Lochinvar Ramp Delay Variations and What The Heck Does The Modulation Setting Do

nosirra1Arrison · February 2023

Lochinvar boilers have a nifty ramp delay adjustment that does several things. First it allows for you to temper the firing rate of your boiler when it starts a cycle. Most modulating boilers seem to fire off hard (100%) and then attempt to modulate back desperately trying to avoid overshoot. Ramp delay lets you tell the boiler to fire initially at a lower rate (say 15%) and then progressively increase toward your maximum firing rate. It will modulate to try and avoid overshoot in all steps, but mellowing out the initial firing rate does wonders to keep overshoot and cycling down to a minimum. The second benefit of ramp delay is that you can limit your maximum firing rate, effectively downsizing an oversized boiler. A ramp delay setting on the sixth (of six adjustable levels) set at 50 will limit your boiler to half its rated capacity. A 155K btu becomes around a 77.5K btu boiler. This setting only effects space heating not domestic hot water production.
Does anyone run anything other than ramp increasing steps such as ramp delay step 1@15%, 2@20%, step 3@25%, 4@30%, 5@40%, 6@50% ? Does it make sense to run that type of stepping up for low mass radiant and fan coil, but run a U shaped set of settings for high mass like cast radiators or slab radiant? 1@50%, 2@40%, 3@35%, 4@40%, 5@45%, 6@50%. High mass can handle much more initial btus than low mass. Steady increasing ramps seem counterproductive for high mass. The U shape steps seem to make more sense.
Another topic altogether is the Modulation setting adjustment. The manual does not give me much help with this one. It is adjustable from a setting of 40 up to 100. 100 is the default. It does not set the maximum firing rate. That is ramp delay setting 6 as just discussed. Through trial and error, I see it seems to adjust how hyperactively it readjusts modulation. A setting of 100 for me (low mass) seemed to make too large firing readjustments as I tried for constant circulation with outdoor reset. It appears to mellow the swings of firing rate when it is closer to 40. Does anyone know what the Modulation adjustment is best used for?

hot_rod · February 2023

As I recall I set the max fire to 30,000 on my Knight, just a bit above my design.
I started a ramp like yours, but with high mass I found it too conservative, I went to 30 degree steps

I don’t think there is a suggested or ideal adjustment for any parameters. Just keep trying trial error until it does what you want

As you know, one input can put you back to factory default, if you get it to balled up.

tocker · March 8

Curious what the OP found to be his best ramp delay settings for the low mass scenario and if he now has a better understanding of the ‘modulation factor’. The manual vaguely states it is ‘reduces responsiveness’ of the temp control function.

nosirra1Arrison · March 11

OP here- I never definitively figured out the modulation factor setting. I did combine some zones to create less micro zoning (ran multiple zones off one thermostat w/jumpers instead of individual thermostats for each zone). Micro zoning required the theoretical modulation control and ramp delays to try to tame them. Larger zones behave much better with less guardrailing.

hot_rod · March 11

There is no "exact" setting when you consider the load on the boiler can change minute by minute depending on the building load/ building use.

So the adjustments to any function need to be based on your system, or your personal preferences.

My thought is the ramp delay can help allow the boiler to tun long on cycles. You ry to match a time period to a estimated load pattern.

I found a 20 minute delay too long and the room temperature would drop on a cold day, I tried 15, and then went down to 10.

What I haven't determined is how the ODR plays into ramp delay.

With ODR, (boost enabled) you set a time period that IF the temperature has not increased, the boiler will ramp up.

But, does ramp delay allow that. Or is it either or?

Since you probably cannot spend days watching the boiler work under varying conditions you can use the Run-time function to look at how the burner was behaving over an elasped period of time.

The goal is to limit the number of ignitions, which indicated how often the boiler cycles. BUT, balance this against the room temperature also. An efficient boiler cycle but an uncomfortable room temperature would not be the win.

You might try the simulator at Lochinvar U, see how much simulation you can do there.

nosirra1Arrison · March 11

Hot Rod - I do not know for sure, but I strongly believe you can do Boost OR Ramp Delay.

Tocker - My ramp Delay settings for low mass on 85K Knight are;

Step 1 - 3 min/ 30%

Step 2 - 3 min/35%

Step 3 - 3 min/40%

Step 4 - 2 min/45%

Step 5 - 1 min/50%

Step6 - 1 min/55%

nosirra1Arrison · March 11

I am able to hook up my laptop and monitor for long periods. This helps really see if you can calm the boilers fluxuations and work on getting as close to constant circulation at the lowest outdoor reset temps.

I agree each boiler/emitter system will be different, and each parameter set will vary. I followed Siggy's (John Siegenthaler) thought process in working towards the most simple system that maximizes the modern technology. I am sure the vast, vast majority of condensing boilers are underperforming their potential.

hot_rod · March 12

I think if you limit firing to a calculated load, and take time to fine tune ODR, you get extremely close to constant circulation

I agree that a small % are aware of the control potential

tocker · 3:43PM

Great discussion. Thank you! Yes, I’m learning but know it wont be the same across applications. I maxed at 70% and start at 10%. It is waaay better… reduces cycling considerably. Of course the weather popped up to 80 degrees so I had to switch to A/C to sleep ! Coming weather should be a good test for how it works in the shoulder period. I’ll drop it to 60 max which is approximately my load next!

Lochinvar Ramp Delay Variations and What The Heck Does The Modulation Setting Do

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