ARTCC RADAR CTLR HAD LESS THAN STANDARD SEPARATION BETWEEN LGT DEVIATION FOR WX AND ANOTHER ACFT AT SAME ALT.

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ON A FLT FROM IAH TO EWR; S OF HOPEWELL VOR; NEEDED TO VISIT LAV. JUST BEFORE I LEFT I SUGGESTED TO F/O HE ASK FOR A SLIGHT DEVIATION TO RIGHT FOR A TSTM BUILD UP AHEAD ON THE ARWY. I DECIDED TO GO TO LAV AT THIS TIME BECAUSE I THOUGHT IT MIGHT GET A LITTLE BUMPY AS WE WENT AROUND THE CELL. THE CTLR APPROVED US TO DEVIATE RIGHT OF COURSE; AND CLRED US DIRECT HOPEWELL WHEN ABLE. AS I WENT BACK LAV WAS OCCUPIED. HAD TO WAIT. AS I CAME BACK INTO COCKPIT; FA AND SO WERE LOOKING OUT RIGHT WINDOW. I ASKED ABOUT CHANGES AND THEY SAID THE CTLR HAD TOLD US WE HAD TFC AT 3 O'CLOCK; 4 MI; FL370. THEY SAID THE CTLR TOLD US NOT TO GO ANY FURTHER RIGHT; BUT WE WERE OK ON THE 080 DEG HDG THE F/O HAD TOLD HIM WE WERE ON. THEY CLAIMED THE CTLR DID NOT TURN EITHER ACFT AND SHOWED NO SENSE OF URGENCY AT ANY TIME. I WAS ALWAYS UNDER THE IMPRESSION THAT CENTER CTLRS NEEDED TO MAINTAIN 5 MI LAT SEP BTWN ACFT AT SAME ALT. AS I GOT BACK IN SEAT WE WERE ABLE TO COME LEFT TO 050 DEGS AND GO DIRECT HOPEWELL AS WE ROUNDED THE BUILDUP. WE TOLD CTLR THIS AND ASKED ABOUT LOCATION OF TFC. HE SAID TFC WAS NO LONGER A FACTOR; THAT HE WAS STILL ON A 090 DEG HDG. NO ONE IN OUR COCKPIT EVER SAW THE TFC. I WILL NEED TO DO SOME RESEARCH REGARDING MIN SEP BTWN IFR ACFT.