Remote Temperature Monitoring

What is a pex line?

a pex line is a plastic, flexable water line. more specifically what i have is wirsbo tubing, simalar to pex but with an oxegen barrier

Think remote BBQ temp and you find what you seek.

ok , where do you find one that works from 80 feet away? all my bbq's had the temp gauge on the cover

Well, genx , you could start

here

or this one

or some more professional versions.

I got mine on sale at a local big box hardware store for much less. Have fun.

thank you sir, i shall let you what i end up with

Outdoor wood boiler. Hmmm, presumably you are heating the house, Therefore you are pumping the water from wood furnace to house. Heat loss in the Pex line from boiler to house would be minimal and a fixed gradient. In other words the loss is going to be pretty much constant all the time. I assume you are running insulated pipes under ground from furnace to house. So measuring at teh house is as effective as remotely measuring at the boiler.

Now you can check the water temp with a $10 thermometer instead of a $79.95 + tax wireless instrument.

So what part of the system are you trying to optimize? The controller on the furnace has adjustable set points. However these are tightly controlled. The water flow will pretty much equalize the water temp from boiler to house and then each radiator or air handler will have a gradient across it. Once you know the gradients you know how much to add to get the temp right in the boiler.

I would think you should be looking at the heat into house and resudual heat as the water exits house as the primary parameters. The upper and lower limits in the boiler are somewhat more fixed. You don't want to mess with that. the critical part of the system is balancing the heat radiators against the heat input from the fire.

What fuel are you using? That will determine how closely you can control the heat input.

Years ago I was playing with the oil furnace jets to find the optimum duty cycle for my home system. Decided the original factory specs were pretty close to ideal and far better than what I selected myself. What I saved I oil I lost in added run time of fan and the cost of electricity.

Now that I heat with wood its a completely different ball game.

Stupid answer: when no heat is needed (during the night) the pump will not work.

A freeze detection on the line can start the pump when needed.

Big chance that the wood boiler has no electricity at all, so he's unable to do this.

Checkout EnOcean. they support a system which works without batteries nor wires, 80 feet is no problem.

Most if not all hydronic systems such as the wood fired boilers used in N. America continue to circulate the water at all times. Failure to do so will cause excessive temperature swings in the boiler casing and that results in stress cycling from heat expansion / contraction.

We have taken as trade in some older model boilers that did not circulate the water continuously and seen the damage that causes. The whole point of the hydronic system is to maintain a fairly closely controlled temperature in the circulating water.

Same thing with chilled water Air conditioning. You do not want to start and stop the liquid circulation since this leads to inefficiencies and unstable temperature control..

If you're right with the pump it would be a complete different set-up than the systems we are used to here.

Here the pump is only activated when heat/cold is needed. (and we sell heat tracing to protect the lines against freezing, nice business)

It's a trade-off: keeping the heat in the stove making its controll more difficult but less loss through the piping is the option we go for here. £But I have to admit that direct wood burning stoves are not commonly used, we burned down the forstest ages ago.

On the EnOcean: you must look deeper in the partners, there are some who offer special systems for piping.

Gwen.Stouthuysen I guess we both made assumptions. I assumed the OP was dealing with a new installation and I assumed he was using the latest system technology. Being involved in the industry of wood burning boilers I concluded (perhaps wrongly) that he would be using a continuously circulating system.

My recent past experience is that Europe is in many cases ahead of North American technology so I assumed that if the OP was located in Europe he would be using something as efficient or perhaps better than anythign developed in N. America. Therefore, regardless of country of origin, I assumed that a continuously circulating system would be used. Outdoor wood boilers are so large in capacity it doesn't make sense to use it for very small heating applications. For that an indoor smaller stove is better. In any case, it is not clear in what geographic area the OP is located nor what specific equipment is being used.

I'm well aware that europe has already burned down most of its forests by now. Which is why BC exports about 90% of its forest fuel products in the form of pellets to Europe. They just built a $45 Million pellet plant just down the road about 20 kilometers from me. The entire production is shipped by rail car down to the coast for shipment to Europe.

Gwen, I am impressed with the quality of your posts in many cases, and therefore look up all the references and read (learn) a lot.

In this case I went over the site you referenced with a keen eye, and did not get any specific product the OP could put to use. The site was excellent for what they offered, however a contact temp sensor was not in their realm as I could discover. Of course they may have that, but not referenced at this link.

Is there a better site for their product line, with some hint at pricing?

Also I noted that Elnav is Canadian. Good likelihood heat will be circulating during the night up there, maybe even in July.

