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Electric Rain
28-09-2010, 09:58 AM
NOTE: All links are tinyurls. So, go to tinyurl dot com slash, and then whatever I have in parentheses. Apparently, "You are only allowed to post URLs to other sites after you have made 15 posts or more." but I'm no spammer!!! >.<

Hey, new here. I was hoping you guys could help me with a design I'm working on.

Okay, I know what you're thinking. Another n00b asking for all the answers to design their system for free. I know. I've been on the other end of that, so I don't want it to seem like that's what I'm doing...

I'm primarily a computer engineer. So, electrical engineering plus computer programming, basically. HVAC is a little foreign to me, and even though I've been researching for months, I can't find all the answers by myself. Before I get into the project, let me state again that I'm not asking for someone to design a system for me. After all, I wouldn't really learn anything from that. I'm just asking for advice, tips, dos and don'ts, and how to get started. Don't get me wrong though, the more info you guys will give me, the easier it is for me. :P



Okay, here's the application. This is all going to be just part of a large automation project. I have air and water, heating and cooling needs.

Fifteen gallons of water will need to be kept heated or cooled to ~72 degrees F, +/- maybe 5 degrees, in this tank (2f3lqdh). Method of insulation, if any, is currently unknown. Open to suggestions, but overall budget is of primary concern.

This is an outdoor system that may be used anywhere in the USA. Ambient temperatures may theoretically vary from -10 degrees to 110 degrees, though the client is recommended to keep the unit as shielded as possible.

The system is modular. The "control unit" will host the water tank, all HVAC components and several other unrelated components. Anywhere from 1-8 "grow units" (okay, this is for a hydroponic system... maybe that makes things easier to understand, but I don't want to get too much into unrelated details) may be attached to the control unit for heating and cooling needs.

Each grow unit is 8 feet long, 4 feet wide and 4 feet tall, exterior. Walls are to be 2 inches thick, filled with polyurethane foam. Units will be decently sealed; R-values should be fair. Interior temperatures, I would say, will need to be maintained between 50-75 degrees, though preferably with a bit tighter of a tolerance.

Because of the modular nature of the design, I would like to use radiant heating and cooling, hopefully with a cheap radiator like this (22l2btu) in each grow unit. Possibly with a small DC fan next to the fins...? Not sure if I will need it. Grow units will all be fairly close to the control unit, but will be on casters and able to move around a foot or two any way, so flexible tubing is a must.

If I were designing a forced air system, things would be easier. I know the units are relatively well insulated, and I know that the maximum total cubic feet to heat/cool will be 1,024 (8x4x4 units, up to 8 units), or, if it were a typical room in a house with 8 foot ceilings, a well-insulated 128 square foot room. There are plenty of calculators online to tell me what kind of BTUs I should be looking at as a consumer buying a window A/C unit, but again, because of the modular nature of the design, I do NOT want to use forced air. 6 inch air ducts are a little more cumbersome than 3/4" water lines. So all of those forced air based calculators are worthless to me. This is radiant cooling, which I imagine is completely different, and I can NOT find any decent source material about it. No formulas, no calculators.

I was hoping that a 3926 BTU compressor I have my eye on, with a decent design, would be able to handle my application. I like this little guy (246mlxa), but to be honest, I don't know if this is complete overkill or extremely underpowered.

I have no idea what I'm going to do for my condenser coil. I don't have a clue how large it needs to be, and I don't know how I'm going to build it yet. All parts have to be new, so I can't go to a junk yard and rip a condenser out of a busted window A/C or anything, unfortunately. I'm not sure if I can get a guy to fabricate them for me at a decent price, or how difficult/expensive it would be to build my own. Help. >.<

Anywhere between 1 and 8 grow units may be attached to the system, and they need to be removable/addable. The plan was to have an 8x output manifold, and an 8x return manifold, with an electric solenoid on each output, and check valves on each return. This will allow complete computerized control over which units get heated/chilled water pumped to them, based on temperature sensors in each unit. Just because one unit may be positioned in the sunlight and in need of cooling at any given time doesn't mean the one sitting in the shade needs it too, you know?

I forgot. Make those 9 output/return manifolds. The water tank needs heating and cooling as well. For this, I was thinking coiled copper tubing placed inside the tank would be sufficient. The output and return manifolds are to be connected to a heat exchanger, which will also be be connected to the evaporator, obviously. What exactly my heat exchanger is going to be, I don't know yet. Wouldn't mind some pointers on this either...

