Circulator efficiency in Solar/Wood radiant system

Unknown

this is what I don't get.

Say you're using a UP15-58 circ on high speed. you're spending, if the pump is on 24/7, something like $5 at 0.10/kwh to run it for a month to run it at max power, right?

not a lot of room for savings there. If you're replacing larger pumps with it, ok, but you can also instead push large houses on small pumps in the first place.

JP in VT

Efficient Circulators??

Greetings all,
I am building a wood furnace (Tarm) / thermal solar (Seido 5) radiant system with storage (800+ gallons) for my "new" old house in central VT. I am also installing a PV system to power the house. Aside from this whole thing is not from anyone's textbook, one problem I am having is that the "typical" circulators spec'd would each consume all the watts I can generate in a day.

I am looking to maximize efficiency and minimize electrical consumption. Wondering if anyone has explored this and has comparison data on pump efficiencies. Seems like if the system requires 100KwH per month to operate it negates the incentive to heat with wood!

Thanks

Mark Hunt_4

Wilo ECO

Depending on your head/flow requirements, the Wilo ECO would do the job. We use ECM technology to modulate the circulator according to the system demand. This lowers the power consumption considerably.

Take a look and e-mail me if you have any questions.

Mark H

Steve Ebels_3

mark

How are the wilos controlled (ie do you need a fancy boiler controls to regulate the circ flow or just tell it when to turn on)?

what is the cost difference b/t one of these and a standard taco or grundfos?

hot_rod

on the solar side

consider a Laing D-5 Strong. It could power directly from the PV, no inverter loss taken. a very efficient little circ. Depending on they type of loads you need to move you may be able to power the heating system with these same DC circs. You will need enough battery bank to run them during prolonged no sun conditions, however. Or no heat for you!

If not, shop for an ECM circ. I just installed a Grundfos Alpha on my drainback solar and dropped consumption from 87 watts to 49 with this high efficiency circ. Not available in the US yet, but some guys are buying them online from UK sources.

I also ran my shop and office on this same Alpha pump last year. It would modulate between 17- 37 watts depending on how many zones were calling for heat. Figure about 40% more efficient then typical wet rotor circs.

I'm still waiting to try that Wilo I suspect it would operate similar to the Alpha's.

hr

Mark Hunt_4

ECM

Hi Steve.

The ECO (and the Stratos) are self controlling and no extra controls are required.

You simply dial in the max head set point and turn it on. The "brain" of the circ monitors the rpm of the rotor in relation to the stator. As zones shut down, a rotor will also begin to slow. This information is Electronically Commutated back to the "brain" and the stator is adjusted accordingly. With a standard, non-ECM circ, the stator remains constant and the power consumption changes only slightly.

The Pump Affinity law dictates that reducing a motors rpm by 50% results in a drop in electrical consumption by the cube. The wear rate is also dropped by the cube.

Standard circulators increase head as flow is diminished i.e. they follow the curve. But an ECM controlled ECO or Stratos do not follow a curve, they modulate along a performance incline. As zones close, our circs slow down. Flow is reduced, head is reduced and power consumption is reduced. In fact, a Stratos or ECO circulator could be dead headed 24/7/365 and they WILL NOT burn out. When I dead head an ECO set to 10 feet of head, the wattage drops to 9. It doesn't even get warm.

Our ECM circs obey the Pump Affinity law. An ECO set at 10 feet of head will modulate along the performance incline down to 5 feet of head.

All of this is done without sensors. The only "sensor" the ECO and Stratos have is a thermistor. Another function available with the ECO is "night set back". If you have a reset control on your system that shifts the reset curve lower during the night time hours, the ECO will "learn" this and will adjust IT'S performance incline as well. So if your ODR lowers the water temps at night, the ECO will run at slower speeds during the same period.

The Stratos has MANY more bells and whistles than the ECO and is considered a light commercial/commercial circ. The ECO is limited to the Delta Pressure Variant mode (DPV) while the Stratos can operate in Delta Pressure Constant (DPC) or Delta Pressure Temperature (DPT) as well as the DPV mode. The Stratos can also be integrated with BMS's via an interface module. (LON or 0-10vdc)

The ECO costs more than a standard pump. I'll e-mail you the details on that.

There is a contractor that monitors this site but rarely ever posts named Pat Nelson. He's on "The Isle of Long".

