Condensing boiler getting too hot and short cycling

Blackhall8

I have a Burnham Alta 150 heat only propane boiler that is consistently throwing an "H01" (anti-short cycle) error code that shuts down the boiler for 3 minutes, then restarts. This happens dozens of times per day. The specific error code is H01/1.0, which the manual says "While thermostat demand present, boiler has cycled off too quickly due to temperature and restart is delayed."

I have a two zone hydro-air system, and can reproduce the issue in this sequence: Both zones are calling for heat and the boiler supply temp is at a steady ~150 degrees. However, as soon as one zone turns off, the boiler temp shoots up to 170 degrees causing the burner to turn off. From there, the temp quickly drops down to 140 which triggers the H01 code. Is this consistent H01 error code causing any damage to my boiler? Curious if anyone knows what the issue could be and if there are any settings I can adjust.

Here is a video I took this morning reproducing the issue:

https://youtube.com/shorts/Sd-6QjnzBGM?feature=share

Alta 150 heat only documentation:

Alta operating instructions

Alta extended features

pedmec

You have flow issue with the unit that is calling. The flashing light on the e007 is an error code which is saying you are air bound. trying purging the hydroair coil. depending on the manufacturer you will have a high point air vent that can be a coil vent or a drawoff (hose connection)

Blackhall8

Thanks, @pedmec for noticing that. I think the flashing light was just due to my iPhone when taking video. For some reason when I take videos, it will appear as the lights are blinking for some odd reason! Anyway, I just took another look at the e007 and it's a solid yellow light throughout all zones.

GroundUp

It's really hard to see in the video, but it sure appears to be piped wrong (no hydraulic separation) which would most definitely cause the issue you're seeing. Can you share some pictures of the piping from different angles, showing any closely spaced tees or hydraulic separator/ low loss header as required by Burnham?

Blackhall8

@GroundUp , thank you for the input. I just took some photos of the piping from various angles. Are these ok?

Also, the video I took prior showed a flashing light on the circulator, which was not actually true. My iPhone camera was making the light appear to flash even though it wasn't. The light is solid yellow when boiler is on, so safe to assume it's not air bound I think.

LRCCBJ

You don't have a flow issue and you don't have any piping issues.

What you do have is the inability of the boiler to modulate fast enough to prevent a shutdown on limit. This is common on mod-cons………especially big ones. I suffered with the same problem for 1.5 years until the manufacturer addressed it.

What you can try with this mod-con (of which I have no experience) is to go into the "modulation menu" and look for "CH1 max modulation". It's probably at 100 right now. Reset it to 50. I am simply guessing on the 50 with the assumption that it will be sufficient to heat the building on the design day. You will know if the building cannot maintain temperature on the design day (would be about 0°F here in CT).

I'm fairly confident this will stop the boiler from shutting down on limit. The delay to restart is normal to prevent this cycling from becoming ridiculous in terms of number of cycles per hour.

This boiler has other parameters that can be adjusted to assist with this situation but try the easiest first as stated above.

pedmec

The no flow was based on the circulator flashing. obviously turned into a camera issue.

GroundUp

Thank you for the clarification, I did not previously see the low loss header below the boiler. It appears to be a well designed and executed system, though as has been mentioned, it now sounds to be a response time issue more than anything. Slow closing valves or a buffer tank are typically the way around this issue, but it does sound like the boiler is a bit oversized as-is so you may be able to manipulate the firing rate as LRCCBJ mentioned or possibly turn the supply water temp down to keep the firing rate lower.

Blackhall8

@LRCCBJ i appreciate your feedback, thank you. I’ll give it a try today by turning down the max modulation rate from the default setting of 100% to 50% and test. I could also turn down the central heat setpoint by 10 degrees or so (i.e. 180 to 170), like @GroundUp mentioned but I’ll try to max modulation rate first.

LRCCBJ

Lowering the setpoint will not accomplish your goal. When one zone shuts down, the boiler will just climb away from 170 and the same thing will happen. The boiler, with the current settings, cannot respond fast enough to cope with the instantaneous drop in load.

There are other parameters on that boiler that address this…………..it has quite a bit of capability.

We'll see if the 50% works.

All mod-cons shutdown if the SWT climbs…………typically 10°F………….above the SWT. My opinion is that most installers and just about every homeowner consider this normal behavior……………..which is not correct.

GroundUp

https://forum.heatinghelp.com/discussion/comment/1835576#Comment_1835576

Lower water temp = lower firing rate. So yes, it would help. Nobody suggested that it would do the job on its own, it's merely an addition to your firing rate limit.

LRCCBJ

A better question is where is the outdoor reset and why is this boiler running at 180°F in the first place?

Blackhall8

@LRCCBJ , I lowered CH1 max modulation rate down to 50% and I could instantly hear the boiler become much quieter. Thanks for this tip! However, the supply temp seemed to climb very slowly and never got above 135 degrees (which is fine for most days). I tested increasing the CH1 max modulating rate to 60% and that seems better. The boiler runs much smoother now (a little more efficient I guess) and doesn't have those sharp spikes in temps causing the boiler to shut down. Thank you!