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Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 8435
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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Ive struggled with McQuay Enfinity Water Source Heat Pumps

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I've struggled with McQuay Enfinity Water Source Heat Pumps for the past (R-410A console models) in my condo. They've been a lemon and NYC Mcquay says same.

I constantly have high pressure switch problems (red blinking light). Random cutout until they just stop the unit completely at initial compressor startup. There is never any high pressure. Have one now (of the the three) cutting out on high pressure during cool, same condo, same water. If I switch to heat, it goes there too. Other units working fine. These units go bad about once a year and repairmen tend to run away from them.

I'm head of the condo and my condo technician has jumped the wire while we order the pressure switch. There is no actual high pressure problem or water source problem. Seems like there may be some risks but I'm not sure. Also, can this switch be repaired in the field? Last time they had to haul another one out (a pain in Manhattan).
Welcome to Just Answer !. I

will stay with you until the situation resolves. I hold questions open after positive ratings to allow for unlimited follow up... with these kinds of things it can take patience however.

If most of the other units are not having trouble with the high pressure switch then it is likely that the water control valve that lets water flow into the units condenser section is opening too slowly, and the head pressure goes high at the start, but is OK later on...

Also air can be trapped in the condenser water loop, if that is not bled out you can have similar problems... look for air vents (bleed valves) in the condenser water loop, and look for line strainers ahead of the water inlet... those may be partically clogged. Such a **combination** of problems can produce what you are seeing.

Tell me how many units there are in the building and what percentage are giving this particular problem, or are there just 3 total, describe any other problems... and tell me please if the name plate on the water cooling unit used to cool this recirculating water says 'closed circuit water cooler' or 'cooling tower' I need the brand name and model number of that unit as well.

It is not safe to run the units with the high pressure switch bypassed, the risks are about 1 in 10 in this case, as a guess only, that there will be damage as a result.

Depending on space available, there should be other options to fit an after market pressure switch, I will have to investigate that however.

Tell me how long the units have been in place please.

We can go from there.

Customer: replied 4 years ago.

This building has 125 apartments with about 400 McQuay units. Only this one unit is causing a problem. Can't get to name plate on tower at this point in the evening. Can check tomorrow. I think it is a closed system but can't say for sure. I have three. They are 18,000 BTU units (largest). The units were put in 10/28/09 in my apartment; not even four years yet. Entire system and all units, no more than 10 years old. I replaced these for higher efficiency and look but turned out to not be a good idea.


Enfinity units cause problems that older Mcquay units do not and unfortunately, I'm one with the new units. We stopped putting these in and no longer recommend Enfinity. Even more modern versions of the older models cause no problems. To us, Enfinity is a lemon. The third unit in my apartment came with a refrigeration leak and had to be fixed in warranty. 100% failure not a good track record and failures not field fixable from what I can tell.


Maybe history on one that acted the same is useful but it may not be same problem. I no longer trust the high pressure relay. Warranty fixed once on one unit, broken again in the same unit, 1 year later. That unit got to point where it wouldn't even come on in both failures. It has been bypassed since end of February though I do want to replace the relay this summer. This second unit is starting to behave the same way though not yet just stopping immediately. The second unit now fails about one minute into operation, maybe a little longer.

The relay is a simple thing to find but I don't think it can be replaced without draining refrigerant. It's inexpensive. Is that what you would think as well about replacement?


Since I seem to have this problem off and on and repairs don't come fast; parts take a little while for Enfinity, when you say 1 in 10, is it only a damage possibility or is there actual danger from bypassing? I know you can only guess. I just have no feel at all; the other one has been without the high pressure control in operation since end of February.


You are right; it's easy to lose patience on this kind of problem especially when the new units seem to be unreliable.



Hello again Dan.

Just to clarify, myself nor Just Answer has any affiliation to McQuay at all, any information or view points you get from me is entirely unbiased. I have no ax to grind with McQuay and no need at all to defend any of their products.

The latest models of many products these days have problems due to the heavy reliance on Chinese made electronics components...those have not been the most reliable in the world.. some of these new units have four (4) micro computers on board..with dozens of frail wire connections. I avoid them at all costs. However these days there are often no other options. What exactly is going on with your units remains to be discovered.

