GB142 Technical question (Glenn H.)

Dave_22

I want to say that there is a parameter for max water temp "with" the RC-10. I may be wrong-check through manual carefully. Also you might want to try disconnecting the RC-10 and jump the thermostat input. Cycle power down though-it may not know the RC is disconnected unless you turn the power off.

Glenn Harrison_2

Had to go to one of our new GB142 installs yesterday

for a lack of heat. I get there and the 4 zones are only 59º to 63º, and set for 66º. I go to the boiler and it's reheating the domestic HW, and the boiler went to max temp of 196º. Then it switched to heating, and the boiler temp would go up to 167º and modulate down to maintain 167º and no more. I then cranked up the RC10 thermostat to 80º, and the boiler still maintained 167º. I then set the boiler temp knob from AUT(omatic) to 190º. The boiler still would not go above 167º. I finally had to force the boiler into manual mode to get it to ramp back up and heat the water to 194º. I did make sure the burner was programmed for full capacity.

Any suggestions over the weekend before I call Buderus on Monday?

Thanks to all in advance.

Constantin

Hmmmm....

I can't speak for the Buderus, but I know that the Vitodens will not allow itself to be set to go higher than 167°F on the supply due to regulations back in the EU. Perhaps you have just bumped into a hard-coded limit that may still be in the controller despite the fact that no mandated 167°F limit exists in the US...

I'd be interested to hear how it turns out. It also raises an interesting question regarding DoE output as the boiler goes from fully-condensing to semi- or non-condensing. Presumably, there are diminishing returns in turns of DoE output as the return water temperatue rises until the boiler operates in non-condensing mode...

Mad Dog_2

We've only put a few in so far, but we have quicky learned

that the RC10 can be problematic if you are trying to control several zones. I think the RC10 is great for a single zone application like they do in Europe with Panel rads and TRVS. Mark Hunt and Darin Cooke are the most knowledgable GB Installers that I know. Mad Dog

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Glenn Harrison_2

I hope that is not the case...

If it is, the three high temp changeouts we did this fall are all going to be problamatic, as when it gets to design temp, the baseboard is going to need 180º to 190º water to maintain comfort levels.

Glenn Harrison_2

Same here MD

I put in my first three this fall with my new boss, (his first three also). I wanted to put the RC10 in on all of them to maximize the efficiency of the boilers. I did not try disconnecting the RC10 and jumping out the t-stat connections on the board, as I thought by reading the manuals the boiler should go to 190º if I change the boiler temp dial from AUT to 190º. Thats why I'm confused. Forutnatly, I did put in a four zone pump panel so if I have to it will be very easy to convert over to a standard 4 zone setup.

I'm waiting for our distributor to bring a GB142 class to our area, so I can learn EVERYTHING these units can (or cannot)do.

Ted_9

rc10

The RC10 may be in a the wrong room. I do know its not recommended with multi zone systems. But it may still work with some adjustments.

But,, the GB142 is not limited to 167 degrees.

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Glenn Harrison_2

But if...

I turn the RC10 up to 80º and the burner still ramps down when it hits 167º, it should not be the RC10, I think.

Ted_9

Can you change the max temp settings?


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Glenn Harrison_2

???

Ted, can you elaborate on your last question? Thanks

Ray Landry

Glen I wonder if your room sensor may be faulty? when you turn your rc10 closer to the current room temperature does the gas valve ramp itself down even more? Turning the max temp knob on the BC10 won't do anything when you have the RC 10 hooked up the the system, the only time that I think the knob adjustmen comes into play is when you're using the GB as an 'on off' boiler bringing a switching relay for example the the WA terminals on the boiler block. Are you sure that your boiler is set up to fire at 100% during heating mode (it should say L--)

Glenn Harrison_2

Hi Ray

The gas valve and temp does ramp down when the RC10 is set close to the room temp.

I guess I will have to go back and read the books again, as I thought I understood the water temp knob would limit the boiler even when a RC10 was connected, such as if you had a radiant system where you wanted indoor reset, but only wanted 120º max water temp. Maybe I'm reading it wrong.

Yes I am sure the boiler is set 100% fire (L--)

jeff_51

set the controller on the boiler to manual

the rc10 controller is just doing what it is programmed to do. It is monitoring the room heat gain and loss and configuring the boiler to meet the demand of that room. You would be better off getting rid of the rc10 and going to a zone relay and outdoor sensor to adjust your boiler temp. It is all layed out in the book.

Ray Landry

I have to disagree Jeff, because he said that he was still three degrees shy at best from room temp to desired temp. And even when he turns the room sensor to 80 the boiler does not fire above 167... I do agree though that the RC10 is a very finicky thing to run.... and that latley I have been setting multiple zoned systems to run only off a zone controller, and the only modulating the burner does is according to the delta t accross the supply and return..

