[sampleDict] has error with [externalWallHeatFluxTemperature]
 

I was using buoyantPimpleFoam to model a heat source in a room and everything seems well with the simulation processing.

However, when I was trying to use sampledict to get data of field T I got the following error.

[CODE]
Time = 0

Reading fields:
volScalarFields: alphat s nut p_rgh p T--> FOAM Warning :
From function Foam::Field<Type>::Field(const Foam::word&, const Foam::dictionary&, Foam::label) [with Type = double; Foam::label = int]
in file /home/minecraftgp/OpenFOAM/OpenFOAM-v1712/src/OpenFOAM/lnInclude/Field.C at line 325
Reading "/home/minecraftgp/openFoam_case/buoyantPImpleFoam/Ibrahim/0/T.boundaryField.heatplane"
expected keyword 'uniform' or 'nonuniform', assuming deprecated Field format from Foam version 2.0.
k epsilon
volVectorFields: U

Executing functionObjects

Time = 60

Reading fields:
volScalarFields: alphat s nut p_rgh p T--> FOAM Warning :
--> FOAM FATAL IO ERROR:
keyword Ta is undefined in dictionary "/home/minecraftgp/openFoam_case/buoyantPImpleFoam/Ibrahim/60/T.boundaryField.heatplane"
[CODE]

I can get the sampleDict results for t= 0s. But for t=60s the error shows there is lack of keyword Ta in my 'heatplane' BC setting in T file.

The following is my BC setting of 'heatplane' for t=0s, as can see the BC type is externalWallHeatFluxTemperature and I have already set the keyword Ta.
But I dont how to set Ta on 60s because they are calculated based on 0...

[CODE]
heatplane
{
type externalWallHeatFluxTemperature;
mode power;
Q 20;
kappaMethod fluidThermo;// calculate kappa=alphaEff*thermo.Cp
relaxation 0.1;
Ta 298.15;
value 300; // place holder
}
[CODE]

I am confused why sampledict the field T will need the value of Ta from externalWallHeatFluxTemperature?

Any help would be appreciated