Heating Multiple Tanks

[Pegasus]

Hi Everyone,

I mentioned some time ago about a no ongoing cost heating system, well here are my thoughts, but I have a few questions.

Fish House Heat.

I’m considering setting up a number of tanks, which will gradually increase over a period of time, with perhaps twenty in the initial stages, and possibly up to five times this or more in the latter stages. (Think big Bill…. Think big)

My problem is heating the tanks, not just the cost of individual heaters at almost fifty bucks a time and such, but the ongoing running costs. Space heating is a non-factor, as I like to sit and observe my fish, and not be sweating to death while I am doing it. A single circulatory heating system was considered feeding each individual tank with preheated water, but the risks of spreading infections are too great, so I have been mulling the following over for some time.

Hypothetical Situation.

Looking at just 20 tanks with a basic 100watt heater in I am looking at 2000watts, and this does not include lighting. Of course these heaters will possibly not all be on together, but it is still an impact on the power account. I am considering the following and would like some input either negative or positive.

Considering that every additional 10 tanks is going to be another 1000watts just using 100watt heaters, but many could be 150’s or 200watts, depending on tank size, plus I intend to have growing on vats and tubs, which will need individual heating, and so the costs can soon spiral for power bills. You wouldn’t get much change out of a thousand dollars for twenty quality heaters, and I can do a lot with a thousand bucks.

I just bought a Visi-Therm 150watt heater last weekend. It cost $45:50NZ.

Really nice heater with the internal moving red bar for the heat settings and the individual coils all set in thin glass tubes with the actual thermostat fully enclosed. Really impressive bit of gear compared to the old style, but again, not cheap if you want a few of them. These are probably standard issue in the styling of today’s heaters, but it’s been a while since I bought one at retail price.

My idea, once I get moving, is to use the domestic hot water cylinder as a heat source.

The concept is to run three lengths of 12mm copper pipe beneath the tanks. These would be approx 75mm apart and central to the tank base. The pipes will fit into a recess in the tank support shelving and would be just clear of the base glass on each tank, which will be sat on the normal 12mm styrene pads with the area for the pipes removed. All exposed piping will be double lagged and insulated, as will the tee junctions that will be used at the ends of each six metre run, which is the length I need to hold banks of at least ten 60cm tanks to a row. All tanks below these would be 90cm to 100cm or bigger. These rows may be three rows high once I get really involved, with the larger tanks at the lower areas, but the piping system and the racking will be designed for future expansion as needed. The rooms (100sq mtrs) would hopefully be kept around 65 to 70deg F, but warmer in summer of course, and here I could have a cooling problem if it gets too hot, which it usually does.

My Questions.

With a DCYL (Domestic Hot Water Cylinder) maintaining say 70deg C, I am wondering if the three pipes would be enough to maintain the temperature in the tanks, or would two manage the job?

I could do a mock setup, but this would involve wasted time and funds, as neither copper pipe nor fittings are cheap, and I would need at least ten tanks and eighteen metres of copper pipe to prove a point, plus all the fittings.

The heat through the pipes would hopefully be quite constant, and due to the heat retention capabilities of copper, it would remain for some time and the temperature drop would be minimal. Industrial standard thermostats would constantly monitor the tank temperatures, and if this should fall within a given parameter a small circulatory pump (12v) would come into action and pump hot water directly from the DCYL and through the piping, and then be returned unused to the cylinder. Heat loss would be minimal, and the DCYL would basically only be running to retain the 70deg C and not be fluctuating due to the tanks.

Power cuts are also not a problem, as the DCYL will hold its heat for over a day, even when switched off. A relay would close in the event of a power cut and allow the circulatory pump to run from a standby battery supply when needed.

Does anyone think this will work, or does anyone think I am dreaming of a reasonable cheap way out? Either way, I intend to get moving with more tanks over the coming months and summer. Under tank heating is nothing new, so there should be some figures out there that will give me some guidelines.

The initial installation would be far from cheap, but the ongoing costs would be non existent, as we already pay for our hot water, which just gets flushed down the drain, many times a day, but this is an enclosed no loss system.

