Operation of the Termovar Mixing Valve

[KenLockett]

Can anyone confirm port operation of the Termovar Mixing Valve that is stamped as 72 DegC. My understanding is that Port 3 is always open while Port 2 is completely closed until the sensed water temperature is greater than 160 DegF (72 DegF). Likewise, Port 1 is completely open until the water temperature is greater than 160 DegF. As the water temperature rises above 160 Deg F, Port 1 begins to close while Port 2 begins to open. Furthermore, Port 2 is completely open when the temperature reaches 172 DegF while Port 1 continues to close but never completely.

My questions are as follows:

(1) Is the theory of operation described above correct?
(2) Is it true that Port 2 does not open fully until the temperature is at 172 DegF? This seems high.
(3) Does Port 1 completely close or not? From what I have read this is never clear. If it does not close completely, how near closed is it?
(4) At what point does the Termovar sense the water temperature (i.e. at Port 1, Port 2, etc.)?
(5) Is operation of the Termovar reverse to what is described above when the measured temperature is falling?

This questions arises because I have measured the output of the boiler (with IR meter) when the Tx was 190 DegF and a particular zone calling for heat likewise just after the header was reading near 190 DegF (i.e. within 3 DegF).

Just a while ago, the temperature of the boiler outlet I measure at 168 DegF while the same zone calling for heat was only reading 154 DegF. I of course am wondering if the return port (Port 2) was partially closed and instead the majority of flow was being diverted back to boiler through Port 1. This is of course very detrimental to maintaing room temps on really cold nights as a wood load is near exhausted.

I had an earlier thread regarding discrepancies in Boiler output and header temperatures and still trying to make 100% sense of what I am observing

Thanks

 

[jebatty]

My answer is based only on my experience. I cannot state exact temperatures for anything. I don't know whether or not return from system port is ever fully closed, I believe that supply from boiler port never completely closes, that is, regardless of how high system return temperature may be I believe there remains some recirculation through the Termovar. A balancing valve is needed to control the volume of recirculation flow from the boiler through the Termovar. The combined action of the balancing valve and Termovar will result in return water to the boiler at your desired return water temperature. I believe return water should not be lower than the low 140'sF, and that if return water is maintained at a higher temperature (150'sF) boiler operation is improved.

A good way for you to understand your valve is to install thermometers or sensors on 1) boiler supply to Termovar/system, 2) system return to Termovar, and 3) Termovar return to boiler. Milk frothing probe thermometers are easy to install (cable tie and insulation), are inexpensive, and accurate enough to provide useful info. A more elegant route is to install sensors in the same locations for electronic meters, and the meters then will continuously display these temperatures so you can see what is going on, including what happens as you may adjust the balancing valve.

Finally, in my system the boiler circulator does not turn "on" until boiler supply temperature is above 160F, and if it should fall 5F below that the circulator will turn "off." But in reality I don't think "off" ever happens because the Termovar recirculation guarantees boiler output at least 15-20F+ greater than boiler return (return after Termovar 145F, boiler supply at least 160F or more, for example).

 

[DaveBP]

This pdf describes the operation of the valve a little more authoritatively.


http://www.acaso.se/Documents/LK Acaso/LK eng/Termovar_Laddventil_ENG.pdf

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