Heat Loss Calculations

[Agile]

House is said to be about 2003 in which case its less likely to be a condensing boiler.

Non condensing boilers are typified for a flow of 80 C and a return of about 70 C. Neither could be touched for more than about a second max!

In that case the rad outputs would have been calculated for an actual flow temp of 80 C. Until that is measured you will not know if the heat input is correct.

Note that currently rads are quoted for a heat output with lower temps so the output would be higher with a non condensing boiler set at 80 C.

Tony

 

[Longclough]

Sorry for the confusion, the heating times were:

Heating turned on at 17:45 it was 13.0 degrees (6 outside) at 18:45 it was 16.0 degrees and by 19:30 it was 18.5 degrees. All radiators get too hot to touch longer than a few seconds and all over. My concern was if the temperature was say -1 outside, I felt it would take a long time to heat the house up. Maybe this is a poor assumption, are there any design rates for heat up times?

Agile, boiler is non condensing, as you have said. I calculated the Heat output of all radiators including hot water heat up (2kw) as approx 9kw. As you have said through, it was using modern radiator calculators, with a smaller flow temp.

 

[Longclough]

Sorry for the confusion, the heating times were:

Heating turned on at 17:45 it was 13.0 degrees (6 outside) at 18:45 it was 16.0 degrees and by 19:30 it was 18.5 degrees. All radiators get too hot to touch longer than a few seconds and all over. My concern was if the temperature was say -1 outside, I felt it would take a long time to heat the house up. Maybe this is a poor assumption, are there any design rates for heat up times?

Agile, boiler is non condensing, as you have said. I calculated the Heat output of all radiators including hot water heat up (2kw) as approx 9kw. As you have said through, it was using modern radiator calculators, with a smaller flow temp.

 

[Agile]

If you wanted to know what is really going on your need to measure the actual flow and return temps with a contact thermometer.

Hailsham will confirm but I expect a rad at 80/70 will give about 20% more heat than one under the current assessment parameters.

Tony

 

[DP]

Tony, in absence of proper instruments, test suggested is valid and need NOT be carried out with boiler at MAX.

Regularly advise customers on balancing systems the practical way as suggested above with good results.


OP, you might want to consider installing a programmable room stat to peg lower temperature a little better.

 

[D_Hailsham]

I expect a rad at 80/70 will give about 20% more heat than one under the current assessment parameters.

Not far out it's 14% more.

 

[Agile]

What about 82/71 though which is the traditional makers expectations for old boilers?

I have always found it very useful to be able to make a well informed engineering guess immediately whilst others are still looking for their slide rules!

 

[D_Hailsham]

What about 82/71 though which is the traditional makers expectations for old boilers?

18%

PS old boilers would have been 180/160 degrees Fahrenheit!!

 

[DP]

All I am going to say is, practice makes perfect, theory and google search (though useful) not always useful in the field.

DH, good to see the calculations and back to basics approach.

 

[Steelmasons]

I have always found it very useful to be able to make a well informed engineering guess immediately whilst others are still looking for their slide rules!

Stop it Tony as we had this conversation the other day.

 

[Steelmasons]

If you wanted to know what is really going on your need to measure the actual flow and return temps with a contact thermometer.



Tony

the experienced use their hands and can guess within a couple of degrees,

 

[Longclough]

Thanks for all your comments about checking balance. I have order myself a Contact K thermometer as I also want to check out our oven temperature as it seems a bit wayward.

As I have said before all radaitors seem to heat up at the same rate and get very hot. One question, although I suspect the answer will be experinece, how do you tell the difference between flow and return with your hand? I have touched the flow and return pipes and they both get very hot

 

[Galoka]

One question, although I suspect the answer will be experinece, how do you tell the difference between flow and return with your hand? I have touched the flow and return pipes and they both get very hot

I can tell the difference at the boiler between ours, With a rad, you can always just check which end warms first when the rad is warming from cold.