Hi All,
Two years ago we had to install a new boiler. Turns out that the boiler is oversized. The house is divided into 6 zones and it is very rare when there is more than 2 circulators running. The circulators are controlled by a Taco zone controller (not the EXP). The boiler is a Burnham V89 rated for 239000 BTU controlled by a honeywell L8148A. I set the high limit to 180 (the lowest setting) and it over shoots to 190. I'm thinking to add a second aquastat and set it to 130 or 140 degrees so the boiler want fire until the water temp goes below 140 in addition I want to go one size down with the nozzle. My other though is to use either an Intellicon HW+ or a tekmar 256 and reduce the nozzle. The last thought is to design my own controll system (use my electronics engineering experience for a change).

Also I'm making the house envelope more tight, we installed new doudle pane windows and doors few years ago. Also we replaced the siding and used vinyl siding that have insulation behind it. My next step is to get an infra-red thermometer to audit the house walls. Caulk and seal every crack, outlet and hole.

Any thoughts and/or advice? Thank you all,

EmilBeer 4U2

 

Keep tightening up the home and replace the new boiler with a properly sized boiler. Not to sound out of line but everything you do to tighten up the home from this point will make the operation worse as far as cycle times and lowering the efficiency. The shorter cycles due to reducing the heat loss will affect the maintenance, mechanicals and fuel bills.
How many rooms in the home to have six zones? Micro zones are more problems that larger zones.
Be cautious with dropping the water too far and no boiler protection. I would be more concerned with cycle rates than outdoor reset. Your fuel expense is more to cycle rate than home leaks.
For more info on boiler protection see the following link
http://www.comfort-calc.net/Bypass_P...laination.html

 

rbeck,
I'm heating 7000 sf and the largest zone is about 2000 sf and the smallest zone is about 600 sf. I did install a boiler bypass to help with the flue gas codensation. As for the low limit I was not planning on going below 140 degrees. The reason I wanted to go to a lower limit was to lower the cycle rate.

 

With your aquastat idea, are you then going to be maintaining water temperature? If yes, you will use more fuel. I would lean towards either of the other choices instead of the aquastat idea. How much oversized is the boiler? What was the heat loss and what is the DOE output?
As far as downsizing the nozzle one size is OK but I would not go lower than one size. Going too low is an issue of flue products and amount of fireside heating surface. The smaller the flame the less thermal transfer. When the amount of flue gasses to exit the fire area decrease too much the faster they move out.

 

Hi,
The boiler will not fire unless there is a call for heat, it is a cold start boiler. I'm hoping that by aving a lower limit and a smaller nozzel that it will have longer cycles.

I have to figure out the heat loss and DOE. Is there more to gain by installing an outdoor reset controller or an intellicon HW+? or just adding a honeywell L6006C would be enough?

 

Hi esalman, I agree with rbeck that you need a working heat loss, preferably your own, so you can adjust as changes are made. That will tell you where you stand. With six zones you have them all moving towards a call for heat at different rates, thus the potential of satisfying them one at a time for short intervals. Since you like electronics, create a system of temperature monitoring that will respond to one or more primary zones, but fulfill the secondary zones at the same time with shorter circulator cycles. Short cycling the extra circulators is not inefficient and will force a longer run time for each call.

With a 7,000 sq ft home, you may find your boiler is not all that oversized, but your six zones are aggravating the short cycle situation. Once you get a feel for the frequency of call for each zone you will be able to fine tune the overall response and even tie in outside temperatures.

Also, anything you do to increase the thermal mass within the home will slow the cycle time as well. May not be cost effective, but it might get your wife that slate floor she has been wanting .

Have fun
Bud

 

From experience I believe that ODR is the best way to go. About the L6006C, the issue I see with it is which zone would you purge to? Odds are that it will end up over heating that zone.

If you want to have some fun while puttering around with the boiler. Grab a micro-controller, some temperature sensors (thermistor or IC type), and some opto-couplers. Set up the micro to communicate with a laptop via USB or serial.

Then for the temperature sensors: one on the boiler water, one each on the zone returns, one for outside temperature. These go to ADC channels on the micro. Can add an analog mux for additional inputs.

Then use the opto-couplers as a digital input to the micro. Have the thermostats 24vac enable/disable the input LED on the opto's. These will be inverse logic, no call for heat the opto is active, with a call for heat the 24v AC goes away and the opto is off.

At this point get it all up and running and you will have a decent monitoring system.

Can also add an opto to the burner oil valve to know when it is actually running.

