Welcoming advice on Lochinvar Noble combination Boiler hydronic baseboard heating system performance

centralMA

Hi,

I recently moved into a house with a new Lochinvar Noble combination Boiler. This is its first winter.

The house is 1500 square feet and hasn’t been heating up very well. It is consistently struggling to get up to 68F by night time after raising the thermostat from our 59F overnight to 68F when we wake in the morning. It has hydronic baseboard heating with different zones for the first and second floors.

If anyone is willing to take a look and see if they think one of these settings are causing problems, that would be awesome.

Installer Outdoor reset menu Settings

SH SETPT (Cold day)
170F (this was set to 125F when we moved in but we have since raised it to 170F)
MAX SH SETPT
185F
OUTDOOR TEMP COLDEST (pg.65)
10F
WARM WEATHER SHUTDOWN
72F
SHIFT RESET
0F
OUTDOOR TEMP - WARM
75F
SH SETPT (WARM DAY)
100F


I am pretty sure the person who installed the boiler did not know about how to program these settings…

The house also needs insulation which we are working on, but I’ve lived in many New England houses without insulation, where the heating bill might have been high, but it was able to heat to 68 degrees…

Thank you!

GroundUp

It's no fault of the boiler. If it's piped correctly, the water temp is too low for the amount of radiation- you need a higher water temp or more radiation.

bburd

I think the main problem here is that if you have a condensing boiler, outdoor reset is not meant to be used with temperature setbacks. Outdoor reset operates most efficiently, and keeps the boiler in the condensing range most often, if you leave the thermostat set at a steady temperature. It’s meant to supply heat to the house at the rate at which it’s lost, not to increase the temperature.

Non-condensing boilers sometimes have a morning boost mode that allows set back to be used with ODR, but that requires higher supply water temperatures in the morning, which defeats the purpose of having a condensing boiler because it generally won’t condense at those higher temperatures.

EBEBRATT-Ed

For starters a thermostat setback when using outdoor reset of 10 degrees is too much. At least reduce your setback to 4-5 degrees. Your wasting fuel trying to reheat the house. Don't forget. when you reduce the set point it's not just air temp you lose the walls the floors the furniture ceilings all lose temperature and that is a lot of mass to reheat.

There may be other issues with the install set up. If you in Ma try @Charlie from wmass or @GW you can PM them

Charlie from wmass

How many lineal feet of baseboard? What size Noble? Settings are off kilter.

centralMA

bburd said:

I think the main problem here is that if you have a condensing boiler, outdoor reset is not meant to be used with temperature setbacks. Outdoor reset operates most efficiently, and keeps the boiler in the condensing range most often, if you leave the thermostat set at a steady temperature. It’s meant to supply heat to the house at the rate at which it’s lost, not to increase the temperature.

Non-condensing boilers sometimes have a morning boost mode that allows set back to be used with ODR, but that requires higher supply water temperatures in the morning, which defeats the purpose of having a condensing boiler because it generally won’t condense at those higher temperatures.

Ok, interesting. It is a condensing boiler.

Charlie from wmass

outdoor reset and setbacks work fine together as long as the settings take this into account and the expectations are realistic.

centralMA

Okay,
I am not sure how many lineal feet of baseboard there are. It was installed by the previous owner/renovator who is now unresponsive.

The information sticker on the unit says the “input rating” is 150,000 BTU/HR. I think that answers the “size” question?

Other info: it is natural gas fueled. It is “on-demand”. The Model # is NKC150N.
https://www.lochinvar.com/products/residential-boilers/noble-fire-tube-combi-boiler/

The amount of baseboard lineal feet doesn’t seem obviously inadequate, based on what I’ve seen in other buildings. I can see how that is potentially a source of the poor performance though

Thanks everyone

bburd

You can measure the “lineal feet” of baseboard heating element yourself. Only count the finned part, not the bare pipes. Ignore the length of the enclosure.

pedmec

I set my SH at 180 @ 20 degree outdoor. its gives a little more heating output. my max i put SH MAX @ 10 degree about the SH.

