[Quantumcat]

Unless you play checkback, it is very important to raise the major response when you have three card support and 12-14(15) HCP. If responder has only 4 cards himself, with inviational values he can bid 2NT (which you can correct to 3♥ when not accepting and holding 4 card support, or pass with 3-card support and not accepting, or bid 3NT if accepting with 3-card support, or bid 4♥ if accepting with 4-card support), or 3NT with game values (which you can correct to 4♥ with four card support), or 3♥ with invitational values and five cards, or 4♥ with five hearts and game values.

If you have about (15)16-17 HCP, change suits, then support hearts. This shows only three-card support (otherwise you would have bid 3♥ instead of changing suit), and more than 12-14 (otherwise you would have bid 2♥ right away).