At this point it is then a matter of using opto-triacs (or relays) to activate the burner or zones via the micro. Easy to then build in your own ODR (partial) curve.

You can even go as far as using a thermocouple to monitor the flue temperature. Pressure transducers for water and burner oil pressure, and so on.

Al.

 

Bud,
I like the idea of short cycling the pumps and also agree that the boiler is not grossly oversized if the house wasn't divided to 6 zones. As for the thermal mass We have a field stone fireplace and I'm sure the wife would love a slate floor. I would like a slate floor too, I'll have a reason to switch to radiant floor heat.

Al,
I'm leaning more toward the ODR (tekmar 260), it offers more than the intellicon. But the intellicon is much easier to install and no programing is required. I was going to use the L6006C to monitor the water temp leaving the boiler, and have the boiler fire if there is a call for heat and the water temp is 140 degrees or below, it is a cold start boiler and I'm going to keep it this way. I like the idea of the monitoring system, and maybe use variable speed circulators with it. Right now I have 5 Taco 110 circulators and a Taco 0. The circulators are installed at the retun of each zone and it causing the pressure to go up when there is more than 2 circulator running. I wish I had more time to address the pumps when I replaced the boiler, I would installed them on the supply side instead. I had to get the new boiler up and running beacuse the old boiler cracked in the middle of january and it was cold.

Thank you guys.

Emil Beer 4U2

 

I gotcha' on the L6006C. You mentioned that in the first post but missed it this time around. I saw at Honeywell that it is sold as a circulator control. So assumed it was a low limit switch.

But now see that it has both high & low limit switches (SPDT).

Note about the slate floor. That is what I put in the Den here, it was carpeted when we moved in. Hated the carpet, the slate over slab with radiant is really, really nice.

Al.

 

This exactly what the Intellicon HW will do. You will be able to set the intellicon to any degree you want it to fire (of course you will want to keep it a safe temp for your boiler). This is exactly what I did instead of adding another aquastat. It would work great for what you are thinking.

That being said people love the odr and I sure it would be a better set up and more of a fuel saver. I quess it depends on what you want to do.

Good Luck

 

Please keep in mind that the Intellicon requires that the boiler bounces off the high limit before it takes any action. If the heat call is satisfied before the boiler hits 170°, it won't do anything.

One caution I would like to interject. All boiler controls are required to be UL Listed. If you design your own system, no matter how well designed, and exectuted, if higher power forbid, the unthinkable happens and there is a fire... and your HO insurance discovers that there is homebrewed controls, they may well deny your claims.

 

As long as a UL listed flame safeguard and a high limit control are installed and take precedence, the operating control could be a non-listed control of anybody's design and the insurance company would be hard-pressed to prove any damage as a result of a non-listed control. Quite honestly, it is doubtful that any insurance company would even consider not covering a residential claim unless there was evidence of a known defect in the controls. Since very few homeowners have even the slightest knowledge of boiler controls it would be incumbent on the insurance company to prove the homeowner was grossly negligent, something that would likely cost the insurance company more than the claim.

The stories of the insurance company refusing to pay a claim on a residential loss due to the homeowner being a DIYer and having non-UL listed equipment and/or not having required building permits (and inspections) are mostly urban legends.

 

Maybe so, but I don't like to throw caution to the wind! And that's all it was, a caution to consider.

That aside, homebrewing and debugging a control system for a residential boiler, and deriving any real benefit from doing so is a very ambitious endeavor, even for a PhD in EE. Why reinvent the wheel anyway? Unless it's done as a hobby... where it just doesn't matter how much time and money is thrown at the project... (Lord knows I've done similar things just for the enjoyment of being able to say I did it!)

 

You're right, of course, very seldom anything to gain by engineering from step one for any residential control.

I once built a thermostat for my single-zone, two-stage furnace using an $800 process controller and platinum RTD sensor. It looked really cool but it didn't work one darn bit better than the $100 Robertshaw programmable thermostat. Furthermore, if anything had happened to me no one would have had any idea of how that controller was being used and would have just tossed it for a regular thermostat.

Just today I was looking at an Automation Direct catalog and musing about getting a PLC to control the heating system. Then I slapped myself. When I die my sister will get my home and she will probably have trouble with the Robertshaw thermostat even though the instruction manual is on the shelf right next to it. Why would I want to make life harder for her?

 

These are good points about a home brew system for boiler control. As mentioned the important areas are to leave the primary and the high limits intact and un-touched. So that if the monitor/control box in error requests the burner forever and ever, the standard high limit will still be in play.

