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Thread: Looking for a small size (>10hp) DUAL circuit chiller? or maybe DIY this setup?

  1. #1
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    Looking for a small size (>10hp) DUAL circuit chiller? or maybe DIY this setup?

    so long story short- PGE the local utility is trying to tell us they want us to put a transformer in the sidewalk to power the new brewpub. Any load over 75kva requires this apparently. They only supply 208V three phase. But since our power is underground we need to trench into the street, and then maybe all the way to the nearest intersection if no closer manhole/vaults exist. we are in the middle of the block on a major street, with 24/7 bus lines, subway underneath, etc. just the transformer could be $100k. The very idea of even approaching that full project cost estimate terrifies me.

    So, thats the predicament. I'm cutting down power needs everywhere i can. No more HLT elements. (92amps, for 33kva) No more dual stage knockout. etc. etc. I also noticed that our Kva load calcs are lower when using 1 phase. (something about line to line three phase? 208V, not 230V?) So abandoning the HLT elements and downsizing the glcyol unit could put us under the 75kva limit. So without the HLT, refrigeration is now our biggest energy load.

    Our load for fermenters is about 23-25k btus. No brites. But we will have serving tanks in a 24x17x13H walk in, which calcs at about 17k btu. And a small kitchen walkin, call it 3k btu. So i was thinking we could get some efficiency savings if we went with a chiller to handle all those loads, instead of 3 different units. If so we're looking at about 45k btu.

    Now if basically all cooling is now running off one unit, i want dual compressors for redundancy/safety. But of the few that ive seen, 5+5 or 10hp is the smallest. which is like 80k btu. alot more than we need. (expansion is extremely unlikely at this location, bordering on impossible).

    so im wondering if its possible to get two smaller units, say 3 or 4hp each, and run them/wire them in such a way that they effectively act like a dual unit. one in master mode, one in backup, and the ability to swap them every month or two so we dont burn them out as quickly.

    im trying to think it out for having two separate units tied together, a base chiller, and a booster. the booster would pull from the main trunk line when the base reservoir gets too warm, and then chill and dump back into the main reservoir? or via an HX? but that doesnt sound like you could swap base and booster units very easily. the other idea is that since this will be a rooftop installation we could have remote units up top with a separate reservoir either on the roof or in the walkin cooler below. but extra pumping would add a bit of heat so not sure that's a big deal or not.

    would also like to get some hot side gas recovery abilities in order to heat the HLT. i'll look into getting a custom dual unit built, but given the prices on the new 5+5 dual units, we might end up just having to settle for the DIY approach. so if anyone has some other ideas im all ears at this point.

  2. #2
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    Its pretty easy, you need a common reservoir for the glycol, then just wire the controller for each unit with a temperature probe in the reservoir. The master unit will have a set point of say 25, and a differential of 3 degrees(whatever you want really), the slave unit will have the same set point, but a differential of a degree or two more than the master. That way, if load is low, the master can handle it and if load is high, the tank will warm past the second units cut in point. And they will both stop at the set point.

  3. #3
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    Quote Originally Posted by brain medicine View Post
    [...] They only supply 208V three phase. [...] I also noticed that our Kva load calcs are lower when using 1 phase. (something about line to line three phase? 208V, not 230V?)
    Single phase motors are far less efficient that three phase motors, and even if they would supply a delta connected transformer, you don't gain anything. Since you're eliminating the high energy heating loads, there's no advantage to the slightly higher voltage anyway. Stick with 208V 3ph wye.

    Quote Originally Posted by brain medicine View Post

    so im wondering if its possible to get two smaller units, say 3 or 4hp each, and run them/wire them in such a way that they effectively act like a dual unit. one in master mode, one in backup, and the ability to swap them every month or two so we dont burn them out as quickly.
    I would say any competent industrial electrician could wire up two small chillers in this way. I've done it with both chillers and air compressors. Rotate them weekly, not monthly, unless the secondary chiller runs often during the week. You don't want the chiller sitting for 30 days without running.