Pat over-hauled the heating system in an elementary school there last year. Before removing the 7.5 horsepower circ that serviced the school, he amped it out. It drew 20 amps/hr and ran non-stop for the entire heating season. Pat used the largest Stratos (1.5 hp) for the replacement and it was controlled exactly the same way as the pump Pat removed.

Using 14 cents/Kwh (Pat tells me this is too low) the 7.5 HP circ cost the school $3800 PER SEASON to operate. The Stratos, running the SAME amount of time, cost the school $325.00. Oh....and the old circ blew water past the zone valves as well. The Stratos does not. Now the teachers do not have to open windows to control the heat in their class rooms any more like they did with the old circ. (Yes, there is a "wild loop" in the building)

Darin Cook has a few panel rad jobs he is currently working on and he is using the ECO. NO BY-PASS REQUIRED. He should be posting some pics here soon.

Thanks for asking Steve!

Mark H

Unknown

is that a newer laing HR? we had bad experiences with DC laing pumps in the past (loud, high failure rate)

Tim_41

Tim_41

Eco

Here is a Eco with 15 panel rads and a vitodens 200. After closing TRV's etc I could tell the ECO was doing what it is suppose to do. Installation is no different than a normal circ except for selecting the pump head. I have one on a vitorond 100 with a AQ2000 ODR relay. There old system had 5 circs.

[Deleted User]

Stratosfaction guaranteed!!

By far the best circ on the market. I have been using them both on commercial and residential systems. I have no complaints. Any multiple zone system should have one.

JP in VT

Missing something?

First, I'm really happy with all the responses. I had considered both variable speed pumps and tiny DC pumps in parallel and now have more to think about. But WRT this comment I have to say I'm not sure I understand...

If your rate is $0.10/kwh (and I'm jealous if it is), then a $5 fee in a month means that you have used 50kwh to run the pump for the stated 24/7. For an 87 watt pump the math doesn't work for me.

But even if it did... my power load without the heat system is approx 100kwh/month (conservatively). I am planning to generate 130-150kwh/month from my PV system. If I have to run 2 pumps each sucking up a minimum of 50kwh/month I'm in trouble. This needs to be able to happen with less power demand.

I have to run one pump when the wood boiler is firing to get the heat to the storage tank. I have to run another when there is a heat call to get the heat to the zone supply. I have low temp needs (plan to run at 90 degrees supply to the floor) and low head needs (final figures not in). I am heating (when all is said and done) +/- 2000SqFt with 2,500 ft of 1/2" pex distributed across 2 zones / 20 loops. No loop exceeds 130'.

I am heating an ancient farm house that I have insulated beyond reason to r26 contiguous minimum and r38+ in the main roof. I am heating to an air temp of 62dF. I have done everything I can to minimize demand and maximize heat transfer. I _have_ to be able to deliver heat to/from the thermal storage without blowing out my PV system. It's not only about $$$.

thanks for any comments and responses!!!

JP in VT

Beautiful system

Tim,

I only wish I could get to something as simple and elegant. Elegant I can hope for... simple, well, I think I have too much space and too many components to hope for that.

Thanks for the photo

hot_rod

you can't get something for

nothing. it's going to cost some energy to spin 3 or more pumps. A high efficiency Dc pump would be my first choice, 120V ECM second. Typical wet rotor circs are fairly inefficient animals, running mid 20% wire o water efficiency. But still less power consumption than spinning a fan and shoving air through duct work

A couple pot bellied stoves would be one "no powered" required way to heat.

Or you could build a gravity radiant wall heating system like Larry W did. No pump required for his off grid home.

hr

WV EGBERT_2

Not for nothing

The energy consumption of the circs. is a concern also regarding solar thermal transfer from an array. A pump running 6-8 hours, continous on a sunny day, will offset potential savings.
Pump manufacturers take notice!

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JP in VT

Radiant or else radiant

WRT the pot-bellied stoves - what I have in my present house I call 'poor man's radiant' - the woodstove in the basement heating up my 800' of stone floor above. It achieves equilibrium around 64dF and all is well (even on the second floor above) -- IF I feed the beast in the basement every few hours.

