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house indoor temp could not be met

asked 2017-07-11 13:12:37 -0600

nancynanxiaodan gravatar image

updated 2017-07-13 13:09:29 -0600

Dear All,

I am using a Air sourced heat pump for a house heat source, with ground floor(heated floor heating), first floor(water convector), and I've changed the outdoor temp always equal to Zero(constant number), and indoor thermostatsetpoint (heating) is set to 25C, simulation running period is whole Jan.

However, when I finish the simulation and looking at the results, it never reach 25C (none rooms).

  1. I am wondering is there any dead band or acceptable range of the desire temperature in EP+, +- 5 degrees?
  2. I've made some changes in the capacity of the heat pumps/fans, but it did not seems could increase the temp.

.

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@nancynanxiaodan Did you check to see if your heated floors are working as they are supposed to?

rsunnam gravatar imagersunnam ( 2017-07-13 09:58:14 -0600 )edit

@rsunnam Hi Raghu, many thanks for looking at my questions. the temp shows above is the firstfloor one room temp which used convective water radiator as the heat emitter, I've checked all rooms in ground floor which all had reasonable temp around 24.5.

nancynanxiaodan gravatar imagenancynanxiaodan ( 2017-07-13 11:43:29 -0600 )edit

@nancynanxiaodan OK got it. Without knowing any further details about all the systems conditioning the first level zones, I would start checking all the internal gain, schedules (internal gains and thermostats). I would also check that the envelope properties are correctly modeled. If all that is fine, I would focus on the specific HVAC components (radiators in this case) and the plant side for these components. Make sure that the hot water temperatures are modeled correctly. You can check the functioning of the radiators by looking at the"baseboard total heating rate variable" in the eso file

rsunnam gravatar imagersunnam ( 2017-07-13 12:23:38 -0600 )edit

@rsunnam for this model, I removed all internal gains(equipment, people, lighting) except for solar gains. I've attached the results am getting regarding the baseboard.

nancynanxiaodan gravatar imagenancynanxiaodan ( 2017-07-13 13:06:36 -0600 )edit

@nancynanxiaodan OK. I am not exactly sure what is happening based on this. If you wish, I can take a look at the model and see if I can find something. My email id is in my profile.

rsunnam gravatar imagersunnam ( 2017-07-13 13:37:48 -0600 )edit

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answered 2017-07-13 15:59:18 -0600

@nancynanxiaodan

Based on what I see, the radiators in the first floor bedroom is not able to meet the heating loads during the winter days. Hence the zone mean air temperature during the winters is not able to reach 25°C. This coupled with low inside surface temperatures for the zones results in low zone operative temperatures during the winter months. The zone tempeatures seem to be within the expected range during summer.

image description

I see two solutions for this -

  1. You can improve the envelope thermal properties so that the winter temperatures can be taken care of
  2. increase the temperature set point for the hot water supply to the radiators

I increased the hot water supply temperature set point to 69°C from 55°C (max tank temperature that you have is 70°C and hence the max value that i chose was 69°C). The graphs now look like this:

image description

Practical solutions like adding internal heat gains or having winter setbacks can also help but it looks like you were trying to evaluate a hypothetical scenario as you edited the OA drybulb temperature.

Hope that helps!

Cheers,

Raghu

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Asked: 2017-07-11 13:12:37 -0600

Seen: 109 times

Last updated: Jul 13