[Equest-users] VAV with Electric Reheat

[Omar Katanani]

Dear all,

I'm sorry I've been nagging a lot lately, but believe me, you guys are my only support!

I was using a VAV system, with the reheat source being the hot water loop. I specified the Reheat delta temperature by trial and error to 25F. Everything is fine.

Now I got updated info from the client saying that the source of the reheat is electric. I am getting an error message:

"Hot Water Loop  has zero design flow. Check input for consistency, or specify design loads."

I read a couple of discussions. I understand that many factors will affect this issue. The "Hot Deck Maximum Supply Temp", the "Reheat Delta Temp", and the "Zone Entering Max Supply Temp".

I tried specifying the hot deck max supply temp to 70F, I got the results attached in the pdf. However, the gas consumption part of the space heating is negligible compared to the electric, while I thought both will be of significant ratios!

My main question is how to get reasonable results, knowing that the main heating source is the hot water loop, and the electric reheat is to fine tune the temperature of zones experiencing different loads or so...

I know that the design temperature of the zones is 70F, and that the temperature that is supplied to the zone should be 30 degrees higher than the zone temperature (70+30=100F).

Any advice on how to choose the "reheat delta temp" and the "hot deck maximum supply temp", or any other input parameter you feel that it affects, is greatly appreciated.

Many thanks,
Omar
___________________________

Omar Katanani
Sustainable Design Engineer
Email: omar at ecoconsulting.net


EcoConsulting (Lebanon)
Nahas Building, 4th floor
4 St-Maron Street / Georges Haddad Avenue
Postal Code: 2028 5806 SAIFI
Beirut, Lebanon
Tel:       +961 (0) 1 971 255
Mobile:    +961 (0) 3 045 045


EcoConsulting (UK) Ltd
28 Marshalsea Road
London, SE1 1HF
Tel: +44 (0)207 939 0989
Fax: +44 (0)207 939 0981
Website: www.ecoconsulting.net



-----Original Message-----
From: Omar Katanani
Sent: Thu 7/15/2010 11:44 AM
To: equest-users at lists.onebuilding.org
Subject: VAV with Electric Reheat
 

Dear all,

I was using a VAV system, with the reheat source being the hot water loop. I specified the Reheat delta temperature by trial and error to 20F. Everything is fine.

Now I got updated info from the client saying that the source of the reheat is electric. I am getting an error message:

"Hot Water Loop  has zero design flow. Check input for consistency, or specify design loads."

I read a couple of discussions. I understand that many factors will affect this issue. The "Hot Deck Maximum Supply Temp", the "Reheat Delta Temp", and the "Zone Entering Max Supply Temp".

First of all, is the sum of the first two equal to the third?

My main question is how to get reasonable results, knowing that the main heating source is the hot water loop, and the electric reheat is just to fine tune the temperature of zones  experiencing different loads or so...

I played with all values but I can't figure out the pattern. I know that the design temperature of the zones is 70F, and that the temperature that is supplied to the zone should be 30 degrees higher than the zone temperature (70+30=100F).

Any advice on how to choose the "reheat delta temp" and the "hot deck maximum supply temp" is greatly appreciated.

Many thanks,
Omar


___________________________

Omar Katanani
Sustainable Design Engineer
Email: omar at ecoconsulting.net


EcoConsulting (Lebanon)
Nahas Building, 4th floor
4 St-Maron Street / Georges Haddad Avenue
Postal Code: 2028 5806 SAIFI
Beirut, Lebanon
Tel:       +961 (0) 1 971 255
Mobile:    +961 (0) 3 045 045


EcoConsulting (UK) Ltd
28 Marshalsea Road
London, SE1 1HF
Tel: +44 (0)207 939 0989
Fax: +44 (0)207 939 0981
Website: www.ecoconsulting.net



-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.onebuilding.org/pipermail/equest-users-onebuilding.org/attachments/20100721/f891e27b/attachment.htm>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: Hot deck max 70, reheat 25.pdf
Type: application/pdf
Size: 43514 bytes
Desc: Hot deck max 70, reheat 25.pdf
URL: <http://lists.onebuilding.org/pipermail/equest-users-onebuilding.org/attachments/20100721/f891e27b/attachment.pdf>