[TRNSYS-users] Air-Water Heat Pump (Type 941) doesn't converge

[Adrian Riebel Brummer]

Hello Jeff,

thanks very much for your answer. Maybe I didn't explain myself very well.

The waterflow of the heat pump is zero because the pump which controls the
flow is turned off. The control signals of the heat pump (heating and
cooling control signals) are zero too, so the heat pump should be turned
off and nothing should happen. The problem is, the outlet temperature of
the heat pump is unstable. I think the reason is that the heat pump is not
completely turned off and is trying to solve this equation:

[image: image.png]

Obviously the equation can't be solved because m_dot_liq is zero, but the
heat pump shouldn't be trying to solve it either.

As I said before, the documentation says something about a "Fan Control
Signal" which should be set to zero, in order that the heat pump doesn't
make any calculations. The problem is, I can't find that input when I look
for it in the Simulation Studio.

I hope that I managed to explain myself well (English is not my native
language). I would be very grateful if you can tell me if I'm wrong or what
should I do.

Thanks very much,

Adrian Riebel






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El mar., 7 jul. 2020 a las 13:40, Jeff Thornton via TRNSYS-users (<
trnsys-users at lists.onebuilding.org>) escribió:

> Adrian,
>
> Any flow convergence issues you are having is likely due to something
> beyond the AWHP.  This type does not set the water flow rate - it simply
> passes it through the device; heating or cooling it of the device is on or
> simply just passing it through if the device is off.  Pumps are the devices
> in TRNSYS that typically set the flow rates for your loops.  I would
> suggest you use the TRACE feature and watch to see what is happening when
> you are getting convergence issues.
>
>
>
> Jeff
>
>
>
> ---
> Jeff Thornton
> President - TESS LLC
> 3 N. Pinckney Street, Suite 202, Madison WI USA 53703
> Office: (608) 274-2577  Fax: (608) 278-1475www.tess-inc.com
> E-Mail: thornton at tess-inc.com
>
> On 07/05/2020 7:36 pm, Adrian Riebel Brummer via TRNSYS-users wrote:
>
> Dear TRNSYS users,
>
> I have a problem with Type 941 (Air-Water Heat Pump). My problem is that
> the simulation doesn't converge when the waterflow in the heat pump is
> zero, despite the heat pump is also in off mode (heating and cooling
> control signals are both set to zero).
>
> I have read the mathematical reference of this Type and it says something
> about a "Fan control signal", which functions, as I understand, as the
> master on-off switch of the heat pump. The problem is that I can't find
> that Input in the TRNSYS programm.
>
> I would like to know why I can't find that Input, and why the model
> doesn't converge despite the heat pump shouldn't be doing anything.
>
> I send you a picture of all the inputs that I can see for this Type. I
> have TRNSYS18 and TessLibs17.
>
> Regards,
>
> Adrian Riebel
>
> [image: image.png]
>
>
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