Trying to get some feedback from anyone using one of these pumps . I know B&G has one and Taco has one also. The Taco 00 "VS" will operate in a Setpoint or Δ T mode .
thx, Pat
thx, Pat
Anyone using one of the "Variable Setpoint" circulators?
- Thread starter patch53
- Start date
-
Active since 1995, Hearth.com is THE place on the internet for free information and advice about wood stoves, pellet stoves and other energy saving equipment.
We strive to provide opinions, articles, discussions and history related to Hearth Products and in a more general sense, energy issues.
We promote the EFFICIENT, RESPONSIBLE, CLEAN and SAFE use of all fuels, whether renewable or fossil. -
Super Cedar firestarters 30% discount Use code Hearth2024 Click here
- Status
Just athought here as I am playing with the alpha pump . You can build your own with a tekmar 157 ( I think I have that right ) i actually have thought about doing that and in some of my cases it would work till my storage cools off. Just another idea
What I'm wondering about is if it is possible to use one of these pumps to only pump fast enough to allow a set temperature of water to leave your boiler. for example, when I put storage in next year, can the pump be set up to only return lets say 190F water to the tank? Will the pump speed up or slow down automatically so that 190F water is exiting the boiler and going into to storage? I would think this feature would be even better than just a ΔT circulator. I think you can do this with a Tekmar, but it would be nice if its allready incorporated into the pump? I'm sure these pumps are pricey, but if they can operate like that I would consider one.
Pat
Pat
tell you what Pat if i could find a circulator that could return temps to my boiler at a constant 160 + no matter what my storage is or system retun would be I would be one of the first in line . I think maybe we need to think in reverse here how about a minimum return temp circ would be cool . something that says hey the boiler is so hot I need to run so fast to cool it down . Gues I am daydreaming .
I believe Taco and Grundfos use a tekmar built board on those pumps. You can use them for return temperature protection if you set them up as such and get the sensors in the correct location.
Currently I am using a solar differential control to do this on my EKO. As the return to the boiler cools, the pump slows or stops if necessary. As the boiler temperature rises, sensed at the return piping, so does the pump speed. On a previous post I showed a data logger view of how this works.
tekmar has good info about the options for doing this. Page 7 of this document shows how the return protection function works.
I prefer the external variable speed controls as they have digital displays and more adjustment options.
On some of the solar variable speed differential controllers you also get data logging with the control.
hr
Currently I am using a solar differential control to do this on my EKO. As the return to the boiler cools, the pump slows or stops if necessary. As the boiler temperature rises, sensed at the return piping, so does the pump speed. On a previous post I showed a data logger view of how this works.
tekmar has good info about the options for doing this. Page 7 of this document shows how the return protection function works.
I prefer the external variable speed controls as they have digital displays and more adjustment options.
On some of the solar variable speed differential controllers you also get data logging with the control.
hr
If you look at the data logger thread you will see some boiler temperature data on page 3, which might be helpful.
Most boilers have a lot of thermal mass stored either in the refractory or the boiler water jacket or both. That mass makes it difficult to hold a boiler water temperature constant. I wouldn't expect a very tight temperature control. With a constant velocity pump on my boiler I can control the temperature to within +-5F.
Other variables would be how hot the fire is or heat input, number of gallons of water in the boiler, heat transfer rate of the heat exchanger.
As to your other question about controlling the water temperature to your future storage:
The storage will charge with a wide range of hot water input temperatures, which can be controlled with the mixing valve setting and the size of the circulator pump.
For example: If you start with 145F water leaving the boiler and going into the storage. The storage temperature will eventually increase to the boiler's set point (perhaps 180F). It will likely take three cycles of the storage water through the boiler. This is said to be the most efficient method since the colder the water entering the boiler the better the heat transfer.
If the mixing valve is adjusted so the boiler has a higher temperature water output there will be less cycles of water needed (the flow to the storage will be reduced by the mixing valve).
In either of these cases the boiler has a heat output that is being transferred to loads, in the case of storage it is insensitive to the heat input temperature, eventually the system will reach the set point temperature.
Most boilers have a lot of thermal mass stored either in the refractory or the boiler water jacket or both. That mass makes it difficult to hold a boiler water temperature constant. I wouldn't expect a very tight temperature control. With a constant velocity pump on my boiler I can control the temperature to within +-5F.
Other variables would be how hot the fire is or heat input, number of gallons of water in the boiler, heat transfer rate of the heat exchanger.
