For those who thought venting heat out isn't important

[DaveS]

For some it may be obvious and for others it may not. When you have a MH light, chiller, dehumidifier, or some other source of heat, venting it away from the tank area is important for efficiency and water temperature stability.

 

Background:

 

I have a display tank and frag tank which combines to be about 300 gallons. The DT has 2 400W MH lights and one DIY LED fixture. The frag tank has T5's. I have a 1/2 HP chiller which goes off about once a day to cool down the tank. This is all in a tank room which is also our HVAC closet ~100 square feet. The chiller vents into the fish room but there is a strong fan next to the chiller exhaust which turns on at the same time and pulls most of the hot air out of the fish room. You can see pictures of everything in by build thread (link in signature) but below is a picture of where the chiller is positioned. I generally don't notice the closet getting warm with the chiller on except in the back corner where it exhausts to get pulled out by the fan.

 

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I recently set up an independent ~40 gallon QT/Isolation system in the fish room. It is on the shelf just above the chiller (where the stock tank is in the picture above). Since it's completely independent, I added a 2nd temperature probe to my Apex to control a heater for the system.

 

I came across the following graph and thought it was very enlightening. They say a picture is worth 1,000 words...

 

 

The blue line is the temp of the main system. The red line is temp for the QT/isolation system. As you can see, once a day the chiller kicks on and drops my main system temp by 3 degrees. At the same time this happens, my QT system temp jumps up by about 3 degrees! I figured there could have be some heating of the QT from the chiller exhaust but I didn't expect it to be that much. To put it in perspective, we are talking about 300G vs. 40G so while it's a 3 degree increase for a 3 degree drop, when you factor in volume, 86.7% of the heat is not transferred. But still, this causes a concern as I have a significant source of heating for the QT system and I need to be careful to prevent high temps there.

 

As the title indicates, this thread is mostly just to help show the importance of venting heat away from the fish systems. Whether it's with a chiller, lighting canopy, or anything else that hot air can make a difference!

 

If people want to provide some suggestions on how to make my situation better, I open to ideas. Here are some thoughts I've already had for possible solutions.

 

- It would be nice to vent the chiller directly out of the closet but plumbing issues make it tough so I didn't do it initially. Not sure how to route the pipes without blocking chiller intake/exhaust given the there is no space above the chiller.

 

-I would love to vent the heat out of the entire house entirely (or have a way to switch depending on summer/winter) but the closet is in the middle of the home so haven't come up with a good way for that. There is the gas water heater exhaust flue and a 1.5" pipe for the central house vacuum but no good ways to utilize them yet.

 

-Having a command in the Apex to turn off the chiller if the QT temps get high isn't the right thing to do .

 

-Yes Zygote, one possibility is to move completely over to LEDs (yes Ryan, Radions!) but I'm still in the middle of my LED experiment so not ready for that yet.

 

If anyone has some ideas they want to mention, they would be welcome.

[Ryan S]

When you have a MH light, chiller, dehumidifier, or some other source of heat, venting it away from the tank area is important for efficiency and water temperature stability.

 

The DT has 2 400W MH lights and one DIY LED fixture. The frag tank has T5's. I have a 1/2 HP chiller which goes off about once a day to cool down the tank.

 

-Yes Zygote, one possibility is to move completely over to LEDs (yes Ryan, Radions!) but I'm still in the middle of my LED experiment so not ready for that yet.

 

If anyone has some ideas they want to mention, they would be welcome.

 

You obviously already know what I would recommend, so I will just type it really small...

Just sell off the metal halides, the chiller, and the dehumidifier, and replace them with 6 radions over your tank... No more heat issues... No need for a chiller... Electric bill would plummet...

 

[Jon Lazar]

Dave,

 

You've probably already thought of this, but do you run lights over the QT?

 

If you do, you could shift the QT lighting schedule to even out the daily temperature.

 

Jon

[smallreef]

Is this in a basement or 1st floor of a house/condo? There should be 6 inches between the ceiling and the floor above and you could put in something like a bathroom exhaust fan on a timer(there are ones normally used for a whole house exhaust system also) and vent it outside just like a dryer...

[Ne0eN]

Have you considered lowering your chiller thermostat from 81F to 80F? That may eliminate some of these spikes. Your chiller has to work longer to get the temp down from 81F to 78F.

[DaveS]

Thanks for the thoughts guys. They are appreciated!

 

You've probably already thought of this, but do you run lights over the QT?