For heating, as much as I'd like to design a heat pump so I can just reverse everything and be on my way, I'm told heat pumps are worthless in colder climates without auxiliary heat. Well, I live in Michigan, and most of my customers probably will too... so yeah. If I need to add a resistance heater to the system anyway, I don't see a point in over-complicating the refrigeration system with four-way reversing valves or whatever else I'd need. I was thinking of simply placing an inline water heater in the loop and leaving the refrigeration system offline in the hot months, like this (27ctrmu) with a T, perhaps. Any thoughts about this?

Um... I think that's about all for now. I'm so very sorry about the essay. Again, I'm looking for any help I can get, guides I can read that contain actual useful information for designing a system, with practical figures, examples and formulas, not a bunch of HVAC theory that I've already read over a dozen times. Any tips about anything would be helpful. My budget for this component of the system is... lower than I know it's going to cost me. I was hoping for $500 or less, but I don't see how that's going to happen.

So... Anything? Anything at all? Is this even in the right forum? XD Thanks a lot if you've even read this far...


Don

NoNickName
28-09-2010, 10:29 AM
I don't see anything impossible here.
Where do you want to start, first?

Electric Rain
28-09-2010, 11:31 AM
Wow, someone actually read my post. And this soon... Thank you! XD

I don't know where to start, is part of the problem. I know only about 50% of what I'm doing. Um... I guess the first thing I should know is if the equipment I've chosen is anywhere close to adequate. I've searched and searched, but I can't find a reasonably priced compressor that's any bigger than the one I linked to. I have a gut feeling that it's going to be just the right size, but I don't put too much stake in my gut feelings. Also, do you think that little 2FT baseboard radiator is adequate for a well-insulated 8x4x4 enclosure? I can't see how it wouldn't be for heat, but info about radiant cooling is severely lacking. O_o

I won't ask any more questions for now... I'll do this bit by bit so as to avoid the novel that is my first post. And I know my priorities are probably mixed up, but like I said, not quite sure where to start piecing the design together because there are a good handful of things I don't have figured out yet. Heh... Thanks so much for anyone's help.


Don

NoNickName
28-09-2010, 11:52 AM
The first step is calculating the heat load for chilling the water.
I'm not familiar with imperial units, so I will do it with metric system.
I assume you would like to chill the water with a plate heat exchanger, am I correct?
You don't say how you would like to reject the heat into space.
I assume an air cooled condenser, am I correct?

So you need to cool 56 litres of water from 42°C to 22°C, let's say in 1 hour, and then keep it at 22°C against an unknown heat gain from the system (we will calculate it later).

Qp = m cp dt = 56Kg x 4.1 kJ/KgK x 20K = 4592 kJ
Capacity = Qp / time = 4592/3600s = 1.275 kJ/s = 1.275 kW

We have to find whether your compressor is capable of deliverying that capacity in that time. (continues)

NoNickName
28-09-2010, 11:54 AM
3926BTU/h (we don't know at what conditions) are equivalent to 1.15kW.
It's probably too little, but we could gain the extra 10-15% by playing with the evaporating temperature. Do you have any data sheet of that compressor?

Brian_UK
28-09-2010, 07:45 PM
Hi ER and welcome.

If I have understood you, and in simple terms, you want to cool a tank of water and then, via a branch manifold, circulate the cooled water around 8+ distant units.

You mention using a copper coil in the water tank; makes sense as it keeps the costs down.

Why complicate the system and add further expense by using plate heat exchangers? Feed the remote units directly from your stored cold water tank.

Perhaps stop looking at a single compressor, start looking at a 'condensing unit'. This will be complete with condenser coil and base plate etc.

NoNickName
28-09-2010, 08:01 PM
I'm so upset, Brian. You are taking the fun out of this thread. :-)
I think it can become quite teaching to others.

Electric Rain
28-09-2010, 09:35 PM
Cost is quite a pressing issue for me. I have competition to beat, and there are a lot of other components, unrelated to HVAC, that I have to pour money into. So yes, since I believe it's the cheapest way, I did plan to air cool the condenser coil. And yes, the plan is for a heat plate exchanger, but I'm still not sure how I want to do this yet.