Happy Days.

Bill (Pegasus)

[Ira]

Sounds like just a modification of a type of central heating called, I think, radiant heating. I used to live in a house with it.

I think usually in a household system you'd want to add antifreeze and things to the water, but I don't know if that's necessary in this case. You could always experiment with the water temperature, 70° might heat the tanks at the beginning of the loop a bit much and towards the end of the loop the temperature would drop a bit. That's if the pipes are running in parallel instead of just a single long pipe looped back and forth. Which would seem to be a good thing, it'd give you a small range of temperatures for different fish instead of everyone being at the same temp. I think you could increase the temperature difference by by adjusting the speed the water is pumped. A higher volume would bring the end tanks up closer and lower would let them cool a bit. I also wonder if having the pipes against the back of the tanks instead of the bottom might not work better? Then you wouldn't have the thicker bottom glass and any substrate insulating the water a bit....Hmmm, Nah, probably would add a bit too much complexity.

I don't know if you can easily get the piping that has little radiator fins on it here in NZ, but if you can it might be useful. But I think it's normally quite a bit bigger than 12 mm, at least I think the ones at my parents house are. Depending on the cost of piping, I'd say the more you use the better. You're not going to get the greatest heat transfer from the pipes to the tanks with just bare pipes pressed against the bottom of the tank. I think you'd be better off running more pipes running at a cooler temperature. But I guess hotter and fewer would probably work just as well as cooler and more, but more pipes would give you extra heating if it's needed.

Ok, that's enough typing and not saying much useful for now.

[Bruce]

Hi Pegasus

The easiest solution I think is a centrally heated tank which is pumped to your smaller tanks, I have this setup in my fish room, also I have a 2400w fan heater setup in there as well

This is hooked up to a thermostat set to 23 degrees

If you are worried about infection by having all tanks connected then use a UV filter in the line this should eliminate this problem

MTCW anyway

/Bruce

[Caryl]

Assuming a well-insulated room, the simplest, cheapest option would be to heat the room. If the room is well insulated even a 2kW electric fan heater would maintain the required temperature. It could always be supplemented with an extra heater if the temperature did drop. An air conditioning unit would be more efficient to run and could be used to maintain the temperature in summer as well. For heating, the cheapest option in your area could well be gas - but not so easy to cool the room with it.

The disadvantage being it is heating the room, which you didn’t want to do. However, at what temperature are you going to run the tanks? For example, running at 25 degs C is not exactly uncomfortable and if you had some tanks requiring a higher temperature, add supplementary heating to those tanks only. Heating the room is a lot safer as no heaters and thermostats are in the tanks, which also reduces their clutter.

If you are heating the tanks separately from the room then remember that the tanks will heat the room due to heat loss from the tanks and lighting so to keep the temp of the room at a comfortable level below that of the tanks, you are going to have to have a cooling system for the room. More running costs apart from the initial installation costs. Because the room is cooler than the tanks, there will be greater heat loss from the tanks so even more energy will be required to heat the tanks. You could perhaps be clever and harness the heat output from the air conditioning unit to heat the tanks or to supplement the tank heating.

If heating the tanks separately, I would recommend using heat pads (I can send you building instructions if you like as we have made them ourselves). This would require thermostats in each tank because you can’t guarantee they are all going to be the same temperature (drafts, end tanks etc). When the room temperature is high in summer you may still have to cool the tanks however you have already got the cooling system to keep the room cooler than your tanks.

As for using the domestic hot water cylinder, this is not a free source of heat as you are extracting energy from the cylinder therefore cooling the water in the cylinder, which has to be reheated. If this is an electric system on a controlled circuit you probably only have the cylinder heating running for about 10 – 12 hours in a 24 hour cycle (usually overnight) which means you will have no hot water by the end of the day – if not sooner. The tanks will then cool off because of this. If the tanks are being heated correctly by the pipes which you intend running from the cylinder then they will be absorbing heat from the water in those pipes meaning that the water returned to the cylinder will be at approximately ambient temperature. This is obviously not a loss-less system. In case of power cuts, the cylinder will only retain its heat if the water is not used, or your circulating system is switched off so it will not absorb energy from the water in the tank.

