I'd like to know if anyone has the answer. Outdoor unit, wired correcty (both unit's power and DC voltage from & to each unit were ok), both transformers performing well. Have had no trouble for 4 or
5 years. Till the other day - outdoor unit will not come up. Shows P8 on controller display. LED 2 blinking on outdoor control (phase open) BUT per tech book and company rep this LED error means nothing on this model. Checked ALL saftey controls (thermisters) - OK. Unit is single phase 208v. All I did is swap the power leads (208v single phase) and the unit lit up like a christmas tree. Working great now. Rep could not explain it. Does anyone have an explanation and I already know I was lucky. AND it's good to see your doing well Paul, I haven't posted here since '97.
Did you by chance disconnect the power [before you swapped wiring] to the unit? Some times, the computers must be "reset" before they will allow the unit to restart. You may have reset the computer board during the swap. The wire swapping may not have had anything to do with it. I honestly don't know if that's the case, but it sounds like it.
The power was shut off several times in order to check thermisters, safety switches, compressor contactor, compressor and finally changing the 208v legs when it finally ran ok. I don't understand why changing single-phase legs on the outdoor unit had anything to do with it. Before the unit came on line, the P8 did clear but after 9 minutes of outdoor failure it then goes back into the P8 warning. When the inside unit called for cooling during the 9 minutes I did get correct DC voltage at S1, S2, and S3. I also had 208v (wired 208v which as you know is ok for this unit) at the junction plug for the outdoor motor coming out of the board. The fan did not start. I hooked up another test motor to the plug, which uses a much less amp draw than the unit's motor and it did not start as well. In thought I may have had a back bleed of voltage, but due to the internal "FC" (fan controller in the board itself) it could not be checked. In other words, it mystifies other mechanics, Mitsubishi and myself. I went ahead and installed a new board with the same results. I do believe I'd rather have a "Mini-Chiller". I appreciate both of your input. "Mysticalbishi"
If you swap the 208v line leads back, the failures should all return if the power supply is the problem.
Wait,,, 208v single phase!???? Where are you getting your power supply from? A common 240/3phase is 120,208,120 to ground. Are you using a single 208 w/ a ground leg? What voltage do have w/each leg to ground?
Sorry, I should have stated that this isn't residential power. It is
208 single phase with ground wire for unit protection. I do get 115v from each leg to ground, which is normal. I have borrowed power from the disconnect from many rooftop's or any other unit I may find close. After removing the unit side supply where I could put one clip to power and one to ground, as long as I don't over amp. This is why I don't understand the switching of the two legs on 208 single phase had anything to do with it, surely Mitzubishi does not understand rhyme or reason why it worked. I did convey with him that the DC voltage being polar and coming off the outside unit, may have had everything to do with the 4 lead secondary 12VDC. He disclaimed that, but it is the only reason I can come up with or at least the "control board" can.
I'm inclined to go with *zero's* thinking. When you measure the line to ground [either L1 or L2] are you measuring with an open disconnect? It seems to me if you single legging from a three phase supply, switching the legs could have "funny" reaction with it.
i think zyp has a point , are you measuring voltage with disconecct open or closed ?
cant help but wonder if your not tied into a "crazy" leg this is three phase service right , your just using two legs ? some areas still have this type of service ,ithink its called delta t darn leg will swing from 90 to 180 volts , depending on load, just a thought ?
"Zyp" wrote:
9p>>> minutes I did get correct DC voltage at S1, S2, and S3. I also hadp>>>
208v (wired 208v which as you know is ok for this unit) at the:>>> junction plug for the outdoor motor coming out of the board. The>>> fan did not start. I hooked up another test motor to the plug,>>> which uses a much less amp draw than the unit's motor and it did?>>> not start as well. In thought I may have had a back bleed ofp>>> voltage, but due to the internal "FC" (fan controller in the boardE>>> itself) it could not be checked. In other words, it mystifies">>> other mechanics, Mitsubishi and myself. I went ahead and installedØ>>> a new board with the same results. I do believe I'd rather have a>>> "Mini-Chiller". I appreciate both of your input. "Mysticalbishi"S>>
.p>>T>>> Kitch>>p>> If you swap the 208v line leads back, the failures should allW>> return if the power supply is the problem.>>p>> Wait,,, 208v single phase!???? Where are you getting your powerp>> supply from? A common
240/3phase is 120,208,120 to ground. >> Are you using a single 208 w/ a ground leg? What voltage
-p>>h>> - Show quoted text -- Hide quoted text -j>>^>> - Show quoted text
-?>p> Sorry, I should have stated that this isn't residential power. It isp>
208 single phase with ground wire for unit protection. I do get 115vp> from each leg to ground, which is normal. I have borrowed power fromp> the disconnect from many rooftop's or any other unit I may findz> close. After removing the unit side supply where I could put one clip~> to power and one to ground, as long as I don't over amp. This is why> I don't understand the switching of the two legs on 208 single phaseD> had anything to do with it, surely Mitzubishi does not understandÊ> rhyme or reason why it worked. I did convey with him that the DC`> voltage being polar and coming off the outside unit, may have hadÓ> everything to do with the 4 lead secondary 12VDC. He disclaimed that,?> but it is the only reason I can come up with or at least the "control?> board" can.>?> Kitch?pI'm inclined to go with *zero's* thinking. When you measure the line to zground [either L1 or L2] are you measuring with an open disconnect? It seems to me if you single legging from a three phase supply, switching the ¤legs could have "funny" reaction with it.½-- ìZyp
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