Buderus 2107 control questions

Steeve

I just finished talking with my heating contractor and I would like confirmation of his recommendations.  I am technically aware homeowner (actually a scientist, which is probably worse than an engineer!).



My Logamatic R2107 controls a Logano GA124 boiler in a 100 year old New England farmhouse with cast iron radiators converted from steam.  None of the radiators in the house have thermostatic valves.  The system uses outdoor reset, constant circulation (RMSETBACK mode), and a BFU room sensor in the first floor living room (the BFU is as far as possible from the radiators). REFTEMP is 167 (default), OFFSET is zero, and ROOMCOMP is set at 18.  The main house is heated reasonably well.  But there’s a bedroom over the garage that is insufficiently heated during the coldest weather conditions. This room is heated by a separate zone controlled by a standard thermostat that turns its circulator on or off (no mixing valves).  So the problem is that the circulating water temperature determined by the R2107 for the main zone is insufficient to keep the room over the garage warm enough.  What is the best solution?



1)    Set the ROOMCOMP down to 6 (from 18)

2)    Increase the radiator capacity in the room over the garage (e.g., put in a larger cast iron radiator, or add some fin tube baseboard radiators)

3)    Change system to SETBACK mode and get rid of the BFU room sensor.  Use standard on/off thermostats to control the main house and the room over the garage.

4)    Move the BFU to the room over the garage, since it’s the room that requires the highest system water temperatures. Then use an on/off thermostat to control the circulator for the main house.



I’m trying option 1 right now as it’s the easiest to test.  But might this lead to over-heating in the other rooms of the main house?



My heating guy recommended option 3.  I think I also like option 3 but would I be losing system efficiency (i.e., $$$) by going from constant circulation to intermittent circulation?



Thanks for any help or ideas!

Charlie from wmass

I say # 2

why not use the system as it is meant to work. too bad you lost the steam though. Steam gives 240 btu's per square foot of radiator surface. With set back and hot water you could be as low as 130 or less btus per square foot. why not add a trv to that room and have the whole system on constant circ?

Charlie from wmass

are you using a Delta P

circulator? If you did and added trvs it would be even nicer.

Mellow_2

hard to balance

the room over the garage sounds like it will change temp at a diff. rate than the rest of the house. To get the control you want you might need to change to t'stats. If you turn up the room t'stat over the garage as high as it will go what happens?  Will the room over heat? Will it stay the same as the house? or will it still be cooler? if it is cool you will need t'stats to control or warm that room (or add a rad).......the room sensor might work in the room but because the room is much smaller than the house I think the house will suffer.....

BUT if the room stays warm I would make the whole house one big zone. I would stop using the t'stat as a control leave it all the way up.....if it is too hot you can add a nonelectric to the rad. this will slow the water flow through the rad. not stop it. this allows the rad. to stay warm......this room still might not be perfect but this would be the most eff way to heat.

Big Ed_4

Heat Loss

First run a heat loss calculation for the room over the garage to find out what you need in output of radiation ... You can increase the baseboard . But would some of it be blocked by furniture ? You may what to look into a panel radiator instead .. For the smaller wall space taken they can crank out a lot of btus .Buderus 22's are a nice radiator , easy to install and you can flip them if need be for installing the feeds ... I would leave the thermostat and use it as a limit. This way you can go with a larger radiator ... I like to install them under the window were furniture most like would not be place ... The convection heat of the radiator creates a nice heat curtain , the radiant panel also will warm you across the room ... I like the looks of sizing the width just within the window molding and just below the window sill ...