Well, a watt is a joule per second, and there's ~4.2 Joules per calorie
(true calorie, not Kilocalorie). Let's round to 4 for simplicity.
Then the 300w heater is running at 75 calories per second. Assuming
60gph for the worst-case calculation, and a rough conversion of 4L per
gallon, we get that the water goes through the heater at a rate of
240L/H, or 240/3600=.06666....L per second. So the water runs through
at ~67ml a second. A calorie raises 1ml of water 1 degree celsius, so
we get around a 1 degree temperature increase for the output water over
the input water in the pessimistic case. I think this should be no
problem. The heater should arrive in a few days, and I'll post what
the actual difference is. (Note: in the best case, it should be
something closer to .3-.4 degrees celsius).

-Wes

NetMax wrote:
wrote in message
oups.com...
Yeah, doing the calculations in my head, I come up with a (worst case)
temperature difference on the order of 1 degree celsius between the
input and output water, which should be fine I think. My canister is
an eheim 2215, with a rated throughput of 164gph.

-Wes


*Whew* I can't do those calculations in my head, but I can help with the
data. The 2215 pump is rated at 620 L/H (169 US gph) and the filter is
510 L/H (135 gph). I think you should use the 135gph.

Assumptions:
1. 135 gph for best case (filter flow rate)
2. 65 gph for worse running rate (50% is reasonable with the 2215's good
head pressure)
3. 78F target temperature
4. 77F is heater trigger (target - 1)
5. 100% thermal transfer from heater (basically sound)

At the two flow rates, what temperature rise would you get? Someone
needs to pull out their calculator and do the conversions to joules and
apply the formula for 100% transfer to water's specific gravity (or
something like that ;~), can you tell I'm gracefully bowing out to the
experts now?

If it is 1C (or 1.8F), I suspect you would be fine. For greater swings,
there might be some bacteria experts here who could comment.
--
www.NetMax.tk