Anyone here experienced with Lochinvar boilers? I am having high limit reset issues

the boiler is a WHN055.

6 years ago I installed it with the contractor who is a good friend and scorched air guy.

Pex was new to me at the time, and having 100psi @ 180 deg printed on it, I opted to run a 170 setpoint with a 10 deg offset so as to not go above the 180.

I recently read that pex can go up to 200 @ a psi that I am quite a bit below. So, I turned my setpoint up to 190 and offset to 9deg, so as not to breach 200

The unit has both a manual and automatic reset high limit that keep tripping. they are both maxed at 195 and 200 respectively. The manual states that they have a max of 195 and 210 respectively but mine will not adjust that high for some reason...

I have now turned the offset down to 3 deg to attempt avoiding tripping the high resets. I thought that a 190 deg setpoint with a 3 deg offset would result in an outlet water temp of 193. Is this not the case?

DW

You might state what fuel in case it makes a difference.
Bill

Do you really need the water so hot? What is the root-problem you're trying to solve? I'm guessing you are cranking up the heat for house or shop, and hotter water may not be the best solution..??

I don't have experience with your boiler, but have worked with control integration for some time. My suspicion is that you are operating too close to your trip points.

Most industrial temperature sensors are based on thermocouples (TC), and are accurate to +/- 2degF. (You can specify 'precision' TCs and get +/- 1degF.)

If your boiler is typical, the TC feeds a loop controller that reads the temp and turns the burner on and off as needed (just like any domestic water heater). All controllers have some amount of hysteresis, which manifests itself as over- or under-shoot of the setpoint (SP). This might be as little as 2-3degF on a normal system, or 10-20degF on a low quality or defective system. (Put a thermometer in your cold oven, set at 350degF, and see if it hits 350 - or over-shoots - - same principal.)

Some control systems even use 2 or more TCs, one for control and a second redundant one for the safety limit - and this introduces another source of error. Do the TCs both read the same at any given time, or are they even located in the same place - and so sense the exact same water at the exact same time? Not sure if it applies here, but something else to consider.

I have no idea how the 'offset' is used in your specific case. I've seen industrial systems that adjust the SP (offset it) based on the actual outside air temp. Delivering slightly hotter water to radiators when the outside temp drops (or cooler water when it's balmy). This potentially introduces another ambient air TC and it's inherent error. Again, not sure if this is your case..?

Another factor to consider is 'spot boiling'. Even though the average temp of a boiler's tank/water may be 190degF, if the burner is firing and the water is already >200degF, there may be points on the tank hot enough to cause localized boiling (you'll usually hear it banging). The banging is the steam bubbles collapsing, and its generally not good for the tank's life expectancy.

Bottom line is that all these small errors may very well be adding up and resulting in the controller over-shooting the SP - and the high limits - with the resulting trips. Since I seriously doubt your system is rated for steam, I'd recommend you stay well below 200degF. It sounds like it's operating normally, just too close to the limits.

....lotta theory, but hope it helps.

Good luck. I don't have any knowledge of boilers (I have lived in Florida all my life).

But the mention of "Lochinvar" brought back memories. My Dad used to quote the poem Lochinvar by Sir Walter Scott. Dad passed on 37 years ago last month and sometimes little things like this bring up memories. I haven't thought of that particular poem in years until I read this post.

For those who may be interested - https://www.poetryfoundation.org/poems/52300/lochinvar

I guess I had to comment as part of the memory/grieving process. Thanks for the memory.

Malcom gave you alot of good info. Your running way to hot.. Also, your missing some additional key information. What appliances are you running to? Fin Tube, Cast iron radiators or is this a slab heat type situation. Are you running a on demand water heater off this boiler? I would recomend consulting with a local heating contractor that knows boilers to get your system set up correctly or do alot of reading on hydronic heating to learn how to set up the system correctly.