Hi everyone,
I have a Lochinvar Knight (KBN080) boiler that was installed this past summer. It has an outdoor reset and as such seems to make its own decisions on how warm my house should be, regardless of my thermostat setting.
Today was the first really cold day that we had (14єF/-10єC) with lots of strong wind (40 mph).
My house temp had been steady at 22єC (72єF) since the heating season began, but today I came home and it was at 18єC (64.5єF) so I cranked the thermostat to no avail. My home is now 17єC (62.6єF) and falling. My thermostat is set to maximum right now, but my radiators remain lukewarm.
What gets me is my boiler reads: BLR:SH 20% RATE which tells me that it's modulating, and only firing at 20% of its capacity. I could be wrong on this, but if I'm not, I'm mad. It has not been above 20% yet that I can tell.
If anyone is familiar with this boiler, how can I get it to fire at a higher rate and heat my home? I can link to the installation and service manuals in PDF if it would help.
Thank you!
I can't get anywhere on Lockinvars website.
Maybe you can send the manuals if you them in PDF
Here's the IO:
http://www.knightheatingboiler.com/knight/pdf/KB-IO.pdf
This is the manual for the PC software, but it lists all the available parameters and such:
http://www.knightheatingboiler.com/k...pdf/KB-PCP.pdf
Probably just needs an upward adjustment of the colder end of the reset curve. This is a new installation and the installer might be able to just tell you over the phone which parameter to adjust. Or he should just come over. Chances are it's not at the default for one or more parameters.
Thank you xiphias.
Here is the link to the service manual also.
http://www.lochinvar.com/_linefiles/KB-SER-07.pdf
Yeah, something is definitely not set right, because the boiler is definitely running, just not heating enough.
Am I right in thinking that it's not modulating correctly, as opposed to just not being able to keep up with the demand for heat?
It sounds like a simple reset curve problem.
Wherever it is on the reset curve, in order to supply the specified water temperature, it only needs to run at 20%.
Changing the reset curve upward will increase the water temperature for a given outdoor temperature. That increased water temperature will probably get the boiler to fire at 20%.
Not familiar enough with the Knight control to say precisely what parameter(s) should be adjusted. A very quick glance at the service manual suggest that perhaps B1 is too low (see page 17). The default is 125F. Maybe try changing that to 140F. This should basically make the reset curve steeper. If it works, this is a quick fix only.
There are adjustments you can play with to move B1 and F1 (outdoor design cold temperature) around to change the slope of the reset curve. Just making it steeper may cause more cycling at warmer outdoor temperatures. And of course there's a ton of other tweaks that can be done to this control. Training and experience would help for all that.
Ideally, you'd want to take your heat loss calculation and compare it to the output of your radiation at various water temperatures to determine values for B1 and F1.
Say your design temp is 0F. Say your design temp heat loss is 50,000 BTU/hr. Say your radiation can output 50,000 BTU/hr using 140F supply water.
You'd set F1 for your design outdoor temperature (0F), and set B1 for the supply water temperature that gives radiation output equal to the heat loss at design (140F).
Okay, this (the calculation) is a bit more complicated than I thought it would be based on how I understood it from the manuals. However, I'm always willing to learn.
I did play with some of the F values (IIRC, F3, max air temp) (because the boiler would not heat my home when it was 60єF or above outside. I never did fix that problem before it got colder).
I know my design temp (5єF) and my design heat loss (40,000 BTU). What I do not know is my radiation output for the supply water temperature.
According to the display on the boiler, my current supply water temperature is 130єF. I know it's not high enough but I don't know figure out what it should be set to. (in other words, calculate B1).
Should I just call the installer or is this something I can do myself?
Thanks for all the help, I appreciate it.
For now, set B1 to 145 and see how it does.
Before going to bed last night my house was 15єC (59єF). Outdoor was -10C/15єF and windy. I didn't change the curve parameters, but I did change the SH SETPOINT in the user menu from 130єF to 145єF as suggested. I noticed that the firing rate went from 20% to about 35%.
