2 stage heating

If it were me, I would configure PID_TEMP for stage 1, get it commissioned and working in auto, then add appropriate control logic to kick it into manual mode when stage 2 is required.

Or, do I not understand?

1 burner per furnace and 2 furnaces, or 1 furnace and 2 burners?

If it is 2 burners in a single furnace, what do you mean by "1 deg difference" ?  1 deg delta between what and what?

1 deg is the default accuracy of thermocouples.  If you want better control, you need RTDs.  What feedback devices are being used and how close are they to the heat source?

Are the gas burners heating up space or something above the burners?  Is the point to get some generic point within the "something" at some specified temperature, or several very specific points all within a specified temperature delta, or something else?

A modestly designed gas furnace might light up all burners at startup, and upon reaching an experimentally determined temperature will turn off "auxiliary" heat (in your case, 2nd burner for a 2-burner-1-furnace application) and begin automatic temperature control using PID on a single burner.   The 2nd burner might not ever come back on except upon burner 1 reaching end of life.

You may want to consider periodically alternating which burner is used for aux heat (startup) and which burner is used for maintaining temperature.

AutoGen_6483535

Hello! I need help in Tia Portal.

I have 2 gas burners to control. Each with 2 stages. Stage 1 is modulation and stage 2 is max.set heating.

I have setpoint temp. and room temp. sensor. So if the room temp. is close to setpoint temp. (<1 degree) it should run on stage 1 modulation and go off if reached the setpoint and if its more then 1 degree diference it should run on stage 2.

How to do this with LAD in Tia Portal?

 

At least your burners are staying well below boiling point.  The furnace suddenly converts to a boiler and lots of rules and regulations come into play as well as lots more maintenance (periodic blowdowns and tube cleaning), plus the water then needs to be pure, which increases cost for the chemistry testing and filtering and water quality monitoring.

It can get expensive.  Luckily your project avoids that mess.

Make sure your overtemp device prevents any localized boiling near heated surfaces.

PID_TEMP with 1 heater using enabling contactor and SSR for modulation. 

Include auto/manual mode logic, watch table control for commissioning and tuning. 

Heater 2 simple on or off depending on some temperature setpoint using a contactor, and SSR if you are going to toggle control between HTR 1 and HTR 2 periodically.

AutoGen_6483535

 I have RTDs. It's 1 furnance with 2 burners. So yes it starts with 2 burners on 2nd stage and then if some temperature is reached it should go on stage 1 to maintain the temperature.

This furnance heats water witch goes to heat exchanger and heats up the air in a production company.

0_Einstein

If it were me, I would configure PID_TEMP for stage 1, get it commissioned and working in auto, then add appropriate control logic to kick it into manual mode when stage 2 is required.

Or, do I not understand?

1 burner per furnace and 2 furnaces, or 1 furnace and 2 burners?

If it is 2 burners in a single furnace, what do you mean by "1 deg difference" ?  1 deg delta between what and what?

1 deg is the default accuracy of thermocouples.  If you want better control, you need RTDs.  What feedback devices are being used and how close are they to the heat source?

Are the gas burners heating up space or something above the burners?  Is the point to get some generic point within the "something" at some specified temperature, or several very specific points all within a specified temperature delta, or something else?

A modestly designed gas furnace might light up all burners at startup, and upon reaching an experimentally determined temperature will turn off "auxiliary" heat (in your case, 2nd burner for a 2-burner-1-furnace application) and begin automatic temperature control using PID on a single burner.   The 2nd burner might not ever come back on except upon burner 1 reaching end of life.

You may want to consider periodically alternating which burner is used for aux heat (startup) and which burner is used for maintaining temperature.

AutoGen_6483535

Hello! I need help in Tia Portal.

I have 2 gas burners to control. Each with 2 stages. Stage 1 is modulation and stage 2 is max.set heating.

I have setpoint temp. and room temp. sensor. So if the room temp. is close to setpoint temp. (<1 degree) it should run on stage 1 modulation and go off if reached the setpoint and if its more then 1 degree diference it should run on stage 2.

How to do this with LAD in Tia Portal?