Modulation of new Lochinvar KHB-155

timccarpenter

This is all new to me and I want to be sure my new high efficiency boiler is operating or set properly. I'm in northern Minnesota and we just had a new boiler installed. Every time it fires, it seems to be at 100% (which is what I believe the screen is telling me). Temps are not that low yet (40 degrees), Our home is an old 2 1/2 story house with cast iron radiators. I would have assumed that the boiler would not be firing at 100% every time. I believe it stays at 100% until it shuts off. Can anyone provide some insight on settings I should check, etc.? Does this seem normal (other info you need to help)?

Thanks

Hot_water_fan

No, it should not be doing that. It should be both modulating and using lower temperatures. The installer should come back to fix it, this is their job.

timccarpenter

When you say it should be using lower temps, do you mean water temps due to the more moderate outdoor temp? What is the best way for me to explain to them what I am experiencing (so they know I know something about what I'm talking about)? Incidentally, I just looked at the total space heat cycles (not using for domestic hot water) at it looks like about 8/day in outdoor temps that range from 45-55

Hot_water_fan

When you say it should be using lower temps, do you mean water temps due to the more moderate outdoor temp?

Bingo - pay attention next cycle and see what temperatures are displayed. If the outdoor reset is installed and enabled, they should be ~100-130 or so (depends on the curve selected).

Incidentally, I just looked at the total space heat cycles (not using for domestic hot water) at it looks like about 8/day in outdoor temps that range from 45-55

Interesting. I don't know if we can determine if that's proper modulation or not. When it gets colder, you should have very few cycles per day. It actually could run non-stop for months if dialed in perfectly.

Every time it fires, it seems to be at 100% (which is what I believe the screen is telling me

Can you post the screen you see? Often these kinds of boilers start a cycle at high fire (usually adjustable) then step down. So if it's starting at 100% and dropping, that'd be normal behavior. It is likely oversized for your home, so it could be electronically limited to say...50% and do just fine. If it starts and stays at 100%, that's bad setup. There's usually a few ways to handle that if that's what's truly going on.

hot_rod

Did you do the programing of the control? The manual is pretty good about stepping you through all the parameters to adjust and typical examples.
Probably a tutorial at the Lochinvar site also or on YouTube.

It would be good for you to learn the control to optimize its use, and get it set to your exact needs.

timccarpenter

hot_rod said:

Did you do the programing of the control?

I did not. The installer did. He actually just called me back and is going to look at it. He thinks that the set point ranges for temp (based on outside temps) may have not saved correctly. He said he had put the high temp at 130 degrees for an outside temp of 30-50...and from what I saw, it was showing 160 degrees as the target temp (even though the outside temp is 45 degrees). I do need to learn the setup info as I'll want to dial this in perfectly :-)

pedmec

Sounds like you have a lot of radiators too. Its trying to hit that target temperature but it just takes a long time too get there due to the water content of the system. It probably satisfying the thermostat before its getting close to the target temperature. Radiators will satisfy space temperatures much sooner at a lower temperature due to radiator output. Plus if you have a house built in the early years of hydronics the radiators could be grossly oversized. Great for condensing boilers.

timccarpenter

pedmec said:

Sounds like you have a lot of radiators too. Its trying to hit that target temperature but it just takes a long time too get there due to the water content of the system. It probably satisfying the thermostat before its getting close to the target temperature.

Interesting. I was just coming to that conclusion. I turned up the heat, the radiators are getting hot and the inside temp is going up. The system temp was still at 118 degrees compared to the target of 160. Boiler is firing at 100% trying to get there. I'm sure the household temp will be reached before the system temp is. I understand the old hot water systems with radiators are high heat systems. However, is the 160 in fact going to be too high for any time? Also, some of our radiators are quite large (home built in 1910)

pedmec

And the closer you get to the 160 it will start to modulate down if there is still a demand. On a positive note you know you have an idea of how to set your system curve. Satisfying the house demand with roughly with 120 supply temperature at whatever is the outdoor temperature is a good baseline to start. Finding that sweet spot with resetting the supply water temperature it's always trial and error.