No matter what form of heating you use you need some sort of monitoring system to alert you when the tanks’ temperatures are outside safe limits. This is more likely to happen if you have separately heated tanks than if you heat the whole room as you have a larger number of heaters and thermostats to possibly fail. If the room is well-insulated it would be highly unlikely to have a rapid change in temperature that you wouldn’t notice on your daily visits however one tank in a group of 20 could well be either too hot or too cold without your knowledge unless there are alarms.

Heating the room also prevents the possibility of cross infection when using a centrally heated tank to provide water for the rest.

I think that has covered all your questions and the replies from others in the 3 forums I have seen this thread posted.

[Pegasus]

Hi Caryl,

Thanks for the lengthy reply which I have pasted in my notes.

You make a lot of valid points, and I would like to clarify one or two things.

The particular cylinder in question is not on any form of power saving option, so therefore would never be switched off.

Keeping a room at 25deg C does not mean the tanks will be at 25C, as water is 800 times denser than air.

With the cylinder at a regulated 70deg C, which the pipes on full flow would roughly remain at, the heat loss in these pipes would be very small in order to keep the tanks at say a given 23 to 25C, and as the water is in a continuous loop only when required, I can only imagine that the loss of heat would be miniscule and hardly affect the huge volume of water held in the cylinder, which would take very little time to preheat anyway. The ambient temperature of the room would certainly be no less than 23 to 28deg C anyway I would think.

My saying the running costs for a system such as this would be "non existant", I am referring to any major variations in our present power account and by using the system above.

Running twenty or more heaters, or an air conditioner, or other means of heating would certainly bump the power bill up a considerable amount, but I feel that using this method the difference would hardly be noticed.

Even in the event of a prolonged power failure, the cylinder would obviously cool to some degree, but it would have to drop below 28C to be inaffective, which could take quite some time as the system is not actually "using" the water, but returning it at a very slightly lower temperature.

Nothing is absolutely free, but to me this seems as if it may work.

I really appreciate your feedback on this Caryl, and hope you will post your Heat Pad system in some of the DIY sections for us all to share.

Regards,

Bill (Pegasus)

[Caryl]

I have avoided posting an article on how to make heatpads as you really need to have expert knowledge, and appropriate qualifications, in the electrical field to get it right. I also did not want anybody suing me after following the article and then managing to burn their house down!

Grant has his electrical technician's certificate so knows his amps from his watts. I am happy to email the article to you if you want. It was originally written as an article for the NZ Aquarium World magazine with loads of disclaimers!!

BTW it was actually Grant who replied to your heating question, not me, and he still thinks your theory is flawed. We will follow your project with interest though and wish you all the best with it.

Ain't fishkeeping fun and interesting?

[Pegasus]

Hi Caryl (forth time today

Just a question or two (or three),

Do you know the actual temperature of your Heat Pad under the tank ?

Do you know how long it is on per day, and how it compares to a conventional heating system ?

I also know my watts from my amps, but thermodynamics is not one of my knowledgable subjects, hence the posts

Regards,

Bill (Pegasus)

[Ira]

DAMNIT! I wrote a whole long post and lost it all when my internet connection died just after hitting submit. So, here's the shortened version...

Pegasus, if you need, say 50 watts of heating per tank to keep it at a constant temp using internal heaters, you'll need at least that in the system using the piped water. Actually, you'd need more because you'd lose some heat downwards into the stand instead of all of it going into the tank. It might be more flexible and managable to use a bunch of Caryl's heating pads if they can be made relatively cheaply and in different

Caryl, can I have the plans, please? Promise not to electrocute myself.

[Pegasus]

Hi Ira,

Same bloddy thing just happened to me and I lost my long post, so I'll try again.

Thanks for both your posts

I may have to just splash out and invest in a twenty tank setup.

Seperate heat pads are really not an option as I am trying to reduce ongoing cost, which over a year can really mount up.

