This past Spring I was told by Taco that they would be coming out with a revised bumblebee pump that would be more powerful and have reverse acting capability "before the next heating season". I touched base with them today for an update and was told nothing would be forthcoming "until some time maybe next year"....Ugh.
Update on the taco bumblebee update
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Coal Reaper
Minister of Fire
Thats a bummer. I am happy with the current one. Just gotta see for sure if it moves enough btus to the during a high demand. It does recharge DHW awefully quick, but idk how much that actaully says. I know some of you guys are looking forward to the reverse acting and that should be interesting if/when it actually comes to fruition. Thanks for the update.
Figures. The first go-around was late by years, so looks like they decided to double down and throw away any hope of gaining any credibility. Since it is a different and bigger pump I wouldn't be surprised if they abandon the attractive price-point if and when it is ever released. Perhaps if they spent less time worrying about a cute name and concentrated more on product development they would have fewer of these embarrassing episodes.
So in time for the 2013-2014 heating season was pushed to in time for the 2014-2015 season, which has now been pushed to in time for the 2015-2016 heating season.
They've introduced an HEC-2 replacement called the VT2218 that has reverse acting capability, but inexplicably some bonehead decided to limit the reverse-acting setpoint to a range of 32 degF to 100 degF. From what I can tell it is being sold only in New England for the time being.
(broken link removed to http://www.irrsupply.com/2010/pdf/VT2218_Viridian_Delta-T_Instruction_Sheet_102-483_Rev_May_12_2014%20.pdf)
Also there is now a Taco ECM variable speed, constant deltaP, and proportional deltaP pump called the VR1816. Proportional deltaP should work better with TRVs scattered about on long distribution runs.
(broken link removed to http://flopro.taco-hvac.com/media/1816/VR1816-Viridian-Instructions_102-499.pdf)
The model numbers now have meaning (beyond smaller number smaller pump). VT is variable temperature, VR is variable pressure (resistance ?). VT2218 is max head 22 ft H2O, max flow 18 gpm, and similarly for the VR1816. So presumably the VT2218 will be sold as a TV6.7-4.1 in France.
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If I'm understanding the capabilities of the VT2218, could this circulator be used to keep constant the temperature of the water coming out of your boiler? In other words, could it speed up or slow down to keep lets say just 190F water from leaving the boiler?
Pat
Pat
I would envision having a thermostatic return temperature mixing valve as normally configured, then have the boiler loop pump VT2218 slow down or speed up in reverse-acting mode -- a.k.a. cooling mode -- to produce constant supply temperature.
Except Taco decided to limit the setpoint range of the pump's cooling mode to 32 degF to 100 degF.
Kuribo has suggested inserting a resistor in series with the 10k thermistor so that the pump would (for example) see 80 degF when the actual temperature is 180 degF. I think this field expedient would work correctly and reliably.
But perhaps the same thing could be accomplished at least as well for the same or less money with an aquastat that disabled the boiler loop pump on temperature fall to 182 degF (for instance) and re-enabled on temperature rise to 185 degF (for instance).
Or an inexpensive PID controller that controls the percent on-time of a fixed time cycle of something like 75 to 150 seconds would also perform nicely.
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Robert V
Member
So this is probably a silly question. When you say the pump is reverse acting, this means the pump will rotate the opposite direction to flow the water the other direction? In what type of application would this be needed?
You're right, it sure sounds like they're talking about pumping the opposite direction, but direct acting and reverse acting are terms Taco has used to describe modes of speed control for their temperature controlled variable speed pumps, for instance in their Variable Speed Setpoint “00” Circulator (00-VS) documentation:
But now it looks like they may have changed their terminology to set point heat and set point cool, as in their VT2218 sheet:
It also looks like they now prefer set point to setpoint, however set point is a tennis term, whereas setpoint is the correct term in the context of control automation.
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They are displaying their new VS lineup at the AHR show in Chicago this week. I hear from industry friends that are there they look like very good pumps.
How would it be possible for it to pump both directions?
I could see reversing the motor, but what about reversing the inlet and outlet? The pump impeller would also have to change?
maple1
Minister of Fire
That's likely why he asked the question - he likely thought the same thing so just asked to be clear on terminology.
