I have a worcester heatslave 15/19 and the nameplate displays a 55usg 60'H nozzle. I purchased one from HRPC and when i went to fit it, the old one was 55usg 80'H. On looking in the service manual, there was no mention of the 55usg 60'H nozzle in the specifications section. If I go ahead and fit it, what are the requirements for the oil pressure etc?