Regarding the 1 in 10 immediate risk of running the system without a high pressure switch... if it loses cooling water it will overheat and possibly blow the soft plug and release all of the refrigerant, then it is possible that the compressor will keep running without refrigerant in it and burn out. As long it has cooling water it will most likely be OK however.

McQuay is an old line company with a decent reputation, recently bought out by Daikin Kogyo Company in Japan, 2 years ago I believe, (one of the worlds largest refrigeration and air conditioning equipment manufacturers with very high standards).

There is no telling whats going on with the 3 you bought however.

I would hazard a guess that the technician that recharged one of them with refrigerant failed to evacuate the air out of it before recharging, or over charged the unit slightly and that would definitely cause the problem you are having with the pressure switch... getting the refrigerant charge right is as much of an art as a science.. it takes some experience that person may or may not have had...

We can do some tests. You will need a thermometer, a cheap one will work just fine.

Run each of your units in cooling mode for 5 minutes set at maximum cooling, fans on high speed.... and measure the difference between the cold air blowing out and the air going into the unit at the bottom...that will tell me if one of the units is over charged or not.

Lets see how that goes.


Customer: replied 4 years ago.
Phil, In fairness to McQuay, these units have far better circulation and efficiency than the prior models. But,, they seem to be far more sensitive to the vagaries of our building supply side. When the building has problems, they go down first, older mcquay units take a lot more variability and are the last to shut off. Hear it is their higher operating pressure, but don't know.

When our building has problems, it is temperature or flow. Our building should have fewer problems. I'm not sure how often others have building problems.

Temperatures for the two that work are below. #1 had similar problems to the one not working. We had to disable the high pressure sensor. #2 works and hasn't caused problems. I have an extech thermometer. #2 room was already way cool but ran it anyway to get numbers.. #1would not come on at all in February until high temp sensor disabled. Switch replaced once in warranty, Looks like failed again. It's still disabled. # XXXXX has switch enabled and now shuts down in 7-20 seconds.

#1 80.6 to 51.6 (high temp switch disabled)
#2 67.8 to 42.4
#3 failing on high pressure


Hello again Dan. thanks for the tests and the additional background information.

The new units use a much higher pressure refrigerant than the older units, R-22 for the old ones, and R 410a or one of its clones for the ones...these do run very high pressures and very well may be up against their high limits if the water flow is even slightly less than it should be. Your analysis is pretty much correct.

Due to slight variations in how each unit gets water, the #3 unit might be getting just a little bit less.

The other two units are producing 29 and 26 deg F temperature differentials, thats about as close to perfect as you can get...

You will be looking for the same differentials from the #3 unit once it is running again, 29F when it is running in a semi warm room, 26F in a cool room. If you get less of a differential reading, especially by more than 3 or 4 degrees, the unit would have been over charged.

If it runs those 29-26F differentials then it is most likely not getting the cooling water it needs... there may or may not be a valve in the water line that can be adjusted to give that unit more flow... an experienced technician can look that over and tell you what options you have.


Another option is to replace the existing pressure sensor, then run the system, then watch the head pressure and suction pressure, then very gradually let an ounce or two of the refrigerant out, so that the head pressure drops by 5 pounds per square inch or so, and the suction pressure drops by no more than 2 pounds per square inch. That will make the unit a lot less sensitive to restricted cooling water flows.

That would be the next most recommended step... there are no time limits here, you can have that work done, and be very specific with the technician that you want those pressure readings before and after he adjusts the charge... if he lets too much refrigerant out, the cooling coil will tend to ice... an experienced technician will now just how far he can go in that direction... less experienced technicians tend to run the suction pressure a few pounds higher than necessary... in a case like this with questionable water flow, that could cause the problem.

Let me know how it all goes, I will hold the question open indefinitely, even for months after your positive rating.


Customer: replied 4 years ago.

Phil, Thanks for the info and I'll definitely be giving you a high rating. I wish I were able to find a technician that would listen to me that well here but maybe I'll be lucky. Let me return to where I was and ask these questions briefly. I guess that close to the threshold part is not giving the units as good a reputation as might have been desired.

