Depth of water sensing 1

[alternety]

I would like to monitor the water depth in well. Maximum depth is 500" and minimum is 0'.

I have been thinking pressure sensor but everything I have found is quite expensive packaged sensors.

Any ideas on other ways to monitor depth or sources of something I can use for a sensor in a 500' well.

 

[VEBill]

Tear it all out and install some cheap electric baseboard heaters. My house: 2800+ sq ft, 21 degrees C all day with setback to 18C at night, heating costs about Cdn$1.2k per year (varies slightly). Capital cost, maybe Cdn$500.

Aren't there some PLC type industrial controllers that can be interfaced to virtually anything and can be programmed to do virtually anything? I believe that some even have some control loop support built-in (or maybe fuzzy logic).

Google 'PLC' to start.

 

[itsmoked]

Welcome back alternety ..our own private little New Orleans...


Well that system looks like the kind of nightmare I would want.
Its own technical entertainment.. (for life)

First with a system that complex, I am astounded that you filled it with "whatever water was lying around". If you don't replace that rot gut with distilled or deionized or at the very least R.O. water you are going to be very sorry down the road.

Next don't listen to VE1BLL. It's obvious he has never luxuriated upon a heated floor. aaaaaaah.

What exactly is your pump/speed controller?

 

[VEBill]

"...never luxuriated upon a heated floor."

I used the money I saved with my cost efficient $500 heating system (vice $15k+) and bought something called 'fur-ni-ture' so I don't have to luxuriate directly on the floor.

;-) !!!!

 

[Warpspeed]

Wonderful to see you back here alternety, I felt rather guilty about pressuring you for details on the heating system. I can definitely identify with all of your problems ! I once worked on a large solar/hydronic heating system for a school here in Melbourne, hence my great interest in all this. It also had some rather interesting control problems.

First up, the control of flow will definitely require some sort of PID controller that can be tuned to suit the dynamics of your system. Motor speed may be one method of flow control, but another would be a motorised valve. We used a system like that with a two way valve to divert flow either around the main heating loop or bypass the constant speed circulating pump.

Buried floor heating is obviously going to be slow to respond because of the large thermal mass, fan coil units would offer much faster and tighter control of room temperature. The ideal system might be to use the floor heaters to provide minimal "background" heating, and switch fan coil units on and off in the occupied rooms.

 

[felixc]

I'm no heating specialist but I like this thread. I'd be tempted to say to put an op-amp with a DC-offset potentiometer, to shift the feedback from the pressure sensor and provide a "thermostat" adjustment with a little hysterisis. But my notions of a closed loop system are a bit fooled by your system description.

How do you relate the differential pressure to the desired temperature? How will this single point of feedback ensure comfort everywhere in the house?

The flow adjustmetns for all of your loops, how do you control them? And for all these rooms or loop segments, what is the desired temperature feedback signal?

 

[itsmoked]

felix; picture a pump running creating a pressure. Now picture a manifold that the pump feeds. The manifold has, say, 10 electric valves on it. Each one feeds a ZONE or specific space requiring heating. To control the temperature in a ZONE you locate a thermostat in each ZONE. That! Is what controls the temperature. All the zones feed back to the pump suction.

What alternety is dealing with is that the flow through the zones needs to remain at a certain rate. Each zone has a valve that is adjusted to allow that specific flow WITH A FIXED HEAD PRESSURE. Each time a zone goes on the head would change. If the pressure changes the flows change. The standard "we don't care about electricity" solution is to run the pump against a relief valve that just bypasses everything over X pounds of pressure so that the zones always get the same flow because the head is constant.

alternety wants to stop wasting electric power on running against a relief valve by instead running the motor only at the speed required to just maintain the head constant.

alternety can use just about any junk PID controller that puts out 0-10V to control the head.

Normally this would be pointless because the energy that is lost in the bypass valve immediately appears as heat in the water DOH! So what if some minuscule percentage of the water heating is electrical? But if you are off the grid it could make an important difference.

 

[felixc]

Got it! This control has nothing to do with the temp control itself.
Well, the rising energy costs might someday justify a mass production of such controls.

 

[Warpspeed]

Interesting point Itsmoked, I had not really thought about reducing pumping power. We used a three phase induction motor direct coupled to a centrifugal pump, and direct pump speed control was not an option. The sort of ubiquitous plant room circulating pump used everywhere.

One concern I have is that boiler water flow will vary if it is in the main loop. When running at very light total load, the system flow will fall, and the boiler will short cycle. That may cause problems with large cyclic temperature variations in the boiler tubes.

A better way may be to use a pump bypass and keep boiler water flow high all the time, and also have sufficient stored water volume in the boiler circuit to minimize cyclic temperature fluctuations. Water flow through the load can then be cut right back.

