Post in 'The Boiler Room - Wood Boilers and Furnaces' started by Tattooz, Nov 9, 2008.
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Some updated photos..... Someone asked about "outdoor reset" we are going to use a Tekmar 356 Control that will be able to vary the pump speed to change the system temp according to the outside temp..
So as the weather gets colder the control will try and maintain higher temps at the house HX by speeding up the pumps.... Thanks Chris!
looks good! what is the estimated cost of a set up like this? Also what is the life span of a garn boiler?
Can that pump be installed like that with the rotor shaft in a vertical plane? Most circs are installed with the rotor shaft in a horz. plane. The bearing surfaces are designed for a radial load not a constant thrust load.
What are you controlling with the JC A419? I'm formilar with this controller, it can be set in a couple of configurations for heating and cooling applications, but I'm not sure what you would be controlling? Also, what model number is the wilo pump you are using? Looks like your comming right along.
I will look into it..... I have the manuel right in my hands.....
This pump is a Top s1.25X25 Wilo.
sorry but im still learning this stuff. but thats an aquastat and well next to the temp gauge correct?
tat,can you clear this up for me, i was under the impression that the concept of outdoor reset was to use the variable speed pump to mix the supply temp based on the reset control calculations, however the gpm delivered to the hx would stay constant. and that if you wanted to vary the flow rate to the hx, that would be with a vsd pump controlled by the delta t with sensors on the supply and return, as your delta t became larger the pump speed would increase to try to close the differential. thanks tom
Let me look into it .... I will need some help with that question. But I will ask the people that are helping me with this!
From what I understand it's just a set point control for the auquatat
Outdoor reset can be accomplished in different ways but the essential thing is the max btu's you can deliver is controlled by the outside conditions. The idea is the heating equipment output is adjusted to match the houses heat loss.
You can do this by constant circ and a controller run 4 way, or variable speed injection, or temperature setting on a mod-con or well, lots of ways. When it is really cold out it runs the exact same as a conventional setup. When its not the reduced output leads to less overshoot of temperatures for some high challenge designs.
Outdoor reset isn't appropriate to throw at everything.
If you're trying to use outdoor reset the control the water temp, then you're correct.
However, I would presume that the idea here is to accept that a lower water temp is allowable during warmer conditions, and slow the pump to save electricity. In other words, slowing the pump is the goal, rather than lowering the supply water temp - the lower acceptable temp is what allows the pump to be slowed.
joe, being that the garn is a burn and store, with a widely fluctuating supply water temp as the day progresses, and not a relatively constant temp boiler that can controlled with a setpoint high limit. would the outdoor reset be beneficial. with the garn burned 12 months a year would it be better realizing the fluctuating supply temp to use a variable speed circ based on a delta t between the supply and return, basically only if there is demand will the circ be pumping supply water based on the delta t need, if no need the hot supply water will stay in storage, thanks tom
"Beneficial" will depend upon what you're trying to accomplish, and what your potential inefficiencies are.
For example, dropping the pump speed based upon outdoor temp will save electricity, and will reduce heat loss from piping (particularly important for buried pipe, where heat is lost to the outdoors, versus indoor pipes where the heat is just lost to the wrong part of the building). However, while heat loss will be lower, temperature loss will be higher, so if the heat delivery system requires higher water temps (eg, a fan coil, or baseboard), the heat loss may not be as big of a factor as the temperature loss - heat is only usable if it is at the correct temperature.
Controlling based upon the delta-T will give you a very controllable delivery of heat, as you will be in an essentially-linear relationship at your heat exchanger (with a fixed delta-T, double the flow means double the heat transfer). Higher flow rates than are actually necessary for conditions will result in greater heat loss from underground pipe (but lower temperature loss), so the issues above apply, but reversed.
Another option is to control for a fixed return water temperature. This is frequently done to keep a condensing boiler in condensing operation, by slowing down flow when the return temp gets too high. However, you can speed up flow to a zone pump in order to keep the return temperature up, which can be very important with things like fan coils - by keeping the average coil temperature over a certain setpoint, you never have the issue of blowing air that feels cool. You can even operate based upon discharge-air-temperature, if you are dealing with a process that requires a certain temp (eg, an incubator). Or based upon discharge-water-temp from the other side of a plate heat exchanger (or other heat exchanger) when that is the critical value (as in heating domestic water, or water for an aquarium, pool, or hot tub).
Variable-speed technology allows for a wide variety of control possibilities. Adding "smart" controllers can allow for control based upon multiple functions at the same time, or establish certain limits. For example, you could operate based upon outdoor temperature, but also have a hard limit programmed into the controller that will monitor the discharge temperature of the heat exchanger, and control based upon that if the outdoor reset curve tries to push the temperature too low (standard outdoor reset controllers provide that in a rudimentary way).
Chris here it is.. Go ahead and cut and paste it in.
