constant circulation

copper kip_2

Is it necessary to constantly circulate RFH underneath hardwood flooring, a job that we will be starting has around 5400 sq. ft. of hardwood. I have done RFH under hardwood many times and not had any problems using a set point control but the homeowner and i was talking about the trestlewood flooring that was to be installed and they had stated that they heard the wood should be heated at all times, so this has got me a little curious so i called the mill from which they were getting this wood and asked them about this and they said that this would help with expansion and contration.I understand that constant heat would always keep the flooring expanded i guess? but i,am wondering how would you do this and not over heat the house, and even if the fluid is always circulating would this be somthing that is necessary 24/7/365. has any body delt with this before? is it over engineering ?

Alan(CaliforniaRadiant)Forbes_2

Hardwood

You have to allow the wood to equilibrate before it's installed; that is, you have to let it get used to it's environment before you nail it down. Let it sit in the house with the heat on for a week. That will reduce the amount of shrinking or swelling once it's installed.

Read more about hardwood here: http://www.heatinghelp.com/newsletter.cfm?Id=19

Once it's installed, constant circulation will gradually change the water temperature as the outdoor temperature changes, but it won't work all the time; it's usually programmed to only come on when the ouside temperature drops below 68 F.

No, it's not over engineering. Many of the boilers that we talk about here on The Wall have built-in outdoor reset controls; Viessmann Vitodens, Munchkin with the Vision I control. Many radiant contractors won't even install a hydronic heating system without outdoor reset.

Mark Hunt

Alan nails it


He is one of the best.

Make the system responsive to the actual demand.

Mark H

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Weezbo

Huh? ....:)

When in the jungle a blind man would ask directions... however would asking another blindman Really Help that much:)))
...You acclimate the materials ,prior to installation. constant circulation doesnt meant constant Heat.First examine the source.
..Let me suggest there may be other applications for constant circulation lets call it Moderating the environment.
...today it was like 80¡ãF my recircs been on all day in the rooms with radiant "Heating" it is 7o ish ...out here in the living room where i have baseboard(our word for convector heaters) it is near 80. Go figure:)
... i am not an engineer however the term "space conditioning "though , makes sence to me.
... soon this room will be lashed up too:) then i intend to do some heat shedding to the ground , Typically the radiant i install has out door reset.DPO an variable speed injection,with excercising:) etc.
...The idea that you need to constantly Pump heat to this Wood the guys selling sounds like he doesnt Kiln dry it and is talking BS...

Weezbo

I just thought of something sorry,

do you live or are you building the place in Anartica?

Unknown

Careful Weezy

I have a customer with ten oil boilers at McMurdo Station, in Antarctica.

They burn jet fuel. Becket burners.

They run year round, too.

Noel

copper kip_2

constant circulation

I know about letting the wood aclimate, the installer wants it stacked for 4 weeks prior to install. as for reset controls i usually use the taco pc 705 variable speed control w/ outdoor reset. i like weil mclain gv boilers(very reliable, and bulletproof no calls from the homeowner in the middle of the night), but what i guess i,am asking is what type of controls would be used to keep the zone circulators going constantly until the outdoor temp. shut it down.

Mark Hunt

A simple


outdoor t-stat would work.

Bring on the pumps at say 60 degrees and let the injection controls decide what temp the water should be.

Use room sensors to control whether the injection pump needs to run.

Mark H

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Unknown

well

No, you don't need constant circulation all the time. You only get *true* constant circulation in single zone systems, unless you want to use a mixing device for each seperate zone in your system. Much more commonly, you will use outdoor (and possibly indoor) reset to run a mixing valve or variable speed injection pump to modulate the system water temperature, and let zone pumps/zone valves act normally.

Using reset to reduce water temps will result in the zones operating in longer, smoother demands, but it won't be *true* constant circulation with one mixed temp and multiple zones. And that's usually fine.
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Mike T., Swampeast MO

One Relatively Easy Way

that you can have *truly* constant circulation with multiple radiant zones is with Danfoss FHV series valves.

Danfoss FHV

While extremely uncommon in the U.S. lots of neat features: built-in air purging; inherent adjustment for flow balancing; lots of connection options; true proportional control.

No mixing/injection required unless needed for other things. No need for separate balancing manifold. No t-stats or associated wiring. Many can be supplied with only a single circulator. Reset essentially required.

Application/adjustment data from Danfoss is in all metric measures so lots of conversions needed. While they are ¾" devices, flow is limited to about 1.1 gpm. Output limit with 18° delta-t is about 10,200 btu/hr; with 27° delta-t about 15,300 btu/hr.

Am working on a computer program to size and set balance for these. Nearly done, but have been busy with other things and am still adding some "goodies" to give suggestions, identify poor applications and reject bad data.

Mark J Strawcutter

mixing?

Would mixing still be necessary to limit max floor temp?

Mark

Mike T., Swampeast MO

With a decent reset curve you shouldn't have to mix down the temp unless requred to protect the boiler or unless different panel constructions demand different temperatures.

You're very correct in noticing that they offer no built-in function to limit panel temperature. One model does modulate on return temp, but if you "cranked" the operator...

These devices are going to be "about" space temperature maintenance. Once maintenance is achieved, I believe that delta-t will change in individual loops based on the changing load in the space due to sun, occupancy, etc.