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Doc Holliday 12-01-2011 06:22 PM

Heat Pump Crisis, Help!
Brand new Ruud heat pump. New complete 410-A system, actually. In cooling mode it showed low vapor temperature, just at 30 degrees, not sure what that equates to in pressure for 410-A but regardless, I juiced it up to get it to where the txv was keeping it at a steady 42. I did that just to make sure it had enough for heating.

Now I turn the system via old non digital heat pump stat to heat. Blower begins to run, heat pump is on five minute delay, alternating flashing on defrost board. Finally she comes on and flash code changes to dual simultaneous slow, normal.

Warm air still drawing from top of heat pump and liquid side pressure rises to a near 700 :eek:, tripping the high pressure switch. That was as far as I got, home owner had to leave. I was only at the home for a total of fifteen minutes.

I'll be going back first thing in the morning. I did get ahold of a Rheem/Ruud distributor technician, said that the charge must be precise for heat pump and that reversing valve actuates via B on stat. I myself at this point was wondering if the rev. valve was powered or not with the warm air still drawing from the top of heat pump and the vapor line not changing pressures between cool and heat. Anyone?

So far that's all I have to check and go on in the morning so any and all help appreciated.


ps, aux light on old stat was on as soon as stat was calling for heat but only cold air the entire time. the orginal call was no heat. home owner said the aux light was on the entire time and nothing happened, never had even warm air.

pss, I did not get a look at any stat wiring or any wiring

Houston204 12-01-2011 06:47 PM

Restriction, probably at the TXV.

Marty S. 12-01-2011 06:48 PM

First thing to check is air flow Doc. It has to be 370-400 per ton or you're going to get near freezing saturation temps in cool and high pressure lock out in heat. Once the air is correct then adjust the charge to get the correct BTU output. Guessing you are low on air and over charged right now. If all else fails suck it out and weigh in a fresh charge.

Can you explain "Warm air still drawing from top of heat pump"? Rheem/Ruud draws in from the side like all the rest and blows out the top. Is your fan running backwards?

Doc Holliday 12-01-2011 06:51 PM

I meant blowing out of the top, like a condenser in cooling mode.

Houston204 12-01-2011 06:52 PM

It's easy to want to add refrigerant with restrictions. It is probably overcharged.

Houston204 12-01-2011 06:55 PM

Marty has an excellent point with the airflow. Are you running near .5 ESP?

Doc Holliday 12-01-2011 07:00 PM


Originally Posted by Houston204 (Post 783547)
Restriction, probably at the TXV.

I came across that on a heat pump a few months ago in cooling, new txv correcting the problem. This being a brand new complete system with a new txv (I think. It should be) I'm hoping this is not the case.

Century tech support guy (Steve Villars, you know him?) said that it's most likely overcharged, the liquid pressure skyrocketing in heating being a tell tale symptom.

So the plan is to :whistling2: recover :whistling2: a slight bit of 410-A until the pressure remains stable and check the wiring, reversing valve specifically.

Doc Holliday 12-01-2011 07:01 PM


Originally Posted by Houston204 (Post 783560)
Marty has an excellent point with the airflow. Are you running near .5 ESP?

I didn't get that far. I'll check tomorrow though.

beenthere 12-01-2011 07:59 PM

Don't try recovering until the pressure looks better. recover the entire charge, and then weigh in the factory charge. I'd swap out the LLFD right a ways also, while its empty.

Lots of techs add gas to over come restrictions or low air flow cause they don't know any better.

Doc Holliday 12-01-2011 08:49 PM

I added just to get it above freezing which it was below in cooling, not because I thought of any resriction. I know what you are saying though.

Today I certainly didn't charge it to any calculation like I will tomorrow so I'm almost certain it's overcharged as well.

Not sure I'm going to recover the entire charge, I don't have that kind of time. I'll recover a little bit at a tme until the charge stabilizes without shoOting into high pressure in both modes and work the wiring from there.

That's the plan so far, at least. I only have about one hour, possibly one and half.


beenthere 12-01-2011 08:58 PM

Let it recover while you are working on the wiring.

A good recovery machine won't take long to recover it.

Doc Holliday 12-02-2011 04:32 AM

Btw, I've been under the impression that you are supposed to ONLY charge a heat pump on coOling mode. Tech support said I can in heating as well, to use the compressor shraeder port and not the vapor line and there'll be a heating mode charging chart on the unit.

If I do not recover and weigh in the entire charge, you have any tips on charging it while in heating mode? Never done it before. Is it like regular subcool charging or what?


beenthere 12-02-2011 04:37 AM

We charge them in heating mode quite often, since most of our year is a heating season. Follow the factory charging chart. SC is not the same value as in cooling mode.

Doc Holliday 12-02-2011 07:05 PM

Old Comortmaker hp stat, no B terminal. Ruud B wire not hooked up. Hooked O to B, all backwardss but works. New hp stat tomorrow.


Doc Holliday 12-02-2011 09:22 PM

Thought I'd add a few pics. First thing I did was recover a few ounces of 410-A. Then I noticed the blue wire coming from the B terminal of the defrost simply hanging and wire nut capped off. I knew that wasn't right. Went to the stat and sure enough, only an O terminal (no switch of any kind to transfer to the much needed B) with an orange wire attached to it. Same orange wire was not attached to anything at the hp. I attached the O to the B and turned on cool only to have it heat up. Turned on heat and it blew cool.

Ass backwards, but at least no high pressure switch tripping now.

Going to pick up a compatible programmable heat pump thermostat in the morning.

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