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Herpstat HP (version 2) Safety Fuse Replacement

Safety fuse concern with the Herpstat HP (version 2).


When an oil filled heater was used on its highest setting and the thermostat was set at a temperature that the oil filled heater could not reach for prolonged periods the internal safety fuse can overheat.  Typically the fuse trips and the unit no longer is powered. This overheat can cause deformation of the Herpstat HP enclosure and damage to its fuse holder.


Our Diagnosis:
The pcb assembler replaced our specified fuse with another brand of fuse that is of questionable quality.  While the majority of these seem to be performing properly we have experienced a few that perform poorly and cause the unit to shutdown requiring repair.


Our Testing:
We tested several options before identifying the fuse quality issue.  Vents were added to the enclosures and a updated fuse holder was also used.  After identifying the actual issue was the fuse we performed additional tests with the original non-vented enclosure and fuse holder which performed properly.


IMPORTANT: Check the bottom of your Herpstat HP for its product label.  If it says version 1.2 or greater then unit has already been updated.  

Image of upgraded fuse.

We recommend any Herpstat HP (version 2) customers that do not have the 1.2 label to replace their safety fuse.  If you purchased the unit used then check which fuse is installed per the instructions at the back of the user manual


To order the fuse upgrade at no charge:

Click the ADD TO CART at the bottom of this page and complete the checkout.  We will ship a new fuse at no charge.  Fuse replacement instructions are in the back of user manual. We recommend to only use the heater on medium or low power until the replacement fuse has been installed.

IMPORTANT:  If you have a unit that has shutdown due to an overheated fuse then discontinue use.  The unit can be sent in for warranty using the info here.  

Optional: If you have a unit that does not have the vents and would like it updated or you would like us to perform the fuse replacement you can send the unit in to us using the info here

If you purchased spare fuses for the Herpstat HP (Version 2) they are our original specified fuse and would still work with the unit.  It is advisable to swap the fuse out with the spare.    We still recommend taking advantage of this program and getting the new fuse style which performs even better than our original specified fuse.