carrier economizer

[hvac17011]

this is a smaller unit with just the standard economizer board. this building has 2 rooftiops. they are set up for differential enthalpy control set on d. the problem was they were calling for free cooling with 80 deg temps. i replaced the od air sensors to foolow up from another techs service call. i replaced them. with set on d mechanical cooling came on damper closed. switched to a and economizer came on mechanical cooling off. now today same thing no ac both calling for free cooling with 80 deg temps. everything wired right. control board is a hhg3aw001 od sensor hh57ac074 any ideas

[Dallas Duster]

Is it the honeywell board and where are you located ,like outside airtemp and humidity? Maybe a full model # too.

[airdata870]

When you say the standard econo board, most of us would think honeywell W7459. but the #'s you gave look like the Novar EconoMi$er+ package.did you verify 18 to 24VDC from contoller? and did you you measure the 4 to 20mA signal in the enthalphy circuit compared to ambiet conditions? before you replaced sensors. Do you have any more info? we want to help

[xarralu]

I heard another tech at the shop had almost the same thing going on with a couple of carriers but the units were calling for 100 OA damper position and the compressors were coming on! I would like to hear if anyone else has the same thing going on.

He said he just ended up pulling the 24 volts from the OA controller. He also stated that he checked for the right connections and wiring of the differential ethalpy and all was OK on that end of it.


things that make you go HHHHHHUUUUMMMMM....

[klrogers]

this is a smaller unit with just the standard economizer board. this building has 2 rooftiops. they are set up for differential enthalpy control set on d. the problem was they were calling for free cooling with 80 deg temps. i replaced the od air sensors to foolow up from another techs service call. i replaced them. with set on d mechanical cooling came on damper closed. switched to a and economizer came on mechanical cooling off. now today same thing no ac both calling for free cooling with 80 deg temps. everything wired right. control board is a hhg3aw001 od sensor hh57ac074 any ideas

If you are using differential enthalpy, you need to check the return air enthalpy sensor, if that is faulty then the control could be reading higher enthalpy in the return air than the outside air.

Kevin

[hvac17011]

The model of the unit is a 48tme009601hq. the numbers in previous were carriers numbers. i tried removing return sensor which should make it just looking at outside air but it did the same thing. I have 2 units sitting side by side doing the same thing the one unit has 2 stages of cooling and the compressor was running. the manual says doing a checkout with several resistors and a 9v battery but i didnt have resistors.

[y7turbo]

I heard another tech at the shop had almost the same thing going on with a couple of carriers but the units were calling for 100 OA damper position and the compressors were coming on! I would like to hear if anyone else has the same thing going on.

He said he just ended up pulling the 24 volts from the OA controller. He also stated that he checked for the right connections and wiring of the differential ethalpy and all was OK on that end of it.


things that make you go HHHHHHUUUUMMMMM....

a call from y2 will bring the mechanical cooling online even with free cooling available.

[xarralu]

Huh, did not know that. Ill pass it on...

[brandewski]

a call from y2 will bring the mechanical cooling online even with free cooling available.

but shouldnt the oa damper shut to minimum at that point?

[airdata870]

but shouldnt the oa damper shut to minimum at that point?

not with a 2 stage t-stat and the OA is ok for free cooling,the economizer is first stage and the compressor is second stage creating an integrated economizer.

[y7turbo]

but shouldnt the oa damper shut to minimum at that point?

if were talking about your normal honeywell 7459 , he dampers should modulate to keep a discharge temp of 50-55. or is it 55-60? i have to look in my book. too many damn things to remember! lol

[flange]

Differential enthalpy set up look at the total heat content of each airstream. If the oa was less than the return, it could do what you suggest. Are you using the right sensors? the carriers usually ship with a single sensor which is temp only, and for diff enthalpy you need to replace both. When you removed the return sensor, did you install the resistor across the terminals?? confusing the controller will only confuse you more.

[JRINJAX]

According to EPIC, you have a digit off in your part number for the econo controller. I think it should be HH63AW001. The sensor number is correct.