As to your other question about controlling the water temperature to your future storage:
The storage will charge with a wide range of hot water input temperatures, which can be controlled with the mixing valve setting and the size of the circulator pump.
For example: If you start with 145F water leaving the boiler and going into the storage. The storage temperature will eventually increase to the boiler's set point (perhaps 180F). It will likely take three cycles of the storage water through the boiler. This is said to be the most efficient method since the colder the water entering the boiler the better the heat transfer.
If the mixing valve is adjusted so the boiler has a higher temperature water output there will be less cycles of water needed (the flow to the storage will be reduced by the mixing valve).
In either of these cases the boiler has a heat output that is being transferred to loads, in the case of storage it is insensitive to the heat input temperature, eventually the system will reach the set point temperature.
sgschwend said:
Thanks Steve. What I am planning on doing is only letting my storage get down to about 150F before having the boiler re-fire. Now when the boiler re-fires, is it possible to have a system that will only allow the pump to move 190F water off the boiler. In other words, as the boiler starts to re-fire, the water temp will still be relatively cool, so the pump would be running very slow, only moving a little water thru the HX tubes. As the boiler gets cranking, the pump speeds up faster and faster to keep the output water temp at 190F. This way you're only adding 190F water to your storage tank. Obviously you would need a pump that was big enough so that even running at top speed it was able to keep up with the heat output of the boiler.
Eventually as your return water from storage gets closer to 190F the pump would be unable to keep the return water from getting above 190F , but then your aquastat would shut down your boiler at say 195F. The pump would continue to pump at high speed until any residual heat was removed from the boiler and then the pump would slow down, but still be sending 190F water to storage for some time probably.
Is something like this possible, or just wishful thinking?
thx, Pat
Sure it is possible, and to some degree that is how they all work.
When you look at the data logger thread you will see temperature graphs. The graph show that the storage will be at several temperatures at the same time, in a perfect system the storage would be at two temperatures. So it is helpful to think of storage that way. The top of the tank will be hot and the bottom will be cold. Your question refers to when the storage is down to 150F, is this the top, middle or bottom or anywhere in between?
I normally will recharge my storage at a convenient time for me. If I am busy one day I may choose to wait till the next day, as it become warmer I am sure the number of days between fires will increase. I like that. I do this by looking at my storage temperature to see how much hot water is left.
There are multiple methods to set the boiler temperature, lots of info here on that. Mixing valves are one way, they have performance limitations (some limitations are brand based). As the mixing system (be it a valve or other similar motor/valve group of parts) in adjusted up in temperature the boiler output temperature will also rise (for a given pump). The circulator pump can be (and should be) controlled to run only after the boiler has reached a set point temperature. If the temperature is not reached then the pump is switched off. In your example the set point would be set high, perhaps 185F, (this value is scary to me). If the boiler output water is below 185F there would be no flow to the storage. I use Dwyer's Instruments dual temperate switches to control the boiler high limit set point and the circulator pump run temperature.
I could look at your system documentation to see how you are setup. Do you have a system drawing or is there an online manual showing your boiler controls?
When you look at the data logger thread you will see temperature graphs. The graph show that the storage will be at several temperatures at the same time, in a perfect system the storage would be at two temperatures. So it is helpful to think of storage that way. The top of the tank will be hot and the bottom will be cold. Your question refers to when the storage is down to 150F, is this the top, middle or bottom or anywhere in between?
I normally will recharge my storage at a convenient time for me. If I am busy one day I may choose to wait till the next day, as it become warmer I am sure the number of days between fires will increase. I like that. I do this by looking at my storage temperature to see how much hot water is left.
There are multiple methods to set the boiler temperature, lots of info here on that. Mixing valves are one way, they have performance limitations (some limitations are brand based). As the mixing system (be it a valve or other similar motor/valve group of parts) in adjusted up in temperature the boiler output temperature will also rise (for a given pump). The circulator pump can be (and should be) controlled to run only after the boiler has reached a set point temperature. If the temperature is not reached then the pump is switched off. In your example the set point would be set high, perhaps 185F, (this value is scary to me). If the boiler output water is below 185F there would be no flow to the storage. I use Dwyer's Instruments dual temperate switches to control the boiler high limit set point and the circulator pump run temperature.
I could look at your system documentation to see how you are setup. Do you have a system drawing or is there an online manual showing your boiler controls?
sgschwend said:
Steve, I don't have a drawing, but basically all this would be is a primary loop with water going from the boiler to a 500 gallon propane storage tank (which I found today for a decent price). Water from storage to the house loads and back to storage would be another loop, very similar to the "simplest pressurized storage" system that nofossil produced.