It would be great if I could use the water tank as my coolant to pipe to the remote units, Brian, but unfortunately that 15 gallons is usually going to be tied up within the systems, watering the actual plants growing inside the remote units, and the temperature of that water won't be low enough anyway for hydronic cooling.

Datasheet for the compressor is here: tinyurl dot com slash 29dppwn.

That's nearly 4,000BTU. I'm told that 6,000BTU is half a ton, which I think is a lot closer to a "comfortable" size. But I can't find any half ton compressors. And yes, a complete condenser unit would be a lot easier, and while it wouldn't be nearly as much fun, it makes a lot more sense from a business standpoint. Problem is, I can NOT find a half ton condenser unit. Not at all. Smallest I can usually find is 1.5 ton, which I think is far too large, heavy and expensive. But, I looked again right before I started this post, and I DID find this... tinyurl dot com slash 32jefrh. Okay, I'm guessing it's still a little oversized, I did NOT want to use a 230 volt compressor since that's another circuit that will need to be installed for the customer, and I didn't want to use R22. I was hoping for 134A or better. But still, the price is definitely right. Is this everything I think it is? Condenser coil, cooling fan, compressor, etc? If it's all there, I think that's a killer deal, even though it is oversized. Any opinions on this unit?

Thanks a lot guys.


Don

NoNickName
29-09-2010, 07:31 AM
The compressor you selected is ok, but I think that building up a complete condensing unit would cost more than buying an already made one.

There you can find condensing units down to 3/4TR.

http://www.frascold.it/pdf/CATALOGUES/FCAT07-10.pdf

Once your mind is made up, I will select the PHE for you.

Electric Rain
29-09-2010, 08:19 AM
Hey, I'm totally on board with a pre-built condenser unit if it will cost less, and I have no doubt that it would. But, Italy is a good Atlantic Ocean and a couple countries away from me. Shipping might be a bit unreasonable. :P

They've got a nice selection of condensers though. But you have put me on the right path. I think it's safe to start looking for affordable complete condenser units. I'll look around and see what I can find, but there are other issues of the design I need help with too. Maybe it's best to move onto those.

Thanks a lot.


Don

NoNickName
29-09-2010, 08:24 AM
Come on, look for the distributor or dealer in your country on their website.

Electric Rain
29-09-2010, 08:30 AM
Okay, well the have a place in Canada. That's not too bad I guess. I assume you already know I don't have to buy in bulk or anything? The big problem here is that I can't find any prices. I suppose I could just email them... Hey, not that I'm questioning you or anything, but what's your loyalty to the place? Have you gotten stuff from them before or something? ...Do you work there? :P

My bad on the Grainger unit for $300 USD by the way. That's on clearance at a massive discount, so...

NoNickName
29-09-2010, 08:35 AM
I would go for the 300 bucks.

Electric Rain
29-09-2010, 08:39 AM
Me too, but it's not going to be $300 forever. It's on clearance, marked down from $1,100 or something. Sure, I could get it for my initial prototype, but I need a small-volume supplier (literally one at a time) that's going to be able to give me that same $300 price every time.

NoNickName
29-09-2010, 08:45 AM
As far as I know, freezeco sell in pieces.
Despite, what is the BTU/h of the granger's at +60F (evaporating)/+130F (condensing).
Based on that, I will post a selection for a PHE

Electric Rain
29-09-2010, 08:58 AM
The Grainger unit doesn't seem to specify, on the page, and I can't find a datasheet. But still, this unit is probably at least a half ton too powerful, and I won't be able to find it for that price again after they sell them all, so I can't use them in future designs, and that's not cool with me.

As convenient as clicking an "Add to Cart" button is and knowing exactly how much something will cost immediately is, it doesn't look like that's the solution I should be looking for. I have to stop being lazy and start asking for quotes instead at some of these refrigeration companies. I just found this place, and their M-series units look PERFECT for me. They're the cutest little condensers I've ever seen, too! ...You know... as cute as a condensing unit can be... Seriously though, don't you agree? Plenty of info available about them too... except of course, the price. Look at the brochure for a clearer view of the M-series models. I love them. What do you think?

