[TRNSYS-users] Design of heat power in type 56 (heating manager with limited power )in an intermittent set temperature scenario

[David BRADLEY via TRNSYS-users]

Grégoire,

   A 30% oversize on necessary heating capacity is not unusual in US 
HVAC design practice. I will refrain from adding personal opinions about 
whether this is a good practice or not. ASHRAE 90.1 suggests a 25% 
oversize in their Appendix G.


   You mention that you have sized the heating based on envelope losses 
and infiltration. Don't forget that there is also usually some fresh air 
that must be supplied to a space and that air must also be conditioned 
(ie be part of your heating capacity).

   The recovery time also has a good bit to do with the thermal capacity 
of a zone and of the delivery systems. In some work that we have done on 
radiant floor systems we have seen that aggressive night time setbacks 
are a bad idea because the thermal flywheel of the radiant floor becomes 
very hard to control.


kind regards,

  David



On 04/26/2017 06:48, Greg B via TRNSYS-users wrote:
>
> Hello,
>
>
> I'm currently modeling an old terraced building (construction type 
> bricks / 8 zones / North Europa - Belgium) with a certain level of 
> refurbishement (let's say an overall of 8cm insulation). I designed 
> the heating power of the different zones, in the heating manger of 
> type 56 in limited power, based on the heating losses by transmission 
> and infiltration (design temperatures :  internal temp 20°C / external 
> -10°C). But when I launch the simulation in winter in a intermittent 
> set point scenario (0h-6h : 16°C 6-8h: 20°C 8h-15h :16°C 15h-22h:20°C 
> 22h-0h :16°C) the recovery time is very high and in some cases it is 
> not even possible to reach the high set point even after more than 8 
> hours.
>
>
> I don't know if some of you experienced this same problem (such long 
> recovery times)? I read in most of documentations that I have to 
> oversize the heating power in order to have a reasonnable recovery 
> time (let's say between 1 or 2 hours to reach the high set 
> temperature). When I do this I have to oversize at least 30% of the 
> original power and this seems quiet high, isn't it? Any idea or 
> doucmentation about a such issue?
>
>
> Thank you in adavance.
>
>
> Best regards,
>
>
> Grégoire
>
>
>
>
> _______________________________________________
> TRNSYS-users mailing list
> TRNSYS-users at lists.onebuilding.org
> http://lists.onebuilding.org/listinfo.cgi/trnsys-users-onebuilding.org

-- 
***************************
David BRADLEY
Principal
Thermal Energy Systems Specialists, LLC
22 North Carroll Street - suite 370
Madison, WI  53703 USA

P:+1.608.274.2577
F:+1.608.278.1475
d.bradley at tess-inc.com

http://www.tess-inc.com
http://www.trnsys.com

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.onebuilding.org/pipermail/trnsys-users-onebuilding.org/attachments/20170426/2adb5208/attachment-0003.htm>