Elapsed time between 2 columns that are more than 24:00

[druidruid]

I am trying to add time from several rows, and when they add up to more than 24 hours I do not get correct results I am looking for. I do understand that [time(0)] will not hold values larger than 24:00 Below is my script

SELECT
Codes = (DeptCode + '-' + OpCode)
,TotalTime = convert(time(0),dateadd(second,sum(datediff(second,StartTime,FinishTime)),0))    
,Units = SUM(Units)
,UPH = cast(isnull(sum(Units) / nullif(sum(datediff(minute,StartTime,FinishTime))*1.0,0),0.0)*60  as decimal(10,0))
,'Goal%' = (convert(varchar,cast((isnull(sum(Units) / nullif(sum(datediff(minute,StartTime,FinishTime))*1.0,0),0.0)*60)/1552*100 as decimal(10,0))) + '%') 
FROM PTW.dbo.TimeLog
WHERE DeptCode = 'HS' and OpCode = 'HY'
GROUP BY DeptCode,OpCode

Results are below

Codes   TotalTime   Units   UPH     Goal%
HS-HY   14:07:00    69204   1114    72%

This can not be true because this is the breakdown.

ID#     Codes   TotalTime   Units   UPH     Goal%   AssociateName
---     -----   ---------   -----   ---     -----   -------------
2377    HS-HY   11:25:00    20891   1830    118%    NAME
3476    HS-HY   04:50:00    6978    1444    93%     NAME
43864   HS-HY   12:20:00    17628   1429    92%     NAME
2372127 HS-HY   03:20:00    4748    1424    92%     NAME
2372129 HS-HY   07:00:00    9158    1308    84%     NAME
2422946 HS-HY   00:47:00    949     1211    78%     NAME
21437   HS-HY   06:02:00    6530    1082    70%     NAME
2372090 HS-HY   11:00:00    2322    211     14%     NAME
63448   HS-HY   03:43:00    0       0       0%      NAME
2372061 HS-HY   01:40:00    0       0       0%      NAME
 

When TotalTime yields more than 24:00 I am not getting correct result. Need help changing script to allow more than 24:
Can not figure a way around this......

BTW
My data types for StartTime and FinishTime are varchar(8)