VHO questions for DIYer

[mattgreene22]

I'm looking at URI bulbs that have 180 degree internal reflectors.

1) So for T12 bulbs, how much space is needed in regards to separation?

2) If I make a custom enclosure, should I even bother with a reflector to get 20 or more degrees reflection in addition the internal 180? If so, how far down below the lamp do you think is necessary for the reflector to catch and redirect the sideways light coming off the bulb?

3) How much distance do stand-offs and sockets take in addition to the diameter of the bulb itself?

4) If I'm using 18" VHO bulbs, how do I determine how many bulbs a single ballast will fire? Is there actually a rule of thumb...or is it specific to each ballast? I haven't seen a whole lot of ratings for F18T12...so I need to know how to calculate it.

thanks!

 

[Waylander]

1) Most 4 bulb retros will come with a 10" wide reflector. That is about right on spacing so that you can get fingers in to change bulbs. I did do one in 9" but it is very very difficult to change the bulbs.

2)Doubt there will be much gain. Most people just paint the inside a bright white. I have thought about using the 3" aqualux reflectors to see if there is any gain - thinking is as far as I have gotten.

3)Endcaps are 2 3/8". Standoff will add another 1/4". I imagine that with the bulb in the fitting, you will be looking at 2 7/8" to 3" from the base.

4)Ballast specific.

 

[mattgreene22]

Thanks Waylander

So...

1) So 4 bulbs in a 10 inch reflector...I should allow 2.5 inches per bulb then I assume. 1.5 inch in width for T12 bulbs...so I should allow for 1 inch in between bulbs (.5 inches for each bulb on either side). Right?

2) I'll have to look at the aqualux and do the same

3) So what is the diameter of the Endcap itself? If I were mount behind a curved reflector and run them through it...what diameter would be necessary for the reflector to allow for to accomodate the light tube itself and the the endcap socket??

4) Well crap...how does someone figre that out? If I was to light 2 or 4 30w VHO bulbs of 18" length...where do I start in order to figure out if a particular ballast will work?

 

[Entropy]

I like to allow three inches per VHO bulb. That gives you about an inch between bulbs normally. I would add a reflector if you can or at the least paint the inside of the canopy white. 3 inches from the mounting to the bottom of the endcap sounds about right to me, but you can have the bulbs as close to the water as you like IMO.

For the ballast I would go with a www.Fulham.com Workhorse 7 ballast. $40 shipped from www.reefgeek.com and more than enough to power four 30w bulbs, or up to 7 if you want to get creative.

 

[mattgreene22]

Thanks Entropy.

So you guys know where I'm coming from...I won't be building a canopy. I've got a 96w PC quad fixture that I want to supplement with 1 or 2 VHO actinics bulbs. However, it'd be nice to buy a ballast that could run more bulbs later should I decide to ditch the PC fixture alltogether at some point.

So, I'm looking to mount the 2 bulbs in homemade fixture...not hood. Right now, I'd like to put a VHO bulb on either side of the PC fixture...so it gets interesting. My latest thought is that I could cut PVC tubing in half and mount the bulbs in there. In doing so...I'd likely just have the sockets themselves in the half tube with the VHO bulband any other pieces of the endcap pushed through and external to the PVC.

So....I'm thinking of using two half-PVC-tubes containing a single VHO light in each...and placing these on each side of the PC fixture. I'll have to connect them together somehow to hide my wiring since I'll use a single ballast...but I'd probably use PVC to keep the material consistent.

Ok...that's longwinded.

3) So what is the diameter of the Endcap itself? If I were mount behind a curved reflector and run them through it...what diameter would be necessary for the reflector to allow for to accomodate the light tube itself and the the endcap socket??

4) So Fullham workhorse 7 sounds good...is it quiet and what kind of bulb replacement schedule should I follow??