Outdoor Reset for Buderus GB-142 by end of August

Mike T., Swampeast MO

Yes, in that reduced flow = greater delta-t = lower average temperature = lower output.

This is one of the MAJOR considerations when adding a condensing/modulating boiler to a system that also allows <I>variable</I> flow, e.g. TRVs/FHVs. Don't forget that with such a boiler lowest possible return temperature <I>as much of the time as possible</I> = highest possible efficiency.

With such a system it only makes sense take advantage of any over-capacity in the emitters by increasing delta-t with load. In other words, the colder the weather and the higher the supply temp you need, the more you want to increase delta-t.

Unfortunately loop systems do not work via this method. They are designed around a <I>known</I> flow for the loop as a whole and a temperature drop calculated for each element. This is the <B>good</B> situation for a nicely designed and <I>unmodified</I> system. With poorly designed, or more commonly <I>poorly modified</I> systems the usual solution is to increase flow rate to in turn increase average temperature and decrease delta-t throughout the loop.

Significantly reducing the flow in even a nicely designed loop system will have a corresponding effect on the balance-the elements at the beginning of the loop will have a relatively higher average temperature.

As a consequence, you must accept somewhat reduced efficiency in a loop system driven by a condensing and modulating boiler.

D107

AM10 Module

Just heard from Joe Kennard at Buderus.

..."The AM10 module, which is scheduled to be released by the end of this month, August 2006, will provide the outdoor reset feature for the GB142. The AM10 can be installed on existing GB142 boilers. The plugs to tie in the AM10 module have been included in all GB142 offered here in the United States."

So now I'm taking another look at installing one for my home.

I heard that in Europe they (not Buderus specifically but in general) use a 30 degree Delta T and get more efficient heat that way. Anybody do that here?

David

Mike T., Swampeast MO

Higher delta-t = lower return temperature = higher efficiency from a condensing boiler.

Two things MUST HAPPEN to allow this:

1) Lower flow. This means lower flow throughout the ENTIRE system! Primary-secondary piping breaks apart when secondary (emission) flow greatly exceeds primary (boiler) flow as it still increases return temperature to the boiler regardless of the isolation strategy used.

2) The emitters must be able to transfer the additional heat AT THE REDUCED FLOW.

USE TRVs or FHVs!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

D107

so if emitter load is 2x heat loss can they transfer at reduced

flow? And are there circulators that pump slowly enough? Steamhead's chart indicates a gpm flow rate of a little over 10% of MBH heat load for a 'modern' piping system. What's the flow rate you're proposing with the higher Delta T?

(Unfortunately my piping is series loop; I'd have to put in some kind of monoflo or two-pipe system to be able to use TRVs.)

Thanks,

David

Ted_9

Dianorm handbook



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singh

Indoor reset was just fine. RC10 multiple zones a pain though.

Can they be used together??

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Ted_9

PDF

Im going to email a pdf that you may find helpful.

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Big Ed

What's the Deal...

.....with previous bought and installed units? Is Buderus still giving the controls for already sold and installed units ?

Joe@buderus_2

AM10

It is suggested to contact your distributor regarding the AM10 modules on already installed units. At this point we are not recommending using the RC10 and the AM10 together.

ScottMP

Joe

My understanding was that Buderus is waiting for all the new paperwork and instructions for this control to be released ? Is that so ?

I would think at this point indorr and outdoor re-set would be difficult to mesh together. I can't wait for the AM10 to be released.

Thanks for keeping us informed.

Scott


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D107

isn't it best if indoor and outdoor reset work together?

--as I think they do in some other mod cons. Certainly in the other Buderus boilers you get them both together.

So given the choice would installers choose the outdoor to avoid multiple indoor sensors, wire routing through walls, etc?

David

Big Ed

Which is Best

Which is recommend ? Does it depend on the mass of the radiation?




I am looking at a bit of back paddling here,I thought we could use both... Nothing but good reviews so far... One gas to gas job said the gas company dropped her budjet $70 per month even with last years increase .....

Unknown

indoor/outdoor

quite a few mod/con manufaturers implement this quite effectively, i know Baxi and Viessmann both have indoor/outdoor reset controllers for their boilers, typically you would only need one indoor sensor to reset the water temp, just locate it in the coldest room/area and have thermostats in other areas only controlling zone valves not directly connected to the boiler control (not able to call for heat themselves) to limit heat in certain areas.

also, Tekmar has indoor/outdoor reset controls that are compatible with mod/con boilers, check out their new tn4 system.

Dave_22

outdoor reset and night time setback?

I use indoor reset with the rc module now and TRV's with panel rads- the only thing i don't really like is that i would like to do temp setback at night. Do you think it would be more efficient to do outdoor reset instead and switch to a programmable thermostat? i could cutback the temp for at least 8 hours at night. I also worry that since there is not a "boost" function, it could take quite a while to re heat in the morning. Thoughts?

Ted_9

PDF

I cant send the pdf, so try the www.heatlines.com

check out some of the pdf's

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