PID Thermostat

hydronicsmike

...been unbelievably busy lately with the end of the year near.

You are correct, all tekmar thermostat use PID.

tN4 is the way to go. Even if the tN4 thermostats are used in a stand alone system without a tN4 system control, as soon as they are networked together, a lot of features are gained. Those features include Zone Synchornization, Cooling Zone Grouping, Schedule Grouping and the USB Gateway compatibility. The new Gateway will be out this coming June.

Merry Christmas!

Mike

Glenn Begis

PID Thermostat

I bought a house with hydronic heating. I'm very satisfied with all aspects of it except the control- it requires a manual process to adjust the thermostat setpoints depending on outside temperature to keep things comfortable.

A web search revealed that PID is a close loop technology that can be applied to problems such as this, but I am unable to find any turnkey thermostat products. Any pointers or advice would be much appreciated.

Thanks,

Glenn Begis

Aidan (UK)

PID thermostats

Something similar was discussed here a short while back;

http://forums.invision.net/Thread.cfm?CFApp=2&&Message_ID=211306&_#Message211306

I don't think there are any PID thermostats; a thermostat is generally an electro-mechanical heat activated switch.

What you're looking for ( adjust the thermostat setpoints depending on outside temperature) is outdoor reset; the heating flow temperature is adjusted according to outside air temperature with, possibly, some adjustments according to the room temperature.

This would usually use several temperature sensors (NTC thermistors monitoring room, outside & flow temperatures). The PID control would be done in an electronic controller. I believe Tekmar can supply a suitable controller.

Steve D._4

I believe that the honeywell vision pro is a PI control, no D. Other makers also use this control scheme for electronic thermostats. Mine seems to hold temp very well. In the 3 months since I added it I only see actual vs set temp as different at the beginning of a setback period. This is because the look-ahead is only for restoring to the occupied temp. It will have the correct temp at the end of the setback when the higher temp is set.

It keeps track of the response of the zone over the previous 5 days to estimate the requirements of the zone.

Adding the derivative to the control is not practical given the control of the boiler. It would be useful if the rate of heat input were under control, like a modulating boiler.

Steve

Barbarossa

My first question would be; do you have outside reset controling the water temp as a function of out side air temp. Then what are you changing in manual mode to remain comfortable.P+I and or PID would no be where I would start on a problem like this.

Terry

I believe all Tekmar t'stats (including Tn4) use PID.

where MIke when you need him?

tekmarcontrols.com

EIN

Unknown

I wonder if this is a job for that exquisite heat guy that pops into the forums every few months to spam about his products.

It depends on what you mean though. Why are you adjusting thermostat setpoints w/outdoor temperature? Temp should be temp. What are you trying to achieve?

Glenn Begis

Thanks for all the responses. I have not investigated outside reset but I will do so. In regards to the question about what I'm trying to achieve, the heart of the quest is to get a control system my wife is more comfortable with, she has a hard time staying comfortable when the weather goes through extreme temperature changes.

Barbarossa

The need for outside reset is generally indicated by having to adjust the t stat set point as the outside conditions change to remain comfortable.