[urgent] Is there a way to limit maximum firing rate for Lochinvar Knight boiler?
Woke up to a cold house and no hot water. Lochinvar Knight boiler starts up - the firing rate climbs up and then it shuts down at 98%. Repeat 5 times, then red lockout screen with "flame fail running" error. If I'm lucky - tech will come tomorrow, but it's c-c-c-cold!
I tried switching DHW type from Zone to Normal hoping that space heating demand will take over and it would use a ramp up curve that I have (which I can limit last stage to 90% for example), but it looks like DHW demand requires max firing rate regardless. I also tried to set SH/DHW Switching time to 0 and the other one to 15 min, and vice versa - but regardless - it still tries to ramp up to a 100%…
Thank you all!
Comments
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the manual explains the many control functions
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream0 -
yes, i looked at those ramp settings, thank you. unfortunately for me, they only apply to space heating. when DHW heat comes in - the boiler tries to get to a 100% and i can't find a setting that would limit or override that…
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You need to confirm that you’re getting sufficient flow through the boiler and indirect. A failing circulator or air binding can cause what you’re describing.
Bob Boan
You can choose to do what you want, but you cannot choose the consequences.
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What problem are you hoping to solve by limiting the dhw firing rate? There are some legitimate answers to that but I don't see anything in your question to indicate that would solve your problem but maybe you have some information you didn't mention. If it isn't burning correctly, lowering the firing rate won't solve the problem. If there is some sort of issue with the gas supply then it could work around that problem temporarily
That being said, you could turn off DHW, then it won't make a DHW call.
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Your trying to make hot water that's why you don't limit the firing rate. As the boiler approaches 180 it will modulate down to try and maintain 180.
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Possibly the issue has something to do with the indirect water tank or controls.
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you can in fact change the temperature the boiler run on a DHW call. Factory default is 180, I don’t remember the adjustment range.
If you had an indirect with dual coils, or a high output HeatFlo, you could generate DHW and tun low enough to condense.
Same with adding an external plate HX. With a close approach HX design the B side can get within a few degrees of the SWT.
Generate 120 DHW with 125 supply, for example. A plate HX is a much more efficient way to exchange temperature.
It’s the key to the EK efficiency, the plate HX for DHW.Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream2 -
This is old literature, but 4 tries and lockout, symptoms are the same.
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resurrecting the old thread. issue is coming up again. last time it ended up (most likely) being issue with propane regulator upstream. started happening again this year. so, is there a way to limit the firing rate to some number below 100%? the reason why i want to do that is to keep house warm until technician gets here, which might be few days at least if i'm lucky…
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I'm trying just to keep house warm until tech can get here and fix the underlying issue… is there a way to lower the maximum firing rate below 100%? thank you!
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look at the manual and the installer menu items. i'm sure there is the option in there.
check the vents on your regulators, if they ice over then the regulators for the propane won't work right.
you can also have too much drawdown from a tank for its size and the ambient temp and it can't boil off enough propane to cover the demand.
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From the manual, the ramp delay allows you to limit the 6th final ramp output.
So maybe start with 5 minutes on each step, put the last one to 50% or whatever you want to limit the max firing rate to.step 1 10%, step 2 20, step 3 30, step 4 40, step 5 50% and whatever you need on step 6, maybe 60%
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream1 -
This first
https://www.youtube.com/watch?v=6WTdTwcmxyo
The password to access to the installer access comes from this song. 5309
It is easy to get kicked out of service mode, until you get the buttons sequence memorized, so the song keeps the 5309 in your head, to jump back in.
In this section you will find the ramp delay parameter. The factory default once you enable this parameter are 15, 30, 45, 60, 80, 100% 2 minute on step 1, 1 minute on the rest.
You could leave the time intervals and just change the ramp %. End up on step 6 at the % you want.
Page 60 of the I&O manual explains the settings
Page 25 in the Service Manual has a graph showing the ramp delay setting intervals. I made notes right on this graph of my settings
If you have a newer version Knight Smart System with a twist knob, there is a USB port to insert a stick and save settings.
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream1 -
fantastic, thank you all!!
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