constant circulation

Mike T., Swampeast MO

A proportional flow valve for each zone or emitter with setpoint feedback will produce a true constant circulation system with only a single circulator and no mixing requirement. (Well--no mixing requirement as long as all of the emitters are similar.)

Such can be done with any two-pipe system including large radiant panels like floors. With modification can be implemented into one-pipe systems as well.

For floors, a device like <A href=http://heating.danfoss.com/PCM/search/Products.asp?VMenu=BLANK&DepartmentID=1&LanguageID=1&Show=&Search=FHV>Danfoss FHV</A> is preferable to "standard" devices (TRVs) as they have a built-in restriction adjustment to help balance loops of different sizes. This helps prevent overheating when an operator is "cranked".

Unfortunately, FHVs (floor heat valves) have very limited use in North America. They are ideally suited to systems with modulating/condensing boilers.

If you (or any heating pro or <I>very</I> knowledgeable homeowner) is seriously interested in using FHVs in a low-temp residential system with a modulating/condensing boiler, write me. I'll do everything possible to help you design an incredible system at no charge.

radmix

constant circulation

I am looking for any information on constant circulation heating. If anyone is using this method,and information on how Europeans pipe their heating systems

John Ruhnke

Outdoor Reset Controls........

Radmix,

Outdoor reset controls can be set up for constant circulation. A computerized control calculates the exact water temperature required to heat the house on that particular day. By way of a four way, three way or injection mixing it sets the temperature. It measures the delta tee or difference in temperature of the outside and inside temps. If it is 40 outside and the control wants to achieve 70 the control might run 130 degree water in the radiators instead of 180 degree water that it might need at the coldest days of the year.

Also I have run constant circulation with injection mixing on a house that didn't have outdoor reset. The thermostat put heat into the secondary loop when the thermostat called for heat. The purpose was to keep the water moving through outside walls so that it didn't freeze. The pipe was pex and I didn't want to put antifreeze into the system. It was in a condo complex about ten years old.

JR

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radmix

constant circulation

It seems to me to have true constant circ. each zone would have to have its owne independant distrubution circ. and independant mixing device because of the individual zone heat loss and responce time. I do use weather respance controls most of which have several zones comming off of one mix. thay claim to have constant system flow but that is done by staggering zone valve starting points. Does anyone have piping schematics of a true constant circ. system.

John Ruhnke

You are right.

Radmix,

If you have a single zone it is easy to set up for constant circ. Once you have zone valves it is not constant any more. Roth made a manifold that had adjustable water temps. Emmeti makes a remote manifold with a pump on it that has adjustable water temps too. Just like you describe. Emmeti unfortunatly is not yet available here in this country. I think you would like the Emmeti manifold. I have attached a picture of it.

JR

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Paul Pollets

The Defining Article

By Joe Friedrich appeared in 1981. I've been using the method since '91 and can confirm it's the most efficient way to control HW heating, regardless if radiators or radiant floors are the heat emitters. The article can be found on Rich Trethewey's site at the Hydronic Heating Assoc.

http://www.comfortableheat.net/pdfs/continuous.pdf

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