the manual as I input them. Maybe just run through all of the parameters again
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream0 -
From your screen shots, the DHW icon is not lit up which means there's no call for DHW, but it's still high DHW temperatures at your faucet. Something is screwy.
Does the red light on top of the flow sensor turn on when you turn on a hot water faucet and then go out when you turn the faucet off?
8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour
Two btu per sq ft for degree difference for a slab0 -
Hot_Rod , settings are all set I believe, because I set those over the phone with Lochinvar assistence guy, DHW is 125 and Max DHW is 130 , i set the temp for cold days and warm days also. I also set the DHW temp on 60 ( lowest possible) and still the temp there go very high. I open the hot water tap in that moment and after hot water in pipes went off, no more hot water was coming on, only cold ( normaly this, because the set temp for DHW was 60). Maybe is something at controll panel/electric controll panel thats wrong, and this happened from electric, we shut down and turn on boiler to many times and "maybe shut down electricial without turning off boiler".
Alan,
I just tried that and I don't see any light going on or off at Flow Sensor. Sure that is light in top of the flue wsensor?! I replaced that yesterday, same with diverter valve.
The only light that goes onn when I open hot water faucet is a light down in boiler that its goes off when I close the hot water faucet. Maybe is light that show "boiler is running". I did photo when the faucet was open.
Thank you,
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The DHW is only heated when there is a call for DHW. Water temp when there is a thermostat call for space heating is irrelevant to the DHW temp. A sink will have less flow than the sink and shower together, so if you turn off the thermostats and open just a sink versus the sink and shower together, what happens? If somebody was messing with the space heating piping, it's probably airlocked which is what's causing the high limits and cold air temp. There isn't anything wrong with the boiler, if that's the case. The flow sensor is down on the exchanger at the bottom under that steel bracket, not the temp sensor you show in the first photo at the top- just FYI.
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This is the light I’m talking about and it looks to be on.
The other thing to check is the low voltage circuit board - the large one behind the metal cover. Turn off the power, remove all the molex plugs, take the circuit board off and check the back to see if there are any burn marks or irregularities. If so, replace the board. I just did this yesterday. It's not that hard.
8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour
Two btu per sq ft for degree difference for a slab0 -
Alan, that light that is in photos goes onn when water is open in sink or when ever. And it went off when the water is "closed/shut". I Checked this when you commented in morning.
Latter I will check the circuit board if something is there.
I thought the Flow Sensor was this in photo that I marked with blue. That was replaced yesterday, together with Diverter Valve.
Thank you for all your help.
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Your blue mark looks to be flue sensors to me, similar sounding words but different functions. Flow sensor will sense flow on the water side, flue sensor will measure temperature of the flue gas
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Groudup,
Right after the day that we replaced some heating and water supply pipes I noticed this issue, not sure if is connection or just I found this that weekend because hapenned to be very cold. I shut the water/valves and let water running for minutes to remove all the air leaks if were and I don't think is that the issue, I follow the pipes and baseboards and they seems hot in same level everywehere.
If I turn off the thermostats and open the hot water on sink, the water in sink is normal hot and the DHW temp is going in normal level at boiler. Soo something is coming "from heatint part".
Will check the flue sensor agaian, I thought the flue sensor was the one on "exhaust air pipe", even that didnt made sense when I saw. It mean that flue sensor is this with blue under metal plate with light?
Thank you for help
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That - what you have circled in blue - is the flow sensor.
8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour
Two btu per sq ft for degree difference for a slab1 -
Thank you,
Will check that next step and the board.
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Thank you
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So what's actually the issue here? You say all baseboards are hot and you have adequate DHW. Right? But also state that the house is cold. Hot baseboard and cold house don't go together. HL is almost always due to lack of flow, which if they were messing with the piping and then immediately afterward you started having high limit and cold house problems, I'd bet my paycheck on either an airlock or a closed valve.
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Hi,
The baseboards are warm/hot but not enough to warm the house. This week for example that is cold the temperature inside can go up to 68F in middle of the day, morning or overnight less than that ( thermostat is set at 70). Couple of days ago when was warmer the temperature inside reached 70. Before unit worked good and reached without problem 72-74 degrees. I replaced also the thermostats just in case but is the same.
What I see is that "heating water is going into DHW pipes", not sure why, more I increase the Space Heat Temp on boiler more higher DHW temperature go. I checked the pipes and valves and they looks good. Guys that replaced pipes "removed the air when they finished", I also did that myself latter and I touched all baseboard & pipes in basement and they seems all same temperature.
