UPDATE 2-China copper smelters skip Q2 treatment charge floor, citing ample inventory

* Smelter group sets no quarterly floor for only 3rd time ever

* 2 mln tpy smelting capacity to undergo Q2 maintenance - source

* Group likely wants to avoid ‘unachievable’ floor - miners (Adds details, comment)

SHANGHAI/BEIJING, March 26 (Reuters) - China’s top copper smelters on Friday set no floor for treatment and refining charges (TC/RCs) in the second quarter, arguing they have enough concentrate in stock as a wave of maintenance gets under way, three smelter sources said.

TC/RCs, an important source of revenue for smelters, are paid by miners when they sell copper concentrate, or semi-processed ore, to be refined into metal. The charges typically go down when the concentrate market tightens and smelters have to accept lower terms to secure feedstock.

The state-backed members of the China Smelters Purchase Team (CSPT) are supposed to adhere to the quarterly floor in any spot concentrate deals.

The lack of a floor - for only the third time in the CSPT's history - paves the way for transactions to be done at TC/RCs well below first-quarter floor levels of $53 a tonne and 5.3 cents a pound, as market rates AM-CN-CUCONC languish at 10-year-lows closer to $30 and 3 cents amid tight mine supply.

But one of the sources who attended a CSPT meeting in Shanghai on Friday said: “We have purchased enough copper concentrate.”

A second attendee said it was difficult to set a floor price due to volatile market conditions and already low TC/RCs. All three sources declined to be identified as the meeting was private.

However, two miner sources said the CSPT would want to save face by avoiding an “unachievable” floor that would be flouted by concentrate-hungry members, although one acknowledged upcoming maintenance might “reduce the pressure to buy”.

More than 2 million tonnes of annual smelting capacity will be on maintenance in the second quarter, taking 200,000 tonnes of copper metal out of the market, the second meeting attendee said.

A source with a non-CSPT smelter concurred that any floor at the moment was not realistic. “So they just leave it to market and don’t set the floor.”

Reporting by Emily Chow in Shanghai, Shivani Singh in Beijing; Writing by Tom Daly and Mai Nguyen Editing by Muralikumar Anantharaman, Robert Birsel