Rack liquid level up and down

[crackertech]

I've never seen a heat reclaim coil piped in before the AC coil.

Always after.

Mcy is cool first than heat.

[icemeister]

Yep, the HR coil is supposed to be placed in the reheat position, immediately after the cooling coil...and before the main heat source.

For dehumidification, you're basically running the A/C get the moisture out and at the same time adding sensible heat with the HR to avoid overcooling the store. Markets are different animals for when it comes to dehumidification because there's a high latent load with a relatively low sensible load...even in the summer due to the mostly sensible cooling effect from the cases.

A 50,000 Sq Ft department store might have 120 tons of A/C whereas the same size supermarket might only need 80 tons. The problem is their latent loads are nearly the same, so lots of reheat is needed.

[markettech]

Yeah, that's what I meant ......

[markettech]

I figured it out

Well - we're waiting.........

[Dowadudda]

Heat reclaim is always after DX cooling in just about every supermarket application I have seen. Not saying it can not be the other way. But what I have experience with is HR always after.

It is because its for Dehumid in a central HVAC system. When in Dehumid, we DX cool ( our only means to dehumidify) and if the DX cooling falls below AC setpoint, we reheat with HR up to cool setpoint so we don't over cool the space in dehumidification.

Guys often mistake reheat as something to do with dewpoint. Not so. Were just reheating so we don't over cool below cool setpoint on a dehumid call because we have to use the dx cooling to do the removal of moisture in the air.

The fact that your falling to 0% during HR, also tells me the Heat Reclaim is condensing liquid all by itself, as Mathew is saying.

What Matt (phaseloss) is saying is, a Series Heat Reclaim would only be big enough to desuperheat. And you may have proven this this. You forced reclaim, with Blower off. It did not condense. You did not swallow up all of your liquid in the receiver. You turn the blower on, and whammo, she drops.

When the blower is on and the fact it is condensing, Matt, and I agree, were speculating the Heat Reclaim was intentionally designed to be a parallel design, which is not all that uncommon but misunderstood. In a parallel design, you do not divert to air cooled condenser while in Heat Reclaim, but use HR as the condenser. It's sized to do all the work by itself.

When Not in HR for either heat or Dehumid, you use the air cooled condenser.

It's either or. It's in HR for either heat or dehumid aka >>> reheat. If either one of them guys is not being asked for, we are asking the normal condenser to do the work.

In series, it calls, it goes through the HR coil first, it desuperheats the discharge gas, and routes up to the aircooled condenser to get the rest of the work done, condensing and subcooling.

The other issue here we have to think out is the fact that in Hot Gas defrost, we falsely raise head pressure, (creating pressure difference from the discharge to the liquid manifold) to send superheated gas to the defrosting case, coming back as condensed liquid to liquid manifold as to feed the other circuits. This will cause the receiver to spike and trend upward during hot gas. It has to. Returning liquid is what will feed the other liquid hungry circuits, because this liquid coming back typically (use this word "typically" very loosely) will be a tad higher than receiver at this point while the liquid returning from what ever condenser is active, is being held up in the receiver.

I am here to learn as well. But below is how I have always seen this stuff and successful with setting up, with these truths:

So if the drop leg is common to the receiver (captain obvious is me) and it gets liquid either from the Heat Reclaim Condenser or from the Air Cooled condenser, if we in fact (we did not see these, but not sure yet ) if we are using low ambient valves to flood it would be on that drop leg, and getting liquid from the active condenser, which ever is active. This is where that guy would be.

Low ambient valves (flooded condenser) are to achieve some set minimum receiver pressure and only actuating when we fall below all other lines of defense to keep minimum head pressure from falling below some pre engineered, predetermined point (above my paygrade)?

Split is a line of defense for maintaining minimum head pressure in low ambient also but intentionally designed and it is an objective to reduce refrigerant charge.

You will require less overall refrigerant charge, since you always first split, and if so equipped with flooded condenser low ambient valving arrangement, your not using the extra liquid to flood a full condenser to maintain minimum receiver pressure.

So the low ambient valves would be our LAST line of defense to maintain minimum receiver pressure.

You split first, and only off the ambient value. And that is it. Nothing more. As our ambient drops, we need to downsize condenser capacity, or we go too big a condenser.

You Fan cycle only off the head pressure value.

These two settings are totally indenpendant of each other.

Your Hold back (flood condenser) is always last line of defense and on some set minimum receiver desired. likely the lowest liquid you want flowing to the TXV'x.

I think you guys understand why I keep saying flood condenser low ambient valve arrangement is to set minimum receiver. But maybe some guys who are with us here do not. So. When your holding back, there is always a receiver pressure regulator off discharge. It is set to the difference between discharge and receiver. If the receiver falls say 20psi below discharge, it's goon divert hot gas to the receiver. So, while actively holding back drop leg to reduce condenser effective surface area, our receiver may fall below that by 20 psi difference. So it's our goal to always set valves with the end game what is the lowest receiver pressure desired. Which is basically our lowest full column liquid pressure to the TXV.

[Dowadudda]

http://sporlanonline.com/30-217.pdf

I am wrong about hold back position. Damn it.

[markettech]

The fact that your falling to 0% during HR, also tells me the Heat Reclaim is condensing liquid all by itself, as Mathew is saying.

