Delta T

Unknown

even heating of a floor (for example)? Wouldn't a larger Delta T tend to make the inlet area of the floor warmer than the outlet area. (if you know what I mean. bad wording I think)

SpeyFitter

20 - 30 - 40 Delta T?

I'm a certified Radiant heat designer but the course isn't that "comprehensive". After doing a bit of reading of Dan H's Primary Secondary Pumping made easy book, I'm curious when you guys are designed your systems why more people don't go with larger Delta T's? The norm seems to be 20 degree (which is rammed down our throats at design school as the number one scenario) Delta T but thinking about going to a 40 degree Delta seems to offer more benefits i.e. smaller pipes, smaller pumps (well, potentially anyways), and it may keep some boilers that don't modulate down low enough working a little longer increasing their efficiency.

Also, after attending a recent Tekmar school I understand they offer a feature in their contrals called an "auto differential" where it will automatically incresae the Delta T to keep the boiler running longer thus increasing its efficiency in low demand times.

Andrew Hagen_2

Delta-T

There is absolutely no reason why 20°F is the preferred delta-t except it makes the math easy when calculating flow rates without a calculator.

There are some reasons to limit delta-t. For instance a condensing boiler connected to radiant floors only. If the maximum supply temperature is 110°F, then you really only have 25°F or so to work with. However, say you have a boiler with an internal pump and you want that to be the only circulator in the system. Going to a 30°F delta-T might make everything work without the second circulator.

In reality, delta-t is all over the place and only 20°F under a specific set of circumstances.

Andrew Hagen_2

Loop Lengths & Layout

It definitely will increase the temperature variations across the floor, but shorter loop lengths can help spread those variations out. It's a trade off, and it depends on the situation. Sometimes an extra 10° delta-t can make a big difference in the design and installed cost of the system. For this reason, panel radiators or radiant walls/ceilings can be run at a much higher delta-t than can radiant floors.

It can also depend on the homeowner. Some people will be much pickier about their floor temperatures than others. Those people will want a smaller delta-t across the radiant loop.

Unknown

Geez,

I hate picky people! Juuuust kidding.

Thanks Andrew!