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nemoorellc
Senior Member


Joined: 21 Sep 2007
Posts: 84
Location: Cincinnati
Expertise: Professional

Espresso: Scale: Uber 6kg
Grinder: Baratza Virtuoso
Drip: Bunn CW15-TC
Posted Fri Oct 12, 2007, 6:42pm
Subject: Re: Bunn commercial brewer - CW15-TC
 

My type A personality is getting the best of me.  My laser focus now is on getting the perfect brew time.

As a starting point, my Bunn has a brew time of 3 minutes.  This is typical of all Bunns.
In order to get the desired 4-5 minute brew time, I called Bunn and got a recommendation for a new spray
head that reduces the flow rate.  I've now ordered 2 new spray heads.  Why two?  Because it wasn't clear
from anyone I spoke to, from Bunn or some of the Bunn parts suppliers, which spray head was designed to specifically
brew more slowly.  So I ordered a 5 hole nozzle and a "high lime" nozzle.
I did find out two  interesting "fun facts".  1)  That the bunn coffee filters swell more if you have
soft water, so the water level is likely to go higher in the basket, which is one way to get a little more residence time and
2) Bunn makes nozzles specifically for "high lime" areas to minimize spray head clogging.  It funny the odd little things you
learn in casual conversation.

Back to my type A.  I didn't want to wait 3 days before I test the new nozzles, so tonight I plugged 2 of the 6 holes
in the stock sprayhead.  With only 4 active holes, the brew time went up to 4 min 36 seconds.  Lucky guess.

Believe it or not, I did actually taste a subtle difference in the flavor of the coffee compared to the 3 minute brew.  It has a little more
of an earthy, hearty note to it.

In 2 days, I should get my stainless steel brew basket and two nozzles to play with.  Oh, one other recommendation was to
use 2 filters to increase residence time in the basket.  I might try that as well.

Nathan
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gime2much
Senior Member


Joined: 10 Dec 2004
Posts: 1,965
Location: Sunny S Fl
Expertise: I love coffee

Espresso: La Pavoni, Astoria comm, 2...
Grinder: La Pavoni Zip, Bunn...
Drip: Bunn comm
Roaster: Popcorn popper (air),co/ufo
Posted Fri Oct 12, 2007, 6:55pm
Subject: Re: Bunn commercial brewer - CW15-TC
 

nemoorellc Said:

My type A personality is getting the best of me.  My laser focus now is on getting the perfect brew time.

As a starting point, my Bunn has a brew time of 3 minutes.  This is typical of all Bunns.
In order to get the desired 4-5 minute brew time, I called Bunn and got a recommendation for a new spray
head that reduces the flow rate.  I've now ordered 2 new spray heads.  Why two?  Because it wasn't clear
from anyone I spoke to, from Bunn or some of the Bunn parts suppliers, which spray head was designed to specifically
brew more slowly.  So I ordered a 5 hole nozzle and a "high lime" nozzle.
I did find out two  interesting "fun facts".  1)  That the bunn coffee filters swell more if you have
soft water, so the water level is likely to go higher in the basket, which is one way to get a little more residence time and
2) Bunn makes nozzles specifically for "high lime" areas to minimize spray head clogging.  It funny the odd little things you
learn in casual conversation.

Back to my type A.  I didn't want to wait 3 days before I test the new nozzles, so tonight I plugged 2 of the 6 holes
in the stock sprayhead.  With only 4 active holes, the brew time went up to 4 min 36 seconds.  Lucky guess.

Believe it or not, I did actually taste a subtle difference in the flavor of the coffee compared to the 3 minute brew.  It has a little more
of an earthy, hearty note to it.

In 2 days, I should get my stainless steel brew basket and two nozzles to play with.  Oh, one other recommendation was to
use 2 filters to increase residence time in the basket.  I might try that as well.

Nathan

Posted October 12, 2007 link

Looks like you found the information before I could get back to you.