The thought for hydronic radiant was firstly to leverage the sun for the transition seasons. Not having to cut, haul and split ALL my fuel seemed like a good idea. So a reasonably sized thermal solar set pretty much demands storage. If you're going to store then you might as well have enough storage to be meaningful. If I have storage and wood then I next add a wood gasification boiler to fire now and then to replenish the storage in the dead of winter.

Now you know how I got here. I am presently tightening up on all the load and loss calcs. I am finding that most of the 'rules of thumb' that were presented to me at the beginning of this odyssey are really not appropriate for a truly efficient system. I am trying to find a model that is without going so far as to cheat the whole system.

I am still trying to work out how to minimize pump run times while still unloading enough BTUs to maintain equilibrium. I will have the final supply routing (and therefore able to finalize calcs) later today and have a better picture of the minimum pump demand.

JP in VT

pump on solar array

Good point Devan. I guess this is why so many thermal solar installs use the separate 20W PV panel connected directly to an el-SID. In this configuration when the sun is hitting the array the pump runs, when the sun goes away the pump stops. Independent from any other power source or controls. I can't think of a better way to do the solar thermal transfer.

hot_rod

Even with a PV powered

solar pump you will want a differential or solar control. You don't always want the pump to run when the sun shines.

This fellow has an interesting website, and builds a simple PV pump controller. You can watch Guy at work in his shop at times.

www.arttec.net

hot_rod

another formula for you

knowing the wire to water efficiency may help you. selecting the "best" circ for the application based on workload.

This is from Siggy's Wire to Water article www.pmmag Dec. 1998 archive

Circ efficiency= .00302 x D (fluid density) X F (flow) x H( head) divided by W (watts)

So suppose you have an 80W circ (15-58 on speed 3) moving water at 10 gpm and 10 feet of head.

.00302 X 60.7 X 10 x 10 = 18.3314 divided by 80Watts = .229 or about 23% efficiency.

You want to pick a circ that operates mid point on the curve with the least amount of power consumption.

The typical wet rotor circ starts with a fairly inefficient motor design. Then the added penalty of spinning the rotor in the fluid.

The newer ECM type motors circ might look like 18.3314 divided by 35W= 52%

It would be interesting to see how the PV powered pumps stack up, like the ElSid or Laing with DC powered "dry" motors. The Laing Solar adjusts it output based on the energy from the sun. Sort of a self regulating variable speed mechanism.

hr

Steve Ebels_3

FYI Mark

I did not write the post above that is attributed to me. I was at my nephew's wedding at the time the post was written. Don't know what's going on with that.

Bob Greenleaf

solar... with wood as adjunct

My local plumber suggested I contact this website to get ideas regarding the following...


I've been investigating solar heat -- and overall systems for my home. I would like to do DHW aswell as space heating. I have a large roof that faces southerly. The home is 4,000 sq. ft.



I am considering converting from a large oil boiler (15 years old) to a wall-mount propane unit to heat both domestic and radiant floor systems. My radiant isstaple-up pex tubing --and the houseis insulated with R-19 walls and R-30 attic.


My quandry is in getting responses that don't conflict (different installers tell me different things). Any
advice you may have on the following would be helpful.



1. Reservoir sizes vary from 80 gal to 330 gal. I understand there is a 60-80 gal/per 4x8 panel (or equivalent)

as a general rule of thumb. Would it really be less efficient to use a larger super-insulated reservoir than the 80 gal/panel system? (My thinking was to have the solar heat the reservoir to it's capacity, and supplement
the system at night with the propane unit.



2. Type of panel. I'm told that:

a. flat panels last longer than evacuated tubes. Correct?

b. evacuated tubes outperform flat panels. Correct?

c. It makes no sense to position the panels at a 60-65 degree angle to maximize winter efficiency and
minimize summer need to dump excess heat. (I'm in MAINE).

d. a drain back system is now outdated and will have significant maintenance issues. Correct? (my thought
was that such a system could be shut off in the hot months and eliminate pumping--as well as the need for a dump zone.



3. Lastly... is it at all viable to use solar for heating purposes in Maine (reasonable pay-back)?


thanks for any info you might provide!

best,

Bob

Unknown

bob,

there is no payback for solar heating in maine. not as true for solar hot water.

evacs do not really outperform flat plates. drainbacks can be superior to glycol non-drainback systems, but improperly installed can result in major problems.

