Flow Rate Vs BTUh

Brad White_9

Check out any fin-tube catalog for example. They rate it at either 1.0 GPM or 4.0 GPM (alternately 500 lbs. of water per hour or 2,000 lbs. of water per hour).

The relative differences are (just making up these numbers but you will see for yourself) say 600 BTUH per LF at 1.0 GPM and maybe 640 BTUH per LF at 4.0 GPM. Four times the flow and fractional increase in output.

Check temperature ratings now. Drop the water from 180F entering to 140F and your BTUH per LF rate drops from 600 to gee-why-bother.... so you add radiation or increase your water temperature.

Same applies to kickspace heaters. If you use them, select them for reduced water temperatures and prepare to install multiples. Enjoy the concert though, they can be noisy. Some are less so.

Xc8p2dC_2

Please, help me understand

Hi Gang. Now that my Ultra80 is up and puurring like a sleeping cat, need some info for my next project.

Starting to make a rumpus room in the cellar. hoping to utilize a hydr fan convector [miss having something that blows].

Looking at the Myson type, they list a couple of different flow rates [1.0 and 3.0} I will ****-o-me here that the rated BTU is based upon at the total GPH?.

Not currently knowing what my flow rate [for my 2zone 88ft 3/4 fin baseboard, and approx 135' 1/2" hePex with an 007]... Does the GPH of the system, have to match the new zone emitter GPH? or does that create ghost flows?

If I go with a unit that is 3.0 gph and my system doesn't put out that. my thoughts are I wouldn't be getting the advertised BTU output? yes/no?

Guess I should have asked for one of Dan's books for Christmas>>> Hmmm I-B-R or Modn Hydro #2...thanks

Xc8p2dC_2

Thanks Brad

Their chart does give a good breakdown, on the different supply temps Vs BTU, but also shows nearly 3000=3600 BTU difference between the 1.0GPM and the 3.0GPM of the same unit. This is what lead me to my concern about if proper flow is really important? Given I do run down to condensing temps

http://www.mysoninc.com/Pages/FanConvectors/slmlnt.html

Brad White_159

I do not see

anywhere near that difference in the PDF literature I have.

The Whispa II 5000 at say, 180F has a 5,310 BTU rating at Boost and 1.0 GPM. With 3.0 GPM this goes to 6,188. Higher than I would expect but pretty thin increase for all of that flow.

The Whispa II 9000 goes from 10,431 to 10,875 respectively at 1.0 and 3.0 GPM.

Remember, all increasing or decreasing the flow can do is to raise or lower the average temperature from the incoming reference temperature. Your entering water is the same at the rating point so how far can one depart from that?

Naturally the selection you should make would be at 130 or less EWT. This will get you the low temperature fan switch. Personally, I think that is a good idea, that fan switch. But you would double the number of heaters.

J.C.A._3

Xc etc....

IF you choose to go the fan coil/toespace W/wall kit units, please remember to size for the proper temps., AND to make sure you get a sensor that will allow them to turn on at the (lower than) desired temp. for their output.

I've seen this a few times. The things JUST WON'T turn on !...The factory sensor is set for a minimum 160°...and the design was for 140°. Opt for the extra "low temp. sensor". Just a heads up. Most come with a 160° sensor and it's FAR easier to change them before they are installed.(trust me...I'm pre-Med) JCA

Xc8p2dC_2

Strange

The unit I was heading towards, was the Slim line.. It is rated at 180deg supply / 3.0 gph is 15,293btu and 1.0 is 11,678... at 120/3.0 is 7,404 and 1.0 is 5,663>>
Seems to be the only one that has that big of a differential

So is it safe to say, that if I went with the 3.0 unit but wasn't pushing 3.0gph, worst case was I would use the 1.0 specs?

Brad White_160

Strange Indeed....

I may have to take a look at that literature myself.

Yes, I believe it would be safe to use the 1.0 GPM category. I doubt you would flow that much if your delta-T was to be preserved and 3.0 GPM seems excessive. If you run 0.50 GPM in the end, I would select the KSH at about 85-90% of the 1.0 GPM listing just to be sure.