And the burner primary does not get bypassed for any reason. Use the TT terminals to request burner activity.

To control the burner I opened the zone relays dry contacts to the burner primary TT terminal wires (24 V AC). Then just close the primary TT terminals via the controller via an opto-triac. Low voltage/power, isolated, and leaves the primary control and high limit wiring un-touched.

One does need to use common sense and good practices. No running 120 V from zone relays or oil valves to the controller. This needs to be isolated at those boxes. Then only low voltage and ISOLATED wiring gets run to the controller/monitoring box.

Isolated can be via opto-couplers or relays. Relays being more immune to noise and transients. Which is why broadcast stations use them.

All circuitry with the exception of the interface wires reside in metal boxes.

As for why to do something like this? I like to keep sharp on electronics and software. I was also able to use the development of the boiler monitor/ODR to help with another project I had. Didn't have a PCB for a working proto yet. So used this to put together some firmware/software to test out some ideas & techniques.

Once it was together and monitoring, the ODR was easy. Just an output to control the burner via the TT terminals. And some look up tables.

It will now report combustion efficiency when the lambda sensor is installed. The screen is still just text (sorry NJ, I'll get gauges on it some day). But it does the trick.

Al.

 

Thank you guys for your advice. I can’t decide if I should go with an ODR or heat manager. I can still make my own monitoring system just for fun and gain more experience.
A year ago I started burning a mix of HHO and WVO and started learning about boilers and controls. I'm learning something new everyday, it is very interesting and I'm thinking about obtaining an HVAC license just to learn more and maybe start my own business. I don't want to re-invent the wheel, I like making things more efficient in general. I met lots of HVAC technicians (my brother in-law is one) who are set in their way, not willing to learn something new and negligent of new technology that might increase their business.

Beer 4U2

 

Al,
Are you using C to interface and control your system or are you using some sort of a PLC ?

 

This was posted on another thread by the inventor of the Intellicon which contradicts what you are posting in addition to how I have seen numerous installs of the Intellicon in use....The author is contrasting the older technology used in outdoor resets compared to the more sophisticated Intellicon HW technology, regardless the Intellicon does not have to bounce off the high limit before it will economize, the work is done on the low end when there is a call for heat and there is excess btu's still available in the boiler where by the economizing takes place but holding off the burner and allowing the circulators to exhaust the excess btu's first. Anyway here is the quote....
"The other thing about OATR is that they are considered by most boiler / burner manufacturer’s (as well as the Department of Energy) as duty-cycle controls. One of the reasons that the manufactures don’t like duty-cycle controls is that since they not only control when the burner is started, they also control when it is stopped. This may prevent the boiler from getting up to proper operational temperatures and leave condensation in the flue. Also, trying to maintain a lower average water temperature leaving the boiler, may lead to shorter on cycles which actually decreases burner efficiency, since the boiler would rarely get to a steady-state condition. That inefficient method of cycling is exactly what the HW+ does not do. The HW+ varies the average water temperature by only affecting the low end. This can still yield the same average water temperature as the OATR, but the boiler is always brought to the same operational temperature. This results is fewer cycles, but cycles that are slightly longer (to make up for the btu’s shed while the burner was being held off) and more efficient. The HW+ does its calculation by reading the temperature of the water leaving the boiler, and the rate at which this water temperature is changing"

Here is the link for the complete narrative Intellicon HW on a Columbia Emerald Boiler? [Archive] - DoItYourself.com Community Forums
Beer 4U2

 

The boiler monitor/ODR is a stand alone box. It uses a MicroChip PIC (16F series) with the firmware written in assembly. The particular PIC I used is self-flashable, so the firmware can be updated via the comm link (has a boot loader).

There isn't a display or buttons (other then on/off) on the controller. Just a box with a bunch of I/O and terminal strips to connections. As it is stand alone there is no need for a PC to run it. Just turn it on and it is off and running. Oh, there is a status LED, but it really isn't used for much at the moment.

The PC side is a Windows program (win32 console) that receives data via the serial link. Can tell the 'box' how often to send the data (once a sec, 4 times a second, and so on). It has a loader to load new firmware into the box. Along with other odds and ends for updating the box.

The PC program has a display that shows the various temperatures. Boiler water, zone supplies and returns, intake air to the burner, outdoor, flue temperature and so on. It shows which zone(s) is active along with the burner being active.

