Case of the random midnight no heat call, this Fridays case

RayWohlfarth

In this case, the customer said they had no heat at night. It would happen every few days. The building had a control system that allowed us to track the boiler starts and stops and the hydronic loop temperature. The control system showed the loop temperature dropping and it was calling for heat. This led us to the boilers. They were reading standby which meant they had no call for heat. We replaced the relay that was used by the control system to enable the boilers. We still had issues. I will post the video on Friday morning

Regards

Ray

ratio

Hmmmmmm… Not a lot to go on, but I'm guessing something was tied in to a light switch.

EdTheHeaterMan

Although the type of boiler is not stated, I have heard of an oil fired boiler fail to operate when a basement light was turned on, then operate properly when the basement light was turned off,

The RA117A stack relay was still the most popular primary control when I started learning about heating system maintenance and repair.  The R8084 and its grandson the R8184 were all very new to the residential oil burner control scene.  And there were lots of Coal Conversion boilers still heating the homes in Philadelphia.  The company had just completed installing a new Carlin CRD100 with a new Time Saver Combustion chamber in one of those old boilers.  The combustion chamber was a pristine white ceramic fiber masterpiece inside that beautiful generator of warmth for the stately townhouse home on Camac street..  

As it was the normal practice to drill a ¼” hole in the fire door, in order to take an over fire draft reading, this was no different and that hole just happen to line up perfectly with the basement light bulb to cast a beam of light on that chamber at the exact spot where the cad cell would view the flame.  That white dot of illumination, no larger than a dime would send that Cad Cell Relay a false flame signal keeping the burner for operating.   Every time the homeowner was in the basement, they had no heat. Once the basement work was completed, or someone passed between the light bulb and the boiler door, the burner would start.

What are the chances?

Alan Welch

The thermostat was located above a lamp on the desk of the nighttime custodian.

RPK

So you confirmed that the control system is calling for heat at the very same time the boiler(s) are not getting the command. My first thought was that there could be a timer wired in series with the enable output. I ran into that exact scenario years ago with some newly installed Lochinvar Crests that the electrician powered via a lighting panel. Turns out the whole panel was powered via a contractor that was on a timer. We figured it out because the outtages were at regular times down to the minute.

I don’t think you’re dealing with the same thing in your example. In the trend log you shared it shows the supply temp dropping at different times. In fact, the 12/21 temp drop appears to have occurred about late morning. The December 24th drop occurs at night. This is contrary to the title which references midnight….

I’m down to a few possibilities:

1. Intermittent bad output on BMS controller
2. Intermittent control wire connection between BMS controller and boiler

RayWohlfarth

The midnight title was something I should have named nighttime I guess. Sorry. We would get random calls in the morning saying the heat went out at night. Anyway, I digress. The cause of the issue was although the building controls called for heat, the internal relay would work sometimes. We disconnected the boiler and used the boilers control system to control the boilers and the morning calls ended. Here is the video.

https://www.youtube.com/watch?v=ptKB_rN7vWw

mattmia2

The relay in the BMS?

They have the same problem with if the mechanical design of the board isn't good the solder will fatigue and break just like any other relay…

RayWohlfarth

@mattmia2 I never had one do that What's strange is that it only did it occasionally

mattmia2

The solder cracks from the little bit of flexing every time the relay makes or breaks then that crack sometimes makes a connection, sometimes not. It is really common in appliances. It can happen to the contact or the coil connections.

JoeEngineer

not for anything but why does the display indicate "Chiller Load Response?"

ratio

It's a trend log with all the other points turned off except one of the water temps.

I make lots of these, tracking all sorts of stuff on the same screen. It makes diagnostics much easier to see everything at once.

Intplm.

I'm wondering. Grasping at straws here, but could there be a dead spot in the motor?

RayWohlfarth

Thank you all. It turned out the building controls and the boiler controls didnt like each other.

pell

Seems to me it was working correctly. That's why we put these overpriced and over rated controls, on to save fuel, correct?

RayWohlfarth

@pell I am not sure if the two control systems were fighting each other but as soon as we disconnected them from each other, the system worked.