constant circ tech question

MIke_Jonas

I'm a relatively new ('bout 3 years) hvac contractor, work by myself, do service and replacments. I like the water end of the business best, instead of forced air. Anyway, I've installed a bunch of Buderus boilers, along with the 2107 Logamatic controller. I really have come to like the constant main zone circulation when the outside temp is below the wwsd temp. On tube/fin baseboards as well as cast iron radiators. Keep in mind, my concern only applies to a single zone residence, along with indirect dhw. I don't see this (constant circulation) listed on any of the tekmar controls or Honeywell control literature. I'm looking for this feature for when I install a non-Buderus Logamatic boiler, and also as an improvement to the many gravity to pump system conversions I run into all the time. I like the Honeywell AQ475. It has the outdoor reset and wwsd. Any way to use this control for constant circ, and still keep dhw priority? Or is there another control that would suit my needs better?

S Ebels

You could use

Taco makes their SR series circ controls in what they call their EXP version. This will allow you to add an outdoor reset control with WWSD and provide DHW priority. AFA the constant circ goes, you can choose to just tie the TT connections on the SR control together, or simply connect them to a room thermostat to provide protection from temp overshoot. Check them out at taco-hvac.com

Here's a copy and paste link

http://www.taco-hvac.com/search.html?return_url=/en/products/Zone+Controls/products.html?current_category=138&PHPSESSID=7f760cc0c42ec38ed2df301d301e2276

Joe Mattiello

Taco Switching relay, exp version

The Taco EXP version of the Switching relay has the capacity to interface a PC700-2 outdoor reset control with PID technology to generate a curve for modulating the boiler based on outdoor temperature. Additionally, it has many other attributes for facilitating the wiring, and running your system efficiently. Typically, ZR terminal on the control is hot when any zone calls for heat would be used for energizing a system circulator. However, it can not switch over to constant circulation when the outside air temperature drops below WWSD setpoint. Truthfully, I don’t understand the advantage. Perhaps someone can explain

Unknown

the Tekmar 362 and 363 use a room sensor in addition to an outdoor sensor and control a mixing device to provide a single zone of perfectly modulated constant circulation, and boiler firing controls. the 363 does domestic as well.

the 360 and 361 will give constant circulation as well but you set room temp at the controllers in that case.. kind of strange, but it works.

Otherwise, any number of controls can be made to have a constant demand on only outdoor reset, but then the emitters need TRVs or other methods to restrict or stop flow.