How about one VT2218 in the boiler loop to control the boiler outlet temp at 190 and another VT2218 in the loop to pressurized storage, on at 190 and controlled by a set boiler return temp (for boiler protection) say at 150 ? No TCV....???
Certainly looks good on paper.
The pump in the boiler loop with a sensor on boiler outlet port can cool the supply temperature by running faster.
And the pump injecting into the loop with a sensor on the boiler return port can cool the return temperature by running faster.
It doesn't seem to me that either pump would interfere with the control of the other pump by causing hunting or other instability.
I don't think you need any logic to keep the injection pump from running depending on supply temperature, it should shut itself off if return temperature is below setpoint.
I say the pump should shut itself off if setpoint is reached in cooling mode, but now that I think about it you would want to make very sure that the Taco control doesn't just keep running at some minimum speed or some such silliness because they decided how it has to work without putting enough thought into it.
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Yeah, I was wondering about the two pumps interfering with each other...I need to think about it some more....Since two pumps are needed anyway, seems like a chance to get rid of the TCV as it would be redundant.
I talked to Taco today and have good news and bad news: the good news is the pump should work fine in reverse or setpoint cool mode out of its published range by inserting a resistor in line with the sensor. The bad news is these pumps do not shut off when the set point is reached but rather continue to operate at the lowest speed.
I don't understand how the pump could control to a set point if it never shuts off- if it never shuts off, wouldn't it have to have a very loose control band in order to meet the set point?
So, to use these pumps as I have proposed would entail an aquastat or other such switch to turn them off completely...seems if you have to use an aquastat to turn them on and off you could just use a regular pump instead....Hmmmmm......
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Naw, still getting all the components and dialing in the design and controls. I will start plumbing things up in a month or so.....Waiting on these new Taco pumps and trying to figure out how to make them do what I want....
JP11
Minister of Fire
I looked at that viridian. Won't pump enough GPM to get the heat out of my 60kw. close.. but short.
How is your storage charging set up? What I want to do is send the boiler output through 50' of 1" pex to my tanks in one pass. I also have a 60kW boiler and according to what I have calculated, my flows are between 4-6gpm at a 100delta T and max boiler output of 225,000BTU/hr. With my calculated head loss of around 12 feet, the Viridian seems to be fine....
maple1
Minister of Fire
JP11
Minister of Fire
you need more pump... WAY more pump.
I'm running a taco 0011. About 25 to 30 feet of 1.5 inch copper. rated output on boiler at 20 degree delta T. If I remember correctly.. I'm pumping 23 to 25gpm.
if you can't get the heat out of the boiler, it will go into idle and wait till your too slow flow gets the temp down. pump will run a ton, and boiler won't burn well at all.
JP
I'm running a taco 0011. About 25 to 30 feet of 1.5 inch copper. rated output on boiler at 20 degree delta T. If I remember correctly.. I'm pumping 23 to 25gpm.
if you can't get the heat out of the boiler, it will go into idle and wait till your too slow flow gets the temp down. pump will run a ton, and boiler won't burn well at all.
JP
JP11
Minister of Fire
The key is the delta T.
My storage-to-boiler injection loop is a 15-58 on low speed on a duty-cycle controller and it runs about 75% of the time with a deltaT of 70 degF. Call it 4 gpm, times 70, times 500, 140,000 btu per hour, easy peasy.
And I'm heating the whole house with nominal 3/4 inch PEX, 110 feet round-trip. Same 70 degF deltaT, draws less than 1 gpm on the average.
225,000Btu/hr = 500 Q dT
dT= 90
Q= 5gpm
Don't see why?
There is a boiler loop with another pump that does about 16-18gpm with a 30F dT through the boiler. It's like injection mixing. The large dT means I can pump a lot less water....
On my zone supply side I will use 2 Viridian pumps as I have two supply runs, each with 2 zones and want the redundancy....
Whoops, see Mr. Dudley has already explained....
dT= 90
Q= 5gpm
Don't see why?
There is a boiler loop with another pump that does about 16-18gpm with a 30F dT through the boiler. It's like injection mixing. The large dT means I can pump a lot less water....
On my zone supply side I will use 2 Viridian pumps as I have two supply runs, each with 2 zones and want the redundancy....
Whoops, see Mr. Dudley has already explained....
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