Residential Radiant at 160 Degrees?

Bill Clinton_5

At the other end, I almost never use plates: Just suspended tube, barrier, two tubes to standard joist bay, insulate beneath, and at ends of joists. AND often use 160 degrees.

Would plates transfer heat bette? Absolutely! Would plates allow you to operate at lower water temperatures? For sure! Could you get fuel savings by using plates and lower water temperatures? Umhum! If you're using a modcon boiler, you can keep it in condensing mode more of the time if you use plates. Every pound of water condensed in that boiler gives you back 900 btu heat. More condensate: more heat recovery.

So why would I use suspended tube?
1. Because I can. In my work area heat loads are generally well below 20 BTU/sq ft. Twenty btu/sq ft is about the upper limit for suspended tube. I'm more comfortable around 15.

2. Suspended tube is cheaper. Cost is ALWAYS a factor.

3. Efficiency, while not as good as can be obtained by plates can be pretty danged good. My suspended tube systems also use ModCon boilers. They make condensate a good deal of the time. My considered opinion is the efficiency difference is small.

4.Plates have a reputation for expansion noises. Various constant circulation strategies are recommended to minimize temperature changes and therefore minimize noise.
In mild weather areas such as we enjoy in northern california, people often turn the heat off everytime they lease the house--save a lot of fuel that way.

Starting and stopping the heating system makes constant circulation and outdoor reset pretty problematical. AND, it exacerbates expansion contraction noises, which in turn makes me skeptical of plates.

Don't get me wrong: suspended tube can make noise too. Over the past twelve years and dozens of installed systems, we've learned to deal with it. Our systems are quiet.

So: Are plates a better way to go? Depends on what parameters you're working with; what your goals are; even your heating ideology.

Bill

Bill F_2

Residential Radiant at 160 Degrees?

We recently purchased a 2400 sq ft home built in the early 1900’s. I just received my first proposal for a new heating system and I am already confused. A contractor, not one of the pros, presented a plan for radiant heat operating at 160 degrees, oxygen barrier tubing and a 30% glycol mix. That seems counterintuitive to me. Isn’t the benefit of radiant heat low operating temperature?

It is a busy time of year and the contractors I am interested in hearing from are dedicated to their current customers (something I certainly appreciate) and will take a while to get their proposals to me.

In regards to payment 1/3 on contractor signing, 1/3 upon delivery and install of materials and 1/3 at final inspection from the town has always worked for me.

Thanks again.

kevin coppinger_4

sounds like....

a staple up plateless design...some guys don't use plates...I for one will not do a dry system w/o plates...it will raise the cost, it will take longer to install but the water emps will be lower... and hopfully the energy savings greater....also some lumber manufactuers don't want those high tepms in the floor because it could compromise the strength of the floor systems over time....kpc

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rumn8r

To quote John Barba and John Siegenthaler...

DO THE MATH FIRST.

I'm just guessing that a 1900's era home is going to have a heat loss greater than 15 btu's/sq ft/hr.

It is also obvious to me that the consumer is aware of his operating options, and wants a HIGH efficiency system, and appears WILLING to pay the freight necessary to get that option, and rightfully so.

To Bill, with all due respect, what you cited is absolutely on the mark. The problem is, many unknowing, uncaring contractors and wholesalers who have recently jumped on the radiant band wagon think it is an end all do all system, and it is NOT. They have yet to do the math as have you, but "By golly, it worked in the last house they did, so it'll work in the next one too".

No offense meant towards anyone who chooses this methodology as thier method of application. Just do yourself and the consumer a favor, and do the math first to make sure its a right fit. Don't assume it will work every where every time.

Personally, I like using plates because it does result in significant reductions in operating temperatures, and it also gives me some wiggle room when the humonguous throw rugs suprisingly show up out of nowhere on the floor you were told would be tile, or hardwood covered...

Once its covered with sheet rock from below, you don't have a lot of options, especially if you are riding the jagged edge of reality. And the last thing the lady of the house wants to hear is "Sorry ma'am, you're going to have to roll up those nice rugs when it gets cold outside.."

I had a lady tell me (after she'd rolled out the rugs) that if she had been told in advanced that she wouldn't be allowed to put down rugs on her new radiant floor in advance, that she probably wouldn't have allowed them (radiant floors) to be installed in the first place.

OUCH...

Do the math, FIRST.

ME