Your settings might work if your actually hitting your target temperatures. Your target temperatures will be in the brackets. you need to make sure your hitting the target for proper operation. If your target temperatures are being hit then you most likely will need to do a heat load calculation and determine if you have enough heating element, not baseboard. CONNECT ELEMENTS DETERMINE THE HEAT OUTPUT.

If your not hitting your target temperature make sure that the boiler is not being rate limited. With lochinvar combi's you can limit the heat output. This is done because you need to buy a larger boiler to handle the domestic hot water side which would not be needed on the heating side.

Charlie from wmass

Lochinvar boiler can be limited in fan speed if the heat load of the building has been determined to be less than the total available be to use of the boiler.

EBEBRATT-Ed

@centralMA

Surely you have a tape measure. Measure the total length of finned element as @Charlie from wmass & @bburb suggested. If your settings are off we need to be able to compare the boiler load to the size of the boiler to get the settings right

hot_rod

It would be nice to fine out you have enough fin tube that you could run temperatures below 180F even on design day. That gives you the opportunity to get into condensing mode more days. Return needs to be below 120F to start condensing. So 140-F swt running a 20∆t would get you there.
It is a big jump from 180 down to 120 swt for fin tube length required.

This journal details lowering SWT, and also a good explanation on how ODR works.
https://www.caleffi.com/sites/default/files/file/idronics_25_na.pdf

centralMA

Up until a month and a half ago I actually did not own a proper tape measure. I do now though!

There is 77 linear ft. 3 in. of copper fin tube in the baseboards. Thanks for the clarification on only needing to measure the parts with fins.

The house square footage, more precisely, is 1542 ft.

GW

Thanks for tagging Ed. I try to stick with the boilers I know. I don’t know Knight.

Anyway, I know boilers in general. 150000 boiler and 77 feet of baseboard? Dang- gonna short cycle badly. Maybe get a good sized buffer tank 

centralMA

pedmec said:

I set my SH at 180 @ 20 degree outdoor. its gives a little more heating output. my max i put SH MAX @ 10 degree about the SH.

Your settings might work if your actually hitting your target temperatures. Your target temperatures will be in the brackets. you need to make sure your hitting the target for proper operation. If your target temperatures are being hit then you most likely will need to do a heat load calculation and determine if you have enough heating element, not baseboard. CONNECT ELEMENTS DETERMINE THE HEAT OUTPUT.

If your not hitting your target temperature make sure that the boiler is not being rate limited. With lochinvar combi's you can limit the heat output. This is done because you need to buy a larger boiler to handle the domestic hot water side which would not be needed on the heating side.

Ok, thanks.
From the times when I have been at the boiler I think it is typically hitting the target temperatures in the brackets. I’ll track it more systematically over the next few days to get a better idea though

pedmec

Won't short-cycle. noble combi is a mod/com with 10-1 turndown.

hot_rod

77' of fin tube X 500= 38,500 BTU/ hr that fin tube can put into the space at an average temperature of around 170F

Next you need the heat load for the home. assume 25 btu/ sq. ft, puts you real close to the fin tube output.

You have a lot of nice functions in that control to ease the cycling.

First down fire it to maybe 45,000 (SH rate limiting). Maybe enable anti cycling see if that helps, as long as it keeps up on coldest days.
The step fire function can be useful. You just need to play around and find the right combinations.

I down fired mine, since my load is around 30,000. Step it at 15 minute intervals, ODR also.

Hot_water_fan

Oh you’re golden! You should be able to condense most of the winter. Use a smaller setback and the anti-cycling tips hot rod shared.

Charlie from wmass

As a central Massachusetts hime you will need more like 190 temp for the heat load on design days. Just a local observation. 

centralMA

Thanks hot_rod and all. I am starting to understand the interaction of low inlet temperature and condensing as well as ODR
It is nice to know what is going on better. I appreciate the insights and documents.

I am going to look this stuff over. In the end my best bet might be to get someone with experience and/or training to go over it with me in person and help fine tune it. Anyone interested in the job in Central MA, or has a recommendation for the area, feel free to message me!