 

If you do, you could shift the QT lighting schedule to even out the daily temperature.

 

Jon

 

No lights on the QT although if I do put something up, they will probably be LEDs.

 

Is this in a basement or 1st floor of a house/condo? There should be 6 inches between the ceiling and the floor above and you could put in something like a bathroom exhaust fan on a timer(there are ones normally used for a whole house exhaust system also) and vent it outside just like a dryer...

 

This is the middle of a house in the finished basement. It's 20' in any direction to a wall. Going towards the bathroom would require going through 20' worth of floor joints.

 

Have you considered lowering your chiller thermostat from 81F to 80F? That may eliminate some of these spikes. Your chiller has to work longer to get the temp down from 81F to 78F.

 

This is good idea. If I tighten up the temperature range 78-81 to something like 79-80, the chiller will run more often but cause less of a spike. It doesn't eliminate the problem but could make it better. I'll give that a try and see how it goes.

[Coral Hind]

Since this is in the room with your AHU can you cut in a diffuser to supply the room with cool air or one on the return duct to pull the hot air out?

[PotomacBoater]

I know (almost) nothing about Thermodynamics

but isn't the point of a heat sync to heat up quickly and release the heat slowly

if you vented the output past a bunch of heat sync's would that reduce the spike?

[Jon Lazar]

If you aren't able to move the chiller or change/improve the ventilation of the room, you could arrange things so the QT aborbs less heat.

 

- You could wrap at least the back and sides with ~1" styrofoam. A styrofoam lid would help too. QTs are often darkened anyways.

 

- Since the upper parts of the room are generally warmest, you might try putting the QT on a low stand or shelf closer to the ground. You could even try setting it on the concrete floor and see if there's enough thermal contact to act as a heat sink.

[davelin315]

Dave, you've seen the tiny room I have behind my tank and I think you know that when I ran a chiller and didn't vent the room the temperatures rose to 100 degrees in the room. I've had 2 HVAC people look at it and there wasn't really a solution to it but in your case, you've got a great solution right under your nose.

 

Since your HVAC is in the room, if you leave your HVAC fan on all of the time then you can run a full size duct to your chiller to pull air out of it. I would add an air filter on the other side of your chiller, though, to keep it from getting clogged. The big drawback is that you add heat to you AC during the summer but on the other hand you add heat to your furnace during the winter. This was a solution suggested to me by the HVAC people. I had a concern about salty air in the ducts but in your case, it's already there anyway.

[Origami]

Dave, try setting a fan up next to the chiller that goes on when the chiller activates. This will distribute the air and keep it from collecting in that corner, reducing the heat density in that area.

[smallreef]

Oh i wasn't saying run a line to your bathroom...but using ducting between whichever beams you have you could vent it, like a dryer or bathroom,to the outside

depending on when your basement was finished there may not be any insulation inbetween the joists...

[Coral Hind]

I think you have vent grilles already in that wall going to the other room. Adding a fan in those would help to send the heat to the other room.

[zygote2k]

I think that you'll jump through a lot of possibly expensive hoops to solve this problem, but the real answer is the easy one- LED.

[hypertech]

I'd try just putting a fan on it first. The total heat in the room wasn't an issue before. The problem is that it is concentrated by your QT tank. Put a fan in there to get some air movement and disperse it and it might fix the problem.

 

If the fan increases evap and you don't want that, set it up to run when the chiller is on and for an hour after.

[DaveS]

There is currently a fan in the corner which vents the air from the fish closet into the room next door. The fan comes on with the chiller. It looks like this.

 

 

Obviously the ideal configuration for this would be rotate the chiller 90 degrees and have it pointing straight out the vent but plumbing to the chiller makes that difficult. This approach worked fine for a while. As I mentioned, the room doesn't get hot but it does get warm in the corner which is where the QT now sits.

 

Let me think a little more about leveraging the HVAC. I recall from Bemmer's build that the chiller guys say NOT to restrict the exhaust by putting duct work around it to vent it elsewhere. Maybe just an unrestricted intake vent near the exhaust. I also read somewhere that you have to be careful about venting air OUT of a room like this creating negative pressure. The gas hot water heater is in there and I'm worried the negative pressure may keep the carbon monoxide from going up the flue. As it is I installed a grille on the door and generally make a point to keep the door open so the pressure isn't negative. Anyone know more about that concern?

