Harman Red ESP sensor and room temp voltage during operation?

[dimondjack]

Short question - does anyone have voltage (or resistance unplugged) vs temperature curves for the Harman red esp sensor or room temp sensor?

I’m trying to diagnose my Harman HF60 boiler - it throttles back pellet feeding well before it has reached the target temp. I’ve cleaned the boiler and the esp sensor, but it still seems to throttle back after an hour or two of high burn. I checked the room temp resistances on the ESP and room temp probes (which seemed fine) but wanted to check these sensors during operation. The local harman dealer doesn’t have any info to help.

 

[Pelleting In NJ]

I believe the ESP sensor is a thermocouple, which generates a very small voltage. You need a special meter to read it, but you will need to know what "type" it is (K, J, T....)
Amazon product ASIN B018QHQSB8
Room temp sensors are typically thermistors, which can be read with an Ohmeter.

 

[dimondjack]

Thanks - I think both are thermistors, at least according to the Harman description (“ESP thermistor”).

The sensor changes resistance with temp, but when you plug it in to the board I believe it uses a voltage divider to convert that in to a voltage to be read.