    Quote Originally Posted by brain medicine View Post

    im trying to think it out for having two separate units tied together, a base chiller, and a booster. the booster would pull from the main trunk line when the base reservoir gets too warm, and then chill and dump back into the main reservoir? or via an HX? but that doesnt sound like you could swap base and booster units very easily. the other idea is that since this will be a rooftop installation we could have remote units up top with a separate reservoir either on the roof or in the walkin cooler below. but extra pumping would add a bit of heat so not sure that's a big deal or not.
    A variation on this is the best bet, IMO. If you want to minimize your total connected load, then size one of the chillers to meet your daily baseline load (not when crashing or knocking out, if you use glycol for that). The other chiller adds enough capacity to crash a fermenter, etc. to meet peak demands. Ideally they are identical units, so you can swap their roles weekly. They both cool the same glycol reservoir, and your electrician will connect them so that that they run at different setpoints. For example, say your "normal" glycol temp is 28F, and the T-stat is set to turn on at 30F and off at 26F, for a four degree deadband. The second T-stat is set to turn on at 32F and off at 28F. If one chiller can keep up with the baseline load without the glycol reservoir getting above the "turn on" setpoint for the secondary chiller (32F), then that is the only one that runs. Each week the chillers reverse roles. Then let's say you crash two fermenters, and one chiller can't keep up, the second chiller automatically comes on. If the first chiller fails, the secondary chiller also comes on.

    It's not completely redundant, because if a chiller fails, your capacity is reduced by around 50%, but something's gotta give.

    Regards,
    Mike

  4. #4
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    A couple other suggestions...maybe a bit too complex.

    When I worked down in your neck of the woods (SLO and Santa Barbara) I found PG&E to be fairly reasonable. They might accept both the HLT heating loads and the refrigeration loads as being under 75kVA if there was a lockout that prevented them from running at the same time. So maybe you decrease the available KW for the HLT (since you'll use heat recovery to supplement) and lock out one of the chillers when the HLT is heating in preparation for a brew day.

    Or, have them install a larger transformer in the sidewalk, but increase the service voltage to 480/277 volt wye. Use 277 volt lighting throughout. It's cheaper to wire because you can put a boatload of lights on one circuit. A 480:208 dry transformer serves the brewery with a branch circuit to a load center for the brewpub. These are not cheap, but you can find them used. This would probably eliminate the need for the trench and all of that, but you'll need a new service. Back in my day, PG&E didn't charge you for a new transformer at the service entrance, but you have to buy any transformers you use inside. I don't know how they do it these days...it sounds like they want $100K to drop a 75kVA transformer, which seems ridiculous to me.

    Regards,
    Mike

  5. #5
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    the transformer the size wasnt spec'd out yet, but the electrical guy helping us has experience with them and said it could easily cost 100k. used would be a godsend, but again, without specs from pge i cant even shop around for one. i didnt get a clear answer if other voltages like 440/480 or 277 were an option, but i dont recall it being discussed.

    if we at least knew where to trench into the street to pick up the new service that might help give us an idea of feasibility, but they wont even tell us where we can find a connection point, all the underground vaults on our block might be just pull stations, according to their rep. which seems crazy, to make everyone run to the corner for bigger service, it could be 200 feet, with overtime labor for trenching at night so the bus lines arent disturbed during the day. holy crap. but the biggest problem is that getting info from them is impossible. a month to answer one question. everyone here in SF hates them.

    i will ask the engineer if the lockout could work, but the restaurant/bar uses probably 40% of the kva allowance, so not much room to shut off of equipment. if its just for the HLT then it might not be worth the trouble. and we'd still be over the 75kva if we dont downsize the chiller. im not too bummed about the HLT, as i can run a recirc loop to our domestic water heaters or a commercial tankless, since gas is cheap. or maybe a loop to a solar hot water panel that keeps HLT hot. practically free. the biggest issue is fitting in the cooling and trying to get under 75kva.