Heat loss via the stand will be at a minimum as the pipes will fit into recesses in the support boards that will be filled with insulation before the pipes are laid.

There will be a small air gap between the pipes and tank base.

Regards,

Bill (Pegasus)

[Ira]

You'll still have a little heat going through the stand that would make it less efficient than an in tank heater, though. Maybe only be a tiny amount of loss, I'm not really sure. If you can get some kind of radiator or fins on the pipes that would help make the system work better. The ongoing cost of the heating pads and the pipe system won't be that much different though. I think the pads might end up a bit more efficient, though. The piping system you'll be using the electricity to heat the water and then using the water to heat the air that will heat the tanks. But with the pads you'll use the electricity to heat the pad which heats the tank. That's cutting out one stage and would probably cut out a bit of loss. I'd bet the heating element in the water heater and the heating element in the pad would have pretty similar efficiencies. So you'd probably get more heat out of the pad for less money.

[Caryl]

The actual temperature of the pad under the tank is the same as the temperature of the water, apart from a very small differential due to the glass. However as glass is a very good conductor of heat, in practise you can ignore that loss. The glass is in direct contact with the wire. The wire sits on a backing board of Pinex which then sits on your under tank insulation. This means efficiency is very good.

If the insulation is working correctly there will only be very small losses of heat under the tank.

Our pad is made up of two 150 watt elements because 150 watts meant the length of wire used was a good length to fit neatly under, and support, the tank.

A 300 watt heating pad will be on almost the same amount of time as a 300 watt internal heater in the tank, assuming the same amount of insulation for the tank. With an internal heater there will be heat loss through the bottom of the tank the same as if you were using the pad because your insulation will be the same.

As we have a well insulated house, the heater doesn't have to work too hard even in the middle of winter. In summer the heater is never on because the ambient temperature of the room is usually higher than the desired temperature of the tank. Some years we have had to turn off the lights and lift the lid (even having to drop a slikka pad in at times) to get the temperature of the tank down to a manageable level for the fishies.

I will email you both a copy of the plans.

Ira, if you have any questions you can ask Grant about it at the fish display weekend.

[Midas]

As I know something on the subject of thermodynamics (I deal with heat transfer daily and have also taught the basics of the subject) I thought I would add MTCW also.

I think your system would work but as far as running costs go you will still have to supply the same amount of heat into the tank water to heat it up whether it is via an in tank heater, heat pad or your water cylinder heater. I doubt whether the thermal effeicency of the copper pipes would be better than that for an in tank heater or heat pad. Therefore, all these three systems would probably have similar running costs (in terms of electricity usage).

Another issue I see is having a temperature gradient across your tanks. As the heat source is much hotter than the tank temperature how will you get an even temperature across all your tanks? I acn forsee some tanks heating to much more than 25^C while others could be much less. I haven't calculated the rate of heat loss from the pipes to the water to work out how many you would need under the tank to heat it effectively, this would depend on flow rate of the hot water amoungst other things.

Also how many litres is your hot water cylinder and how many litres of water in your tanks where you planning on heating? This would give some idea on the potential rate of temperature drop in your cylinder when it is heating your tanks.

I disagree with your statement about the tank water temperature differing from that of the room temperature due to density differences. Yes water is denser than air (and probably more importantly in this case has a higher specific heat capacity). But if your room is constantly held at 25^C and the room is resonably well insulated the tank water temperature will eventually reach 25^C also, it will just take longer than it took to heat up the room.

This room heating method has the potential to be the most energy efficient out of the ones discussed. Once the room and tanks are up to the target temperature only a minimum of energy should only need to be applied if the room is insulated well. This energy would need to compensate for looses from the room (which should be small if insulated properly) and also to heat up any incoming cold water into the room. Compare this to the situation in a not so well insulated room, whether heating directly or the room.

[Joey]

I would like to personally thank you Bill. I thought that I was over the DIY bug until I read this post.

Not that it really applies to me, I don't have plans for that many tanks (yet). :lol:

[ajbroome]

Midas said...