What Matt (phaseloss) is saying is, a Series Heat Reclaim would only be big enough to desuperheat. And you may have proven this this. You forced reclaim, with Blower off. It did not condense. You did not swallow up all of your liquid in the receiver. You turn the blower on, and whammo, she drops.

When the blower is on and the fact it is condensing, Matt, and I agree, were speculating the Heat Reclaim was intentionally designed to be a parallel design, which is not all that uncommon but misunderstood. In a parallel design, you do not divert to air cooled condenser while in Heat Reclaim, but use HR as the condenser. It's sized to do all the work by itself.

If the HR coil is being used as the condenser (parallel), and is sized to take on the rack load in the same manner as the roof condenser is sized to reject the heat....why 0% receiver in HR and 40% w/no HR?

With all things being equal, and the refrigerant not caring through which condenser coil it changes from a superheated vapor to a subcooled liquid, wouldn't one expect a minimal effect on receiver level regardless of whether HR is active or not?

[Dowadudda]

Pat, I though I understood it that when he goes into HR it drops. Let me go reread it. MY Add MAY HAVE BEEN RELAPSING.

[markettech]

Pat, I though I understood it that when he goes into HR it drops. Let me go reread it. MY Add MAY HAVE BEEN RELAPSING.

Maybe it's me that's suffering from dumba$$ syndrome today.........I think you read it correctly. Obviously I'm missing something.

[Dowadudda]

he's undercharged was my interpretation. here I am going on and on and on.

My theory and what made me think along the lines of parallel. And it's just a theory.

in normal condenser, he's in split and has 40. Split it not gonna not be the same capacity as full. But when he goes into HR, he loses it all. (Full capacity).

or: Not isolating the other condenser.

[dangpgt97]

They think that the HR coil was sized for a parallel set up and ended up being piped series? Would you have to pump out the condenser in a parallel setup when it switches to the heat reclaim?

[markettech]

he's undercharged was my interpretation. here I am going on and on and on.

My theory and what made me think along the lines of parallel. And it's just a theory.

in normal condenser, he's in split and has 40. Split it not gonna not be the same capacity as full. But when he goes into HR, he loses it all. (Full capacity).

I guess I didn't see where steelsparky mentioned the condenser was in split with no HR.....only that he noticed there was the ability to do so via RMCC.

Now I gotta read the whole fuggen OP again...

[Phase Loss]

If the HR coil is being used as the condenser (parallel), and is sized to take on the rack load in the same manner as the roof condenser is sized to reject the heat....why 0% receiver in HR and 40% w/no HR?

Because I believe his reclaim coil was designed for parallel operation, but is actually running in series.

[markettech]

So today right around 15:00 I noticed something but didn't have time to get into it as I just went on call for the weekend. I was leak checking the Mcquay heat reclaim AGAIN so I shut it down, my 3 way valve de-energizes and liquid goes up to 40%. So I force on the 3way valve to pressurize the coil, don't find anything and come back to the rack. The blower for the McQuay is now off, reclaim is on and the liquid level is staying dead nuts @ 20%. I actually had liquid coming back, it climbed up to 30% and stayed for 30 mins. It was maintaining 190 head but now ALL of my condenser fans were on. Then I said WTF, turned the blower back on, reclaim comes on and all condenser fans shut off and runs 190 head and there goes my liquid level again down the tank.

Shane, if this were a parallel set up - wouldn't we expect the rack to trip on head instead of.....

True but while simulating this condition I did not have the A/C or blower on in the McQuay. It was powered down @ the service disconnect. And the HR shift was not in place (220) bc the relay was forced. And the fans did start cutting out for me after about 20 mins but I still had more than usually.

[markettech]

Because I believe his reclaim coil was designed for parallel operation, but is actually running in series.

Oh.....I'm with ya now.

[Phase Loss]

They think that the HR coil was sized for a parallel set up and ended up being piped series? Would you have to pump out the condenser in a parallel setup when it switches to the heat reclaim?

Yes, it must pump out the inactive coil. Either one of them, depending on which mode it is in.

[Phase Loss]

I guess I didn't see where steelsparky mentioned the condenser was in split with no HR.....only that he noticed there was the ability to do so via RMCC.

Now I gotta read the whole fuggen OP again...

I'm with MT on this.

The OP mentioned that the condenser has the ability to split.

but never said if it was in split or not, or even whats controlling split... ambient? pressure? nobody knows

[markettech]

So, juice the rack up to 80% receiver level and let 'er fly...........

[Dowadudda]

0% in HR with blower on. 20% in HR with blower off. 40% in air cooled and no HR.

It is equipped with split. We don't know if it was in split. I thought it was first read.

I see what your saying Matt.

[Dowadudda]

I was thinking that if it were in split, when not in HR, thats my 40%. Say it was not split and no HR. Correctly done with parallel I would expect to see 0% in normal since I see 0% in HR = Undercharged.

I am assuming correct application of parallel. That they did not do a parallel as a series.

That was my theory. And just needs to be proved.

To answer Pat, to go high head on HR with out Blower on, then you know this makes Matt's theory. If it were in true parallel you ought to expect to go high with no blower (condenser fan).

I dunno. I hope we get updates on this guy.