HQI-TS verses HCI-TS

I'm looking at refitting a torcherie which takes a 500W
RX-7 halogen lamp with a 70W metal halide lamp instead,
and electronic control gear (Tridonic PCI 0070 A001).
Just wondering on the pros and cons of HQI-TS verses HCI-TS
lamps. As far as I have been able to tell from datasheets:

HQI-TS: slightly better CRI,
cheaper,
more stockists.

HCT-TS: better long term colour stability,
longer life.

Also, the Osram booklet I have on their Metal Halide lamps
says that some of the lamps require glass screens for UV
protection and/or lamp explosion protection, but it doesn't
say which lamps do require such protection. Does anyone
know if the HQI-TS or HCT-TS need any such screen? They both
have an outer envelope around the arc tube.

 

Yes, they do require an additional screen. The HQI-TS/WWD 75W I have in my
living room has a 5mm thick glass screen in front of the luminaire
reflector. It's not airtight and allows ventilation from the sides, but it
would certainly prevent any broken glass from flying on my face in case the
bulb exploded.

The outer lamp envelope is there to facilitate UV protection.

Also, there are several color options for the HQI-TS. The best, imho is the
/WWD, with a 2,700K color temp.

However, you might find that 75W is a bit on the low side for a 500W
replacement.

 

The ceramic metal halide is far superior in terms of colour and colour
stability, especially whern used on aan electronic ballast. The 3000K colour
temp is fine for somestic use and complements nicely any halogen you may
already have.
Useful life is better too with ceramic type as the colour temp and lumen
output remain more stable towards the end of life compared with the quartz
MH lamps. The CRI is actually better too.
A protective glass cover is mandatory for all non-protected MH lamps. The
double-ended types (TS) are of course, non-protected, as are linear halogen
with the R7s caps.

JB