Some sort of large insulated thermal storage tank would then enable the boiler to run for longer periods and shut off for longer periods. Short cycling of boilers is bad news for both wear and tear and efficiency. I doubt if circulating pump power will be a significant cost compared to original outlay and final running cost. It might be best to just let it run at normal speed continuously during the heating months. A duplicate backup pump might be a good idea too just in case...

 

[itsmoked]

Warp; You make a good point about short cycling boilers. I know short cycling furnaces is bad...

But in alts 'heating' post he does point out a hot water storage tank for short cycling prevention. AND! He has a variable rate burner. That should permit longer lower energy cycles when needed.

Now let me ask: Is there such a thing as short cycling when referring to "condensing" burner systems?? I thought the problem with short cycling was because a burner system would end up not drying out and the sheet metal would then rust out. Here we have a system designed to have water condensing out on the innards and running down the walls to a drain... The walls are Monel or SS. Not going to rust out. So why not short cycle? Might be an efficiency issue?

 

[alternety]

Sorry - I started this up again and then disappeared. My computer has had problems and tonight we lost power.

Oh well. itsmoked has saved me a bunch of typing. Yes the zone control valves and individual zone flow adjustments control each loops flow. An objective is to make each loop about the same length (read - pressure drop). The assumption is more or less constant pressure across the circuits (zones).

Re comfort. A guy I am using to finish some things left behind by the latest builder when he went on to the next project came in after I had the boiler running for 2 days to purge air. He said he told his wife that she really would have to experience how comfortabe the bulding was to believe it.

Short cycling is bad for most any mechanical equipment. In a normal boiler or furnace it also causes significant losses up the flue as the unit heats, only to shut off and allow the residual heat in the core to dissapate. Solution - low mass (i.e., not much water) boilers, forced draft combustion, and condensing temperatures. In older boiler designs it was important to avoid condensing because the cold water return temperatures could actually damage (crack) the boiler. Condensing boilers want to see return water temps low enough to condense all the flue gas water vapor components. The heat of condensation (evaporation) released significantly improves efficiency. My design water temp in the radiant heating loops is about 85 degrees F. When the boiler is runing you can watch the water running out the condensate line. The flue gas temp was, I believe, less than 110 degrees.

Regarding the idea of "let the pump run all the time". There are definate proponents of radiant systems that use constant circulation. The idea is that it provides smoother heating response by adjusting temperature of the water more slowley. It is also supposed to eliminate noises from a sudden influx of hot water. At 85 degrees I don't feel this is a superior solution. And the pump energy costs just keep going on as well. Granted not a big number but anything multiplied by 24X7 adds up eventaully. The cost of the installed solution was not a whole lot more than the alternative. Granted this costing left out the requisite controller. But I suspect it could have been done correctly for about what this has cost so far.

The Grundfos pump has also turned out to have what I consider excessive noise/vibration. It appears to be a conventional capacitor start motor with a Triac rather than a brushless DC motor. I suspect that the DC approach would have reduced the noise.

Incidentially, the heat exchanger in this unit is aluminum. All the nasty condensates go through this or plastic. My sense from research is that the stainless steel exchangers do not seem to have a clear durability advantage for a number of reasons. Lower conductivity/higher differential temp stress seems to be popular. But there are well respected units using both core materials.

I do indeed have a buffer tank in the system to mitigate short cycling. This equates to having a bunch of water in the boiler circuit but localizes it to an insulated tank. Some zones are quite small (e.g., a bathroom). The boiler capacity is only 85 K BTU. This is adequate for a design day with everything in the house heated to 70 degrees. This is all the basement, the garages, the green house, and other areas normally not heated. One bathroom is not much of a load. When heat demand occurs, it circulates water from the buffer tank. When the return water temp from the buffer tank drops low enough the boiler comes online and heats up the system water including the buffer tank. The rate of heating is adjusted by varying the boiler firing rate. I believe it can throttle down to 15 or 20K BTU. Even this is way too much for a single zone.

The installed variable speed pump is a Grundfos 26-96. The pressure sensor is an Alta Labs PWL 050. Both units can use either a 20ma or 10V interface. There is nothing here to actually set the pressure. At full flow it reaches equilibrium at about the right pressure. But if flow drops the pressure goes up. The pressure sensor output goes up and the pump changes speed but there is no set point. So it just reaches another equilibrium point but it has no real realtionship with the target pressure.

I believe a simple processor with an A/D input and a D/A output would fix this. I was hoping for something not terribly expensive that was pretty much setup to do this. I really don't have the time to screw with building one and bulding inspectors are really fond of things like UL labels.