I also set the DHW temperature on 60F, lowest possible on boiler and still when I turn onn thermostat the DHW temperature went 150F-160F. In that moment I opened the shower or hot water in sink and if the heating was working was hot water coming, but if I turned off the thermostat than hot water stoped coming from sink/shower tap.
Someone suggested maybe electric control board has something wrong, from shuting down boiler something burned there.
This is my last "idea to check".
Thank you,
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Yeah, that "someone" was me. Check the back of your low voltage circuit board like I described above. If that looks OK and if you stay connected with us, we'll move on to the next thing until we figure it out. That's the way it works here.
8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour
Two btu per sq ft for degree difference for a slab
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No matter what you have DHW set for, when it sees the flowrate the valve switches position. At that point The hot water from the boiler flows through the DHW heat exchanger, the boiler water is already hot because it was heating your house, too hot to produce the temp DHW you have set. now that heat transfers to the domestic water, overtemping your domestic for a period of time until the water in the boiler cools off enough that it can't keep up with DHW, at that point the boiler begins its ignition process and you probably also get a slug of cold water. You need a mixing with a combi boiler when it is running high tem space heating.
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I've seen many of these Lochinvar combi's and none of them have mixing valves on the DHW. Does Lochinvar provide them with the boiler? I know Triangle Tube did when they sold the Excellence boilers.
8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour
Two btu per sq ft for degree difference for a slab0 -
Doubt they would supply them, too expensive. It's one of those deals where, unless a company sees a liability issue, they would just put it on local codes to require one. first time I saw this was on a viessmann combi running max temp for baseboard, kitchen faucet would output 140-156 DHW for a lot longer than you would think after the boiler ran for heating calls, eventually it would calm down but not near as quickly as I would have though. Definitely was a burn hazard at this place. Some brands seem to have them as "required" and others either say recommended, or "where code requires" The reality is that if the combi does a really good job of transferring heat to the DHW, it can and often will overtemp DHW when the boiler water is already sitting at or near 180 and a DHW call is initiated. Once I saw that happened I had an existential crisis briefly thinking about all the other jobs I had sold without one, I just assumed the temp sensors would act as a safety as well, in hindsight I don't know how they could have!
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I know a few states require mixing valves on all DHW devices. Tanks, tankless, indirect, combi, etc. I don’t know how well that gets enforced? It seems like a good liability protection, regardless.
Just know any moving valved used in DHW will need periodic maintenance. In some instances yearly, maybe bi yearly.
Install it with that in mind. Isolation valves are an inexpensive upgrade.
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream0 -
Hi Alan,
I just opened the electric control board and for my eyes was everything ok. Not sure if from photos you can notice anything?
I did a small test: I turned off the heating on both zones and in boiler screen I saw this:
After I opened the sink hot water in house and after 1 minute the DHW went down at 110F. I let the hot water on sink about 10 minutes running and in this period the max temp of DHW went 136F and in that moment boiler stopped working ( DHW set temp is 125F and Max DHW is 130F).
After I turned onn the heating on both zones and still the DHW temperature was staying in those temperatures.
When I turned off the hot water in sink, after less than 5 minutes the DHW temperature went 167F.
This I had noticed even before, DHW temp went down after someone started using shower or turning on sink hot water.
Not sure whats going on here.
Thanks again for helping !
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So again, what is the actual problem? DHW temp will always read within a few degrees of what the outlet temp reads outside of a DHW call. When you open a faucet, it stops the SH call in favor of the DHW call which drops the temps. If your flow isn't high enough (such as just one sink faucet), the boiler can't modulate down far enough to avoid overshooting so it needs to cycle. That's how every combi boiler works. I'm not seeing the issue here.
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Problem is that DHW temperature is going "very high", even above 170F-175F ( DHW set temp is 125F and Max DHW temp is 130F). My home thermostat dosn't go more than 68F after this issue started, before its goes very easy 72F ( I set 72F my thermostat ussually).Even in sink/kitchen or shower people notice that the water is more hotter than normal, specially first seconds because after it goes little down, I assume because in pipes is water that supposed to be"for heating".
I have checked 4-5 times pipes and they looks ok, not mixed together.
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The issue is with the right boiler in photo, if you can see the blue pipe that is supplying boilers is coming from right, first supplying the right boiler that has issue and after the other boiler that, is showing higher DHW but not crazy.
Left boiler at circulating pumps show 3GPM - 4GPM but right boiler both pumps shows 3GPM max.