If the lambda sensor is installed it will show the CO2 level along with the combustion efficiency. Items such as these are calculated locally in the PC. I'll see about getting a screen shot. With it being text it isn't all that impressive, but is informative.

There are still some items I'd like to add to the box. Such as accumulated burner run time, min/max runs times, and so on. Along with a real time clock (RTC).

Al.

 

I've decided to go with the intellicon because of its easy and quick installation. Plus it has more intelligence than just adding another aquastat. NJ trooper I read some of your earlier threads and I understand your point of view about the 10% savings in fuel, specially that the inellicon has no way to process data from previous years. I kept track of how much oil I used for the past 8 years and I'll compare with this year's oil consumption. Still it will not be accurate due to the fact that the heating season already started and the boiler has been running, but I would have some feel for it. I used to order oil every 3 weeks and hopefully I’ll be ordering oil less often using the intellicon.
I’m an engineer and I know much goes into developing a product, proving its concept, reliability and quality. Just the fact that I’ll have less cycles should help save on oil, also I’ll be switching to a smaller nozzle (one size down) since I don’t want to heat the water as fast.

Beer 4U2

 

Al,
I'm going to build a system to monitor the heat demand of each zone, boiler cycles, water temp leaving the boiler and coming back from each zone, and maybe CO2 levels. Processing all the data should be fun, also I'll keep track of the outside temp and work my way up to a heat management system utilizing an ODR concept. All this is going to take a while to implement and will give the intellecon a chance to work its magic.

Beer 4U2

 

I knew North Man would be back sooner or later to defend the Intellicon... but I was really saddened that Mr. Hammer never returned to answer the questions I posed.

Emil, I have an open mind. I've yet to hear back from anyone that has installed an Intellicon to provide data on the supposed 'savings'. I would absolutely welcome hearing some FACTS about how yours works for you.

All of my comments are based on real world observation of actual operation of the unit that I have installed on my personal system. And I can absolutely say, without any prejudice that it has not saved me a dime. This is my personal observation of facts, NOT opinion.

I do NOT want this thread to get sidetracked into another Intellicon versus Trooper thread, so let's just drop it... until there is data to be served. If anyone wants to discuss the HW any further, start a new thread please, and let Emil keep his thread.

Thanks!

 

That's cool. This is the same as I did. Got the monitoring going then over time add more functionality. Then the ODR was easy. The only area I ran into trouble was using Excel to observe and graph results.

It is limited in the number of data rows that it can handle. So I've reduced the data packet rate to 1 every 4 seconds for data that I want to graph. This allows excel to graph about a day and a half worth of data.

Excel will read in 64K rows of data. But can only line graph 32K rows.

And having a Beer 4U2

Al.

 

Another boiler efficiency gadget



You might want to look into the Field Control OVD. I am trying it out now. I have had it in about a month now. So far it is working without fault. I read some posts here about it just not sure if anyone else has installed one. It is a pretty easy install. Anybody have likes or dislikes to it?



here is a link to it: http://www.fieldcontrols.com/pdfs/43...ntDamperSS.pdf

 

Mike,
I like the OVD idea, the boiler will stay warm longer after it stop firing. The only concern I have is what if it stuck closed and the burner fire? I'm sure the burner will stop after running for a short period of time but about the CO build up?

I'm going to research it.

Beer 4U2

 

Hi

There are built in safety devices to prevent that scenario but still makes me a little nervous also. Field control is such a major brand name so I am hoping it will be fault free. I think the OVD has been around for a couple of years. Hopefully if there was bad reviews for it, it would have been pulled from the shelf. I will post if I have problems.

 

This is the honeywell version of the OVD or should I call it GVD, this is a simple and very effictive idea and it will work great with the intellicon.

http://customer.honeywell.com/techli...0s/68-0186.pdf

Beer 4U2

 

Mike,
How much did it cost?

Beer 4U2

 

Vent dampers have been used for years on gas fired systems. The problem with oil fired systems is the fact that 'crud' builds up in the flue pipe and impairs the ability of the damper to operate properly. Field has supposedly solved this problem by designing the damper such that it only rotates in one direction, and added self cleaning 'scrapers' to the damper flap.

All of the dampers have limit switches that will prevent the burners from firing unless the damper is fully open first.

Emil, check out Patriot Supply - Industrial, Commercial & Residential HVAC Parts & Equipment ... they carry a huge array of hvac and appliance parts and are a very good company. I have no affiliation other than that of satisfied customer.