Tat's system will utilize a Tekmar 356 to control the pump on the Garn side of the flat plate Hx. The Tekmar 356 is a very reliable, reasonably priced, control that is designed to provide either outdoor reset or setpoint temperature control of a heating system by varying the speed of a circulator that "injects" higher temperature boiler water into the heating circuit through closely spaced tees in a primary / secondary configuration. If you vary the speed of the boiler side pump on a system with a flat plate Hx separating the boiler from the building heating circuit you achieve the same thing. The control is usually used to provide lower temperature water for radiant floor systems but can also be used to improve baseboard and radiator based systems
The control has three sensors. A boiler side sensor that can be used to detect the temperature of either boiler supply or boiler return water. A system sensor that detects the water temperature of the system water that the control is "controlling" and an outdoor temperature sensor. In outdoor reset mode the control will increase pump speed of the injection pump (or in this case the Garn side heat exchanger pump) to raise system water temperature as the outdoor temperature drops. In set point mode the control will increase or decrease the pump speed as necessary to maintain a constant system temperature even as the building load changes or as boiler water temperatures change.
In this application the "system" sensor will be attached to either the side of the Hx or to the boiler return piping at the Hx. The control itself will be installed inside the living space of the house. The control has an LCD screen which will display outdoor temperature, boiler (Garn) water temperature and system water temperature. It also displays relative pump speed.
The control achieves:
- Very low (trickle) pump speed under conditions of no or low heating loads.= lower power consumption
- Reduced underground heat loss through lower average underground flow rates
- Building system water temperature no higher than required depending on outdoor temperature
- Indoor display of Garn water temperature
Tat's system is using the A419 setpoint control (along with two Taco SR-501 relays) to interrupt the demand signal to the Tekmar, and enable the oil boiler when the Garn water temperature drops below a preset minimum. When the Garn temperature is above the setpoint minimum, the Tekmar is enabled, the Garn side variable speed pump runs and the pump between the HX and the house system piping is controlled by the existing house zone control. In the future we will probably replace the A419 with a reset control which will look at outdoor temperature to calculate a minimum Garn temperature at which the oil boiler takes over.
I recently took delivery of a WHS 2000, and have been following tat's progress with appreciation for the opportunity to learn from someone else. My setup will be similar to his, the biggest difference being that I am only heating one building. I have a similar "before" situation, and have been planning a similar "after" situation. I plan to reconfigure my supply/return manifolds into a p/s arrangement, and have the GARN hx and the fossil-backup supply the primary in parallel.
Tat, I've been wondering what kind of control scheme you were going to employ for the GARN-hx-primary config, so thanks for posting the details about the tekmar, etc. I am confused about one thing in that post:
Can you please help me with the following questions?
1) I assume you left the "before" manifold circ in place, and have not changed the control scheme for that?
2) For each of the source circs, are they decoupled from the primary circ? How are you controlling those, especially the circ between the hx and the primary? I didn't follow what was meant by "existing house zone control"?
3) The head loss for my 50 plate hx is less than the loss I currently have through the boiler, so I was thinking I could plumb the hx right into the primary loop and eliminate a circ for the hx secondary and any associated control complexities. I know that there was a thread on this idea somewhere else, but as I recall it didn't wind up with any specific conclusion. Did you consider this, and if so, why did you go the way you did?
4) I can't make out your dial temp gauges, and I was wondering what brand they were. I have about half-dozen Letro gauges in my existing system, and I like them because they have a scale that's more suited to hydronic heating vs. automobiles or biodiesel (I think that they are 50* - 220* ).
Thanks for any answers, and thanks again for sharing your progress with the rest of us ....
Tom, I had to enlist the help of Chris Holley at Floor Heating systems here in MAine for your answers. Chris is my Garn Distributer and has done all the site plan for my set up.
Tom, in answer to your questions:
1) Yes the "before" system circulator is still in place. It is called on by an end switch on an existing Taco ZVC 406 zone control. (the ZVC is the "existing house zone control I previously referred to). The oil boiler circ is controlled by the oil boiler Honeywell L8148 cold start aquastat.
2) Yes the two "source" circs are de-coupled from the system circ. When the Garn is below minimum temperature the ZVC calls on the L8148 boiler aquastat which in turn switches the oil boiler circ.. When the Garn is above minimum temperature the ZVC calls on a Taco SR-501 relay which in turn switches the Hx circ.
3) I think piping the hx directly into the primary loop is good idea. It would save a circ. In Tat's case I was focused on keeping the Hx close to the underground line entry point because his design flow is right up against head loss limits for that underground loop. The run from that underground entry wall to a Hx at the boiler would have added another 80 lineal feet of piping (after adding equivalent fitting losses). So..no it didn't occur to me. Now if that run had been done in 1 1/2" rather than 1 1/4 " copper that would only have added about a foot and a half of head loss and it would have been a good alternative.
4) From the photo I'd say that those are 2 1/2" Pasco or Honeywell/Sparco thermometers which are the supply house norm in Tat's area. I also really like the larger Letra thermometers but they're not generally available at plumbing supply houses in Maine. BTW, I just noticed that Letro also makes relatively inexpensive flow meters.
One more thing..if you go the Tekmar route and and you have an indirect hot water heater as one of your zones you'll want to wire your controls to put full line voltage on the Garn pump during a hot water call.
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