Ray Landry

Glenn you are right, I'm sorry. I thought that the RC 10 didn't respond to settings on the bc10 (Max temp settings) but i just read in the buderus literature that it in fact does for the reasons you mentioned. I've installed a few of these boilers and the only time I used an RC 10 controller was on a panel rad install where are design temp was 170 anyhow.... I'm almost positive though that I have in fact seen the boiler fire above 167 when a major difference in desired/room temp was reached. Let us know how you make out. A temp solution would be to bypass the rc10 and just set the aquastat dial to 180...

Glenn Harrison_2

I'm not disagreeing with you...

on getting rid of the RC10, however, it seems to me, and maybe I'm being too logical, that if it is 62º at the RC10, and the RC10 is set for 80º, the boiler should be going " hey, I have a huige temp differential and I better dump my maximum abilities into the water. It seems that the BC10 boiler control has decided that 167º is it's maximum heating capabilities. I even went as far as to let the system temp go down to about 100º, then I set the boiler temp at 190º, and set the RC10 at 80º. The unit fired, went to full burner capacity, and stayed that way until it hit 167º, then the burner ramped down quickly and maintained 167º.

As far as the outdoor sensor, Joe @ Buderus has stated the outdoor reset is not available yet in the U.S.

jeff_51

maybe a stupid question

but you are not using the rc10 controller and the end switch off of the zone controller are you?

Glenn Harrison_2

Not a stupid question at all...

as I had to read thru the book twice to make sure I could NOT hook up the RC10, and hook the zone panel to the boiler.

However, the zone panel is not hooked up to the boiler.

Glenn Harrison_2

Not a problem Ray

I have to read thru the books a few times to grasp everything they are trying to communicate. I have a hard time understaning the way they wrote parts of the manual.

Mad Dog_2

They are saying summer of 2006

You can still do od reset with a Tekmar I believe. I think it will still modulate on Delta T. Mad Dog

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Mike T., Swampeast MO

Sure sounds as though you've hit some sort of built-in supply limit for fully modulating operation with indoor reset.

That VERY specific 167°F (75°C) value during "normal" space heating operation sure sounds like a German government imposed limitation. It may be utterly hard-coded into the software and undefeatable without going to "other than normal" operation. Am fairly certain that the Vitodens can supply up to 180°F using an "external request for heat". If the Buderus has something similar, perhaps you can link such a request to an external outdoor temp sensor... You'd probably loose "normal" operation with the request but at least it would be "normal" most of the time.

Is the customer using significant nighttime setback? Old habits die hard, but if so perhaps you can get them to use less.

singh

Same

I want to say the 167* is very specific also to the GB.
I noticed that temp on one of my systems and I did not have it hooked up to the RC, but use a zone control relay. Even though I had it dialed in at 190*.

I'm sure If you call Buderus they may help.

Mike T., Swampeast MO

RC10 Location in Multi-Zone System

Finding the "sweet spot" is the exact problem I imagined.

It uses a GREAT scheme for automatically finding the ideal operating temperature, but it's truly all about location, location, location... Wiring the controller to a "tether" long enough to be moved to various locations (observe any cable length limit of course) may well be a good idea before you drill holes for the final spot.

Once you do find the ideal location for the controller, it's still not going to operate like a "typical" American zoned system as the RC10 setting will affect ALL zones in the system.

IMHO it's a GREAT control scheme but it's going to take some re-thinking both by contractors and homeowners to work at its best. Hopefully any upcoming control changes will preserve the good aspects.

jeff_51

still think the rc10 is setting the perameter

plus the bc10 reading supply and return temp. The zone valves are limited by the rc10 calling for heat. We are all playing around with these things and learning them. You will I hope as many have asked, let us know what Buderus suggests. We called them the first time we put one in, and got through right away to tech support. We are about 90% forced air out here, so we don't get to put the numbers in that you guys out east get to.

Glenn Harrison_2

Thanks everybody...

for you thoughts and ideas. I will call Buderus tommorow and let everybody know the answers I get. I'm sure Joe@Buderus will chime in tommorow with answers as well.

Jamie_6

Glenn,

This is a long shot but did you try changing the speed on the pump mounted to the bottom of the boiler?

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Joe@buderus_2

WOW

> Glenn,

>

> This is a long shot but did you try

> changing the speed on the pump mounted to the

> bottom of the boiler?

>

> _A

> HREF="http://www.heatinghelp.com/getListed.cfm?id=

> 289&Step=30"_To Learn More About This

> Professional, Click Here to Visit Their Ad in

> "Find A Professional"_/A_

Joe@buderus_2

WOW!!

Lots of input on this one. I think it is one of two things. The RC10 is limiting the water temperature (raising the set point will take several minutes for the GB142 to respond, especially if a large change is made) or a large delta T is affecting the firing rate.

The GB142 is not limited to 167 degrees. On multizones there can be some issues using the RC10. Pump speed on the manifold should be at #2 - medium. Glenn you did all the right things, I think you are running into the "smarts" of the the GB142 and/or RC10. I suggest removing the RC10 and use the end switch connection from the relay board to the "WA" terminal on the GB142. Note: to prevent short cycling the GB142 allows a ten minute time between heat calls. The GB would flash "OA" in this instance.

