It varies by the credit limit on your HELOC and by CRA.
It appears that HELOC's with a credit limit of $50K and above (possibly as low as $40K) are regarded as mortgage rather than as installment. Those with lower balances can be treated as revolving. MV has a HELOC that's scored as revolving by EX, resulting in a lower score. Others have said that TU does the same.
I just got a negative comment on my most recent EX making it look as though they are now counting the HELOC as revolving, when they didn't used to. Why they would start doing this now, I can't fathom.
And TU includes the balance of my HELOC as revolving debt in the simulator, although as best as I can tell, it doesn't do this for actual scoring. Go figure.
* Credit is a wonderful servant, but a terrible master. * Who's the boss --you or your credit? FICO's: EQ 781 - TU 793 - EX 779 (from PSECU) - Done credit hunting; having fun with credit gardening. - EQ 590 on 5/14/2007