 

Trooper,
I think the damper will help the Intellicon, since the intellicon delays firing the burner at the lower limit. The more heat we keep in the boiler the longer the delay. Also it would help with eliminating condensation inside the boiler.

Beer 4U2

 

The damper is a good idea, no doubt there...

I couldn't find the D896 honeywell on Patriot's site... but they do have the GVD from Field for around $110... but, there is no wiring harness with that, and I didn't see where they sell the harness... strange that! ... I don't imagine there's much to rolling your own harness of course.

 

Just to clarify... the Intellicon will widen the differential based on what it perceives as the boiler's 'load'. It bases this perception on the rate of change of the supply water AFTER the boiler hits a high limit of 170 degrees. This, and knowledge of whether or not the thermostat is calling for heat, is the ONLY data that it knows, and it does NOT store this data. It starts a fresh calculation every time the boiler hits 170.

If the heat call ends before the water hits 170, the Intellicon will take no action.

If the heat call does last long enough for the boiler to go to 170, the burner will shut off on high limit, and the Intellicon will begin measuring the rate of temp change of the still circulating water.

If it sees the temp falling (ahem) "Fast", it will use a narrower diff because it thinks the load is "Heavy".

Vice versa, if the temp falls (cough) "Slowly", it will widen the differential to a maximum of around 30 degrees or so...

This is based on observed behaviour. YES, I do have one on MY system.

I didn't want to start this discussion again, but since you have expressed a desire, I thought you should know what I have observed with mine. Your mileage may vary.

 

Thank you Trooper, I have one more question regarding the L6006C, Howell states that following:
" Circulator controller—prevents circulation of water that is not hot enough. Breaks circulator circuit at temperature setting minus differential; remakes the circuit when the temperature setting is reached. Switching action is as follows: Upon a drop in boiler water temperature (to dial setting, less differential), makes R to B burner contact; breaks R to W contact, preventing circulator operation. Upon a rise in boiler water temperature (to dial setting), breaks R to B burner contact, makes R to W circulator contact."
Is he L6006C going to defeat the cold start operation when used with an L8148A? or just the circulation?
My boiler has an L8148A which I'm using to control the burner. The circulators are being controlled by a TACO zone controller. What I understood from the data sheet is that the L6006C is going to stop the circulator when the water temp go below the low limit, in my case it will not make a difference.

Emil
Beer 4U2

 

Emil, if I understood your original plan, you won't be using the 6006 to control the circulators at all... or did I miss something?

I understood that you would wire the 6006 in series with the high limit in the existing aquastat, and use it's adjustable differential to widen the differential on the existing unit. Is that right?

If this is all true, you can ignore the bit about the circulators, because you won't be controlling the circulators.

Does your burner have a Honeywell primary control on it? If so, take a look at the T T terminals on that control, there should be a jumper. Removing that jumper will disable the burner, and override what the aquastat is telling it to do.

One way that you can widen the differential using a 6006 strapped onto the supply outflow pipe from the boiler is to wire the R-B contacts to the T T terminals on the PRIMARY CONTROL (note: NOT the TT terminals on the aquastat!).

If you set the setpoint on the 6006 to match the high limit on the 8148, you will have a redundant high limit. This is a good thing, if either one fails, the other will still be in control.

Next, you set the DIFF on the 6006 to maximum of 30°.

So let's say the 8148 and the 6006 are both set to 180, and you have a 30° diff setting on the 6006, and the R-B is wired to the TT on the primary.

Heat call comes, if water has fallen below 150, AFTER hitting high limit on the 6006, the burner will fire... if the heat call continues, and the burner hits high limit again, the burner will cut out, but the 6006 will hold off the burner firing until it drops to 150...

I think this was your original idea... and please note that it is almost identical to what the Intell does, with the exception that it is a FIXED setting... but, also remember that if the boiler does NOT hit the high limit with the above setup before the heat call ends, that the burner will remain enabled because you have not hit the top of the hysterisis loop.

You may find when observing your system that 90% of your heat calls end before the boiler hits high limit... in this case, tweak the setpoint on the 6006 DOWN to a point that MOST of them do hit the high limit of the 6006... you can leave the 8148 at the higher setting of 180 and the 6006 will now be in total control of the burner operation, leaving the 8148 to act as secondary HL.

Let's say that you turn the 6006 down to 155, with the diff still at 30. Now, when you get a heat call, the burner will fire to 155, and shut down. The call continues and the boiler will cool to 125 before the burner will refire. Since your circulators are under control of your Taco panel, they can come and go as they please... you are not interfering with their operation at all.