> I disagree with your statement about the tank water temperature

> differing from that of the room temperature due to density

> differences.

Yep, you're right there. Given time, the whole room will settle

out at around 25C assuming decent insulation so it doesn't

matter whether you're heating the room as a unit (where the

tanks suck heat from the air) or if you're heating the tanks

(either via hot water, an individual heater, or undertank heating

wire) in which case the room will suck heat from the tanks.

Water may be a degree or two cooler than the surrounding air

due to evaporative cooling but in a warm humid fishroom this

is less significant than in a cool dry room.

It takes about as many watts to heat a given quantity of water

either way since you're doing the same job. The only advantage

I can see to using the hot water methods is that the rate you're

charged for water heating is usually less than for your household

electricity. However I would expect the setting up costs to be

quite high...

I'd be inclined to heat the room (probably a suitably protected

fan heater at the bottom of the room). All things being equal you'll

find the upper tanks will be warmer than the lower ones.

If you're using any sort of artificial lighting then that will add to

the heat in the room as well. In the summer I expect your

biggest problem will be keeping things cool enough for some

fish rather than the reverse. A lot of fish are typically kept

much warmer than they need and this can shorten their

lifespans and interrupt breeding significantly. This also means they

eat more, excrete more and therefore put more load on your

filter system, at the same time as there is less oxygen in the

water to power the bugs that do some of the biological purification

for you...

Anyway, just my thoughts. I use undertank heating extensively

but haven't decided how I'm going to heat my fishroom yet. I

suspect I will just put heatpads (since I've got them already) under

some of the tanks and leave the rest to equilibrate with the room.

Andrew, who spent actual money in a fishshop on saturday...

[Rob]

Midas said...

The only advantage

I can see to using the hot water methods is that the rate you're

charged for water heating is usually less than for your household

electricity.

Correct because it's controlled by the power company so that it only operates at off peak hours. However, from what Pegasus has said - that it would be operating 24 hours a day (controlled by a thermostat of course) - I would suspect that his would be connected into one of the regular household circuits so would be using the more expensive 'anytime' electricity - therefore negating the cheaper power benefit.

Andrew, who spent actual money in a fishshop on saturday...

I'll have to go have a little lay down now - just what managed to part you from your hard earned cash?

[Caryl]

I am wondering the same as you Rob. Which shop actually had something so spectacular that Andrew forked out cash????

[ajbroome]

Caryl and Rob both wonder...

> ... just what managed to part you from your hard earned cash?

and...

> ... Which shop actually had something so spectacular that Andrew

> forked out cash????

Well, as you have seen, I *did* buy some killies in Wet Pets.

However, I went in there with the full intention of buying some

fluorescent tubes and some filter floss so the killies were just

and extra amount to add to the VISA bill ;-)

On top of that, I cleared away a bookcase on Sunday so I now

have room to set up a community tank in the house so it looks

like I'll be buying non-killie fish at some stage in the future. Once

I've got some concrete blocks to use as a stand, painted the

intended tank black on the back, sorted out some heating and

lighting and so on and so on...

Andrew, shaking his head and wondering why...

[Pegasus]

Hey everyone,

Really great feedback, and a lot of really useful info that is going to take some digesting. I have copied and pasted all your posts for my reference.

Many thanks,

Bill (Pegasus NZ)

[Warren]

I'll add my bit.

Since the laws of physics require that any given mass requires the same amount of energy to heat it to a given temperature regardless of the method, it is sensible to assume that the method used to heat the mass should use the least amount of energy you have to pay for.

Use an airconditioner (a good one) that has at least 4:1 conversion efficency. Then you only have to pay for 400W of energy to get 2000W of heating. Insulate the room very well since once the water is heated, all you pay for is the loss in the system. Put stirring fans in the room so the air temperature does not layer.

[Pegasus]

Thanks Warren,

Seems I have a lot more to think about now.

I'm studying all options with an open mind

Regards,

Bill.

