My Vitodens 100 was just installed and it will not shut off regardless of thermostat setting

bhilton

Hello all,

I am new to this boiler stuff, thanks for taking the time to read this and share your thoughts.

I have a brand new Vitodens 100 and DHW kit and I'm just curious how you guys would set it up with in floor heat closed loop?

1) Does my in floor circ pump have to be on 24/7? I find that a waste of energy, but maybe I'm wrong. Right now it's on constantly. Groundfos 3 setting pump.

2) Right now the boiler seems to be firing constantly and the circ pump runs constantly, the thermostat is set to room temperature 20C and it shows actual room temp at 23.5C and the slab sensor temp is showing 24.0C! Yet everything keeps on humming and heat is increasing in slab. I tried turning down the thermostat as low as it would go and it eventually said OFF, yet the boiler and circ pump continue... my installer is telling me to give it more time and that the boiler will run frequently to keep hot water ready for the DHW. Is this required? I was under the impression this was all on-demand, it will boil water, when something calls for it?

Thank you,
Bill

CMadatMe

Minimum modulation rate of the Vitodens 100 is 37,000 Btu/hr. What's the heat loss of the home? What's the radiant load? What is the boiler set to as far as the heating curve? In other words, what is the dial on the right set to? Is the outdoor sensor hooked up? Has the comfort function been switch on? The comfort function will make sure the heat exchanger in the CombiPlus maintains temperature to provide hot water quickly. Is the boiler piped direct or did the installer use the Low Loss Header? Pictures please.

Might be a good idea to look into installing the Viessmann Como-OT for that radiant instead of having a typical thermostat.

Vitodens 100 is not set up to run a pump constant circulation. Be interested in knowing how its wired.

http://www.kwe-tech.com/index.php?section=Products&subs=Controls&page=Como-OT.html

Robert O'Brien

The boiler will only run for heat on a demand at the RT terminals. Most use a switching relay to turn on the secondary pump(s) and provide the RT demand through the cold terminals in the switching relay.

Jamie Hall

Check for a short circuit...

bhilton

I will get a picture as soon as I can, I'm not there until tonight 8 hrs from now.

The outdoor sensor was not hooked up.

I will ask about the comfort function, I believe yes, it has been turned on.

Boiler is piped direct through the roof above, very short run.

Robert O'Brien

bhilton said:

I will get a picture as soon as I can, I'm not there until tonight 8 hrs from now.

The outdoor sensor was not hooked up.

I will ask about the comfort function, I believe yes, it has been turned on.

Boiler is piped direct through the roof above, very short run.

No ODR? Why?

CMadatMe

No sensor,, smh..... More then likely installer set it at the DOT so it's running to a setpoint of 140 degrees.. Is the boiler/combi plus piped like page 23,24 or 25 in this manual?

http://www.viessmann.ca/content/dam/vi-brands/CA/pdfs/wall-mount/combiplus_tdm.pdf

bhilton

I believe he did set something to hold it at 140 degrees.

I had my painter on site send these pictures over just now.

The installer is back tomorrow to check the Taco relay cause it's clearly not shutting the circ pump off.

And it seems like the boiler is constantly burning on the lowest bar indicator, every time i look at it. We are thinking it's the circ pump returning cool water cause it's always on, so the comfort setting for the Combi is constantly fighting to keep up the temp, your thoughts?

CMadatMe

Need to see a pic from the front but initial thoughts. Is that a cold water feed entering into that mixing valve? Don't see the boiler piped pri/sec but could be mistaken. Hard to tell from the side. Looks like the control setting is on the DOT so the boiler is making a setpoint of 140 and not utilizing the greatest tool to efficiency. Outdoor Reset..

Heating System Return water never touches the CombiPlus HX so you can scrap the idea that the return is cooling the HX.

Robert O'Brien

The 501 is providing a heat demand at the time the pic was taken

bhilton

That 501 has had the same lights on it and they have never changed since the moment we powered the system up.