Also, most boilers have some circulation at all times for several heat/pressure practical reasons.

I take your answer as a rare moment of rapid response and look forward to your posts.

Check out :

google

temperature monitoring

enter

happy trails

jazz

Check out owfs (One Wire File system)

This is linux based, also using some older WRT54G routers (pre Cisco ones) that have the wireless part and the OWFS installed for 1-wire temperature remote monitoring, this could be where your hunting.

http://www.owfs.org/

Honeywell is manufacturing an entire line of remote wireless temperature/ hvac devices.

solved the issue, i purchased a thermometer from the local menards that straps on to the pex line for 16.00. now i can go in the basement take a quick look and i know my water temp. as far as optimization goes, loading the boiler at the right time,( when calling for heat, when not) is almost as important as the temp the boiler is set at and what the thermostat in the house is set at. i am only loosing 1 degree from the boiler to the house so that is a non-issue, and only 6 degrees from the house to the boiler when the blower is running, so another non-issue. if i load the boiler when it is not calling for heat, i can get 11 to 12 hours of burn time before i need to add more wood, however, when i load it when it is calling for heat, i can only get 8 to 9 hours from the same size load. i am burning a mix of green and dry oak, some of which i cut and the rest comes from a company that is involved in forestry management. so the quality of the wood is fine. the boiler itself has a preset temp swing of 10 degrees in a range that is adjustable from 155 degrees to 195 degrees as a max. i am just trying to get as much efficiancy out of this thing as i can, my house is a comfortable 70 degrees all the time and 55% r.h. the boiler is set at 164 degrees and the outdoor temp right now is 12 degrees with 20 mph winds and enough snow to make you stay in and enjoy your whiskey.

A higher max temp setting on the boiler is more efficient as the heat transfer from radiator is greater when water is hottest.

I reset my boiler from 164° to 200°F with a 10° swing.

while i agree that from a heat transfer standpoint it is more efficient, it would seem that maintaining a temp of 200 degrees would require a substantially greater amount of fuel to net the same end result. i heat my domestic hot water, house and shop from a single heat source, while my shop is not maintained at a hi temp, my house is. the blower on my exchanger runs 8-10 min and is off 14-17 min. to keep it at 70 degrees. i tried it at 175 degrees and found the only thing i was doing was burning more wood for no reason. it just seems a little more efficient if you can use less wood to net the same result in the end. but good luck with holding a 200 degree water temp.

Bwire (or others), Please clarify my understanding of your post.

I understand you to be saying, other than the initial warm-up to 200⁰, and the building space getting up to temp, that

(1) the fuel cost to maintain that temp would be about the same for either 164⁰ or 200⁰, since the fuel expenditure during operation equals the energy for a +/- 10⁰ temperature rise for the mass in the boiler at either temp setting, and more importantly,

(2) that the exchange of heat at each radiator is more efficient at the higher temp, resulting in fewer times the boiler calls for the +/- 10⁰ rise.

Could you offer a guesstimate (guess/estimate for you non-native English folks) of the percent efficiency improvement you obtained?

Also where is the savings mainly seen? In the circulation pump, in smaller supply line losses, in shorter re-heat cycles, all of the above, or did I miss the concept altogether?

r

I am not sure I agree with Bwire's proposal that maintaining the boiler water temp at 200 is truly more fuel efficient than maintaining it at 164F. My reasoning is this. The boiler has some insulation. The manufacturer decided on how much based on the value of 164F temp. Therefore the heat loss is "x" value. Likewise the piping has some insulation; also based on a value of 164F and degraded by heat loss through the given insulation. Finally the interior system has exchangers - either coils with fans, radiators like a radiant floor , or transfer to air duct system.

If you start with a higher water jacket temp, the rate of heat loss at the boiler will be greater because of "t" differential across the insulation. Likewise the losses in piping will be greater because the insulation has only so much value and leaks faster as the differential inside / outside is also greater.

The heat transfer ( same as loss) inside the house will be at a greater rate because of differential.. In this bwire is correct. But the return water is likely to be the same as before. Therefore a greater proportion of the fuel ( wood) burned is going into making up for the greater losses before the water gets into the house or shop.

In theory at least, the hotter water will transfer more heat into the house and this in turn means longer interval before next call for heat. But what is the furnace doing in the meantime? It is burning the wood with damper closed ( smoldering) and some of that heat simply escapes out through the insulation. ( this ignores what percentage goes up the chimney.) Heat calls is based on house interior heat not boiler jacket temps.