timccarpenter

should the set point actually be lower than (I assume so and I think was the installer's intent for this outside temp range)

Hot_water_fan

should the set point actually be lower than (I assume so and I think was the installer's intent for this outside temp range)

The set point should be as low as it can be and still satisfy the thermostat. That temperature will depend on the ratio of heat loss to radiation at a given outdoor temp. So it might be 100 degrees at 45 outside, might be 140, it just depends. You can try different temps to narrow it in some. 

timccarpenter

Does the boiler modulate based on the set point and outside temp? For example, if the set point for outside temps below 30 degrees is 160, will the boiler run at 100% to get to the 160 whether it is 25 degrees our or -15 degrees? Or, might it adjust down the fire % based on how quickly it can get to the 160?

flat_twin

Was an outdoor air temp sensor installed?

timccarpenter

flat_twin said:

Was an outdoor air temp sensor installed?

Yes

hot_rod

Trust me, if you read the control section of the manual it explains all the functions and how to set them

I wouldn’t expect the installer to make 4 trips back to set one parameter up or down?

If you are depending on him, spring for the Conxus card and Wi-Fi connection so he can do it remotely from his phone

The high temperature will be a WAG without a load calc and radiator assessment

You may in fact still need 160f on design days, so the reset parameters need to have 160F as the high temperature. Low end will be a guess also, hopefully you can start at 120 or lower to get some condensing operation

https://www.lochinvar.com/news-article/lochinvar-expands-conxus-remote-connectivity-platform/

flat_twin

I will echo what others have said about a knowledgeable home owner getting involved with the outdoor reset programming. It will take an entire heating season or maybe two, to dial it in to account for calm sunny days as well as windy cloudy days, in shoulder seasons and in the dead of winter.

One method is to raise your thermostat to 80 (essentially making it a high limit) and then use the outdoor reset programming to dictate indoor temperature. Once you have a curve established that can just keep up with your desired indoor temperature, bump up your supply water temp just a bit to cover those times when it's very windy. Then set your thermostat to the desired indoor temp.

I made this chart to help me visualize the mod con heating curve from shoulder season temps to coldest temps expected. Your supply temp requirements will of course be different than mine but the general idea is the same. We have 10 cast iron rads in a 1740 sq ft two story house built in 1836. Design day here in central Ohio is 5 degrees though we have seen minus 20 on rare cold snaps.

My original curve ended at minus 5 degrees. It wasn't enough and the inside temps began to sag when we had a polar vortex one year that produced minus 22 outdoor temps. I raised SWT slightly overall and extended the new curve to minus 20.

timccarpenter

I appreciate all of the feedback here. Very helpful. I am working to build by own knowledge as I don't expect the installer to keep coming out (other than to get the initial settings at a decent starting point). I think I'm still missing some basic understanding of how these high efficiency boilers should be working. I think I'm understanding correctly that longer cycles of heating and circulating the water is preferable. Is the idea that this is maintaining the target heat without going high enough that the thermostat shuts the boiler off? What does this mean in terms of number of cycles/hour?

The installer is planning to come out next week but I'm thinking of adjusting some of the settings today to see what i can do. Again, even now, when the thermostat calls for heat, the boiler goes on and is firing at 100% to hit a set point of 160 degrees (working from a temp of about 110). Always shuts off before the set point is reached.