Electric Rain
29-09-2010, 09:00 AM
Uh... okay, that was awesome of me. Forgot the link, and now I have to double post because I can't figure out how to edit. Sweet. >.<

tinyurl dot com slash fmrfw

NoNickName
29-09-2010, 09:07 AM
They don't carry high temp condensing unit. M series is low or medium, with the highest evaporating temp. at +40F which is too low for your application.

Electric Rain
29-09-2010, 09:10 AM
They don't carry high temp condensing unit. M series is low or medium, with the highest evaporating temp. at +40F which is too low for your application.

Oh. Okay. ...Stupid question time... What does that mean? >.> Sorry.

NoNickName
29-09-2010, 09:35 AM
Not a stupid question: low temperature = deep freezing, medium temperature = fridge or food conservation, high temperature = air conditioning and process cooling.
In Europe they call them LBP (low boiling point), MBP and HBP and they have specific ranges of temperatures.
Elsewhere they are called LT, MT and HT.

Electric Rain
29-09-2010, 09:48 AM
Oh, dude, AWESOME for breaking it down for me like that. For some reason I couldn't find the answer to this simple question online. That's pretty much exactly what I thought, though. It makes sense. Thanks for explaining it to me.

Alright then, this place... 28j8tcj

I think those KMH units would be perfect. They do have high-temp versions, but they're all R-22, which I know is being phased out, at least in the US. Should I let this concern me? I know R417A is a direct drop-in replacement for R-22 that I should be able to use, provided I can get my hands on it.

Is there anything that jumps out at you as a deal killer about those KMH units? Because if not, I want to email them and try to get some kind of quote, but I may need your help so I know what to ask for.

Thanks a lot for your help man...


Don

NoNickName
29-09-2010, 10:03 AM
Better, but still limited on the highest evaporating temperature. You should find a units capable of evaporating at least at 12°C (55°F), and not with R22. More likely R407c or R410A

Electric Rain
29-09-2010, 10:28 AM
Is that what "saturated suction temperature" means on the datasheet? That seems to make sense. So the highest temperature I can get out of those ones is 7.2 degrees Celsius...

Well, wait... that may be a bit too cold for forced air applications, but I'm using hydronic cooling. Isn't 7.2 degrees about perfect for that?

For the record, I'm one of only few Americans that think the imperial system is stupid. Really, really stupid. Everything about the metric system makes more sense, and the only reason we haven't adopted it yet is because we're stubborn. It's base ten. All of it is base ten. In what way is that not awesome, you know? I would use it, but I'm basically forced to use the imperial system because everyone else in my country does, and it's what I was taught, so it's what I know best. I'll try to remember to use metric units on this forum, since it seems as though most of you guys aren't American.

So, back on topic, it's 5:15AM where I live, and I'm about done engineering for now... I think I know what I'm looking for now, thanks to you. At least, concerning a condenser unit. I'll continue searching for a TRUE high-temp condenser unit after I get some sleep. Wait... that's right, I reminded you that it's a hydronic system. I'm not questioning you, because you obviously know more than I do on the subject, but I don't know if you forgot that it's hydronic. Based on my research, hydronic chillers usually chill the water to about 4.5 degrees for commercial air conditioning. With that in mind, these units would actually be just perfect. What are your thoughts?

Thanks again!


Don

NoNickName
29-09-2010, 10:38 AM
Consider a DT from evaporating temp and leaving water temperature of about 5-7°C. That means that for a leaving water temeperature of 22°C, the evaporating temperature can be as high as 15°C. I think the majority of high temp condensing units are evaporating at 12°C max, which is also acceptable. 7°C is too low, and would require too much energy because of the increased pressure ration on the compressor.

Electric Rain
29-09-2010, 10:54 AM
Okay, I THINK I understand what you just said. But if I do, why would I want the water temperature to be that high? I think I may be missing an important detail here... Sorry, but could you explain a little more clearly?

NoNickName
29-09-2010, 10:58 AM
In your first post you wrote you wanted water at 72°F, which is 22°C

Electric Rain
29-09-2010, 11:03 AM
Oh, slight mix-up here. Yes, the water in the 15 gallon water tank should be at 72 degrees F, but I also need chilled water to pipe to the radiators in the 1-8 remote units... Sorry about that confusion. But they'll all be plumbed in parallel, with their own solenoids. So, I can turn the solenoid for the copper coil in the water tank on at a different rate (less often, obviously) that the solenoids for the chilled water to pipe to the remote units.