On another note
It is wild that the advice here is to setback minimally. I feel like most of what I have read and the information I have received is to setback as much as possible; without offering any caveats. There seems to be a fairly strong consensus on the matter on this forum, but it is wild to me how that is not at all what I have read or been told in other places.
If I understand the conceptual logic behind it, once the settings are fine-tuned my system is designed to efficiently run just enough to heat the house up just enough. Large setbacks don’t compliment a system designed as such.

I'll start doing smaller setbacks.

hot_rod

centralMA said:

Thanks hot_rod and all. I am starting to understand the interaction of low inlet temperature and condensing as well as ODR
It is nice to know what is going on better. I appreciate the insights and documents.

I am going to look this stuff over. In the end my best bet might be to get someone with experience and/or training to go over it with me in person and help fine tune it. Anyone interested in the job in Central MA, or has a recommendation for the area, feel free to message me!

On another note
It is wild that the advice here is to setback minimally. I feel like most of what I have read and the information I have received is to setback as much as possible; without offering any caveats. There seems to be a fairly strong consensus on the matter on this forum, but it is wild to me how that is not at all what I have read or been told in other places.
If I understand the conceptual logic behind it, once the settings are fine-tuned my system is designed to efficiently run just enough to heat the house up just enough. Large setbacks don’t compliment a system designed as such.

I'll start doing smaller setbacks.

If you are bent that way, it would be good for you to learn how to make adjustments. It can take a few try’s to get things exact.

If you find a knowledgable service person, you could add the Conxus module that lets you or others watch and adjust remotely

Probably You Tube videos on that control and maybe some at Lochinvar site.

centralMA

I am finding this paper helpful https://www.nrel.gov/docs/fy14osti/61151.pdf
Measure Guideline: Condensing Boilers—Optimizing Efficiency and Response Time During Setback Operation

Hot_water_fan

Nothing is set in stone here - try 0,5, and 10 degree setbacks. Try different water temps. You’ll get it figured out eventually 

Charlie from wmass

Remember thermodynamics is thermodynamics. You can't get heat without some wasted energy. Deep setbacks are only useful if the recovery energy does not exceed the saved energy. Central heating is a modern comfort luxury we now treat like a necessity. Like indoor plumbing and washing our bodies more than once a year.

Jamie Hall

All the above is great stuff, and if you can get @Charlie from wmass to come and take a look, you'll be well ahead -- but he's really busy, and I think you can get things straightened out pretty well on your own.

On setbacks and the general stuff one reads and hears on the 'net and elsewhere. Remember two things: first, almost all of those recommendations for deep setbacks were written for houses with forced air heat, which is a little more tolerant of them and, second, they were written by people living in the DC metro area or southern and central California, who have absolutely no clue as to what a New England winter is like!

centralMA

Thanks again all.

Okay, now that I've known what to look for I have realized that my Delta T is in the range of 5 to 9 degrees F most of the time. At last check the outlet was 150F and inlet was 142F. I realize that at 150F supply temp even 20 deltaT with a return at 130F still doesn't help me much in the way of condensing. But it is the same pattern when it is warmer out and the supply temp of the water is down to 140F.

My current hypothesis is that the supply water temperature is not running through enough heating element and that's why the return temperature isn't going low enough to condense. I have 77 ft. 3 inches of copper fin heating element, but this is split into 2 zones. The first floor with 42.8ft and second floor with 34.4ft. So my hypothesis is that the house being split into two zones is messing with the ability of the water to shed enough Btus as it is going through each zone. But maybe I am dead wrong about that and the two zones are not an important factor...


FYI as far as setbacks go I am setting back 3 degrees from 68 to 65 and it is recovering fine and comfortable, so that is a win.

Hot_water_fan

To lower return temp, lower supply temp and/or decrease flow rate  .

hot_rod

Did you down fire boiler? I think the smallest Nobel combi is a 110 or 120. Your baseboard can only emit around 38- 40,000, with both loops running

Adjust the boiler”size” to better match the load, then tweak the ODR and maybe the ramp time periods.

