Delaware high head pressure lock out

Just because you have not walked on the moon does not mean it is not possible or highly unlikely.

If people knew what was in water they would not drink it. All manner of things grow without O2. There is not enough attention paid to the water in our systems. We had a system turn city water into green snot in a bit over a year. Plugged the heat-X and caused a HP lock out.

 

Eric reported that the system indicated not enough flow, which was the complaint by the HVAC tech and the manufacturers representative.
So how did they determine that the flow was too low?
Eric installed a 2 pump flow center and measured 10 psi delta P, indicating way to much flow. He also reported that he took the flow center apart and it was clean. So no slime in the loop.

The point is that the knowledge we have so far points to a refrigerant issue, with the TXV high on the list.
Just because you experienced a system were the heat exchanger was plugged up it does not mean that this is the case here, especially when everything we know strikingly points to a different direction.
Again, unless proven otherwise, high delta P means a lot of flow.

While indeed not impossible, I would say it is highly unlikely that either you or me will soon walk on the moon....

 

No call back from the Hvav today, so the bill is going out. I also got the bosch/carrier install book on the way.
Eric

 

Eric:

If needed I will have the file shipped electronically to you. PM your current email.

Mark

 

Soooo the hvac did call today and I am meeting him tomorrow to repurge after they change a compressor??? He reported wildly fluctuating gas pressures during monitoring of the cooling cycle. He also reported no lock outs. Thoughts?
Eric
eric@waterpirate.net
thanx Mark

 

I think they changed a compressor when they should have changed a heat-X.

 

And I think that they changed the compressor when they should have changed the TXV valve.
How can a faulty heat exchanger cause wildly fluctuating pressures?
Wildly fluctuating pressures usually (until proven otherwise) is a TXV valve not modulating correctly.
But Eric, why would you need to re-purge the loop when they exchanged the compressor? A compressor is not connected to the source water (loop field) at all.

 

It was a heat-x failure. It the TXV was bad, which I am sure it is now, why would the refrigerant circuit be wet and they want Eric to re-purge?

 

If there is a connection between refrigerant and water circuit, the pressures are much higher on the refrigerant side. Thus refrigerant would leak into the water, not the other way around. And you would have a low pressure lockout, not a high pressure lockout.
And how do you know the refrigerant circuit is wet?

 

In heating or in cooling?

Testing tools. Why a re-flush after refrigerant surgery?

 

As a close to this thread, the hvac guy waived me off prior to the re-flush visit. It was a gas side issue causing the fluctuating pressures and lock outs. No word on what or if the customer is finally happy. It is stinking hot here this weekend and the owners flew in for the holiday.....
Eric

 

So they had you come out to change the flow center for nothing.....great.

 

I removed the flow center and installed it at a reduced rate at 1 of my allstar hvac's jobs. If his system goes up and live with no issues, also a 2 unit 5 ton set-up. The B team will be getting the invoice they deserve.
Eric

This just validates what we know here. A fleet of shiny trucks and a slick sales team, do not make GSHP pro's.

 

Yes. The key statement being that the mfr. rep is the sales guy from the supply house, Not the regional mfr. rep or even the factory guy. They go looking for the low hanging fruit-the water side. Before a good diagnostic is done on the unit side or the water side for that matter. As the saying goes, its always the loop guys fault.
Eric

 

EWT, LWT and pressure drop across the heat exchanger are all that is needed to evaluate water side performance. I would have demanded them before rolling a service call requested by the HVAC guy. PT ports and <$50 worth of pressure and temperature instruments gets that job done. I insist on PT ports being present before taking any ownership of geo system performance.

The HVAC guy owns two other groups of data:

1) Refrigerant - high and low side pressures, high and low side temperatures. He should be prepared to state his superheat (SH) and subcool (SC) values and that they are within spec (Absent docs it's hard to go far wrong with 10 degrees each for SH and SC) Also ask for compressor amps compared to labeled RLA or FLA (Running / Full load amps) - typically measure 50-75% of rating.

2) Air side - delta-T across the air handler at minimum. He should also be prepared to substantiate that his ductwork and air filter don't result in TESP (Total External Static Pressure) in excess of air handler rating for wet (cooling) and dry (heating) coil.

If the HVAC guy can't readily supply the above data while casting aspersions on the waterside he's a charlatan not to be trusted.

 

I do not disagree with anything posted. My observation: if an hvac tech is not very, very careful to use good hoses (equipment) with like new gaskets and careful purging procedures, air could be introduced to a system. This why I always pre purged vapor from older refrigerants from the top of the bottle. To my knowledge, I have never introduced air to an hvac system.

This is also why you have to be extremely careful of systems that are in vacuum. (Vacuum will suck air in) It is why I always use hoses with either good check valves or a positive ball valve at the end of the hose. This also why I use 4 hose manifolds which allow vacuum hoses, refrigerant hoses and suction and high side hoses to be hooked up all at the same time. (You vacuum EVERYTHING at once, and then open the charge line from the refrigerant bottle)

(Air collected at the top of any refrigerant bottle would leave from the top of the bottle when you open the vapor valve to pre purge) Most pros today recover EVERYTHING, pull a deep vacuum, and weigh in a brand new EXACT charge, ( or at least charge by measured superheat 7 - 14 degrees) which is almost 100% foolproof.

Boyles law basically tells us you will get the total pressure of the number of gases present as the final pressure, thus allowing air (or other gasses) to mix with the primary refrigerant spells trouble since air simply wanders around in the system with the existing charge. (and begins acid formation) To my experience the only way to get high head pressures in cooling in geo is either insufficient water flow, clogged heat removing device, overcharge, or contaminated charge.

You would (in real time) see the head pressures going from normal to high or "all over the place". Overcharges can cause higher head pressures. With an undercharge or leak, you are doing less work because there is not enough refrigerant to keep a coil or evaporator "filled". Restrictions (around the TXV expansion valve for example) starve the evaporator (which means less work is done there) and refrigerant restriction causes condensed liquid to COLLECT or backup somewhere where it also becomes cooler than normal (because it is not flowing normally). Higher than normal subcooling is the giveaway.