I should have drawn up a schematic for this... Sorry. Does it makes sense now?

NoNickName
29-09-2010, 11:28 AM
I should have drawn up a schematic for this... Sorry. Does it makes sense now?

So you need two headers with two supply temperatures?

Electric Rain
29-09-2010, 11:40 AM
I don't think so, as I think that would over-complicate things. I don't see why the coil in the water tank needs to have water running through it of the target temperature. If the water tank rises above, say, 24 degrees, I'll activate the condenser unit and open up the valve for the hydronic cooling coil inside the tank, until the water temperature inside the tank is back down to 22 degrees. With chilled water, I understand that the water closest to the coil inside the tank will be coldest, but it's important to note that it will also be constantly recirculating, and the temperature sensor would be inline with the recirculation pump - not inside the tank.

NoNickName
29-09-2010, 11:47 AM
So you want to cool it down at 22°C as I said, right?

Electric Rain
29-09-2010, 11:53 AM
The water in the tank, yes. But I also need a supply of chilled water to sent to the remote units, for air cooling. Each of these lines will be on a computer controlled solenoid, and the solenoids will turn on as they need to to send the chilled water to the unit that's requesting it. The water tank cooling coil will operate the same way.

Seriously, I don't want anybody getting frustrated. If you don't understand what I'm trying to say, just let me know and I'll work on a diagram or something. I needed to start working on one anyway. :D


Don

NoNickName
29-09-2010, 12:46 PM
And what is the temperature of this chilled water? How are you supposed to deliver two different water temperatures with just one header?

Electric Rain
29-09-2010, 08:21 PM
Well, like I said, chilled water for hydronic cooling is usually around 4.5 degrees. I don't need two heads with two different temperatures any more than a fancy house with individually climate controlled rooms needs multiple heads on the condenser. For forced air, they simply open and close motorized duct dampers as needed, and this is exactly what I plan to do with solenoid valves in my hydronic system.

Let's make things easier. For now, there is no tank of water. What I truly need is to produce chilled water, ~4.5 degrees, for hydronic cooling. With that in mind, what are your thoughts on the most recent condensing unit I linked to, as well as the M-series one before that?

Thanks for your continued help and sorry for the confusion.


Don

mad fridgie
29-09-2010, 08:59 PM
From what I can see, you need
Cool
Cool and Heat
Heat,
which means you need two fluid heat exchangers and one air heat exchanger
You are best to buy an air conditioning outdoor unit, with integeral defrost controls, 2 PHE, heat reclaim diverting valve, 4 way valve, and some smarts to drive it. Easier said that done, if you do not have a clue about refrigeration!!

Electric Rain
29-09-2010, 09:11 PM
A heat pump? I'm not so sure about that one. That's more cost and more complication. Also, I don't think I'll need cold and heat at the same time. The application is flexible enough to allow the system to be in one mode or the other... it doesn't need to keep the temperatures within such tight tolerances.

mad fridgie
29-09-2010, 09:36 PM
A heat pump? I'm not so sure about that one. That's more cost and more complication. Also, I don't think I'll need cold and heat at the same time. The application is flexible enough to allow the system to be in one mode or the other... it doesn't need to keep the temperatures within such tight tolerances.
A heat pump is cheaper than a refrigeration unit, and is designed to heat and cool. What happenns when the tank falls below set point and you still need cooling in the other part of the process

Electric Rain
29-09-2010, 10:18 PM
A heat pump is cheaper than a refrigeration unit, and is designed to heat and cool. What happenns when the tank falls below set point and you still need cooling in the other part of the process

I get where you're coming from, but for my application, this the difference between the water tank temperature and the remote unit air temperatures will never be great enough to worry about heating and cooling simultaneously.

I know what heat pumps are designed to do, and I LOVE what they do... in theory. At any given time, they produce heat and cold, so why not reverse it and take advantage of the heat when you need it? Yeah, makes sense, but at ambient temperatures below 0 degrees, which is quite common for several months out of the year in my country, heat pumps are horribly inefficient, and frequently require supplementary heat.