    the single reservoir with dual remote compressors is what we have at our other brewpub. but its spread between the floor and the roof 40' up and i dont recall how its all wired up. i guess i'll have to climb up there and take a look. but yes, stepped set points would be obvious. the system i referred to was an example from another brewery with a similar issue, but now that i think about it the master had a big ass reservoir, i guess that was why it was plumbed that way with slave feeding into the master reservoir.

    i guess if a single compressor could handle 30 or 40k then we could be safe enough. just have to stop any crash cooling and wait for repairs. but at least in SF the techs seem to always be able to get parts quickly. sometimes same day. and most calculators probably overstate our cooling needs as its rarely even 80F in this town.

    what about the hot side gas recovery? i was thinking this could also be used to heat the HLT. is it plumbed just like the regular refrigerant lines? drop an HX inline and run recirc to the HLT or something like that? if we were cooling say 30k btu is that system efficient enough to send to HLT?

  6. #6
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    Quote Originally Posted by rdcpro View Post
    Single phase motors are far less efficient that three phase motors, and even if they would supply a delta connected transformer, you don't gain anything. Since you're eliminating the high energy heating loads, there's no advantage to the slightly higher voltage anyway. Stick with 208V 3ph wye.
    again, what we're really trying to do is avoid going over the 75kva mark. per one manufacturer their 10ton unit at single 240 is 70amp. as 3phase 208 its 49amp. so single phase gets us 16.8kva. three phase gives us 17.6 at 208. seems odd to me, but that's whats coming out of the calculator.

    and the cost savings to wire things in 3phase are nothing compared to the cost of going over the 75kva mark. in a normal situation it probably seems bit silly, but if we gotta shave another 1 or 2 kva off the list, then thats what we gotta do.

  7. #7
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    Quote Originally Posted by brain medicine View Post
    again, what we're really trying to do is avoid going over the 75kva mark. per one manufacturer their 10ton unit at single 240 is 70amp. as 3phase 208 its 49amp. so single phase gets us 16.8kva. three phase gives us 17.6 at 208. seems odd to me, but that's whats coming out of the calculator.

    and the cost savings to wire things in 3phase are nothing compared to the cost of going over the 75kva mark. in a normal situation it probably seems bit silly, but if we gotta shave another 1 or 2 kva off the list, then thats what we gotta do.
    That's an odd result, for sure. It should be the other way around. Out of curiosity, I calculated it for two different chillers, and the numbers don't make sense to me. For the "brewery" chiller the 3ph RLA is much higher than the "standard" chiller (26.5 A vs. 17.2 A). But the 1ph RLA is nearly the same for each (34.5 A vs. 36.5 A). Something is odd about how they're sizing the components for the single phase unit:

    Brewery Chiller For 28F Degree Water / Glycol Mixture

    5.0 Nominal Ton - CAVCS0501-BC – 208-230/1/60 – Single Phase 34.5 A @ 240 V = 8.28 kVA

    5.0 Nominal Ton - CAVCS0503-BC – 208-230/3/60 – Three Phase 26.5 A @ 208 V = 9.547 kVA

    "Standard" Chiller

    5.0 Ton – CAVSS0501-TZ – 208-230/1/60 – Single Phase 36.4 A @ 240 V = 8.76 kVA

    5.0 Ton – CAVSS0503-TZ – 208-230/3/60 – Three Phase 17.2 A @ 208 V = 6.197 kVA

    It's almost like they use the exact same single phase compressor in each unit, but a much different three phase compressor in each, with the "brewery" unit being much larger.

    Regards,
    Mike

  8. #8
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    Been there...