If you are going to upsize an array for heating, orienting for winter (since it will be oversized in the summer) of course makes sense. If your array is not oversized for the summer, then leave it at optimal collection for summer, use it all, and use whatever you get in the winter. as long as you're using what you collect, it works out.

JP in VT

Using Thermal Solar

Hi Bob,

I thought I'd answer you because where you are is where I started last Feb on my path to install a solar/wood radiant system. I am NOT a heating professional so take any advice with that grain or two of salt.

First, do a heat loss calc for your space. Then do some analysis on what you can collect and how much you want to store. Also think about how to replenish heat in the storage and/or if you want to directly heat the circulating loops with a backup.

Your space is about 2x mine and your insulation is 75% of mine so my numbers are not relevant to you. But here's the thought process.

I have a design air temp of 62dF in my house. I am in central VT. I figure my heat loss at min 650,000BTU/day in the winter. I figure I can collect about 75,000BTU/day from the evac tube arrays I have chosen on that same winter day. So I need 575,000 BTUs from somewhere else.

I collect all my BTUs and put them in a big (800 gallon) tank because I need them more at the times when they are not being produced. I also fire my wood boiler now and then to add BTUs to the storage. If I "fill" my tank with BTUs to 180dF, and my design radiant supply temp is, say 80dF then I have maximum usable storage of 640,000 BTUs so I need only fire the boiler once per day in the worst of the winter. (all very round numbers and I have left out the minor amounts of DHW I will also pull)

My arrays are oriented for max winter collection. Even so I plan to be giving away hot showers to the neighborhood in the summer.

Only you can decide if the numbers WRT how much you can collect/store/use are worth it. For me they work. Good luck.

WV EGBERT_2

I concur

with NRT.Rob. ; )

Install an array just for DHW, if you want to get some space heat out of that fine. But don't add extra panels (FP or Evac) for space heat, payback is a long ways away, and not just for Maine either.
I'm not convinced about supersized storaged tanks either.



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Unknown

of course you do

the more I think about it, if you do an on demand booster for DHW, I'm not sure there is a downside to bigger tanks. that is, as long as you can utilize low-utility BTUs (perhaps with bob's "partial load heat dump" on the heating side"), large tanks mean lower water temps mean greater solar efficiency....

just thinking out loud. I'm sure there is a diminishing return...

Unknown

Good pitch

Mark,

You have really honed your pitch. I can't imagine that in this (energy) climate these products will not be tremendously successful, especially given the lead that Wilo has in bringing this technology to NA. You do an excellent job of making the advantages of this technology compelling. Not sure why grundfoss is so slow to do a residential 60 cycle smart pump. I guess it says something about the american market. Wilo gets high marks for investing in this market first. Bad enough that our indigenous industries have fallen so far behind, but doubly discouraging that some of the best euro technology takes so many extra years to make it here.

Tekmar tells me that the energy consumption on their 157 variable speed difference settpiont control is linear, as in 50% speed reduction =50% power savings. They said this is close enough (to reality) that it permits their control to clock btu transfer with variable speed operation. Can you help me understand the math of this cubed relation ship your speak of, sorry to be so dense, but if you could lay that math out for me in actual numbers it would be appreciated.

For the original poster , why not consider a gravity system? or perhaps just thermosyphon piping to your storage tank if that is possible. This would have the added benefit of preventing a blow off or worse in the event of a power or circulator failure. A fully stacked wood boiler that fully depends on a nonfail-safe means to to move heat away from the boiler seems a bit risky to me, since turning off a raging wood fire (in my experience) is next to impossible.

Unknown

Rob,

@ .10/kw on site combustion is not even competitive at curent fuel prices. In-fact why even pump, just imbed some resistance, or do electric base.

I'm just being provocative, but it's weird to see electricity so inexpensive relative to other energy sources.

Mark Hunt_6

Scott

Here's a link. Pump Affinity Law.

Mark H

CC.Rob_7

affinity laws

explained simply, here

http://www.flowcontrolnetwork.com/issuearticle.asp?ArticleID=123

more technically, with fewer or no examples, here

http://en.wikipedia.org/wiki/Affinity_laws

and here

http://www.engr.udayton.edu/udiac/Documents/FluidFlow_Pumps.doc

CC.Rob_7

simple math

I did a short calc.

Take two 007s running a constant circ system. Elec rate $0.20/kWh. Runtime ~20 hr/day for 8 months. 4 gpm at 10 ft of head, each.