I don't want a situation where I have to make a new fire every day. With only 500 gallons of storage my thinking is that the boiler would fire for about 45 -60 minutes and then storage would be charged. Then idle for a few hours and then re-fire again. My Seton is oversized for my house and even on the coldest days I can go 12 hours between refilling now, so I would think i could do the same with storage. I am definitely not getting the most out of my boiler now. It runs for no more than 10-12 minutes now and then shuts down, idles for 20-30 minutes and refires again. Obviously I'd like to get away from that scenario. I wouldn't mind the boiler idling for an hour or two between burns because after the initial burn, most if not all the moisture would be out of the wood anyway, and longer hotter burns would presumably keep the boiler running fairly clean.
So, if I can just go out and add wood twice a day like I do now, I'd be happy with that. Even after my wood is basically gone after a cold night, I just have to stir up some hot coals, toss the wood on and it refires back up right away.
I went and read the "data logger" thread and all that stuff makes my head spin. I really don't want to get into all the electronic gizmo's and gadgets. Those are great if you know how to install and play with them, but I'd rather just keep it simple if at all possible. I'm just trying to figure out a way to get hot water into a storage tank as quickly and efficiently as possible using the least amount of electricity and wood, like everyone else I guess.
Thx, Pat
patch53 said:
Pat,
To answer your question; yes pumps like the Taco Variable Speed Setpoint Circulator can be configured for 'reverse acting' mode where pump speed increases as control temperature increases.
I'd say you're lucky in that Seton type boilers lend themselves to much simpler controls and systems because of three inherent advantages: First they appear to be more indifferent to coolish return temperatures; second they are designed for short burn cycles; and third they store a lot of heat in the form of unburned wood.
Since the firebox is large and the unit will hold a fire for hours, you can do a lot more with 500 gallons of storage than a less flexible boiler could accomplish with the same amount of storage, and more simply. The scenario you describe of maintaining storage in the range of plenty-hot to good-and-hot should work quite well I would think.
--ewd
patch53 said:
No, I'm still building mine. I'm using a less expensive gasification type boiler but as you can tell I might have preferred the Seton type if the budget would have allowed.
Instead of a variable speed pump I'm planning to use a home-made hydronic separator tank with one pump to circulate on the boiler side and another on the storage tank side. With a good sized tank (twenty gallon approx.) I'll be able to use a cheap PID controller to drive the storage tanks side on about a forty second cycle, so many seconds on, so many seconds off, first maintaining return temperature high enough, and then switching to maintaining boiler supply temperature low enough after storage heats up. A variable speed control would accomplish the same thing more nicely with less Rube-Goldberg effect if I wasn't so cheap.
--ewd
I'm using a Bell Gossett NRF-VS on my house loop. My system is in a polebarn and I'm running one zone to a air heat exchanger in my NG furnace. Originally I had this zone running 24 hours 7 days a week like it was for my OWB with a 007. The problem was that when the house wasn't calling for heat I was returning hot water back to my storage which absolutely killed my stratification. I'm using this circ at the storage tanks with the sensor in the house at the furnace. I set the set-point to 120 degrees and the circ maintains this with it moving more water if the furnace is running. Now I'm able to keep the tanks stratified so I've been really happy with it and this is my second year using it.
(broken link removed)
(broken link removed)
Sounds interesting, even tho I have no clue what you're talking about . LOL
Well, I usually don't mind paying a bit more for something if it will save in the end, but I guess these Taco VS models sell for around $600 !! Ouch !
But I actually built my Seton rather than buying one and saved about $4K, so I guess that justifies spending a bit more for a fancy pump, right? LOL
Pat
Well, I usually don't mind paying a bit more for something if it will save in the end, but I guess these Taco VS models sell for around $600 !! Ouch !
But I actually built my Seton rather than buying one and saved about $4K, so I guess that justifies spending a bit more for a fancy pump, right? LOL
Pat
patch53 said:
I found this circ when I started looking at the Taco model. I got it from Patriot Supply and it was around $300.00ish. I called them inquiring about the Taco model and they were the one who suggested I look at the B&G. I know what you mean by having no clue.....I get lost reading about others writing their own code and making up graphs and such. This is why I liked this circ as all I had to do was plug it up to power and tape the sensor where I wanted to read the temp at. Turn the knob on the front to 120 degrees and I was set.
