electric heat

[TFoster]

:deadhorse:I have a package unit with electric heat, I put on a new digital t-stat, sometimes it heats then not, fan then not 24v, heat 480 3 ph. went thru 2 stats. Transformer in heat conpartment along with tstat wires anyone have this problem .Im thinking electrical interference from resistence heat.

[VTP99]

What make & model we talking ?

[TFoster]

:deadhorse:I have a package unit with electric heat, I put on a new digital t-stat, sometimes it heats then not, fan then not 24v, heat 480 3 ph. went thru 2 stats. Transformer in heat conpartment along with tstat wires anyone have this problem .Im thinking electrical interference from resistence heat. 30YR OLD YORK 5 TON, Invensys 9725i2 stat

[TFoster]

4 ton York Pathfinder approx 30 yrs old 25 KW resistence heater, New Invensys 9725i2 stat

[TFoster]

25 kw heater

[VTP99]

Did you try running the unit @ the unit with no stat ? It's not a heat pump right ? Does the t-stat have staging ? Yes i see it has 3H & 2C .

[TFoster]

is 2h;2c, jumpered r-w1 run fine for 3 days(todAY)

[TFoster]

.2 AMPS ON W1

[VTP99]

Did you check that stat wire for shorts ? Is it 30years old as well ?

[TFoster]

Unit is on our guard house roof no ladder .Only electric heat we have never seen this problem before, Put new sequencers in,always have had an issue.

[TFoster]

yes i did

[TFoster]

thought of running 7 cond sheilded twire

[VTP99]

How many heat strips ?

[TFoster]

3 ,

[VTP99]

3 ,

I read where that stat has 3heat stages so is there a stage for each strip ? Also have you tryed running the blower in ON mode to see if it shuts off ?

[TFoster]

this is a 2 stage heat ;2 stage cool, with stat off heater works well as suppose to , with face of stat on unit works well with all phaeses heat,blower etc, cycles well, then in about 12 or so ,more or less ,light for heat is onwith no heat no fan.jumper out subbase and everything is fine,next time fan light on heat light on ,i have neither fan nor heat, jumper R-W1 again everything fine to this day ,even put new invensys stat on , does same ,very strange thing.

[TFoster]

somehoe do i have a tpye radio emi?

[VTP99]

somehoe do i have a tpye radio emi?

You stated in your first post that maybe the transformer location was a possible cause. Has that transformer always been in the same location ?

[TFoster]

to my knowledge yes

[VTP99]

Could it be the transformer is border line weak and can't handle the load of the t-stat ?

[TFoster]

That sounds like a good idea, I will have to look into it.

Thank you.