I am going to peruse the ads in Circuit Cellar. I am sure there are devices there that can do it but probably not with the necessary code.

 

[itsmoked]

Sounds pretty nice... I haven't had heat in my house for 5 years.. I'm drooling. I just got a quote for a very simple system all in the attic. I provide the flue and gas and electrical.. 6 ceiling registers one return. $7,963.00 Gesh!

I think I'm faced with doing it all myself, Groan.

alternety; Just get one of these:

http://www.omega.com/ppt/pptsc.asp?ref=CNI_Series&Nav=a03

Most likely you'll want the CNi3253. It has provisions for 0-100mV and 0-1V and 0-20mA one of those should work well for your pressure sensor. It also outputs 0-10V. You can then set up a very robust PI control (skip the D). You will have a direct readout of the pressure differential. Would be very slick.

 

[Warpspeed]

Agree completely with itsmoked, one of those PID controllers would be absolutely ideal. With the software auto-tune function, the proportional gain, and integral time constant will self adjust. The thing will learn what it has to do all by itself to hold a stable setpoint with optimum dynamics.

(Turn off the derivative action, it is not required).

It sounds like you have a very well designed and thought out heating system. Fortunately here in Melbourne the climate is very mild and minimal heating or airconditioning is required.

 

[itsmoked]

More groaning... The idiots faxed me only the first page of the quote... The second page, (mailed to me), added $3,100 more.

I can feel that fiberglass now.

 

[alternety]

itsmoked

If you have not had heat for 5 years it would not seem to be a pressing issue (Austraila, as I recollect, is big on wool - wearing not burning). Can you tell us about your seasonal heating requirements, calculated heating requirements (i.e., heat loss calcualtions) and the cost of a BTU of energy from various fuels in your location?

Insulation may be a better alternative or at least part of the solution. An additional shrimp on the barbie could provide the required BTUs and taste good.

 

[Warpspeed]

alternety,

Looking at my natural gas bill for the last three months, my daily heating cost during mid winter was $US 1.72 per day for 190 Mj per day averaged. That includes all heating, cooking, and hot water combined.

Electricity here in Melbourne is 10.1 c per Kwh for day tariff, and 5.4C per Kwh off peak night tariff. Please note, these costs have already been converted into US dollars.

I have four individual window air-conditioners that are rarely used. A rough guess might be five days per year at ten hours per day. (we may have a heatwave for a few days only).

My home is very well insulated (by me), and has some passive features that reduce the summer cooling load, mainly shading by deciduous trees, and convective ventilation of the roof space. Being a mad inventive scrooge, I take all this fairly seriously.

 

[nbucska]

What does the heating cost have to do with the deep water
sensing ? Anyone interested in discussing the price of the tea in China ?


<nbucska@pcperipherals DOT com> subj: eng-tips
read FAQ240-1032

 

[itsmoked]

nbucska; this post long ago morphed into a discussion about a complex heating system utilizing the the water that was sensed down the deep well.

alternety; Here's that info:

LOCATION: Central Calif. coast, 10 blocks from Pacific Ocean.
COLDEST TEMP: 20F
DAYS BELOW 40F: 5/year
NIGHTS BELOW 40F: 30/year

HOME PERIMETER: 157ft
CEILING: 8ft
GLAZING(DOUBLE VINYL): 250.4sqft
GLAZING(SINGLE): 5.3sqft
FOUNDATION: raised
SIDING: lapped 3/4" Redwood heartwood
INTERNAL FINISH: lath and plaster
INSULATION(wall): none whatsoever
INSULATION(floor): double pad W2W carpet over 2" redwood
INSULATION(attic): 6" fiberglass
INTERNAL HEAT LOAD: 1.2kW
INFILTRATION: moderate to high
ODDITIES: internal 60,000BTU H2O heater
ODDITIES: open fireplace
ODDITIES: dryer in heated space

FUEL(N.Gas) COST: $1.47/therm
ELECTRICITY COST: approx $0.23/kWhr

We have been wearing lots of coats in the winter. My wife looks like a polar bear.. She wears a polyfill coat over a sweater while washing dishes even. We start a roaring fire in the fireplace and it makes the living room nice. But the kids rooms at the back of this rabbit warren are really miserable and the fire exacerbates it with infiltration air. Insulating the walls would be nice but the inner and outer surfaces preclude it and the bigger losses are thru the windows and infiltration. House was built in "49".

 

[alternety]

itsmoked - sorry I got confused about your location. You have an even milder climate than I do in NW Washington (1 mile from ocean).