When I woke up this morning my house was 17єC (62.5F). So before going to work I increased the setpoint to 155єF, and by lunch time the house was at a more comfortable 18.5C (65.3єF). I would like it to be back at 22єC/71.6єF.
It is a bit confusing how you can set the output water temperature in a few different places.
So apparently the water was just not hot enough. I do know that my last, very old, boiler would heat the water to 180єF (but it didn't modulate).
What I need to figure out is set the parameters in the new boiler to make the water hot enough to heat my home to the temperature I want in cold weather, but make the water cooler in warmer weather to stay efficient.
OK, so let's figure out the info you need to set the curve. First, what kind of heat emitters do you have? Cast iron radiators? Fin-tube baseboard? Other?
Second, do you have a heat loss calculation for the building?
This is my radiation system. I think it is the copper fin tube.
Yes, I have had a professional heat loss done. My design temp was 5єF and my heat loss was just a hair under 40,000 BTU/hr.
I increased the water temperature to 160F and outside it is around 20F now with less wind. I'm toasty warm now at 70F. Boiler says it's running at 35%.
i have same boiler and needed to make adjustments, too, for satisfactory operation.
the setpoint is the key to success: this is the temperature you (or the installer) instructed the knight to aim for, and when it gets close to the setpoint, it will modulate down the flame, since it figures its work is nearly done.,
as you have found out, there are many set point options. including which location it monitors,and the actual target temperature . Some adjustments you make are temporary, for that moment's heating cycle, some are permanent.
raising the set point will increase flame size, all else being equal. but all else is never equal.
i spent a lot of time studying the manual in more detail than i wished i needed to, and i think it's time for you to do the same. And it's not particularly well written or organized,either. good luck and happy studying.
Those are cabinet convectors. You are right that the elements are basically fin-tube, though.
How many convectors do you have, how wide are they, and do they all have 3 runs of fin-tube in them? And are they all open at the bottom to allow air to flow in and across the fins (they should be open). Is there a brand name on them?
Those fins are also pretty dirty. They would benefit immensely from a good vacuum and brushing. As NJ Trooper says, even a small amount of dirt and dust can really reduce the output.
Your design temp of 5 degrees F is the value to set for F1. But don't do that yet.
Once we get a handle on convector output, we can estimate B1 and adjust F1 at the same time.
When we get close, then we can also tweak the boost setting to backstop any poor estimates. But we're going to be well in the ballgame.
Can you get into the installer mode? Displaying and modifying F1 requires installer mode access.
msgale, yeah, I'm trying to study the manuals but keep getting lost. I found that things are not explained very well.
xiphias, I know, NJ has already lectured me about the fuzz. I've tried vacuuming them since the photo was taken but it didn't help much; I will need to get some compressed air or something and really go to town.
Most of the radiators have 3 pipes but the smaller ones have 2. I have a total of 9 convectors; 8 on the main floor and 1 in the finished attic. They are all open on the bottom. I cannot find a brand name on them.
I'll get their widths. Did you want me to add them all up for a total length of the pipe?
Yes, I know get into installer mode on the boiler.
An inventory of convector widths and number of rows in each should be sufficient.
a cheapie wisk broom (the corn kind holds up better than nylon) is pretty good for getting in between the fins. You can also cut/pull out extra dense bristles to give you just enough bristles to get down to the bare tube between fins.
Somebody really needs to invent a brush of some sort that makes it easier to clean them things... using an air compressor with a nozzle is the best way, but it sure does put a ton of dust in the air, and unless you spend the whole day and next week vacuuming it back up again, it ends up back in the convectors.
When I moved into this joint, I spent literally weeks... trying to get 40 years worth of dust outta them fins. The air compressor did actually seem to work best. First vacuum as much as you can, then with the vacuum running and the hose under the baseboards, bursts of air from the nozzle with the hose directly underneath seems to work best.
I've thought of spritzing them down first, and then using the air hose... with newspapers underneath... and dropcloths out about 4 feet or so... if the dust is wet, it won't go airborne.