[davelin315]

Dave, if it's a constant draw and is hooked up so that you essentially have an intake vent surrounding the end of the chiller it will never restrict air intake but rather improve air intake as it'll constantly be drawing it through there in addition to the normal fans in a chiller, making the job of the chiller easier. That said, if you are drawing air into the ductwork from the room you might also want it to draw air into the room as well. Essentially, you'd be making the chiller the conduit from the outside (existing vent out of the room) to the HVAC system. This would decrease air draw from other parts of the home but increase air draw from the basement. If you've already got an intake then you can simply dial that one down with a filter or something similar so as to preserve the airflow in your home as most HVAC should theoretically be planned around air flow through your home.

[Origami]

I also read somewhere that you have to be careful about venting air OUT of a room like this creating negative pressure. The gas hot water heater is in there and I'm worried the negative pressure may keep the carbon monoxide from going up the flue. As it is I installed a grille on the door and generally make a point to keep the door open so the pressure isn't negative. Anyone know more about that concern?

Code requires a certain amount of fresh air intake into a room where a gas appliance is installed. (The amount of fresh air access depends on the BTU rating of the appliance.) That's why you have the grill. Depending upon the size of the grill though, I don't think that you'll be able to develop enough of a negative pressure in the room to affect flue performance. However, it's a good thought. In any case, you might want a carbon monoxide detector in the room, don't you think?

[Coral Hind]

The gas water heater is definately something to think about. If you always leave the door open to the room it shouldn't be an issue but if it were to get closed by accident you could have a problem. Check your heater, mine has a fan exhaust so this is less of an issue on a unit like mine.

[zygote2k]

Dave- could you build a duct for the exhaust of the chiller that will fit into the space, then route the duct somewhere? You would put a fan in this duct to actually pull the air out.

[flowerseller]

Can't use a bathroom exhaust fan and route the 4" vent out of the house just like say.. a bathroom.

I know the fan can handle running all day, my kids leave them on all the time.

A temp probe on an ACIII or apex could handle turning on and off the fan as needed.

[Coral Hind]

It looks like you have a three degree differential between when the chiller comes on and when it goes off. I would drop that down to a narrow on off cycle so the temperature swings of both tanks are not so big.

[Chad]

 

I came across the following graph and thought it was very enlightening. They say a picture is worth 1,000 words...

 

 

 

What a cool graph!! I love graphs, so much information can be pulled from such simple data.

 

Lots of good suggestions here, but I have to ask. Why do anything? Although the temperatures change, they stay within an acceptible range. How many times have you been diving or snorkelling on a reef and felt a significant temperature change as a wave crashes over or you move into a current?

 

Although I would say different if it didn't appear that temperature was under control, I think the current setup is fine.

 

On a semi-related note, from the spikes in temperature in both your DT and QT, I wonder how "real" the effect is anyway as opposed to being a transient condition that doesn't well represent bulk system temperature.

[DaveS]

It looks like you have a three degree differential between when the chiller comes on and when it goes off. I would drop that down to a narrow on off cycle so the temperature swings of both tanks are not so big.

 

Yes I have dropped the differential for now to see how it goes. Maybe it will address things enough to allow me to procrastinate on doing things that require more work but I'm not sure.

 

Although I would say different if it didn't appear that temperature was under control, I think the current setup is fine.

 

On a semi-related note, from the spikes in temperature in both your DT and QT, I wonder how "real" the effect is anyway as opposed to being a transient condition that doesn't well represent bulk system temperature.

 

From this graph, it does look like things fall within a narrow range for both the DT and QT. The problem is that this isn't exactly the case. The DT temps will stay within a range because of they can be controlled with both a heater and chiller. The QT on the other hand only has a heater and the top end is unbounded. This means that if the DT has more heat to dissipate or the ambient (house) temp is higher, that the QT temp will climb higher. Looking at the graph, you can see that the low temp each day does tend to be higher than the previous.

 

I just recently put covers on the QT to prevent jumping and reduce evaporation. This is making the high temps climb even higher so I think I need to go with egg crate covers or something.

 

I think the temp spikes are real and not transient. The probe is in the QT sump so it's got good turnover with the rest of the system. Aside from the first and last days (probably me fooling with water changes), the temp drop is pretty gradual. It never seems to hit a floor or state of equilibrium with the room temp.

 

 

Thanks for all the good ideas everyone. I'll keep noodling over this. As Zygote said, switching over to all LEDs may be one solution to this problem. I'm just not ready to pull the trigger yet for the sake of a QT system.