Incidentally the house has a fixed insulation value. So there is also a certain heat loss there. What is the effect of a hotter heat source dumping BTU's into the living space at a higher rate. Does it mean a greater heat loss rate or simply reduced call for heat with resultant longer periods of smoldering a dampened fire without additional heat transfer.

The pellet boilers we sell work on the opposite principle. Because it has electronic ignition of the pellets the fire goes out totally in between calls for heat. There is no wasted fuel burn in between heat calls. The manufacturer recommends a boiler jacket heat of around 160 F based on their extensive testing. 120F is too low and near 20f increases evaporation . Remember this is a vented (non-pressurized) system to prevent dangerous pressure build up. Oxidation of boiler interior surface will increase with the higher water temps. Iron scale is also an insulator. To what extent this affects heat transfer has not been measured as far as I know. But it does means greater maintenance and more use of corrosion preventer.

elnav,

How are ya?

First off the 164°F factory temperature setting is not based upon the boiler casing insulation factor; it is an arbitrary setting only.

Water at 200°F has a greater efficiency of heat exchange and is recommended (hyperlink-is good boiler system info).

I recomend you update your systems to include and upper level tank with relief valve or a modern type small expansion tank and purge valves throughout the circulating system.

I'm completely in with Elnav's explication: The higher the set-point of you're boiler, the higher it's own losses.

It is true that you have more heat from the radiator with higher water temps but you could have bought a bigger radiator to start and go with lower temperatures.

Temperatures of solid fuel burning units are limited to a low temperature level due the prevention of acid condensation in the chimney and ultimately in the burner. The high limit is set by the complete construction: the used alloys and pressure limits inside the water circuit limit the upper level.

You have to work in between these levels as the burner and smoke trajectory have been optimised for this. Working outside voids the warranty and ultimately is illegal as the approval is also only valid within the given set point range.

In Europe there is a trend to lower the water temperatures as much as possible, we even have condensing oil and wood stoves now, equipped with a special smoke trajectory which first condensates the water and acid in the gasses and reheats the smoke again so that no additional condensation occurs in the chimney. Fuel efficiencies go up above 100%.

It is as you say. With exception of the losses argument, thermal losses are a necessary function of radiant heating, superior heat exchange can not be a fault; the physics are immutable.

Solid fuel burning units should be limited to applications where their inherent faults are advantageous; as with in-floor radiant heating.

bwire you are arguing with the wrong guy. I was talking about a particular product design approach; not my "personal" boiler system.

Your recommended link deals with sealed systems. Here and in several other juristictions, sealed pressurized boiler systems are prohibited for residential heat unless attended by a certified steam heat opeator. Here; that means a fourth class steam engineer. Not sure what other juristictions require.

Agreed that 164 F is an arbitratry number. But the range is based on several common sense criteria. 164F is still hot enough to cause a painful burn with direct exposure but 200 F will cause a painful burn much faster.

To get adequate heating from 160F hot water simply requires a larger radiator surface compared to a 200 F system. Just look at how small a gar heater core is.

For any given level of insulation heat losses will be greater at the higher temperatures. When you run an open vented system, you will incur more evaporative losses if your liquid is 200F instead of 160F, Corrosion will be accelerated and scale build up greater at the higher temps.

So the company has settled for a median system temp level that satisfied the most criteria while remaining within the guidelines for consumer products.

oops no offense intended.

Yeah they're inefficient and cost less but not cost efficient.

This is a convoluted subject.

Hi CJMcGill,

Good observation, thanks...

Correct on (1) & (2)

************************************************8

About 30% efficiency improvement mainly seen in all of the above, shorter re-heat cycles, the circulation pump run time is abbreviated, natural convection enabled by the greater rate of heat exchange off sets supply line losses too.

bwire, do I understand you correctly to say the circulation pump is stopped each time the draft fan is also stopped?

I run continuous when outside temperature drops below -20°F

otherwise yes it stops between cycles.

hi, if your circ. pump stops between cycles, how is there heat available at the exchanger? does this rely primarily on convection? just a bit curious. my pump is a continuous flow whether the draft door is open or not. i am pretty sure convection wont work for me because my heat exchanger is about 4 feet lower than the lowest point of my boiler. i did raise my temp to 166 degrees because the night time temps are to be in the sub-zero range with some hi winds.

My heat exchanger is about 15' below the highest point of the system and yes convection works fine.

During the coming year I will move the piping into the living area so I don't need run the pump off cycle. I run it now to eliminate the possibility of freezing in the piping as it runs through the outer wall, and we'll be getting warmer weather next week so convection will be back too.

i was wondering if your system is an open one or is it pressurized? mine is open. if i could use convection some of the time, i could reduce my electric bill a little, no?

