I could use some control wiring ideas for wood fired

Paul Rohrs_2

a 3-way normally open solenoid on the buffer tank inlet wired to the p4 pumpstat so that when that call satisfies, the 3-way closes and diverts flow back through the buffer tank. You stated ideally the buffer tank would charge once the air-handler satisfied.

I had done a similar job so please disregard some of the other secondary zones I didn't delete off of the print.

This is only in keeping with the "Keep It Simple" mentality. Give me some more time and I think I could come up with something more elaborate.

Regards,

PR

hr

Here is what I have so far

The boiler is always powered. It has an aquastat that powers P1 and P2 when it reaches 140° (simple boiler return protection) P2 is also a VS MixiMiser for return protection, although the 140° stat works well.

P3 runs constantly.

P4 runs when the wall stat calls for heat.

P5 is my nemis. It supplies a buffer tank. Ideally the tank would only charge when the air handler has satified. But I would like to pull heat from it if the boiler has died out, and the tank is at least 120°. Right now I have a setpoint turning it on when the primary loop reaches 160° below the AH connections. When the loop drops to 120° P5 drops off.

Be nice to drop P3 off when neither load or boiler is on. maybe just an outdoor t-stat along the outdoor reset control concept.

Thanks for any thoughts or critique.

hot rod

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Dale

Logic

So, if boiler at 140 degrees and tank at least 120 degrees turn P5 on? I guess this is how I need to think about stuff like this. Could you could use a make on temp.fall control to monitor boiler and a make on temp rise to keep closed if the tank is over 120 and those in parallel would start the pump?

Dan Peel

One relay

HR,
Just throw in a relay to slave P5 - enable P5 only when P4 is satisfied, the rest of the controls stay the same. Enjoy......DAn

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Constantin

How about this?

Simplicity itself. Removes a number of pumps.

If the AH requires a separate pump, go for it. Here, the 4-way valve provides the boiler protection. The FC in the second pump prevents the buffer from receiving any BTUs except when its meant to. Once the second pump is engaged, no water will enter the AH.

Then, when the buffer is meant to keep the AH happy, block flow to the 4-way with the ZV and energize P2 until the boiler needs to be re-engaged. Once the boiler fires, turn off the blocking ZV, turn off P2 and you're in business.

Paul Rohrs_2

Constantine....

That is a great idea. Especially to simplify with fewer components that require more parasitic loss. Great Job.


I am curious though, aren't you reversing flow through the air-handler when isolating with the zone-valve? The direction of flow must not be relevent through the air-handler? I have had some experience with toe-kick heaters, but not fan-coils. I know there is a "snap-action" disc which senses flow in some of the toe-kick heaters and I didn't know if the same process was necessary through the air handler.


Regards,

PR

Constantin

Thanks Paul!

Perhaps the bias from taking a class at Viessmann is showing? Either way, I think the diagram above may remove a lot of pumps and hence save some electrical energy, all while leaving the boiler protected.

One additional energy-improvement would be to find a ZV that only requires a momentary burst of energy to open and close, i.e. a non-solenoid variety. Otherwise, that might be sucking down the amps for no good reason while the buffer circulates.

Oh and as far as reverse vs. forward flow... does an air handler care? I don't happen to think so, but I'm happy to be wrong. If it is a problem... let me think about it...

Constantin

... if an air handler really cares...

... how about this?

The 2nd 4-way basically directs flow to the AH when the boiler operates. Then, as the buffer is needed, it switches over. If the buffer is supposed to provide heat, the P2 activates. The CV is a check valve to prevent ghost flow when P2 is running.

hydronicsmike

Hmmmm, Constantin...

....what do the guys at Viessmann tell you how much it costs to operate ten 00 Series Taco Pumps or equivalent size Grundfos Pumps if they run continuously for one month straight?

Hot Rod, let me see what I can dream up for you...

Mike

Constantin

Hey Mike,

I don't install heating systems for a living. Hence, I have no idea which components cost how much. Thus, I cannot design a system with the prospect of life-cycle costs in mind (initial vs. operational costs and all that).

I gather from your post that motorized 4-way valves are very expensive? How many 00-series Taco pumps can I buy for a standard 4-way Tekmar valve? I ask, as the 4-way valve in the first diagram I posted replaced 3 pumps.

