Merrimack, N.H.-based GT Solar International (Nasdaq: SOLR) priced 30.3 million shares at $16.50, pricing its initial public offering at the middle of an expected range.

The company's shares were at $16.21, down 1.76 percent in early morning trading.

The share sale will pull in $500 million for the company's backers, with all of the shares being sold by a holding company controlled by GFI Energy Ventures and Oaktree Capital Management.

GT Solar is expected to start trading on the Nasdaq under the symbol "SOLR."

GT Solar previously set a price range of $15.50 to $17.50 per share. The company provides manufacturing equipment and services to producers of photovoltaic wafers, cells and modules and polysilicon. It's principal products are directional solidification systems and chemical vapor deposition reactors and related equipment.

Credit Suisse and UBS Investment Bank are the lead underwriters on the share sale. The underwriters have an option to purchase an additional 4.5 million shares to cover over-allotments.

The solar firm took a hit earlier this year when Changzhou, China-based Trina Solar (NYSE: TSL) canceled plans to build a $1 billion polysilicon production plant using equipment from GT Solar, saying supplies of the material have become more available (see Trina Solar drops plans for polysilicon plant). But Trina said the two companies will continue to work together.

As of March 31, the company said it had received nine orders for an aggregate of 176 chemical vapor deposition reactors from six customers. The first of the reactors were delivered in August 2007. Chemical vapor deposition reactors are used to react gases at high temperatures and pressures to produce polysilicon, the key raw material used in solar cells.