Yes about 8lbs and convection works well either way heat rises and cold...

what type of pump are you using? i just wonder if the pump would hinder the flow of convection when it is off. i turned my pump off and the temp of the boiler rose to 190 degrees, while my setting was still at 164 degrees, it made me a bit nervous because it only took 30 min. to rise that much so i turned my pump back on, cuz the last thing i need right now is something to go to horse***t. so i am not going to find out if i can use convection to my advantage right now

check out www.centralboiler.com

If you are using one of the regular wood burning water jacketed boilers intended for outdoor use; it likely has the water take-offs lower down on the boiler jacket. It was never intended for convection heating or thermo siphon circulation. Locating the take-offs right at the top would risk entraining air or steam. Not a good idea for a circulating heat system.

When you stopped the pump, water no longer circulated and heat removal also stopped. Naturally the water jacket temperature started to rise, since the fire was still smouldering. Or at least the remaining coals were. The hottest part of the water jacket will always be near the top. Guess where the heat sensor is located. The one that tells you what the water jacket temps is.

You can't just arbitrarily change the whole system configuration with one equipment change and not expect to get unexpected results. Your system was designed and engineered to work in one way. Stick to it if you want best results. But stopping circulation totally in a hot water circulating system is not the way to go.

Second thought. As you cycle the water jacket temp from a low to a high and back down to a low, give some consideration to the thermal expansion and contraction action you subject the fabricated shell to.

We have found that water jackets and boiler compartments that have square corners and angled construction tend to focus these stresses into the corners. guess where any leaks first show up some five years down the road.

Wood boilers with a round drum design have less stressed corners and consequently less potential leak locations. If the boiler is properly handled and teh temperatuer cycling is minimized, you also reduce the amount of cycling and therefore the expansion/contraction you subject the welded joints to. This is not rocket science. Go to steam museums and look at any locomotive boiler for examples of good and not so good design shapes. There is a reason why most boilers are round in shape.

i dont want to change the system, i just want to be able to keep an eye on the temp so i can load it on the temp downswing instead of the upswing. if i can make 6 6" diameter logs last 12 hrs instead of 8 hrs simply by loading it at the right time, that would be more effecient. it seems to be a pretty good system, i have been looking at various types for about 5 years and the one i have seems to be the one that makes sense, i've seen the round ones getting welded up every 2 years, i;ve even welded up a couple of them for friends, the one that impressed me was the guy that had an older one from central boiler that he has been using for 12 years so far with no leaks or corrosion problems, but the oldest round style i've seen is 15 years old but has been repaired 5 times already, i have seen home-built ones that are round and insulated to the hilt and still burn 16 cord of wood in 5 months, they look good but are not efficient. so i'll stick with what works pretty good for now until i have room for a garn.

What type of thermal medium are you using to both protect the boiler casing and radiate heat from the fire? Is it firebrick?

the fire box is completely surrounded by water except the stack and door, of course, but there is no firebrick or anything inside, the firebox is all 3/8" boiler plate, with no ash pan, once a week i scoop out a shovel full of ash, the outside of the water jacket has about 4" of polyurathane foam completely encasing it and the waterline going to and from the house is thermopex that is buried 3' in the ground. seems to work pretty good so far....

Granted and you can increase the effectiveness of the burn and decrease the amount of wood consumed by lining the firebox with firebrick. The firebrick will continue to radiate heat long after the fire has died, think thermal mass, consequently the firebrick extends the life of the firebox by assuring even heating with protracted cool down cycles.

A heat sink. Great input in my opinion. I relate to this as a sort of battery bank buffering varying generational input in electrical terms.

In a water jacketed boiler, the water serves almost the same function as fire bricks in an air surrounded stove. The water serves as a heat sink and moderates the temperature swing. however if you stop the water circulation in between calls for heat, the water in the loop will cool off faster than the water in the boiler jacket. The when a call for heat is made the circulation pump shifts the warmer water to the loop and brings in the cooler water from the house into the water jacket. This means the water jacket volume of water is cycling through more of a temperature change compared to a continuous circulating system.

True but I'd use firebrick anyway

And advise using charcoal to increase BTU potential.

Using charcoal kind defeats the whole point of getting free fire wood. < grin>

GA excellant but convection does occur in return leg

We use pressure relief devices in systems to prevent entrainment issues.

Convection will occur on the other side of the loop regardless of the condition of the pump