1. On the unit where we bypassed it and it kept cutting off, do you think it could be the sensor? That was its original problem. That unit is showing those perfect differentials now. That would mean replacing a sensor and not the refrigerant pressure approach. I haven't put that sensor back into the system yet. It is running without a high pressure sensor; for past 3+ months. Sensor possibly?


2. Does the refrigerant pressure modifications work as well in reducing problems in heating as cooling?


3. Am I correct in saying that the sensor can't easily be replaced in the field? I think the system has to be drained; maybe more for all I know. Manhattan is not a joy for moving equipment in and out and they aren't light.


4. I'm tempted to bypass the sensor on the down one as was done to the other one. The other unit seems to have worked fine despite the risk with perfect differentials. Really bad idea? Moderately bad idea? Somewhat bad idea? Etc. Is there a physical danger to this (no I won't come back and said you said something) or just a damage risk?






Phil, I noticed this and not sure it is what you meant to say:


"If it runs those 29-26F differentials then it is most likely not getting the cooling water it needs... there may or may not be a valve in the water line that can be adjusted to give that unit more flow... an experienced technician can look that over and tell you what options you have." Since you said they were optimal temperatures, maybe you meant different values if it "is not getting what is needed."

Hello again,

Regarding your point #1... the technician involved is going to have to test the sensor and the control card to determine if the sensor should be replaced... if it tests bad it has to be replaced, if it tests OK then the printed circuit board it connects to is bad... I will want to the head pressure readings he gets on the system when it is in cooling mode on a hot day... that may be hard to arrange, but without those readings I cannot assess the cooling water issues. Those are the root of the problem to a very large extent.

#2 Reducing the refrigerant charge by an ounce or two is generally safe... but it should be done by an experienced, old timer type technician... letting refrigerant out if the system if it is over charged will increase the cooling capacity and the temperature differential you measured.. thats why we want to see differential is before any such adjustments are made.. see my previous note on that.

If the system is correctly charged and you let an ounce or two of refrigerant out, it will loose cooling and heating capacity by maybe 2%... a small price to pay if it solves the problem of tripping the high pressure cut out circuit.

#3 Many people would take their welding rig, vacuum pump and charging cylinder with them to the apartment, drag the unit out on to the floor and work on it right there rather than haul it back to the shop. Each shop does what suits them best.

#4 Moderately bad idea, if the soft plug blows when no one is around, the unit will blow about a pint of oil and refrigerant mist into the room ... then the compressor will keep running until the compressor burns out and it trips its internal overload... it could cause a fire, but that is not likely. Just the soft plug blowing by itself would create a big mess. oil vapors throughout the room if not the house coating everything in a thin film of oil. If that unit has a low pressure cut out switch then when the refrigerant is all blown out, the compressor would shut off on its low pressure cut out... some models have that feature, some to not. Either way you sill have the oil mist problem... you would just not burn out the compressor in that case. (any low pressure switch will be shown on the units wiring diagram)

Show my notes here to your technician, let me know what he says in detail and what he thinks... from that i can assess the service company etc... we can go from there.


Customer: replied 4 years ago.

OK, I got it. Now, I'm feeling I'm taking too much of your time but I did find out two other things that may be of value. Also, I just want to see if I have any protection from the suction line temperature sensor. I didn't see a low pressure sensor. Getting a little nervous about the one without a high pressure sensor (not this one; the other unit that is working without it). Not happy with bulding technician not getting back and replacing switch (if it is switch). I have a grand piano next to it!


On new findings, we had a high flow problem in building (not temperature) though as usual, I'm first to go. It eventually shut down all my units, even one with high pressure sensor removed. We fixed it this afternoon and the two others came back on. This unit didn't. For this unit, I took off cover and sides including filter. It ran with everything off. Then, I added the sides, then the cover, then the filter, checking it each time. It runs each time. Unclear why this would make it work (though I think doing it changes pressure)?? This allowed me to get temperature differential. It might be slighlty overcharged??


It is 73.6 to 49.2. 24.4 degrees (with filter, 1/2 inch quited)

It is 74.2 to 53.1 21.1 degrees


To be sure, I would have refrigerant drained if you think that will make it less finicky. Regularly breaking is unpleasnt, especially in winter. Even as head of the board, fixing the building for a couple units will be hard. I've toyed with replacing them because of this. I rarely have cooling problems; it's usually in winter.


