Logamatic

James Day_2

Question about a logamatic 2107.  Why would the temperature in the boiler only go up to 150 on a call for domestic hot water. Shouldn't it go up to 180 or so?



Thanks,  James

David Sutton_6

What was the tank temp at the time?

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meplumber

Couple of things.

Are you using the Buderus DHW sensor plugged into the DHW plug?



Are you getting the tap on the logamatic display?

James Day_2

logamatic

I'm using a buderus tank and tank sensor.  Tank was still calling, boiler burner shut down at 150 and restarted at around 130.  i'm pretty familiar with the logamatic, i always thought that on a call for hot water the temp was supposed to shoot up to high limit.

EddieG

Have...

Have you compared the Logomatic boiler temp. reading to the actual temp. of the boiler? How does the Logomatic operating if you put it into manual operation? I was thinking if the boiler temp sensor was not reading properly, it could be shutting the burner off to soon? I think you are correct in saying it should run up to limit for IDWH call. Maybe ohm the sensors out to compare readings.

meplumber

The boiler should go to high limit on call for DHW.

There are two things that will prevent it from going to high limit on call for DHW.

1.  as suggested, bad boiler sensor reading.



2.  it seems that some of the first 2107 controls that came across the pond had an adjustable dhw burn number built in.  something like dhw tank setpoint + 30 deg or something like that.  I saw a few when we first got the 2107's but hadn't seen one since.



Also, did the manual adjustment knob get bumped off of aut?  I am sure that you checked that James, just pointing out the obvious.



If it isn't one of those things, then you have gone beyond my experience.



Good Luck.

bill nye_3

I thought

I thought the whole concept was about saving energy? Why would it go to high limit if it was close to satisfying the demand for DHW ?

 I was at one time familiar with the Viessmann trimatics and the idea was to conserve energy and try to purge the heat from a demand cycle into the DHW or into the heating circuit. The idea was not to go to high limit. Every three degrees F you can lower the high temp you could save 1 % of your anual energy cost.

The fuzzy logic thing, and the DHW tank talking to the 2107, isn't it supposed to figure out if you are gaining on the target temp. or falling behind ?

Just my 2 cents, I really don't have a clue.

k_2

re

A weakness I perceive in the logamatic is that it does not seem to think much about DHW.



Mine will overshoot to 205 on a call hot DHW. I deliberately set the dial down to 170 so that it no longer does that. It still does its outdoor reset properly



[edit] I am betting your knob is at 150

James Day_2

logamatic

Dial is set to Automatic.   Hot water is set to 120.  I did notice if I raise the temp of the hot water to say 140 the unit will run up to 180.  If it iset to 120 it only shoots up to 150 to 155. 

Jean-David Beyer

Thinking about domestic hot water.

This sounds like it is thinking very hard about the water it supplies to the indirect. If it keeps the boiler water 30F hotter than the set point, it will probably recover pretty fast, and it makes an effort to stay in the condensing range if it can.

Big Ed_4

installer program

.. On a high demand it will rise up to the programed max boiler temp in the installer side ...What is that set to ? On a long slight drop of temp it would use the lower heating temp to build it up