Sounds like a wiring issue?

bhilton

Chris said:

Need to see a pic from the front but initial thoughts. Is that a cold water feed entering into that mixing valve? Don't see the boiler piped pri/sec but could be mistaken. Hard to tell from the side. Looks like the control setting is on the DOT so the boiler is making a setpoint of 140 and not utilizing the greatest tool to efficiency. Outdoor Reset..

Heating System Return water never touches the CombiPlus HX so you can scrap the idea that the return is cooling the HX.

No, it's a second loop running over to my LifeBreath CAF http://www.lifebreath.com/products/clean-air-furnace which is not even turned on yet, and he has shut off valves on the supply and return, both turned off right now.

bhilton

Chris what do you mean "greatest tool to efficiency. Outdoor reset" ? How does the outdoor temp affect things when everything is governed by the thermostat that I set myself based on what I feel inside the house?

CMadatMe

What's more efficient? Putting your gas peddle to the floor in between red lights or getting on the highway and putting the car in cruise control? Outdoor reset is cruise control..

You don't need the same water temperature for the radiant when it's 32F as you do when it's 0F or every where above or in between.

Thermostat is no more then a switch, it doesn't care about what the boiler is making or the water temp through the radiant. If it's a 32 degree day and I only need 100 degree water for the radiant why would I make 140?

That's a 40 degree water difference.. 40/3 = 13.333% of system efficiency you throw out the door.. Not saying you only need 100 degree water at zero, but it's probably close. Most slabs don't need more the 110 degree water and if they do it's because not enough tubing in the floor or lack of insulation under and perimeter.

Jamie Hall

I'll say it again -- before you start getting fancy, check for short circuits in the control wiring. They can be rather stealthy.

bhilton

Jamie's on to something!

So far we've found if we unhook the thermostat, the red light on the Taco 501 stays on... could the boiler/Combi be telling it to be on all the time? could the 501 be dead?

Here are pictures from a better angle.

CMadatMe

Red means stop - Green means Go.. Like a stoplight. If it's red then RT on the boiler should be closed and so boiler should shut off. When the light is Red is that radiant pump running? Boiler isn't piped primary secondary so you are really pumping via the pump inside the CombiPlus as well as the Grundfos pump at the radiant.

bhilton

The Taco 501 relay manual says: "LED diagnostic lights will help find a component that is not working properly. The green LED should always be on, indicating that power is connected and the solid-state fuse is good. When there is a call for heat, the red LED will come on indicating power to the zone circulator. This indicates the thermostat is working correctly. If the red LED does not come on, then check the thermostat and thermostat wiring for errors."

We got it working! there was an improper wire from boiler to the Taco relay.

My question now is, would most people do a primary & secondary pump setup? why?

Thanks for all your help everybody!

Bill

Robert O'Brien

Chris said:

Red means stop - Green means Go.. Like a stoplight. If it's red then RT on the boiler should be closed and so boiler should shut off. When the light is Red is that radiant pump running? Boiler isn't piped primary secondary so you are really pumping via the pump inside the CombiPlus as well as the Grundfos pump at the radiant.

The CombiPlus doesn't provide hydraulic separation?

GW

whoever wired it needs to do a re-do. Is your installer the one who wired the system? or, did someone else wire it?

yes, the green light is power and the red light means the thermostat wants heat and is telling to boiler to go.

if you're overheating why don't you simply turn your heat knob down? Then figure out who wired it wrong.

CMadatMe

Robert O'Brien said:

Chris said:

Red means stop - Green means Go.. Like a stoplight. If it's red then RT on the boiler should be closed and so boiler should shut off. When the light is Red is that radiant pump running? Boiler isn't piped primary secondary so you are really pumping via the pump inside the CombiPlus as well as the Grundfos pump at the radiant.

The CombiPlus doesn't provide hydraulic separation?

No it does not. You have about 5' of remaining head left on the pump for the system side. Can be piped direct as long as about 5gpm gets the job done.