P. I suggest looking at page 3 of the thread so you could see some graphs of storage temperatures and also how fast a tank may charge. You can see how the top tank temp is a lot different than the bottom of the tank.
The storage plumbing needs to guard against turbulence, which I would assume would be more difficult with a larger circulation pump.
I have read in other threads posted here that internal boiler heat exchanger temperatures below 135F is to be avoided, low return water temperatures cause problems. Both creosote and metal eating acid can form otherwise. The design you are following accounts for this issue by using a mixing valve.
The storage plumbing needs to guard against turbulence, which I would assume would be more difficult with a larger circulation pump.
I have read in other threads posted here that internal boiler heat exchanger temperatures below 135F is to be avoided, low return water temperatures cause problems. Both creosote and metal eating acid can form otherwise. The design you are following accounts for this issue by using a mixing valve.
sgschwend said:
Hi Steve, yes, I know you shouldn't be sending relatively cold (135F) water back to the boiler. Thats why I only want my storage temps and return water to fall to about 150F or so before re-firing the boiler.
Someone posted a design for water coming from the boiler into a 500 gallon propane tank that would go thru a piece of pipe with holes cut in the top so as to distribute the hot water more slowly into the top of the tank with very little turbulence. I think they mentioned even extending that pipe all the way to the other side of the tank so that when the house zones were calling for heat they would actually end up pulling a good portion of that water directly from the incoming water rather than just from the tank. That sounds like an excellent idea to me.
I'll check out those graphs too.
thx, Pat
I think how a propane tank is modified to do this (on a horizontal tank) is by cutting a hole near one end and then a length of pipe can be installed in the tank. The pipe would have rows of holes spaced out so that the water would flow slowly into the tank; the far end of the pipe is plugged. It is kinda like a manifold that has so many taps to pull water from the main line. I would love to find a way to do this from a factory center fitting, haven't figured that one out yet.
I did a similar thing for the return line. I installed a vertical pipe that nearly reaches the bottom of the tank with a set of hold around the bottom part allow the water to exit in multiple directions (the end is still plugged). If you have twice the exit area then the velocity should be halved. But if I were to do it again I would put in the long horizontal pipe for the return line too.
I like the Nofossil design; one trick with that design is the location of the 'T' that allows the hot water to either go to the house load or turn down to the tank. Since water has mass it would prefer not to change directions, so it will go to the load first if the load pumps in on, otherwise with the load pump off the storage tank will have the lowest resistance and claim the hot water.
I am uncomfortable about mis leading you. When you add well insulated storage it will hold its temperature unless water is exchanged with a load. By running the boiler 24 hours a day all of the heat load will be supported by the boiler. It will be as if you do not have storage. I don't see that it will help you any. If you change the way you use your boiler you could benefit from storage.
I like storage, I also like starting a fire in a Seton design boiler, I often get to light one, my everyday boiler is a large Essex.
I did a similar thing for the return line. I installed a vertical pipe that nearly reaches the bottom of the tank with a set of hold around the bottom part allow the water to exit in multiple directions (the end is still plugged). If you have twice the exit area then the velocity should be halved. But if I were to do it again I would put in the long horizontal pipe for the return line too.
I like the Nofossil design; one trick with that design is the location of the 'T' that allows the hot water to either go to the house load or turn down to the tank. Since water has mass it would prefer not to change directions, so it will go to the load first if the load pumps in on, otherwise with the load pump off the storage tank will have the lowest resistance and claim the hot water.
I am uncomfortable about mis leading you. When you add well insulated storage it will hold its temperature unless water is exchanged with a load. By running the boiler 24 hours a day all of the heat load will be supported by the boiler. It will be as if you do not have storage. I don't see that it will help you any. If you change the way you use your boiler you could benefit from storage.
I like storage, I also like starting a fire in a Seton design boiler, I often get to light one, my everyday boiler is a large Essex.
I have a Warmrite control (Made by Tekmar) It's variable speed at 10% intervals. I can set the "boiler protect temperature" at 160 and when the boiler temp falls close to that, it slows my injector pump. Any standard Grundfos pump will work.
sgschwend said:
If I understand Pat's goals correctly, he wants to use storage to eliminate short-cycling of the boiler by isolating the load from the boiler with some storage. The boiler would fire when storage gets less hot enough and would idle when storage gets more hot enough. Gasification boilers with storage normally run one burn with maybe some short cycling at the end, a Seton type boiler would allow multiple one hour or so burns, each yielding 150,000 btus or so, spaced in time by hours.