I have no feel for how much time you should spend on a question. If you would like me to ask the above separately to get you some additional $, I will not feel bad and I'm not testing you to see what you will say. I might need you again with these units. The other unit remains for me to work on before I call McQuay. I hate to say it but in NYC, I've found I've needed to know as much as the technicians before they come on these units. I'm not sure the problem with that unit is the sensor but I've not had time to look at it. But, it has no high pressure protection as of today!


Thanks, Dan


Hello again Dan.

The unit running the 21 deg differential with the filter in place could very easily be over charged. That means the cooling coil would be running a higher pressure than it should and thus a higher temperature.. the goal in these cases is to run the cooling coil as cold as possible in the cooling mode, without it running below 33F.. (many technicians think the coil will ice if you run it below 32F, because water freezes at 32F, I have run them at 30F before with no problem in a warm room. that is because warm air keeps the surface fins of the coil above 32F... you can run the coil colder than some technicians think.. I have seen some technicians run the cooling coil at 38F or warmer... thats a gross over charge of refrigerant.. this is a sticking point with more than a few of the newer technicians because some manufacturers recommend 36F for *efficiency* reasons.)

. see R-410a column, notice pressure at 103.6... corresponds to 33F that is as high a suction pressure as the evaporator coil should run with the room at 72F... (this is a critical paragraph, each detail is important).... the suction should not run any cooler than 31F in cooling mode with the room at 72F... that corresponds to a suction pressure a bit lower than 101 psig... it will pay you to understand that chart and this paragraph. The best technicians, about 1 in 10 understand this chart very well, the rest do not, they typically over charge or under charge systems.)

You need a real good HVAC technician to work on it.... building engineers are simply not trained well enough to work on those units at that level... not even close. You need one of McQuays best people to get the refrigerant charge right,.. and you need to show him what Ive written. So he understands the strategy of running a *slight undercharge. or in this case possibly just removing a slight over charge.

If you want to get me back in the future just log into your account at JA and click on this question, I will be notified..

I typically go above and beyond in my coaching efforts.. you can leave a bonus if you like, that is always appreciated.

Stay in touch, and use JA as much as you like. We have a full range of professionals here including medical doctors, attorneys, veterinarians and the like in a few hundred different category.

Customer: replied 4 years ago.
Where do I leave the tip? Also, my presentation may not be clear. That is the same unit. 21.1 degrees is with filter off. 24.2 is with filter on, if that makes a difference.

Have any idea why it just started to work after I opened it and continued to work after that or just a strange conflagrance of circumstance?

Amen to finding a good technician.


Hello again, the fact that removing the doors and replacing them allowed the unit to work, indicates that the door switch was not tripped, panel replaced slightly off last time, not closing the door safety switch... and this time you fit the door properly.

Or... there is a loose wire inside that got jiggled ... if there is no door switch look for loose wire connection problems... you will however most likely find a door switch (on the service panel frame)



The suction line low temperature cut out switch will not suffice for a low pressure cut out switch in the event the refrigerant charge is lost.





With the filter in place there is slightly less air flow so the coil runs cooler and increases the temperature differential. (a person has to think about that for a while until it makes sense, its a worthwhile insight )


You can find a good technician by first understanding that chart and my comments, then grill the potential new tech on it... if he is sharp it will go well.


These pressures vary with fan speed as well so a balance has to be achieved that will not allow the coil to ice at low fan speeds and not be too high at high speeds.


The factory weighs the charge in to solve that problem... tweeking the system by letting an ounce or two of gas out is bit of an art..


Your most recent remarks indicate that there are underlying problems with the liquid cooler.... it may not be properly maintained, the spray nozzles inside need to be kept clean along with the suction filters on the pumps... and elsewhere in the system. If that doesn't solve the problems, then a larger pump might solve the problem. I would focus on that aspect heavily.

The bonus button comes up only after you rate positively... let me know how that goes I will appreciate it!... at times the bonus's don't show up.. lost in space or something.. the servers can have bugs etc

You can stay in touch even after you rate, on the same dime so to speak for a while.


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