Even if I didn't need supplementary heat, I don't see how the added cost of the 4-way reversing valve and other additional costs for a heat pump would be less than a simple inline water heater. But I'm not the pro, either. You guys are. Please, if there's something I'm missing, which is plausible, educate me.

mikeref
30-09-2010, 12:18 AM
Electric Rain, Interesting plans you have. I'm more of a hands on person so maybe some drawings will shed more light on the subject. These "growth" units(8*4*4) are not something the ATF would like to view first hand..right? As for heating, why not use lights?

Electric Rain
30-09-2010, 03:18 AM
Electric Rain, Interesting plans you have. I'm more of a hands on person so maybe some drawings will shed more light on the subject. These "growth" units(8*4*4) are not something the ATF would like to view first hand..right? As for heating, why not use lights?

I'll get started on some diagrams for the HVAC portion so hopefully everyone will understand the plan a bit better, but unfortunately I can't divulge the entire system to the general public yet. I have competition, and I don't want them, or anyone else for that matter, claiming any of my designs as their own.

I have nothing against the helpful members of refrigeration-engineer.com, but if I post too many details on this forum, it's open for the entire world to see. But again, the HVAC portion is relatively unrelated to the rest of it, so if I have the time I can get some sort of diagram for that drawn up tonight.

Thanks for your interest, though. Sorry I have to be so hush hush about it.


Don

Electric Rain
30-09-2010, 04:27 AM
Hah! ATF... just got that... ^-^' Well, I guess it does seem more than a little bit suspicious that I'm keeping everything a secret. Heh.

But, I'm too afraid of the law to do anything like that. I'll be honest though, I HAVE thought about growing hemp, (AKA medical marijuana) legally, but despite how much I know about hydroponics, getting the kind of licensing required is difficult, especially for a 20 year old guy. :P Besides, they only let you grow enough for like, five people so they can keep track of it, so it's not as profitable as I would hope. Not worth it.

NoNickName
30-09-2010, 08:11 AM
what are your thoughts on the most recent condensing unit I linked to, as well as the M-series one before that?


I think so.
Now we need a PHE.
I'll be back on that.

Electric Rain
30-09-2010, 10:59 AM
Okay, make fun of it if you want, but I wasn't trying to win any awards with this one...

http://img153.imageshack.us/img153/9533/hvac.png

If there's anything anyone doesn't understand, just let me know. I think this is a somewhat complete representation of the vision I have in my head... Well, I'd love to hear your thoughts guys. Maybe this will clear up some confusion.

Electric Rain
30-09-2010, 12:13 PM
this is truly the best thing to do.

Erm, thanks, either way, but what do you mean? The design is the best thing to do, or me putting up a diagram so everyone understands the concept (without me having to fail miserably at explaining it with words) is the best thing to do? Or are you talking about something specific in the design?

NoNickName
01-10-2010, 10:16 AM
Please find attached selection to be used in connection with the remote condensing unit model MCHZ0061B.
Allow for slight derating for higher ambient than 90°F, specified in the condensing unit data sheet.

Electric Rain
02-10-2010, 05:08 AM
Okay, I understand about half of what I read from that datasheet... perhaps that's because I don't understand EXACTLY what it is or where it came from... >.<

But if I'm reading it properly, I don't need a very impressive PHE at all, do I? 1.6kW isn't hard. Something like this would work fine, wouldn't it? http://www.amazon.com/Plate-Heat-Exchanger-x2-9-Female/dp/B0039WXZH6/ref=sr_1_13?s=miscellaneous&ie=UTF8&qid=1285992061&sr=1-13

Says it handles up to 5kW, and it's cheaper than anything I could DIY. Thoughts anyone? I think we're just about done here. Looks like most every one of my questions were answered.

I have to email that company for a quote on that condensing unit though. Is there anything specific I need to ask for/about, do you think?

Thanks for all the help guys.


Don

NoNickName
02-10-2010, 09:07 AM
No. Print the selection and go to your supplier or email them and ask for a PHE with the same specs.

Electric Rain
03-10-2010, 10:41 AM
No. Print the selection and go to your supplier or email them and ask for a PHE with the same specs.

Okay, I'll do that when they respond to the email I sent them for a quote on the condensing unit. Hopefully they can add a suitable PHE in at a good price, but $45 seems very cheap for that Amazon one. I wonder if they can beat or match it with something that matches your specs.

In case it would be cheaper for me to use a stock PHE I find on my own, can you tell me why the one I linked to is unsuitable so I know exactly what to look for?

Thanks.


Don