Careful of overflow with 2 filters. Search CG for Craiga's answers as to where to get oversize filters, that might help if you do double up.

How do the finished grinds look? Any parts dryer than others?

Dan






Dan

 
Dan Brewer
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nemoorellc
Senior Member


Joined: 21 Sep 2007
Posts: 84
Location: Cincinnati
Expertise: Professional

Espresso: Scale: Uber 6kg
Grinder: Baratza Virtuoso
Drip: Bunn CW15-TC
Posted Fri Oct 12, 2007, 8:07pm
Subject: Re: Bunn commercial brewer - CW15-TC
 

I've run my finger through the grounds after the brewing is complete, and haven't found any variation
in moisture; however, I have noted that the spray head itself creates a pattern within the grounds that
reflect where the main water flow is going.  For example, with the 6 hole sprayer, the grounds take the form
of a recessed starfish, if you will, in which the areas where the water hits the grounds are more recessed than
the areas where the water is not sprayed.   Also, it is evident that the water fills the brew basket to within
about 3/4" of the top of the filter, as that is where a thin layer of grounds remain when the brew is complete.

It also seems that the finer I grind the coffee, the more predominant the starfish shape takes, which might imply
uneven extraction.  I'll try a coaser grind next time and see how uniform the grounds seem after the brew.

Nathan
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nemoorellc
Senior Member


Joined: 21 Sep 2007
Posts: 84
Location: Cincinnati
Expertise: Professional

Espresso: Scale: Uber 6kg
Grinder: Baratza Virtuoso
Drip: Bunn CW15-TC
Posted Mon Oct 15, 2007, 5:41pm
Subject: Re: Bunn commercial brewer - CW15-TC - test data from new spray nozzles
 

I ordered two different replacement spray head styles.  The stock spray head is a 6 hole version made of SS.  I ordered
a 5 hole version of the same spray head, also made of SS,  and a "high lime" spray nozzle made of plastic.  
I tested each of these versions to determine how
they impacted brew time by controlling water flow rate.  To test the rate, I poured 64 oz of water into the brewer, then timed
the duration of time between when I saw the first water flow out of the brew basket until the time I saw the water stop flowing.  I did
not have coffee or a filter in the brew basket to reduce test variation.
Results:
Spray head:                                                           Brew time
Stock 6 hole spray head:                                      3 minutes (+/- 15 seconds)
Stock 6 hold spray head with 2 holes plugged:    4 min 15 sec (+/- 15 seconds)
5 hole spray head                                                 3 min 30 sec (+/- 15 seconds)
Plastic, High Lime spray head                               3 min 30 sec

What was surprising to me was how much variation there was in brew time with a single spray head.  For the 5 hole sprayer, I got
times that ranged from 3:09 to 3:50.  Seems like the unit should control to a tighter time than that.

For now, it looks like I might have to make a permanent version of the stock sprayer with 2 holes plugged in order to get
a consistent 4 min+ brew time.
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gt
Senior Member


Joined: 29 Jan 2007
Posts: 210
Location: Mpls/St Paul MN
Expertise: I like coffee

Espresso: None
Grinder: Virtuoso
Drip: Cones & CCD
Roaster: P1 w/ variacs
Posted Mon Oct 15, 2007, 8:02pm
Subject: Re: Bunn commercial brewer - CW15-TC - test data from new spray nozzles
 

Nathan,  Do you (or anyone) know if the spray heads, you are ordering for your CW15-TC, will fit the cheaper consumer version Bunn brewers ($100-$150)?
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gime2much
Senior Member


Joined: 10 Dec 2004
Posts: 1,965
Location: Sunny S Fl
Expertise: I love coffee

Espresso: La Pavoni, Astoria comm, 2...
Grinder: La Pavoni Zip, Bunn...
Drip: Bunn comm
Roaster: Popcorn popper (air),co/ufo
Posted Mon Oct 15, 2007, 9:02pm
Subject: Re: Bunn commercial brewer - CW15-TC - test data from new spray nozzles
 

gt Said:

Nathan,  Do you (or anyone) know if the spray heads, you are ordering for your CW15-TC, will fit the cheaper consumer version Bunn brewers ($100-$150)?