    I've rigged three systems like you are talking about doing it. It's the best solution for many breweries. One system features dual 4hp Danfoss roof-mounted condensing units and a single indoor chiller supplied by PRO. Think it's called KOOLWAY. This indoor unit consists of two separate circuits: PHEs, liquid, suction lines & solenoids. Only one glycol tank and pump. I've made each condenser redundant so that I can use either, both, or neither. Great for downsizing your chiller load when demand is low. Turning both units on when we're cranking product through. I can set each circuit so that when both are "on", the one unit is set for -2C, and the other is set for 2C. That way, one unit is primary and the other just runs when it needs to. I usually switch primary to #1 circuit on odd months, and to #2 circuit on even months to make sure that each condenser units are exercised equally. I've also built two systems running side by side using two Hyundai chillers which have two compressors in each. Again, we switch compressor duty every month. In a few very hot months when we're selling lots of beer, we switch both compressors on for both units. Lots of staging means more efficiency. Best of luck!
    Phillip Kelm--Palau Brewing Company Manager--

  9. #9
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    You have some good ideas and good suggestions from other posters. Here are some notes:

    1. For 3 PH kVA = V x A *1.73
    2. You are using RLA, the "Rated Load Amps" of the compressor. Especially in a brewery application, the actual amp draw of the motor is less than the RLA. THe engineer could make an argument that the compressor is able to draw that amperage, and therefore that kVA, but the higher amp draw would only occur when the chiller was pulling down from a warm tank of glycol.

    3. The chiller power will also include the condenser fan if it is an air cooled chiller. You also have your chilled water pumps.

    4. If you start looking and complete chillers, make sure you calculate kVA like you are doing by looking at the actual motors, not off of nameplate MCA or MOP. THose number are not an indication of power of effciency, they are simply to size the branch circuit to the chiller. Most chiller manufacturers calculate these values wrong anway.

    5. You could use a chiller with variable speed or variable capacity compressors. These have the ability to run at lower speeds and power draw with higher chiller water temperatures. Thhe controller can measure amps or power and keep the chiller unloaded. Greater efficiency and energy savings as well.

    6. For your HLT, you could generate hot water with a heat receovery chiller, or a chiller with a heat recovery system. This is either a water cooled chiller where you capture the heat from the condenser, or a partial heat recovery system that recovers a portion of the condenser heat. About 1/3. The water cooled can get all of the BTUs but at a lower temp. The partial heat receovery can some of the BTUs at a higher temp. We are talking like 100F or 125F. You will probably still need supplemental heat, plus the heating and cooling loads have be somewhat in sync.

    7. Have you thought of Thermal Energy Storage? THis is a system where you basically build ice. When the chiller capacity exceeds the load, the chiller freezes up water encapsulated in either tubes of some kind of matrix. Then when the load exceeds the chiller capacity, the warmer water melts off the ice. You have to be careful with the design because the ice can only amke 35-36F water when melting off. THese systems are generally used for load shifting, in situations where you have a high peak load and low base load. Instead of getting a chiller that is greater than the peak load, you build ice for 20 hours then discharge that ice over 4 hours. This reduces total kw-hr because when the chiller runs at night it runs more efficiently. It reduces kW/kva because the utility does not need to delivery as much power at a given instant in time.

    It is the same idea as using a CLT, except for the fact the freezing ices increases the BTU storage capacity by 144 times. So you can get a lot of thermal storage in a smaller footprint.

    This might reduce your bill, if PG&E has you on real time billing. THis means they charge you different power rates during the day. If you push some of your power consumption to parts of the day that cost less this can reduce your total power bill.

    8. The largest signle phase compressor is a 5 HP/5Ton. That is why that MFG shows the same amps for their brewery chiller as their regular chiller. For their 3 phase, they are using a nominal 5 ton/5HP compressor for their 5 ton. For their 5 ton brewery chiller, it is probably a 7.5HP/ton compressor that produces 5 tons at brewery temps. The usual HP, tons, nominal confusion.


    9. Gas Boiler system in lieu of an HLT?


    If you would like to talk about chiller options please let us know. We have 3 EEs on staff, two are licensed PEs and can talk directly with the PG&E engineers.

    Good luck,

    Jeff Johnson
    Johnson Thermal Systems
    208-453-1000

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