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# EDR calculations at different temperatures

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Member Posts: 2,440
Dave is right- Radiation is not heat loss.

As Dave said, knowing your heat loss is primary; knowing your radiation is secondary and tells you how lucky you probably are to run "X" temperature on a design day.

As for de-rating, (assuming that your starting point of 170 degree average water temperature yields 150 BTUH per SF right?) it is this easy:

Subtract 20 BTU's per EDR for every 10 degree drop in average water temperature, assuming a 70 degree room.

So your 150 BTUH at 170 degree AWT becomes:

130 BTUH @ 160F AWT

110 BTUH @ 150F AWT, etc. etc.

Down to 10 BTUH @ 100F AWT

• Member Posts: 1,405
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EDR calculations at different temperatures

Hello,
I have done a total EDR calculation based upon the data I found on this webpage at an avg temp of 170F. If the avg temp in my system is less than 170F, how do I do the calculation? Is there an equation or another table at different temperatures?

Thanks.
• Member Posts: 50
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edr graph

Here is something you might use.
If I attached it correctly.
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Be very careful here,

I would be "very leery" of sizing a HW replacement boiler by the existing EDR alone,,,the only real accuracy is in doing a room by room heat-loss calculation. That way you`ll know the exact water temp. you need in these (possibly now) oversized rads.

Dave
• Member Posts: 592
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• Member Posts: 592
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graph

Don't see it Unless of course my glasses are still dirty
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