Both itsmoked and warpspeed, you need to try a tool to zero in on your heat losses and do a what-if. This can show you where you should put your dollars. Now no heat seems a bit extreme, but you still need to think about where to put the money. Here is one free package

http://www.slantfin.com/he2/orderhe2.html

you can download (172 MB). Wirsbo has one I used but you have to beg a bit harder. There are far more complex models available the can actually analyze walls and sunlight and stuff but they are real complicated and for academics and people really into building engineering.

Generally the ceiling has the higher losses than walls but zero insulation seems bad. Infiltration can be a real big factor. Load analysis will not tell you what infiltration rates are.

What follows is my $0.02 (US) on an approach.

Upgrades to the structure return savings each year. They are more effective dollars. Increasing fuel costs just make them better.

Find someone who can do a blower door test for a reasonable amount. They may be scarce in your area but you might be able to cobble something together yourself. It is a test where they put a blower in the door (duh) and measure the flow at a given pressure. Block you chimney.

Double pane glass is not all that bad particularly if it still works. Vinyl is also a pretty effective window material.

There are ways to insulate the walls. Not nifty but doable. With your walls the inside would be the way in. You can patch plaster better than redwood. It would be ugly and messey but you could put a hole in each stud bay and bring in someone to spray something into the bays. The something would be foam (expensive but high R value) or cellulose. The foam would seal better and also provide a vapor barrier. An alternate would be to put some foam sheets and a vapor barrier on the walls and cover with drywall. You loose some floor space and the penetrations (doors and windows) and electrical outlets need to be handled, but if fixes a number of problems.

The fireplace should have an external air supply. Figure out how to get a duct from the outside to the fireplace. If you have a crawl space this should not be too bad. Be careful - you do not want to creat a situation where the fire can get into the outside air supply unless everything is rated for this. It has to have a damper to close off the outside air when not burning. Put a damper on top of the chimney. Normal controls (particularly old ones) do not seal the chimney. It needs to be on the exterior vent where you can actually get a seal. A sealed glass door helps this whole effort if you can get the air supply inside the doors. Maybe a heat exchanger you can put in the fireplace and circulate some heated air (maybe back to where the kids are huddled under the blankets). Dryer has the same issues. Get outside air with a damper to it and close the door to the laundry room if there is one. Do not vent the dryer to the inside. Bad water vapor problem and small lint in the air.

I am guessing that "foundation- raised" means a crawl space. Insulation and a vapor barrier are relatively inexpensive and you can do it yourself if you do not have a thing about spiders (I do). Air infiltration should be a part of this. You might consider fiberglass batts between the floor joists and then a vapor barrier. The fiberglass with an integral vapor barrier is hard to actually seal. Unfaced batts and poly seems better. You could also do sheet foam and seal the edges. Foam/tape any penetrations. You may need a plastic film on the ground to keep humidity down in the crawl space. Every place you have a pipe or wire going through a wall you will lose energy. The top plate of your walls probably leaks much air into the attic. Ceiling lights (especially recessed) leak a lot. Be careful sealing and insulating lights. They may not be rated for insulation contact. One way is to make a box out of something (there is a ceramic based board used to line commercial range exhasusts) to cover them and then seal that box to the ceiling. Push aside your attic insulation and seal wires, vents, and tops of walls with foam in a can. Be careful about your insulation. You should know what it is before you fool around up there if it has been there for amny years. Make sure there is nothing but fiberglass. Some old granular materials can contain asbestos.

Spray foam on the children. Nah, this makes them too inflexable.

Windows can be improved with another layer of glazing. Adding storm windows can help but an economic analysis will drive this approach. A piece of plastic (not a film but an actual sheet of plastic) can be added to the window. This can be internal or external and removable for the summner. You can use those strips of flexable magnet like on a refrigerator door. Those window air conditiners are probably big leakers. Make some insulated drapes for the windows that can be closed at night. If you or you wife are a bit handy and have a sewing machine that is not hard. Use some fiber insulating batt inside. Put the edged is some sort of track to reduce convevtion losses. Or do the macnetin strip thing.

Upgrade air seals on the doors and windows. Sliding glass doors are particularly bad performers.

The heating system. I have to assume there is some sort of heating system in place that does not work. Can you describe it? What sort of floor plan do you have. You mentioned "warren". If you have an old steam or hot water system it may be usable.

Anyone bidding on a heating system really should do a heat loss analysis before they size the equipment. Heating contractors frequently just pick someting nice and big that will certainly heat the house. Then you wind up with something that short cycles because it is way over sized. Make them show you the numbers.

 

[alternety]

Another heatloss package @ $50

http://www.hvaccomputer.com/

Government list

http://www.eere.energy.gov/building...forms.cfm/pagename=platforms/pagename_menu=pc

 

[alternety]

Yet another

http://www.burnham.com/designpro/engineer.cfm