DC Pumps [RE-wrenches]

[Jeffrey Wolfe, Global Resources]

Hi Kurt,

You're correct that this is closed loop, and that we only need to calculate 
for friction and dynamic losses. That's the way it is in almost all heating 
systems. Need to keep it closed loop to keep the oxygen out of the water. 
(It's the oxygen that causes corrosion and fouling.)

BUT, friction and dynamic losses are real, and do mount up. Using larger 
pipe sizes helps, but heat exchanges, boilers, valves, etc. all create a 
friction drop. The friction drop we calculated took all this into account.

One note for those who may want to size a system with super low friction 
drop. Do not decrease the velocity in any heat exchanger below about 3 feet 
per second. (This is both in-tank exchangers and fin tube radiation. I'm 
not as familiar with radiant heat tubing sizing.) Otherwise, the flow 
becomes laminar and the heat transfer goes WAY down, effectively making the 
system not work. (You can buy special heat exchangers for lower velocity, 
but they need to be designed to create the turbulence required for good 
heat transfer.)

Jeff

----------
From: 	sunwise at cheqnet.net[SMTP:sunwise at cheqnet.net]
Reply To: 	RE-wrenches at topica.com
Sent: 	Sunday, July 01, 2001 2:02 PM
To: 	RE-wrenches at topica.com
Subject: 	Re: DC Pumps [RE-wrenches]

effrey Wolfe, Global Resources wrote:
>
>Both the plumber and I have figured they need about 6 gallons per minute 
and
> about 12 - 14 feet if head. (this is just for from the boiler to the
> storage tank inside. We'll be using El Sids for the radiant loops.)

Hey Jeffrey,

One thought I had in selecting the pump here.  If you are doing a
circulating pump, where-in the piping is closed loop essentially, you
have no head.  You only calculate for friction and restriction losses in
the piping.

Kurt Nelson

- - - -
To send a message: RE-wrenches at topica.com

Archive of previous messages: http://www.topica.com/lists/RE-wrenches/

List rules & etiquette: http://www.mrsharkey.com/wrenches/etiquete.htm

Check out participant bios: www.mrsharkey.com/wrenches/index.html

Hosted by Home Power magazine

Moderator: michael.welch at homepower.com


- - - -
To send a message: RE-wrenches at topica.com

Archive of previous messages: http://www.topica.com/lists/RE-wrenches/

List rules & etiquette: http://www.mrsharkey.com/wrenches/etiquete.htm

Check out participant bios: www.mrsharkey.com/wrenches/index.html

Hosted by Home Power magazine

Moderator: michael.welch at homepower.com

==^================================================================
EASY UNSUBSCRIBE click here: http://topica.com/u/?bz8Qcs.bz9JC9
Or send an email To: RE-wrenches-unsubscribe at topica.com
This email was sent to: michael.welch at homepower.com

T O P I C A -- Register now to manage your mail!
http://www.topica.com/partner/tag02/register
==^================================================================