Posted October 15, 2007 link

I think so but Tim Eggers came up a novel idea for this. Block holes with tooth picks until the desired effect is determined. Remove the picks and melt the cap from a cheap bic ink pen into the holes you have decided to block.

It's just plastic so shouldn't hurt you in any way, it also can be removed if desired.

Ta-Daaa....... Custom spray head!!!

Dan

 
Dan Brewer
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BrotherLehman
Senior Member


Joined: 25 Sep 2005
Posts: 34
Location: PA
Expertise: I live coffee

Espresso: Anita
Grinder: 2 Macap M4 Dosers
Vac Pot: French Press/Brikka
Drip: Bunn VP-17 Commercial
Roaster: RK Drum & Behmor
Posted Tue Oct 16, 2007, 4:57pm
Subject: Re: Bunn commercial brewer - CW15-TC - measured brew temperatures and brew cycle
 

First, I really like all the discussion of Bunn commercial brewers.  I have been using a Bunn VP17-1 for a year and a half and have been very pleased.  As most of us like to perfect our technique and improve our results, the idea of lengthening the brew cycle is intriquing.  I'm not sure though that reducing the flow of water by plugging holes is the answer.  It seems that will only slow the flow of water to the grounds, but will not lengthen the extraction time.  The idea I just had while writing this is to plug 1 hole and use 2 filters and then see what happens.  This would slow the flow to prevent overflowing the filter and lengthen extraction time with the extra filter.  
Maybe I'm missing something but I'll give it a try.


Don
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nemoorellc
Senior Member


Joined: 21 Sep 2007
Posts: 84
Location: Cincinnati
Expertise: Professional

Espresso: Scale: Uber 6kg
Grinder: Baratza Virtuoso
Drip: Bunn CW15-TC
Posted Tue Oct 16, 2007, 6:23pm
Subject: Re: Bunn commercial brewer - CW15-TC - measured brew temperatures and brew cycle
 

Don,

I think you're right on.  The most important factor is that all coffee grounds get the same amount of water flowing
over them.  If you have a perfect 4.5 minute brew, but only 1/3 of the coffee gets water, then your going to get
a really bitter cup.  So, you want to balance flow rate from the spray head and flow pattern through the bed of
coffee.  I talked to a really nice guy from Pamasco (a Bunn Service center) today, who had talked to Bunn about my
interest in dialing in the perfect brew.  He had similar recommendations.  He recommended I go a little coarser on the grind (which
allows water to flow more evenly through the bed of coffee), put a little more coffee in the brew basket (he recommended
3 oz (85g) per 64 oz of water), and if possible, double up on the filters.  So tonight I tried the following tests:

Test        Coffee Amount         Grind                                           Spray nozzle           Result
1             85g                          Coarse (20 on the Virtuoso)       Bunn 5 hole            Water bypassed a lot of the coffee.  Weak cup
2             85g                          Fine (12 on the Virtuoso)            Bunn 5 hole            Still bypass.   Cup stonger, but bitter
3             85g                          Medium (16 on the Virtuoso        Bunn 6 hole   More water flow and medium coarseness produced the most
                                                                                                                                evenly watered grounds, no bitterness, good strength.

Net, making sure the grounds get evenly watered seemed to be just as important as controlling brew time.

Here's a little something I did to help "dial in" the right hole pattern for getting a 4.5 minute brew time.  I took the
brew times from my last post, and based on the number of holes and hole diameters, calculated an equivalent flow area.
I graphed the flow areas against the resulting brew times, and curve fit the graph (see below).  Based on that
graph, I need to have a flow area of around 0.0158 in^2, which is right in between the two 5-hole Bunn spray nozzles
listed below.  I had such a hard time finding Bunn spray nozzles, I included the list here.  I also noticed that
my 6 hole sprayhead, with 2 holes plugged, gets really close to the estimated flow area, which is consistent with
the 4 min 15 sec brew times from my last post.  Isn't math fun?

