Twinning.

[donkpow]

Talking HVAC. Twinning two furnaces is using two furnaces simultaneously instead of one huge unit. I'm looking at an installation that has 2 stage heating and single stage cooling on two units. There is a third unit that is connected to the same duct system that is used for cooling only. The complaint is that air flow is too great in the cooling mode. What advice should I offer?

[bikeman564™]

IIRC, can't the blower motor be wired differently to control it's speed? Slowing down the blower on the tertiary unit should reduce the flow.

[maddmaxx]

Duct tape over the outlets where the flow is too great.  That's what I did at work over my desk when I discovered it was dumping 52 deg air on my head.  

[pedalphile]

1 minute ago, maddmaxx said:

Duct tape over the outlets where the flow is too great.  That's what I did at work over my desk when I discovered it was dumping 52 deg air on my head.  

That's a good idea, that dump of cool air is directed at any1 sitting on the crapper where I work.

[maddmaxx]

1 minute ago, pedalphile said:

That's a good idea, that dump of cool air is directed at any1 sitting on the crapper where I work.

That should increase productivity.

[Longjohn]

Here is how I handle twinning and it works great for me.

[Wilbur]

Two stage motor. 

[donkpow]

Any restriction or reduction of the airflow in cooling mode creates the possibility of causing the evaporator coils to ice over. Icing of the coils further restricts airflow causing the air conditioning to run continuously to meet demand. Essentially burning up the condenser.

[pedalphile]

Venturi effect.

[donkpow]

Just now, Wilbur said:

Two stage motor. 

Two stage fan motor requires two stage operation in the condensing unit, the outside part of the air conditioning system. I did set fan motor speed to Medium Hi speed. It was set to Hi speed. We'll see what happens next summer.

[donkpow]

Just now, pedalphile said:

Venturi effect.

Needs a pitot tube. 

[maddmaxx]

12 minutes ago, donkpow said:

Any restriction or reduction of the airflow in cooling mode creates the possibility of causing the evaporator coils to ice over. Icing of the coils further restricts airflow causing the air conditioning to run continuously to meet demand. Essentially burning up the condenser.

When you have 52 deg air pouring down onto your head, that's an acceptable solution for you.

[donkpow]

Just now, maddmaxx said:

When you have 52 deg air pouring down onto your head, that's an acceptable solution for you.

I'm in the air conditioning business, not the comfort business.

[Kzoo]

1 hour ago, donkpow said:

Essentially burning up the condenser.

In the primitive industry of HVAC I can understand how this could be considered a problem.  In the rest of the world (like aviation and implanted medical devices) we call that planned obsolesce.  It is considered a future revenue stream and is calculated in some SEC annual filings. 

You guys should get with the times.

And for the record, I take off the defuser in the ceiling vent and insert a well crafted cardboard restricter plate and then replace the defuser.  It goes in in the spring and comes out in the fall.

[pedalphile]

1 minute ago, Kzoo said:

In the primitive industry of HVAC I can understand how this could be considered a problem.  In the rest of the world (like aviation and implanted medical devices) we call that planned obsolesce.  It is considered a future revenue stream and is calculated in some SEC annual filings. 

You guys should get with the times.

And for the record, I take off the defuser in the ceiling vent and insert a well crafted cardboard restricter plate and then replace the defuser.  It goes in in the spring and comes out in the fall.

Please tell me more of planned obsolesce, I don't think we have it here, and it seems like a good plan.

[Kzoo]

15 minutes ago, pedalphile said:

Please tell me more of planned obsolesce, I don't think we have it here, and it seems like a good plan.

You have buildings there older than the discovery of our continent by Columbus.  You would not understand the concept of planned obsolesce.  

If I were going to try I would start here....

[parodybot]