Next, does an air handler care which way the heat is being pumped through its hydro-air coil? I suspect it does not, but I simply don't know for sure. Hence my second diagram that allows for "proper" flow through the AH at all times, should it be necessary.

So, does a AH care which way a hydro-air coil is "fired", and if so, what net effect does it have on the performance of the HX in it if the flow is reversed from the usual direction? Do hydro-coil manufacturers actually designate in vs. out on the outside of their cabinets?

Carl PE

This might be a stupid question..

but why don't you pipe the air handler and buffer tank in series?

Maybe hook up P3 to the same aquastat as 1 and 2?

hydronicsmike

Constantin,

I was just wondering if they had a money figure when it was explained that more pumps add operating cost. In my experience, small circulators draw very little power and if it makes a difference of 5$ (would suspect this to be a high number) a month, is it really a big deal? I mean reducing energy and fuel consumption is a definite interest for me, but I want to make sure that you get something in return for it. In other words, would I pay $100 more for a Motorized Mixing Valve System than I would spend for 2 extra pumps that may add a dollar or two to my monthly utility bill? Nope.

The truth, I guess, is that in small Residential Systems, the Mixing Valve and Actuator versus two Pumps comes probably close to the same as far as price is concerned, but I am looking also into maintenance issues. Do we have more Mixing Valves serviced than Pumps, looking at a comparable rate? In my believes we do.

Once we get into larger Residential and then Commercial Systems, the installation Price difference between a Motorized Mixing Valve and a (Variable Speed) Pump Injection System becomes a lot bigger.

In any case, I don't want to go on about this and hope that this is not taken the wrong way. In my opinion, it comes down to personal preference and mine is now Pumps instead of Valves. I used to be a strongly opinionated German Mixing Valve kind of guy myself, until I learned about the alternative. Today, I don't believe in Pump Injection over Mixing Valves because of the company I work for. I work for this Company because I have been a believer and strong supporter once I was sold on the idea. As you mentioned, tekmar does sell Valves and not Pumps. Still, sometimes it is not only about making an extra sale. It could be about making systems better and that is what I believe the company I work for stands for.

So as my final conclusion, I guess, I like to say that everybody should stick with what they are comfortable with. Both options work and work fine. But what bothers me, are baseless comments made. Show me numbers (not you, but the guys who make this claim) that prove to me how much I will save on operating costs if I replaced two Pumps with one Motorized Valve over a years time and then I am in. Until then......

All above is my own personal believe and does not neccessarily reflect the companies standpoint.

Cheers,

Mike

hydronicsmike

HOT ROD

For the MixiMizer, is the Mix Supply Sensor on the P1 or P3 Loop? Would suspect it is on the P3 loop running in a setpoint mode and then the Boiler Sensor is on the P1 loop, right?

Anyways, To keep it simple, which I assume is what we are shooting for here, I would maybe enable and disable the entire system through one Outdoor Stat. Then in order to accomodate everything else that you have asked for, you could switch the power to P5 through a NC contact on the same Relay that brings on P4 when ever the thermostat calls.

Have you thought about possibly running the Storage Tank of two 155 Difference Setpoint Controls? Those could allow P5 to run only if the P3 loop is hotter than the storage tank to load the tank or if the Storage tank is hotter than the P3 loop when ever there is a call for heat in the building and if the boiler is off or disabled?


ANOTHER OPTION in the future could be to use the Boiler to load only the Storage Tank all of the time with fixed differential on an Aquastat. Then, use your MixiMizer, tekmar Injection Mixing Control OR anybodys Motorized Mixing Valve to pull out of the storage tank and Mix the Storage Tank temperature down to a water temperature based on Outdoor Reset when ever there is a call for heat from the Air Handler. This system could be done with only three pumps if Injection, or two Pumps if a mixing valve is used. Only one Controller to give you all, Reset, Warm Weather Shut Down and Exercising. What do you think?

The system as shown above, does the Storage Tank serve any other purpose than adding mass to the system and capacity used in cases where the boiler fails? In my suggestion, the Tank would do the same, except for that I would expect to cycle the boiler less because I draw less hot water out of the Storage Tank for the majority of the year when the supply water temperature to the AH is reduced based on Outdoor Reset. The same Tank would then also become a redundant heat capacity if the boiler fails, which may still buy you an extra couple of days to fix it.

