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REH
Associate

Join Date: Jun 2016
Posts: 29

HVAC Unit Outputs

06/27/2018 12:35 AM

I'm Installing an HVAC unit that has a 2-10 vdc output to control a Hot water mixing valve . However there is no relay output to start pump to supply the hot water.

Could someone suggest a simple, economical way to make a 120vac pump start (with a relay) when the mixing valve control voltage hits 2.1 volts. Thereby running the pump only when it is actually needed.

Thanks for any suggestions.
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lyn
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Join Date: Oct 2008
Posts: 42355
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#1

Re: HVAC Unit Outputs

06/27/2018 12:49 AM

Is this another test question?

Voltage Regulator Circuit
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REH
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Join Date: Jun 2016
Posts: 29
#5
In reply to #1

Re: HVAC Unit Outputs

06/27/2018 11:23 AM

No.
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tonyhemet
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Join Date: Oct 2014
Location: Hemet, Land of milk and honey.
Posts: 2365
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#6
In reply to #1

Re: HVAC Unit Outputs

06/28/2018 2:06 AM

Lyn, I'm sure you know that IHAICI, has seminars that cover this subject, among others.
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SolarEagle
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Join Date: Mar 2007
Location: by the beach in Florida
Posts: 33392
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#2

Re: HVAC Unit Outputs

06/27/2018 12:55 AM

http://www.tekmarcontrols.com/products/hvac-systems/444.html

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PWSlack
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United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

Join Date: Jan 2007
Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain. Kettle's on.
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#3

Re: HVAC Unit Outputs

06/27/2018 4:17 AM

Google "trip amplifiers", and select one that suits the Client's specifications.

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67model
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Join Date: Dec 2010
Posts: 1686
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#4

Re: HVAC Unit Outputs

06/27/2018 5:17 AM

As already given in replies, "trip amplifier" is what you want, for 120VAC supply, 2-10 or 0-10 VDC input with a relay output suitable for 120VAC.

Usually the output relay is not suitable for switching a motor, words like "resistive load" qualify the volt/amp rating. You have not given motor rating or current.

So you will probably also need a motor starter relay or assembly, perhaps with coil spark suppression to avoid spark interfering with trip amp.

Motor starter relay will have to comply with local standard CSA/UL/EN/IEC/VDE for size of motor, which may require an approved assembly like an enclosed starter with isolating switch & overcurrent protection.
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Zvi
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Join Date: Jun 2012
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#7

Re: HVAC Unit Outputs

06/28/2018 5:36 AM

You can install an auxiliary end-switch on your mixing valve that makes contact when the valve starts to open and breaks contact when the valve has closed.

These switches are low-priced and suitable for 120VAC pilot duty. Check with the manufacturer/dealer of the valve.
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67model (1); lyn (1); PWSlack (1); REH (1); SolarEagle (1); tonyhemet (1); Zvi (1)

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