Time Machine

Grand Funk Railroad is another of those overlooked, underrated early 70′s bands that when you give ‘em a listen, you remember just how awesome they were.

Music Mike is kinda creepy, but what I wouldn’t give for a “Time Machine!”

 ”Sherman, set the WABAC Machine for January 31st of this year…”

On that day, my neighbor and I were still friends, the Patriots still had a shot and we didn’t know Ike Libby had a heart of gold.

And we were talking about what “simple” means.

As in “what is a ‘simple’ radiant floor system?”


We tossed this at you:

Four distinct areas with different use patterns, different BTUH/SF heating loads and different finished floor R-values. The installation method is consistent – tubing between the floor joists with extruded aluminum plates – but required supply water temps are all over the map.

Not much we can do about it – the water temps are what they are due to different BTUH/SF loads and different finished floor R-values.

With “simplicity” in mind, there are three ways to go.  Here’s the simplest option:

One water temperature, one zone:

Use one t-stat, one circulator, one relay, one manifold and one fixed temperature tempering valve (if it can handle the flow – that’s another blog post!).  But what water temperature would make sure everything heats adequately?

Tick, tick, tick….

145?  Give that man a cigar!

Second question: where do you put the thermostat?

I don’t know, either.

The Living-Foyer has carpet, a 26 BTUH/SF load and needs 145-degree water under design conditions.  Put the T-stat there and it heats up just fine.  But what about the other areas?

The Family-Kitchen-B’fast has tile and hardwood, a load of 19-22 BTUH/SF and only needs 130-degree water.  Betcha a fiver it’s gonna be too warm pretty much all the time.  Dining room?  Way too warm.

Utility room?  Yowch!

So put the T-stat in the Family-Kitchen-B’fast area and give it 145-degree water (even though it only needs 130). How is that area going to feel?

Tick, tick, tick…

Perfect? Yep, another cigar!

Why wouldn’t it?  When the T-stat’s happy, flow stops.  When flow stops, the floor doesn’t get any warmer.  When the floor doesn’t get any warmer, the room won’t, either.  The only side-affect of running 145-degree water where only 130-degree is needed (as long as that area is controlled by a thermostat!) is the area will heat up a little quicker.

But how’s the Living-Foyer area going to feel?

If you said “cold – anywhere from a little to a lot,” you get another cigar.  There’s a high R-value and a 25% higher BTUH/SF heating load. The zone won’t run long enough to satisfy that area.

Dining and Utility rooms? Still too warm –  a little to a lot.

“Wait a minute,” you say, “why can’t you just ‘tweak the flow?’”

Common suggestion, but the question is “how?”

As in, “how do you know if you get it right?”

Dirty secret about radiant manifolds:  “tweak” the flow in one loop and you affect flow in all the others.  Say the T-stat’s in the Living-Foyer and you want to “tweak” the Kitchen-Family-B’Fast loops.  When you crank down the balancing valve on one of those loops you increase flow in every other loop on the manifold.  Tweak another loop and you change the flow in the loop you just tweaked, as well as all the others.

Remember the 3 Stooges short when Curly starts pulling a loose thread on his suit? Pretty soon all his clothes fall off.

Same thing only different.

Oh, and it may take hours until you notice what, if any, difference your tweaking has actually made.

Your system’s now so far out of whack you’ll need a priest to bring it back.

So one zone, one water temp may be “simple,” but it’s not a ” simple solution.”  We can do better.  Next time, we’ll look at the second option.

Until then, let it rock!

I miss the 70′s!

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