There is one consonant-combination that does not abide by the four syllable rules described before: ch. This combination is never separated. It is another way of writing the letter _g_.\\* For this reason, we regard is as a single consonant. The words below are therefore not separated by three consonants ( _c, h_ and _t_) but by two ( _ch_ and _t_ or _r_ and _ch)_.
lachen | la-chen | to laugh
richel | ri-chel | ridge
zuchten | zuch-ten | to sigh
krachten | krach-ten | forces, energy
rechter | rech-ter | judge
monarchie | mo-nar-chie | monarchy
And of course, observing the 4th rule: if _ch_ is enveloped by consonants (e.g. 'rcht'), we place _ch_ at the end of the preceding syllable (like with koortsig, ambtenaar, etc.). If we do not do this, the second syllable starts with _ch_ \+ another consonant (which will generally make it hard to pronounce).
burchten | burch-ten | castles | not: bur-chten
burchten
The reason why _ch_ is considered to be one consonant is simple. Look what happens if we treat it as two consonants: a word like _lachen_ would be divided as _lac-hen._ This completely changes the pronunciation of the separate syllables: as in English, the _c_ at the end of a syllable is pronounced as _k_. We do get another problem, being the length of the vowel but we will get to that later.
(\*) There used to be a difference between the pronunciation of _ch_ and _g_ but nowadays, most Dutch speakers no longer make this distinction. There is still a substantial minority of Dutch speakers, mainly in Flanders- who pronounce _ch_ and _g_ differently.
lachen, richel, zuchten, krachten, rechter, monarchie burchten.