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Buderus Boiler looking to revamp HELP!

PhilNYer Member Posts: 3
Hey guys,

I have a Buderus boiler and Logomatic control but it seems like the previous owners of the home hired a contractor not familiar with the system to install it

Problem is if we take 2 or 3 showers i get a DHW ERR everytime. I have to keep the boiler in manual mode around 140*. This makes the DHW too hot as well as its not regulating the DHW temp since its always open

I had a Buderus specialist come and they told me i need to install a DHW pump on the system for it to work properly. They also told me they are using old school zoning system that works against the logomatic. hopefully someone here can point me in the right direction. I got a quote for nearly $2,000 for the work and i do not want to pay this. Im a pretty handy mechanic and do most all work on everything i own myself with good results.

Heres what I have:

Boiler - Buderus G215
Logomatic- R2107
Circulator pump- Taco 007 (only 1)
Zone relay- Taco SR501 1 zone switching relay
Zones- (4) controlled by 5 honeywell zone switches (1) DHW (3) heating zones

It seems that the pump runs non stop, and the DHW zone is always open 24/7. it never closes and the pump never shuts off

I have read that there is a 007e which can vary its speed with pressure drops as more or less zones open. I feel like this alone may resolve my issue, I thing the Circulating pump i have now probably cant pump enough water to keep up with DHW when it also haze multiple heating zones open. But on the contrary that still doesn't give the Logomatic the DHW recirc control i think it needs to work correctly

heres some photos showing what im working with.


    HVACNUT Member Posts: 5,736
    Ridiculous. You need a separate circulator for the water heater. 
    The circulator is running constantly because that's what the 2107 wants. But we don't do much constant circulation in the U.S. so it gets wired differently. The SR501 gets constant 120v to terminals 1 and 2. Remove the jumper between 1 and 3. Connect terminal 3 to 63 in the 2107.
    You'll need the well sensor for the water heater and bring it into the 2107 so it knows there's a water heater. 
    The Buderus designers would go bonkers if they saw that. How to make something really efficient, completely inefficient. 
  • BDR529
    BDR529 Member Posts: 280
    Might be a bad zone valve.

    I figure it must have worked at some point.

  • TAG
    TAG Member Posts: 754
    The logmatic should have a sensor running to the indirect tank (also one for the boiler and one for outside)

    The main system pump is activated in heating mode and the water temp of the boiler is adjusted based on outside temp and the curve set in the logmatic. The main system pump is always running.

    When the indirect water tank calls for heat --- the main system pump is turned off and the dedicated pump to the indirect is activated until the indirect tank is satisfied. The water temp of the boiler goes to the max set on the logmatic to quickly heat the tank.

    You need a dedicated pump for the indirect. All of my logmatic systems are set up with the main part of the house always open and running -- controlled by the curve set in the logmatic ... zone valves act as high limits.

    you should get the manual and study how it works. I wonder if they have it set up with a zone valve for the hot water -- using the other controller. Agree with above .... german designers are going bonkers.

    Also -- depending on hot water needs you may have to have a hot tank and use a tempering valve. When I have guests over I have to raise my tank sent point a little to make sure I have enough.

  • PhilNYer
    PhilNYer Member Posts: 3
    edited October 2022
    Awesome information guys, I really could not believe what I was seeing after looking into it. When I purchased the home it was in manual mode and set to 160* pump always running meaning dhw was 160* too. 

    Looks like my first thing will be to install a circulator for the DHW and wire it into the logomatic. I have downloaded and printed both install and user manuals for the logomatic so I can see what terminals control what. 

    I have read the 007e can run and stop based on water pressure is this true? If so it seems like it would be the best unit to run so that it's not wasting power pumping when the valves are closed.

    Also the SR501 zone relay is that necessary with the logomatic? Right now the logomatic circuit 1 seems to be connected directly to the sr501 which powers up the 4 zones and than the thermostats in the bedroom, living room and downstairs open and closed based on a call for heat by them. Zone 4 (dhw) seems to be constantly open when the SR501 lights are on 

    Right now I have the u it set to manual mode and it's lowest temperature (120ish*) which is enough right now to keep the house near 70* when it's 40* outside and also not waste energy keeping dhw hotter than it needs to be. We generally like it around 115*
  • heathead
    heathead Member Posts: 234
    Do you have a Buderus Thermostat, ie a room control. If you do I would set it up with constant circulation to your main zone in the house. The pump will run 24/7 below a certain outdoor temp of say 65 and just vary the water temperature to keep you comfortable. It's a German thing. It helps save fuel because of the lower boiler temp. With the pump running 24/7 make sure you get ecm circulator.
  • PhilNYer
    PhilNYer Member Posts: 3
    No I don't have a room control. House has Honeywell smart thermostat with a phone app. 

    My main goal is using as little oil as possible, curious what is the benefit of the pump running 24/7? I believe the only loop that can circulate while all thermostats are not calling for heat is the DHW circuit that has no pump of its own. Perhaps that is why it's always open.

    My logic tells me the pump should only circulate when there is a call for heat, whether that's from the thermostats in the house or the DHW system calling for heat. If the pumps running when there's no call for heat isn't that both a waste of energy from the pump, and heat loss from all the copper piping running hot water through them? I would think it would be best to keep all the heat in the boiler until it's needed.

    Also is the ECM style you referring to the 007e pump I keep seeing online? 

    One other thing, a side note. The boiler at these 40* days only runs for maybe a minute and than shuts off for 15-20 than repeats that cycle again. I have the temp set to 120* which keeps the house 70 and water plenty hot. Is this a typical duty cycle or is this indicative of something wrong maybe the pump too small or the burner oversized?