The Humax boxes normally support up to 6 different ir channels to avoid this problem (The Youview box is the exception). If you log into your remote harmony setup you should be able to find a way to change the Foxsat-HD from the default channel 1.
If not you will have to change the original Foxsat-HD remote to another channel and use the remote learning capability.
You will likely need to do this anyway before using the Harmony.
See
http://myhumax.org/forum/topic/multi-code-function-hdhdr-remote-1
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