old Intertherm / heat only unit in moble home

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old Intertherm / heat only unit in moble home

Postby paw paw » Wed Jun 01, 2011 11:06 am

m/n-s/n electrical information unavailable....what will it take to wire up an ac unit....because there are only 2 low voltage wires there to make up the heat circuit in the electric furnace....I've pulled new 7 wire(what I had on hand) to the t-stat and outdoor unit from the heat unit.... would I need a different plug at the furnace for the wiring difference or will i need some kind of change over kit to wire in the ac unit.
next -
Before installing this old outdoor unit I ohmed out the compressor (5.4 - 4.5 - 1.4 give or take 3-5) were the readings, if I can remember right this is OK......there were no shorts to ground......no open circuits......240v at the contacts,and when pushed in,fan run, but compressor nothing, not even a buzz....the capacitor on the compressor side read 30 mcf..... the customer said he has had it for 3 years in storage but there's no telling how long or where it was stored before that, it had gray duct tape on the lines that was about gone.......I informed that this unit could be ruined (frozen up due to the elements). Could this be the case here?
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- old Intertherm / heat only unit in moble home

Postby 4ftBanger » Sat Jun 04, 2011 7:37 am

You might need a fan relay to run the furnace fan on a call for AC but other that that the furnace wouldn't need any other connections.

The compressor winding resistance appears normal and assuming the capacitor is a match for the unit - looks normal as well. I would think you should get at least a buzzing noise from a seized compressor until the internal overload trips. It is possible for the compressor rotor to be seized up from being in storage for so long. You could try a hard-start kit, which is like another capacitor with a built in relay that gives the compressor motor additional initial starting torque. That might be enough to free up the compressor motor and get it running. Unfortunately if that doesn't work there's not much else you can do. The compressor is a sealed component and isn't really serviceable.
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- old Intertherm / heat only unit in moble home

Postby paw paw » Sat Jun 04, 2011 2:48 pm

Thanks 4ftBanger
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- old Intertherm / heat only unit in moble home

Postby paw paw » Thu Jun 09, 2011 8:30 am

How do I wire in this fan relay in ? ( 24v from y and r and high voltage from contacts to fan ?) where would I get fan wire ? maybe tie into the same that heat ties into or if there is other speed wires use one of them ?
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- old Intertherm / heat only unit in moble home

Postby nomadpeo » Sat Jun 11, 2011 3:45 pm

correct me if i'm wrong. this was heat only. this means there was no evaporator. you are installing a condensing unit outside. i have to assume you also are installing an evaporator and line set. could you clarify ? then we can advise you regarding controls.
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- old Intertherm / heat only unit in moble home

Postby paw paw » Sat Jun 11, 2011 5:59 pm

lol, yes line set and evap. coil and condensing unit, the air handler/electric heat strips has only 2 wires for the heat only t-stat to call for heat. I have replaced with heat/cool t-stat and replaced all low voltage wiring with 7 wire t-stat wire
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- old Intertherm / heat only unit in moble home

Postby nomadpeo » Sun Jun 12, 2011 8:29 pm

thanks for confirming. you will need 4 wires from the thermostat to the air handler and two to the outside. the heat system should already have accomodation for turning on the heat strip and fan in heat mode. it's possible that this is a single speed motor because it was heat only. in some cases, depending on the age of the mobile home, the blower may be inadequate to deliver the cfm necessary for cooling. you may have already researched and addressed this, but you should be able to confirm with a distributor for the brand.

if it is a single speed motor, you will need a spdt (single pole / double throw) relay with a 24 volt coil. you may also need to change the transformer. a heat only setup could have a 20 VA transformer, which can handle up to about .8 - .9 amps. you will be adding a fan relay and contactor to the load, so i would suggest a 40 VA. there are a few possible configurations for the existing heat control circuit. you may have a contactor or sequencer. you may have a relay for heat and only a thermal fan switch. you should be able to incorporate the existing controls, but you may be better off using a fan relay and sequencer.

if you upload a shot of the control panel and a closer view of the connections, we should be able to help you with a circuit design. also note the va rating of the transformer.
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- old Intertherm / heat only unit in moble home

Postby paw paw » Mon Jun 13, 2011 8:20 am

I will need a few days to get the pictures
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