[Ira]

I had a chat with a breeder in the US once. He runs something like 200 tanks inside his house and said he found it easiest to just heat the entire house to 90ish farenheit and then get used to the house being too hot. Don't know if he was exaggerating and it's just his basement or what, though. Then he could adjust the temperature in the tanks by putting the ones he wants warmer up higher, cooler lower. So layering CAN be useful. He also said that his takes are a little cooler than ambient. Probably due to a little bit of evaporation.

[Warren]

I have a friend who used to have 300+ tanks in a separate room in his house (actually a warehouse). He used induvidual heaters in every tank. Lots of $$ for heaters wot! The room temperature was a constant 26'C, heated by the tanks. It would have worked just as well if the room was heated to 26'C and the heater were removed from the tanks. The room was very well insulated so the cost of the power was mainly for heating water after water changes (done every 3-4 days).

He was looking for a way to reduce the power bill. He looked at gas heating, but it causes too much condensation in a well insulated room. Also have to watch the CO2 level in the air if there is little or no circulation with outside air. The best method was to use about a 6.8kW airconditioner and 10 medium sized stiring fans spread round the room. It was a big room too (approx 9m x 16m). It never eventuated however and now he doesn't have the tanks anymore.

[dennis]

are we talking about roonie that used to live i n tauranga

warren?

if it was his power bill was about $400 a mouth

[Andrew 22]

I think that most of these points have already been covred but i will reitterate them here as it would take me a long time to go back through the replys to check them (happy reading Bill :lol:).

I work part time for a aquarium fish producer having many hundreds (probbly more like thousands) of tanks.

It will take the same amount of energy to heat your water to the required temperature wether you use heat pads, hot water, or in take heaters (excluding external losses) so i would recomend using the on that is on the cheapest rate.

I think that you will find it very difficult to heat your water using the hot water cylinder as you described as there will be an air gap (although small) between the copper pipe and the base of the tank reducing your transfer efficiance dramaticly. If you want to use your hot water system i would recomend simply running the pipe through each tank makinging it act as a heat exchanger. Obviously you would not use copper pipe for this as it will kill your fish. You may need to increase the flowrate to ensure an even temperature spred among the tanks. i personaly would use multiple smaller lengths of pipe.

At the place were i work we heat some tanks up to 30 degrease (discus) by heating the air to aproximatly 31-32 degrease as was mentioned previously, it may take a bit of time to get the water to the required temperature but once this has been reached it takes a long time to cool down.

Humidity occures when the water temperature is greater than that of the sourounding air so i would recomend having lids on all of your tanks if yoou are simply going to heat the water directly or you will be living in the tropics.

If you decide to heat the room to heat your tanks then i would recomend an airconditioner. They are quite efficient and enable to keep the temperature down in the warmer months which is a major probblem with gas or wood fired heating (we have wood fired heating). Airconditioners also have the added advantage of removing moisture from the air wich will keep you humidity down. I wouldn`t be complaning at the prospect at sitting back at 27 degrease admiring what will be a realy impressive set up.

I hope this helps a little bit nothing beats doing it your self

Good luck,

Andrew

[Pegasus]

Hi Andrew, and all others,

Really appreciate all this input, and thanks for all you posts.

I have personal reasons for not wanting to heat my fishroom, besides the obvious expense of ongoing costs.

12 months ago I weighed almost 11 stone, but due to a few probs I have am now just 8.2 stone. This may seem insignificant to the above, but one of my probs is breathing, so I just basically want to heat the tanks in the most economical way and avoid any further problems . (please read and forget.. no related posts)

The air gap I mentioned was thought of in the hope of distributing the heat through the substrate (where the tanks would have it) and I did think of making the pipes being in actual contact with the bases of the tanks, but was concerned about expansion.

A double run in preference to a triple would be easier, of perhaps a larger size pipe, maybe 40mm, but I think the only answer here is to "try it and see".

My good wife is wanting to leave the Bach that I want to use for my fishroom intact, so I may even decide to use one of the sheds, which I could probably fit half the tanks I envisaged in.

The dream continues

Regards,

Bill (Pegasus)

PS: Thanks for the mail Ira