007s = 0.71 amps/ea = $157/season for the two circs

Now replace them with two ECOs. If I'm reading the spec sheet right, the ECO draws ~0.02 kW at 4gpm and 10 ft of head. At 115V, that's ~0.17 amps. Or about 3-4x more efficient than the 007s.

ECOs = ~0.17-0.2 amps/ea = $38-44/season for the two circs

Payback on a truly simple pump swap retrofit is around 4 yr. As a HO, that's pretty appealing. There are equal or longer paybacks for certain CFLs and LEDs. Or SDHW for that matter.

It's certainly got my interest. Anybody got an idea of how long Taco and Grundfos will be getting to market?

A question for Mark Hunt: what's the MTBF for these units?

Unknown

holy cow, I thought our electricity was expensive. who is paying 0.20/kwh??

My payback would at least 50% longer, in maine, and traditionally our electricity has been considered expensive. and a 4 to 6 year payback on a $200 investment or so (order of magnitude, not actual price) would seem trivial enough not to consider very deeply, IMHO. Not a bad thing, mind you, but not a reason to guinea pig new technology (here in the US). one pump failure, after all, and payback stretches out loooooonger....

green for green's sake is fine too, it's just an incremental improvement. I am waiting for those pencil sized mini pumps we saw last year... zone by pump may come back into style when those things are out..

CC.Rob_4

we are...

Barnstable and Dukes counties, MA.

Technically, it's $0.199/kWh. That is the "all in" rate for an average household using 500 kWh/mo. Breaks out per kWh as follows:

Customer Charge $0.00746
Distribution Charge $0.04944
Transmission Charge $0.00748
Transition Charge $0.02083
Renewable Energy Charge $0.0005
Energy Conservation Charge $0.0025
Supply Cost $0.111

Total $0.199/kWh.

I hear you on the early-adopter issue. The 2-yr warranty helps. Please expand on the pencil pump thing, before I go racing off to get a pair of ECOs.

Mark Hunt_6

Not sure

what MTBF is.

Mark H

jp_2

mtbf

mean time between failure ?

CC.Rob_7

mtbf

yes, mean time between failures. It's a useful metric and one I'm most familiar with for items like computer hard drives. Haven't seen it in hydronics, though. However, given that circulators seem to be headed toward the technological complexity of hard drives, it might be useful for comparing lifecycle costs, reliability, etc.

MTBF is not a perfect metric, by any means, but it's a starting point.

http://en.wikipedia.org/wiki/Mean_time_between_failures

Mark Hunt_6

That is a good term to know

Thank you jp and CC.Rob. I thought I had become "computer savvy" when I learned "ctrl-alt-del"......guess not. Always something new to learn here!

In all honesty, I can not answer the MTBF question for the very reason that Rob points out. That statistic is not commonly used in PHVAC equipment.

Wilo employs over 200 engineers world wide and re-invests back into the company every year. In 2006, they spent 50 mil on R&D alone. And all Wilo makes is pumps.

I have spent my entire working career in this industry. 99.9% of that was in the field designing/installing/servicing systems and the components that go into them. The mechanical rooms today look very different from the mechanical rooms I worked in 28 years ago. Heck,,,,even 15 years ago. Wilo turns 136 years old this year. They make one heck of a product.

Mark H

Mike T., Swampeast MO

1) 330 gallons may sound like a lot, but as far as storage for solar space heating goes, it's tiny. Each gallon weighs about 8.33#, so you about 2,750# of water. One BTU will heat one pound of water 1 degree Fahrenheit. Say your system needs at least 120F water to operatate in moderate weather and that you can heat the tank to 160F, a difference of 40F. 40 * 2,750 = 110,000 BTUs available for use. That's not going to last very long in a house of your size in your climate.

2) Evacuated tube panels have to maintain vacuum in the tubes--that's why they are considered less long-lived than flat panels. BUT, this vacuum is what allows them to maintain their efficiency in cold weather. Evacuated tubes aren't really more efficient than flat panels, they just maintain their efficiency in a far broader range of conditions.

3) I believe it utterly impractical to use active solar space heating in your location--unless the house is extraordinarily well-insulated with high consideration for passive solar collection and you have an extremely high budget with little concern for "payback" in any reasonable length of time.