tefilla - When do we say Baruch Hu Uvaruch Shemo?

I'm somewhat confused on when Baruch Hu Uvaruch Shemo (ברוך הוא וברוך שמו) should be said after Hashem's name in a B'racha (I'm taking for granted that it is only said in the context of a bracha, but correct me if I'm wrong), and when it shouldn't.

There appear to be certain times where everyone in the synagogue says it:

• The B'rachos that are said in the morning


• The Chazzan's recitation of Shemoneh Esrei

On the other hand, there appear to be sometimes where no one says it:

• When being yotzei a Bracha

But then there are some "grey areas" where it appears that only some of the congregants do say it, and some remain silent:

• Friday night, by the B'racha mein Sheva


• Hashem's name in Birchas Kohanim

[there are probably lots more examples; these just happen to be the ones that prompted my question]

In short: I'm looking for a rule: when is it said, and when isn't it?

Answer

The rule is to always say it unless it is a hefsek. The two common cases of hefsek are:

• in a place that one cannot answer


• when a person is being yotzai with the mevarech

That is why most people say it by the morning brachos... either because they've already said it, or because they want to make their own.

By shemoneh esrei the idea is that people usually have davened their own shemoneh esrei already. Originally chazaras hashatz was instituted for people who did not know the brochos so they would not have said boruch hu uvoruch shemo.

On Friday night the halocha is not to be mafsik from vayichulu until after kaddish shalem. It is for this reason that many do not say bhu"s.

By birkas kohanim people do not say it as to not be mafsik during the brocha of the kohanim. The same people that do not say baruch hu... do not say those psukim that some people say, but do say yehi rotzon by singing. The reason is that nobody is yotzai with the brocha... it is just on them. However, Halocha forbids to be mafsik if the kohanim are in middle. Some are therefore more careful, but when they are singing thay aren't saying any words. The funny thing is that heimish usually say the psukim by kohanim while not saying baruch hu by meein sheva where the litaim say by meein sheva but not by the kohanim.

Any time you see a certain kehila saying it, it probably has to do with one of the two conditions. E.g. I heard that by birkas hatorah one should have in mind to be yotzai especially on shabbos where its harder to come by meah brachos. The sfardim however do say baruch hu.