Why presure is 4GPM on left boiler and 3GPM on right boiler ? When right boiler get the water "first".
The only thing that changed "with the water flow is "we added 1 kitchen and 1 bath in basement", but pipes are tapped and not in use because we are still under construction .
Heating in basement will be with Mini Split System and we have no plan to add anything at boilers.
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GGross ,
One plumber just told me that "is no place where to install mixing valve because DHW water line and Space Heating Water lines are totally separated and they comes directly from boiler.
He suggested today that probably air was not removed properly and somewhere in system, boiler has still air somewhere and recommeded to do again it, "bleed air".
He told that somepeople "remove the air from bottom of the boiler and that is wrong place", and day that they replaced pipes, they bleed the air from return line and after did same from the "line that is down of boiler and has the drain pipe with the presure valve attached". I marked at photo down.
Tomorrow someone will come and do this again. Hope properly!
Thanks
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As you were already told, the DHW temp will always read similarly to the outlet temp during a space heating call because that's where the sensors are located. As soon as you open a fixture, the DHW temp on the display drops, right? That's exactly what it's supposed to do. The GPM has nothing to do with anything and means nothing- it's simply due to the required flow through the emitters- no two systems are ever the same.
The quick burst of hot on a DHW call is because the exchanger and water is already hot from the space heating call, and since you don't have mixing valves, that hot water gets sent out to the fixture. Add mixing valves (as required by Lochinvar for this very reason) and stop looking at the display. There is nothing wrong with anything, besides the lack of mixing valves.
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I think the same,boiler itself doesn't have any issue. The DHW temperature can go higher than set, but not 50-55 degrees more, its to much and boiler is going into Lockout, more than 10 times only today. And the temperature inside apt is not going more than 68F when before went very easy 72F. And this summer I replaced basement windows and some air gaps that were, soo insulation is improved and should be more easy for it.
Tomorrow contractor that installed them will come and check, hope it will resolve it.
Will keep you posted. Thanks!
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the installation manual mentioned the need to install a DHW mix valve, field supplied.
The red and blue pex piping above the boilers should allow you to easily cut in mix valves? The do not need to be under the boilers should allow.
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream1 -
The lockout is directly related to settings and/or lack of flow- as you were told from the beginning. Factory AHRL setpoint is (I think) 190 or 195 so if you're hitting it anywhere below that, somebody messed with it and it needs to be pushed back up to factory setting.
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respectfully your plumber doesn't know what they are talking about. The water is in fact separated, but ask them where they think the heat for DHW comes from? it comes from the boiler water which transfers heat to the domestic water via a flatplate. You need a mixing valve on the DOMESTIC side piping to control the outlet DHW temp, because when the boiler is sitting with 180+ water and it circulates through the flat plate the DHW will become overtemped.
Getting more air out of the system will be a good thing, but you also need a mixing a valve
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Yes,they are in that level, Auto is set 190F and Manual is 195F.
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Yes, "is easy to install" because we can access them, above or even on bottom, where ever is needed.
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Thanks ,it makes totally sense and explain the issue that I have.
I understood that "yesterday guy" was not very accurate
I will definetley "install mixing valves as fast as I can", hope contractor that installed those will come today or tomorrow at least.
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Hi all,
My contractor that installed boilers left 1 hour ago, first time that he came to check after the issue started. He checked everything and bleeds the air again, and this time I think was done properly.
Both boilers now are better, no more overheating and boiler that was going into Lockout is not going anymore even that I increased the Space Heating Temp in 150F (before was set 140F because it went very fast in overheat if I set more).
In the boiler that had issue before with overheating/lockout the DHW temp is going 145F-150F (set temp 123F and DMH max Temp 125F ). Other parameters looks good. In apt I am not feeling any improvement in heating.
I asked him mixing valves and he told me "in combi boiler the only thing they will do, will keep fixed/same temp in faucets inside house but they will not affect "the boiler efficency or the heating part".
Thanks,
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It will take more than an hour to see effect on heating.
And yes, that's exactly what the mixing valve on DHW side will do, and that's exactly why it was suggested to install here. If it was my house, I would install mixing valve (I have young kids).
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For the 4th time, STOP worrying about the DHW temp reading during a space heating call. That means nothing whatsoever- just ignore it.
As for the mixing valve, again as you were told multiple times, they are required by Lochinvar and will maintain a constant outlet temp to the fixtures. You said you were feeling fluctuations in DHW temp, which would be fixed by installing mixing valves as required by Lochinvar.
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