You will only condense when the return is low, and on design days, you may still need 180f. So it will condense on start up for a few minutes and the days when the ODR can run at 130 SWT or lower.
Now that could still be a good portion of your heating season. Look at a 20 year temperature graph for your location to get an idea of potential condensing operation.

Certainly you could make it run in condensing mode all the time, but I assume you also want to be warm and comfortable 🤭

tim smith

Change the 75 degree at warm outside to 90. This will steepen your curve and give you maybe 10 to 15 degree warmer water at given Od temp. Also might change wwsd to 68 from 72. Maybe drop your temp at night a few degrees less. Baseboards in general have quite low output at cooler water temps. This should get you closer. Also on most Lochinvars we have a boost feature we can set so if in say 30 min we have not reached set point we can increase water temp 5 or 10 degrees, not sure on Noble, would have to look up.
Good luck

centralMA

hi
ok, so, because I don't exactly understand how to down fire this thing:

hot_rod said:

77' of fin tube X 500= 38,500 BTU/ hr that fin tube can put into the space at an average temperature of around 170F

Next you need the heat load for the home. assume 25 btu/ sq. ft, puts you real close to the fin tube output.

You have a lot of nice functions in that control to ease the cycling.

First down fire it to maybe 45,000 (SH rate limiting). Maybe enable anti cycling see if that helps, as long as it keeps up on coldest days.
The step fire function can be useful. You just need to play around and find the right combinations.

I down fired mine, since my load is around 30,000. Step it at 15 minute intervals, ODR also.

The heating capacity of my unit is 139,000 BTU/HR (The input rating is 150,000 BTU/HR if that is relevant).
If I am looking to down fire to 45,000, does that mean I need to adjust the SH rate limiting to 33%?
I got that % by dividing 45,000 by 139,000.
Am I wildly off base with this?

I can't find anything about a step fire function on the unit or in the manual or anything and am thinking it might not be something this unit has? I can't find anything about time periods either.

I can't discern how to turn anti-cycling on or off or how to adjust it. I think maybe i can't. I think it is on automatically though because after the boiler turns off (post purge) it displays "Blocked: anti-cycling" for a period of time and won't turn back on even if the thermostat calls for heat.


Side note: I just had the house insulated through Mass Save. The boiler is now cycling on/off every 4 minutes so I am hoping that down firing can help that. This short cycling was not a problem before the insulation.
From previous comments it sounds like a buffer tank might help. Using the setup we already have would of course be my preference

hot_rod

I think you mentioned you have a combi? I don't think SH limit is on non combis.

Try the set up wizard to get to the parameter. If not you need to use the passcode.
Correct the percentage of the output number, 139,000 btu/ hr.

45,000 sounds like a good number to shoot for.

Chapter 10 & 11 go through all the settings, examples and how to adjust them

You have anti cycling, but not step fire. Anti cycling is just a time delay between firing to help ease short cycles. Use with care, you need enough run time to cover the load.

Installer access from standby screen. The number 5309 is from the Tommy Tutone song, if you are from that generation. 867-5309 = Jenny Sorry I forgot her area code.


https://www.youtube.com/watch?v=6WTdTwcmxyo

centralMA

Yeah it is a combi.

Ok yeah i can access the SH Rate Limiting % setting to change it (defaulted to100%). I did know the code and now i will never forget it haha.

I realized that while i was in the basement watching lochinvar tv and tracking cycle times earlier today my partner was upstairs opening and closing windows while removing old window caulk, inadvertently corrupting my data.

So with the windows all closed my cycle time tonight (48 degrees outside) is a less dire 14 minutes off, 3 minutes on.

I lowered the SH Rate Limiting to 33% (this makes a lot of sense). It didn't end up changing the cycle times.

I don't know, maybe 14 min off, 3 min on isn't a problem? I don't think it's efficient to run for three minutes but only turning on and off 4 times an hour doesn't seem too bad.

Charlie from wmass

As a general note all Lochinvar boilers have an s h fire rate that they are combi or standalones.