If there is any good reading material to direct me to to understand the desired operation, that would be helpful.

neilc

I would start by trying to read and understand the installation, and operation manual for your boiler,
just to know which settings to be adjusting,
then as others have said,
you're trying to set as low a temperature at both ends of that scale so the thermostat "never really satisfies", and you're running on the OA reset,
and it sounds like you're not set to run on the OA, or the reset scaling is mixed up,
another thing to read on in your manual,
do you have them?
or download them from your manufacturer

timccarpenter

I have the manuals and have found a couple of good youtube videos. One thing that is not set at all under the anti-cycling is any ramp delay. From what I understand that is used to essentially force some modulation (at least with the Lochinvar). Otherwise it is going to just go 100% to get to the target temp. The ramp delay will slow that down and extend the cycle...I think. I thought radiators required relatively high temps. However, maybe that is a combo of factors (radiator and room size, heat loss, etc.) to determine best target temp based on the onside temp. The outdoor reset is set up but I think the boiler temps are likely too high. The water temp between cycles now (30 degrees today) may get down to 90 degrees. Then the boiler kicks in at 100% to get to 160 which never happens as the heat is satisfied sooner

pedmec

At some point you will satisfy the thermostat and you do want the thermostat to shut it down. you don't want to find out on the coldest day that your freezing because you can't keep up with the heat loss. Having the thermostat shutting it off will let you know that it is keeping up with the heat loss of the structure.

And yes you do want it to run as long as possible. this is the best way to limit temperature swings in the space.

you need to set your high system temperature/ low outdoor.
low system temperature/high outdoor temperature.

Hot_water_fan

One thing that is not set at all under the anti-cycling is any ramp delay. From what I understand that is used to essentially force some modulation (at least with the Lochinvar). Otherwise it is going to just go 100% to get to the target temp. The ramp delay will slow that down and extend the cycle...I think. I thought radiators required relatively high temps.

Bingo, ramp delay is one great way to do this. Radiators do not require high temps. They output more heat at high temps, but you might not need that. Depends on the ratio of heat loss to radiation, measured by EDR. When it’s mild outside, you definitely do not need high water temps. 

timccarpenter

Hot_water_fan said:

Bingo, ramp delay is one great way to do this.

What is the best way to approach ramp delay? When I enabled it, Lochinvar had it preset with 2 minutes at 15% and then a minute or two for six steps. What is the best way to determine what that should be?

Hot_water_fan

What is the best way to approach ramp delay? When I enabled it, Lochinvar had it preset with 2 minutes at 15% and then a minute or two for six steps. What is the best way to determine what that should be?

Depends on what behavior you want. If responsiveness, then shorter intervals and steeper ramp. If more steady temperatures and longer cycles, longer intervals and smaller steps is what you want. It’s editable, so you can experiment of course. If your boiler is much larger than your heat loss design temp, you can limit the max output to keep it running longer if you want. 

nosirra1Arrison

Tim..
You have a PM (personal message).
Look for the mail envelope in the upper right side of the banner.

pedmec

Ramp delay in this situation will only delay the inevitable. Its still going to try to ramp up to 100%. Your just delaying the time when it gets there and when it does your back to where you started. getting the reset curve to the proper settings is the way for the system to fully modulate and maximize the boiler

Hot_water_fan

No reason not to do both

hot_rod

Do you have this manual? If not download, make notes in the margin to keep track of the settings and changes you make.

This page has some of the best functions in the manual. I set my ramp to 15 minute steps.

If the boiler is racing to 160, both ODR may need adjusting or set up the ramp delay it works well and the boost. The anti cycling overide differential needs to be adjusted also.

Use the limiting function also. If you heat load is 30,000 BTU/hr, no reason to have the boiler fire to full 155,000 output. Lock it doen to 30 or 35,000.

Luckily my son had been a Lochinvar rep, so the learning curve was much shorter, it still took 3 or 4 adjustments to get it near perfect.

My boiler rarely shuts down on my shop. A one zone slab makes adjustments a bit simpler.

Max saw a customers boiler that was only a year old and had run the cycle counter up to max allowable number the control could display!

That cycle counter is a good indicator of how the boiler is adjusted to match the load(s) since you cannot be in front of it constantly. Reset it today and check it in a few days or a week.