Mike T., Swampeast MO

That 167°F (75°C) value seems a bizarre coincidence!

Mark Hunt

Agreed


I think that it is the RC-10 controller.

The RC-10 works great when you have one zone or when you have TRV's controlling individual heat emitters, but it was not designed for use in the "zone crazy" USA.

Disconnect the RC-10 and use a standard digital T-stat connected to the "WA" terminals like Joe said. I'll bet your issue goes away.

The boiler will still modulate according to the Delta T.

Hope this helps!

Mark H


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Glenn Harrison_2

Well I called Buderus,

and just happened to get Joe on the line. After talking for a while, we came to the conclusion that in all likelyhood the RC10 has some kind of a malfunction. What this unit is doing is NOT normal. We did discuss the speed of the boiler pump, which is on high, and I will lower to medium. The temp drop with all zones running is only 10 to 15º, so low return temps is not the case. We also now I have enough BTU's as the boiler was able to achive 195º in a short period of time when I put it into manual mode. So, the only comnclusion is an electronics glitch. I will be going back tomorrow mid morning with an new RC10, which I will install, and then see what happens.

I personally do not want to remove the RC10 unless I absolutly have to, as it provides the additonal bennefit of lowering the water temp to the minimum needed to maintain set temp. But if i must remove it, I will.

I will let everybody know the final results tommorow PM.

Ted_9

Tekmar

Well, you could remove the Rc10 and use tekmar t-stats(510 maybe?). Its not an equal swap, but its better than on/off t-stats.

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Mark Hunt

Hmmm


I can't compare the Vito to the GB.........

So I don't.

Mark H

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Glenn Harrison_2

Went back today...

and replaced the RC10 stat. Still having the same problem. I then replaced the RC10 with a standard stat and rewired the zone panel for a four zone set-up with the panel signaling the boiler at the WA terminals. The boiler went to 195 without a hitch.

So I now know it is not the RC10 that came with the boiler, the boiler works fine if not using indoor reset.

So I either have an improperly programmed boiler module, or, there is a 167º limit programmed into the boiler module when using the RC10, and Buderus is not advertising it in their manuals.

I have ordered a new boiler module that should come in Friday.

Joe @ Buderus, if you could, I would appreciate it if you could run this by your constituants to see if I am still missing something, and/or if I am waisting my time replacing the boiler module because it is programmed to do what I am seeing. If you come up with something, please either post here, e-mail me @ glennhvacman@comcast.net, or you can call me anytime @ 815-651-6745.

Thanks again to all for your input. I will continue to keep everybody advised as we discover answers.

Mark Hunt

Glenn


Ditch the RC-10 completely.

Mark H

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Glenn Harrison_2

Mark, forgive me...

as I'm going to be stubborn on this one. If I have to I will keep the RC-10 out of the system. However, I feel by taking it out I'm sort of false advertising to my customer about the up to 99% eficiency of the boiler. With the RC-10, the boiler will stay in the condensing range much more frequently than it will in the on-off mode. I realize the burner will still modulate without the RC-10, but it will modulate to maintain 195º once it gets to 195º. I was looking at the manual today, and I remember noting the GB142 is only 88% efficient at 176º. So if I can keep the water temps lower with the RC-10, then I'm keeping the efficiencies higher, and staying true to the true capapilities of the boiler. I'm also keeping my boss from having to decide about putting in a Tekmar ??? control for outdoor reset. Besides, the system was working flawlessly with the RC-10 in milder weather. It wasn't a problem until we hit single digit and teens temps over Thanksgiving, when the max temp got limited.

I guess the thing that aggrivates me the most is this is not listed in any of the GB142 manuals, and even Joe@Buderus said it is not limited to 167º. So I want a final answer.

So again, please forgive me for being the stubborn, pig headed anal retentive technician I am. I really can't help myself.

Mark Hunt

Oh stop!


You are FAR from being all of those things you called yourself!

I am just trying to let you know that the GB can still function "as advertised" without the RC.

In the USA, we over-zone everything. The RC just isn't designed for that.

The boiler modulates on delta T.

Your customers would still save a ton of money on fuel consumption, RC or no.

You are top shelf in my book Glenn!

Mark H

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Glenn Harrison_2

Sure I am...

just ask my wife, she will tell you

I just like the RC-10 because it modulates the required water temp, on top of the burner modulating the required BTU's to maintain temp. 120º water is much more efficient than 190º water.

Your right, we do over zone everything, But then again, there are way to many people making way to much money to be able to build these mansions that get so over zoned in the first place.

And your right, they will save a ton of money over the old "mailbox" oil coverted to gas boiler they had.

Thanks for your kind words. I have guys like yourself to give credit to helping me stay "top shelf".

Mad Dog_2

WE will be doing just that on one of our jobs

too. I think its just a bad application unless, as Mark said....single zone w/ panel rads. THe manual says: Max temp output 220 degrees...never tried to put one up that high though. I admire your stubborness. Tell us if you learn anything, Glenn. Mad Dog

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jeff_51

we al want to know, 'cause we are all puttim in