The trick will be to get the boiler to stay off until the top of storage is cool enough and then stay on until the bottom of storage is hot enough.
--ewd
From what I take it then you will want to set a larger hysteresis for the boiler control, so it will want to stay off for a wider temperature range. P. said 150F to 195F, would be about 30 degrees hysteresis.
I would guess you would still be bringing cold water back and the boiler would circulate it, so perhaps the Nofoss design return should change. Don't mean to be dense but the Nofoss design give the boiler loop priority over the storage.
If I have your meaning correctly then you definitely want a digital temperature switch so you can program those values.
I would guess you would still be bringing cold water back and the boiler would circulate it, so perhaps the Nofoss design return should change. Don't mean to be dense but the Nofoss design give the boiler loop priority over the storage.
If I have your meaning correctly then you definitely want a digital temperature switch so you can program those values.
Attachments
![[Hearth.com] Anyone using one of the "Variable Setpoint" circulators?](/talk/data/attachments/25/25272-86456548731ced120fce7973e03135ac.jpg?hash=uaFMG-ULar)
Hi Steve, my design is going to have 2 seperate loops . One from the boiler to storage and back to the boiler. the other would be from storage to the house zones and back to storage. So, any return water to the boiler will be somewhat mixed with the water on the bottom of the tank.
For the incoming water into the tank from the boiler, I had mentioned about running a pipe all the way thru the tank that would have holes on the top half of that pipe to allow the heated water to percolate out into only the very top of the tank, but when the house load circulator was running it would pull some of that water straight thru the pipe and into the house zones. According to everything I've read here, satisfying the house loads first is the way it should be done.
The boiler circulator would run all the time. Even if I go with a Taco ΔT pump, it will still circulate at a minimum speed at all times.
I don't have a clue what a "digital temperature switch" is, but I'll check it out.
Pat
For the incoming water into the tank from the boiler, I had mentioned about running a pipe all the way thru the tank that would have holes on the top half of that pipe to allow the heated water to percolate out into only the very top of the tank, but when the house load circulator was running it would pull some of that water straight thru the pipe and into the house zones. According to everything I've read here, satisfying the house loads first is the way it should be done.
The boiler circulator would run all the time. Even if I go with a Taco ΔT pump, it will still circulate at a minimum speed at all times.
I don't have a clue what a "digital temperature switch" is, but I'll check it out.
Pat
patch53 said:
I'm pretty sure you don't want to run the storage circ once the tank is up to temp, unless the boiler is overheating, then probably you would.
For digital temperature switch think electronic aquastat, but less expensive, doesn't need a probe well, is programmable, has digital readout.
This might run your boiler to storage pump:
Code:
t_storage_bottom_limit = 185F
t_storage_top_limit = 195F
t_storage_top_hysteresis = 50F
t_boiler_output_setpoint = 190F
t_storage_top_not_break_on_rise = (t_storage_top < t_storage_top_limit)
t_storage_bottom_not_break_on_rise = (t_storage_bottom < t_storage_bottom_limit)
t_storage_top_make_on_fall =
(t_storage_top < (t_storage_top_limit - t_storage_top_hysteresis))
boiler_run =
(
(boiler_run) &&
(t_storage_top_not_break_on_rise) &&
(t_storage_bottom_not_break_on_rise)
) ||
(
(boiler_idle) &&
(t_storage_top_make_on_fall)
)
boiler_to_storage_pump_run = (boiler_run) || (boiler_overtemp)
SPDT
relay storage_top_temp_switch storage_bottom_temp_switch
| | |
v v v
_________________________________________________________________________________
|
/ |
_________NEUTRAL |
| |
| |
v |
|
NO |
__boiler_run___storage_top_not_break_on_rise__storage_bottom_not_break_on_rise__|___
24VAC_ | |
__boiler_idle__storage_top_make_on_fall_________________________________________| |
NC |
|
|
______boiler_to_storage_pump_run__________ NC |
| ____________________|
| ___
| NO
|
| ___ NC
| _________________24VAC
|_______
NO
^
|
|_______NEUTRAL
|
|
/
_____boiler_overtemp
^
|
DPDT
relayHi Eliot, I would have to keep the circulator going on the boiler at all times, but with a delta T unit it would slow down some.
The chart you posted is all Greek to me. I can do plumbing work with confidence, but electrical stuff ain't my bag ! LOL
The chart you posted is all Greek to me. I can do plumbing work with confidence, but electrical stuff ain't my bag ! LOL
- Status
Similar threads