The ConX US board and ap is nice to have so both you and the installer can watch and remotely tweak the settings.,

timccarpenter

I found a lochinvar training video for techs. Sounds like the low temp for the outdoor reset should be the average lowest temp vs. the true design temp. This document from energy star put by 99% heating temp (99% of the days are warmer than this) at -21 degrees. Probably need my top temp well before that. Other info I tracked down suggested that the low temp of the curve should be the average low during the coldest month (which is still -5 for me)...seems reasonable.

hot_rod mentioned adjusting the Boost and anti cycling overide differential...having a hard time finding good info on what to do with these.

hot_rod

This is the explanation and setting options right out of the Lochinvar manual.

These are all features that installers ask manufacturers to include when the have contractor input sessions.

Practice with them see if the work, if not, 1 key stroke puts the control back to factory defaults if you get too balled up.

timccarpenter

I cannot seem to find in the documentation how one resets the cycle counter on the Lochinvar Knight. I'd like to do that to monitor the impact changes I make are having

Tinman

It’s in the service manual that comes with the boiler. Access the control parameters and you’ll find it under Data Logging. 

hot_rod

The SH cycles? I know it can be done with a computer plugged in.

Did you use the installer access code? 5309

Then go to service, get into the "service notification" parameter, see if you can highlight and click on the SH cycles. I know this is where you reset the service reminder alert.

You can see on mine where I had trouble with low gas pressure when I first hooked it up, so a few more failed ignition attempts, compared to ignition.

timccarpenter

I can clearly see getting this outdoor reset curve right will take some time. Current status:
Setpoint 160
low outdoor temp -5
boiler high temp 160
high outdoor temp 70

Ramp delay set across a total of 15 minutes with most time middle

Temp today is 30 degrees

Still going through 4 cycles in the last 4hrs or so....is that normal?
Very little of that time is running a low modulation. Gets to temp shuts off. Water cools down to about 90 and starts over again.

When I checked on it a bit ago, it was modulating at 49% with 118 degree water (not part of ramp delay I don't think) --despite the adjusted set point (based on outdoor temp) being at 130. Then is shut down and said "blocked" Anti Cycling.

Any direction on what to adjust here?

hot_rod

So one cycle per hour? What is your goal, are you trying to get constant firing?

The control display should show the target temperature it is shooting for, what is that when it is at 49% 118f?

timccarpenter

hot_rod said:

So one cycle per hour? What is your goal, are you trying to get constant firing?

The control display should show the target temperature it is shooting for, what is that when it is at 49% 118f?

I’m hoping to even out the heating a bit. The Tstat will be satisfied and the boiler will go off. Probably doesn’t run for an hour or more. Things cool slightly and then it kicks back on. I’d likely longer cooler cycles to even things out a bit.  I also get the impression on this forum that fewer longer cycles is better and more efficient (although there seems to be some debate about it).

I looked at total cycles for a 12hr period and there were only 6 (25-30 degree weather) which by itself seems like a good thing. 

With respect to the target temp above…target was 132f and when I was looking at it it was currently at 118f

timccarpenter

Not sure if I have my system dialed in the best that it can be (possibly). I'm not sure if it is realistic to keep the system water a little warmer (longer, possibly lower temp cycles) or what I have going on is the most common. For example, 22 degree F here today. With Outdoor reset, the target temp is 136 degrees. With ramp delay, the firing of the boiler is making it's way up to 100%. Once the Tstat is satisfied, the system will go off and then be off for around 1 1/2 hrs. The heat inside will slowly drop by a degree and will kick in again. At that point, the system temp has dropped to 80 degrees (so a lot of work to get back up to 136).

Is there a way (and is this the right way to think about it) to even the heating out a bit? Is this just the reality of radiators that once heated up keep emitting?

I'd just like the system to be maximizing efficiency and I'm not sure if there is more to be done/can be done.

hot_rod

The lower you can run the supply temperature, the more efficient it, any boiler, will be. Just keep backing off the high temperature setting in the ODR until it cannot keep the space comfortable, then set it up 5 degrees

Really this is something you need to monitor and adjust. What works in my system may not be ideal for yours

The boiler control folks put all these adjustable functions to allow every boiler to be dialed in perfectly. It is not a set it and forget it procedure Eid you are trying to optimize efficiency without sacrificing comfort