You may find that with this setup you will need to tweak the settings of the 6006 a few times during the heating season... lower during the shoulder seasons, higher when it's a55-chillin cold out.

 

I believe your description is based on adding the 6006 and wiring it to the aquastat as shown in the diagram under the cover of the 8148?

That is NOT what you want to do... that setup will indeed defeat the cold start function of the 8148... turning it into the equivalent of the 8124...

Your application will not be found in any of the Honeywell manuals...

 

With all that said, you owe it to yourself to investigate and research both the Tekmar 256 and the 260.

Both of these devices are more sophistacated than the simple algoritims that the Intell uses.

The 256 not only monitors your boiler supply temp, it ALSO monitors the OUTDOOR temp and adjusts the firing of the boiler so that it will only supply water as hot as necessary to achieve the heating of the home.

The 260 adds to this in that it will ALSO allow the use of an indoor sensor (or sensors in a bridge configuration to average the temp in multiple zones) 'Indoor Feedback' is a VERY good way to control the boiler.

Both the 256 and the 260 will automagically adjust the differential, or they can be set to a FIXED differential...

You may also be interested in another type of boiler control that monitors the frequency and duration of heat calls from the thermostat, and adjusts boiler behaviour based on that data. I believe that using the home thermostat to provide heat load data is very accurate because it provides ACTUAL REAL WORLD load data to the system. It can account for all the variables. It doesn't have to 'guess'. Even an outdoor reset is 'guessing' to some extent. Take a situation where it is cold outside, but there is a crapload of solar gain. ODR systems, and the Intellicon can't/won't account for this. INDOOR SENSORS on the 260 CAN though...

Check out:

Exquisite Heat

This is a VERY interesting idea for controlling a boiler...

 

Hi

I bought the OVD at Patriot Supply (they are a great store). I think it was in the $155.00 area.

Hi, NJ Trooper Since you brought it up again is there anyway the Beckett HM is different from the Intellicon. I know I bought the Beckett HM and read that the temperature must reach 170 deg and did not like that fact so I returned it. The Intellicon does not state that it has to reach 170 in there instructions. Back a year + ago I called both on the phone Intellicon and Beckett to ask about that. Beckett told me yes to the boiler temp reaching 170 deg. Intellicon said it does not matter.
On my boiler I have seen a call for heat turn on the circulator (without the burner firing), intellicon sensor reading 165 deg, circulation continues and temp drops into economy mode until it allows burner to fire. Although, sometimes it comes off economy to fire the burner sooner than others. I would say anywhere in a 8 deg range above its limit setting. I guess due to heat-loss calculations it is making? That annoys me a little when it fires to soon but I guess it is going on the safer side of boiler temps dropping to much.
I do not really believe all the claims about the savings both products make (Beckett & intellicon). I do think it works well for stretching out boiler run times and circulating cooler temp water. It gave me more adjustment to be able to lower my low limit which is all I was hoping it would do. Like I said before, I do average around 30% time in economize function.


I am glad for this post because It made me realize I wired my Ovd in the wrong place. My vent opens when I am in economy mode. Stupid mistake.

Emil, if you want something easy and quick the Intellicon might make you happy and do what you were looking to do but you have a nice new boiler some of the more sophistocated equipment mentioned might be a better match. I guess it depends what you are looking to do, time and money.

Good Luck

 

Thank you guys. I did look into the tekmar early on, it is a nice product, the only thing i'm not sure about is solar gain. Also Because the house is divded to 6 zones i will not benefit from the indoor sensor that can be used with the 260 (decididng which zone will get the sensor and how this will efect the rest of the zones). The 260 costs twice as much compared to the 256 and the heat manager.
I like trooper's idea of using a second high limit switch and setting the L6006 differential to 30. It will not cost me a penny, I already have a 6006.
I know somebody whose going to school for an HVAC license, he is looking into getting discounted prices for the 256, 260, intellicon, and the OVD. Budget and features are the biggest factor, installation is not a big deal, of course the quicker the better.

Beer 4U2

 

FYI:

You can use multiple indoor sensors.

Wire them up in a 'bridge' (or series/parallel) configuration and you can average different areas of the home. There is a tech note at the Tekmar site that explains how to wire...

Found it...

Service Bulletin 018

 

i didnt spring for the indoor on my 260 when it was installed. is there any guesstimate as to how much more id save if i added the indoor sensor? I'm assuming it's as easy as me finding the sensor online and then hanging it on the wall?