DIY Home Improvement Forum banner
1 - 4 of 4 Posts

·
Registered
Joined
·
1,435 Posts
Discussion Starter · #1 ·
Why dual port pressure switches (-0.10wc for example) in Coleman down-flow furnaces/80%-ers), but single port pressure switches (metal if I remember correctly) in regular residential homes. Although, I believe one of the few stick-built homes I've gone to so far, did have a dual port pressure switch... was a Goodman 80%-er.
 

·
Hvac Pro
Joined
·
23,688 Posts
Dual port are for high efficiency sealed combustion, generally. Single port are mostly for 80% mid efficiency. There are a few dual port mids ( old ICPs ) that measure the pressure drop across a metal orifice plate after the ventor discharge.

Dual port measure the pressure drop across the heat exchanger. Also check for venting blockages, poor drainage.

Single port just make sure the inducer is running up to speed and producing enough vacuum/draft.

Also depends on the Brand and model.

Trailers are different as they measure pressure drop across a orifice built into the inducer. Has to do with Bernoullli's principles. You can measure flow by equating it to pressure drop across a orifice. Used all the time to measure steam flow in large boiler plants.
 

·
Banned
Joined
·
14,506 Posts
They actually ALL have two ports. The difference is that the 'single port' are open to atmosphere (the second port) and are measuring difference to it. The 'dual port' are measuring difference between two specific locations.

Dual port are usually used in sealed systems not open to atmosphere or areas where difference is pretty small so that the diaphragm can have an (amplified) push-pull effect instead of simply relying on a push OR a pull.
 

·
Registered
Joined
·
14,590 Posts
They actually ALL have two ports. The difference is that the 'single port' are open to atmosphere (the second port) and are measuring difference to it. The 'dual port' are measuring difference between two specific locations.

Dual port are usually used in sealed systems not open to atmosphere or areas where difference is pretty small so that the diaphragm can have an (amplified) push-pull effect instead of simply relying on a push OR a pull.
Pressure transducers and some types of sealed pressure switches are mostly immune to atmospheric pressure changes. I wouldn't say that those compare to atmospheric pressure, instead compare to a fixed force. (mechanical or otherwise)

Semantics.....

https://en.m.wikipedia.org/wiki/Pressure_switch

Cheers!
 
1 - 4 of 4 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top