Please let me know if I can help to a wiring sketch in either of the two setups mentioned here.

Best Regards,

Mike

Constantin

Let me understand...

Enclosed you will find a little image with a bit of math I did. It is but a rough guess how many kWh three 1/25 hp pumps will consume a year, assuming 100% motor efficiency, a 6 month heating season, and a 50% duty cycle. At 12 cents a kWh, that comes out to $23 a year, or a little over $7 a pump. Granted, that's not a lot of dough. But ten 00-series pumps, are going to cost your clients around $77 per annum using the above assumptions...

Now, assuming the marginal cost of one motorized 4-way valve over three 1/25 hp circulators is $100, you'll make up the marginal difference by year 4. Whether that justifies installing a motorized valve is a function of your ROI requirements. However, it does beat the historical return on equities in the stock market... without any of the attendant risks.

Lastly, if you do constant circulation during the 6 months of the heating season, the annual energy consumption doubles and the payback period drops in half.

hydronicsmike

Great Stuff Constantin...

...I hate arguing with a guy who is into facts and numbers like I am
You sure did your homework and I respect that a lot! Wish we had more guys like you...


Ok, I either missed mentioning it or didnt explain it right, but when we compare the Mixing Valve versus a Variable Speed injection System, we must not forget that even with a typical Mixing Valve installation, two Pumps are required if you care for Boiler Protection. One on the Boiler Loop and one on the System Loop. The Valve sits in between (and should be isolated from the Boiler loop with Primary / Secondary). At least with most North American Boilers that I am aware of. Most of those require proper flow through their heat exchangers. Some European Boilers may not need the flow across their heat exchangers and those could get away with one pump less. I guess I'll have to take and accept this one. But I dont have a problem with that.

Again, what I heard in the past, were claims that Injection is more expensive operation wise. Which again, is not true (in my opinion). If you have two pumps in a Mixing Valve System and two Pumps in an Injection System for the Boiler and System Loops each, than the Injection would only require one extra Pump (instead of Mixing Valve and Actuator) at $7.73 per year. With Variable Speed Injection we reduce the speed of the pump and also reduce energy consumption and as I was told shaves another 30% (roughly) off that $7.73 per year, bringing it now to $5.41.

What does the Actuator use is the next thing we'll have to figure out. This number will then be taken off this value again and then we'll have the real number we all should look at.

Maybe I am missing something.

Your statement about continuous circulation is also taken, but what is an indication for not having continuous circulation?? Well, it would mean that the water temperature delivered to your heating system is too hot. Would you loose more money by running your pumps longer than you would by increased stack, jacket, distribution losses. Not even thinking about compromizing comfort level and such?

Again, it was fun. Looking forward to your thoughts....

Mike

hr

WOW! thanks wetheads

plenty to think over. This system is up and running, I just want to fine tune controls, and also come up with a better design for the next one.

Wood boilers are getting a lot of interest around here, I'd like to have a design that I use over and over.

I like Dan and Mikes idea with the double throw relay for this one, simple fix for more control.

Mike I will take you up on your offers. Siggy had mentioned a dual differental control, in Boston, perhaps you are doing some control work for a system he is designing with wood and dual oil boiler backup Maybe tekmar could build a dual differental control in one box

The buffer tank in this case is to take output from the boiler when the weather turns warm suddenly and the firebox has a full load. Pretty common around here to have those wide temperature swings. With a larger buffer I would consider your idea of charging the buffer and pulling from it directly. Maybe 500 gallons or more. A pricey tank when insulation is considered, and space is not always available on these retro fits.

I like the 4 way as another option. Perhaps I could use the Paxton flow reverser.

hot rod

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Constantin

Interesting...

I had no idea that my first diagram would require yet another pump on the other side of the 4-way to keep the system side flowing...

Considering the simplicity of the system, I'm not convinced yet that a 3rd pump is necessary. The 4-way valve is fast enough to respond for boiler protection, so that side is taken care of. Any excess heat is dumped into the other circuit, ditto for the flow.

So, here is yet another diagram that will allow the AH always to be fed one way, that allows the BU to be charged whenever the Boiler has excess heating capacity, and which has only one secondary pump. I presume that zone valves are relatively cheap and that they consume almost no energy, particularly if you can find some of the latching variety.