After I dial in the amount of coffee and nozzle time, I will likely get the "no hole" Bunn sprayer and drill 6 of the correct
sized holes in it to get the right spray pattern and flow rate.

Nathan

Bunn Part Number    Description                              # holes    Diameter (in)           Total Area (in^2)
01082.0000             6 hole (stock)                             6            0.070                0.023
01082.0000             6 hole - 2 holes plugged              4            0.070                0.015
01082.0002             6 hole - large                             6            0.098                0.045
01082.0003             7 hole                                        7            0.078                0.033
01082.0004             5 hole                                        5            0.070                0.019
01082.0005             5 hole                                        5            0.057                0.013
01082.0006             1 hole                                        1            0.141                0.016
01082.0007             1 hole                                        1            0.182                0.026
01082.0008             no hole                                       0

nemoorellc: Bunn Brew time.JPG
(Click for larger image)
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gime2much
Senior Member


Joined: 10 Dec 2004
Posts: 1,965
Location: Sunny S Fl
Expertise: I love coffee

Espresso: La Pavoni, Astoria comm, 2...
Grinder: La Pavoni Zip, Bunn...
Drip: Bunn comm
Roaster: Popcorn popper (air),co/ufo
Posted Tue Oct 16, 2007, 10:02pm
Subject: Re: Bunn commercial brewer - CW15-TC - measured brew temperatures and brew cycle
 

BrotherLehman Said:

i I'm not sure though that reducing the flow of water by plugging holes is the answer.  It seems that will only slow the flow of water to the grounds, but will not lengthen the extraction time.  The idea I just had while writing this is to plug 1 hole and use 2 filters and then see what happens.  This would slow the flow to prevent overflowing the filter and lengthen extraction time with the extra filter.  
Maybe I'm missing something but I'll give it a try.


Don

Posted October 16, 2007 link

2 filters tend to remove too many of the flavor oils. Been there, done that.

With spray head restricted you have slowed the input. To increase extraction time try also restricting the output by making the hole in the bottom of the basket smaller (slightly). Larger and taller paper filters are available to reduce overflow.

Dan

 
Dan Brewer
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nemoorellc
Senior Member


Joined: 21 Sep 2007
Posts: 84
Location: Cincinnati
Expertise: Professional

Espresso: Scale: Uber 6kg
Grinder: Baratza Virtuoso
Drip: Bunn CW15-TC
Posted Thu Oct 18, 2007, 6:07pm
Subject: CW15-TC - convergence on grind size, spray head, and dosing
 

My stainless steel brew basket arrived.  I love it.  After I brew a pot, I don't get that "plastic like" smell
which makes me feel better about the brew.  

On brewing, I did a lot of testing in the last few days to find the right combination
of grind size, dosing weight, and spray nozzle sizing (and associated water flow rate) to get the most
optimal cup out of the machine.  For now, I think I've found a decent combination.

For grind size, I settled on a 14-15 setting on the Virtuoso.  I ground coffee ranging from 8 to 20 and put into
some cups for visual inspection (I don't have a screener or laser for actual size analysis).  As it turns out the 14-15
setting looks about  like the same size as coffee you'd buy on the shelf.  

For dosing, I've settled on 2.6 oz (75g).

For flow, I'm using the 5 hole nozzle from Bunn (model 01082.0004) which yields a 3 min 30 sec brew.

I've used these settings on several pots of coffee now, using both lighter roasted Kenyan beans
and a darker roasted Kenyan AA beans.  In both cases, the brew was very flavorful without any bitterness. The real
testimonial has been that my wife (Mrs. Cream & Sugar), drinks the coffee black now and really enjoys it.

Nathan
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