Whatever, however, it is not a 'nice' job. Sometimes you find 'treasures' though... I found a postcard from 1951 from 'Aunt Jo'. Nice view of Asbury Park back in the day.
my setpoint is 179, set permanently, and the outdoor reset is turned off
Okay! Here is my inventory. I measured only the part with the fins on it.
1. 43, 3 pipes
2. 21, 2 pipes
3. 32, 3 pipes
4. 38, 3 pipes
5. 21, 2 pipes
6. 52, 3 pipes
7. 36, 3 pipes
8. 21, 2 pipes
9. 43, 3 pipes
@NJ - I think I am going to try the wisk broom method, since my radiators are hot all the time now. If it doesn't work well, I will probably wait until summer to try the compressed air, or maybe even your spritzer idea. (I would be afraid of cool water or that compressed gas warping the fins or something). The worst part I think will be removing those darn cabinets - they are almost impossible to get back on.
@msgale - I have honestly thought of doing that, since I like the way my old boiler would just heat to whatever the thermostat told it to; but then I think of all the money I just paid for this sophisticated energy saving technology and figure I should probably try and get it working the way it was intended.
OK, let's try this. Set
B1 = 180 Fahrenheit
F1 = 5 Fahrenheit
and see how it goes for a few days.
I looked up the output of a couple common cabinet convectors (Beacon-Morris SR-A and someone else I forget), and figured things a couple different ways.
With 180F water, you have a nominal total output of around 45-55k BTU/hr. (You may be on the lower end due to all that crud on the fins. )
So that means for your design temperature (5F) and heat loss (40k BTU/hr), 180F supply water should meet the heat loss with a bit of headroom to spare.
Assuming that you were on your way to getting the house back up to temperature with 155F water when it was 20F outside, after you set B1 and F1 above, the reset curve should pass through ~155,20. Which means that next time you have a 20F cold snap, the house should hold temperature. (FWIW, This is a reset ratio of ~1.7.)
What are the values for B2 and F4? Need to know this so we know the true slope of the curve and make sure the warmer weather performance meets your needs.
Okay,
I've set B1 (SH Setpoint User) to 180єF (was previously set at 160єF which is where I set it)
And F1 (Minumum Air Temperature) is now 5єF (was previously 24.8єF)
B2 (SH Minimum Setpoint) is set at 69.8єF
F4 (Minimum SH Setpoint) is set to 70.7єF
To be honest, I don't really understand the difference between the two.
Thanks, xiphias, for all of your help. It is appreciated. I'll try this setting for a few days, but it's been quite mild (mid-30's). We might go into the 20s on Wednesday.
Don't thank me yet!
What's F2 set at? The default is 70F, which should be ok.
Cold coming later this week. Should be a good test.
As you watch/feel what happens over the next few days, keep an eye on (+write down if possible) the space temperature, outdoor temperature, firing rate, etc.
F2 is 69.8єF.
I'll try to document these next few days. I haven't ever seen the boiler go above 35% for space heating. It's usually at 29%.
If the heat loss is 40k, and the boiler is 80k, it probably won't ever modulate above 50k. And because the heat loss is usually an overestimate, maybe not above 40-45k. So less than 50%.
Avatar, I assume you got your boiler problem under control. I have a Lochinvar 105 and had the same problem you were having. Our boiler would take about 2.5 hours to bring the heat up in the morning. I talked to a Lochinvar technician and he recommended the following settings:
F1 - 20 degrees F
F2 - 69 degrees F
F3 - 175 degrees F
F4 - 120 degrees F
B1 sh setpoint - 175 degrees F
He said if it still lags too much to increase F4 to 125 degrees or to 130 degrees to increase the water temperature.
My situation improved after I used his recommended settings. The boiler still goes into the 20% rate mode and slows the rate of heating but I compensated for it by setting my programmable thermostat to turn on earlier in the morning.
Tags: anyone, familiar, lochinvar, knight, problem, heat, rate, heat loss, water temperature, pipes pipes
