UFH pump running continuously

[Rekusu]

Hi there,

Been in the house for one month and trying to understand the boiler / UFH system.

Viessmann boiler with weather compensation, directly heating the UFH. The house is well insulated with 3G and does not require a lot of heat input, Most of the time, the boiler seems to not be operating (no heat required) but from 06:00 to 22:00 (default on / off times) the UFH circulation pump, which is controlled by the boiler, is running.

Given that Viessemann tell me how much energy I save with WC, with he pump running continuously, that savings seems to be written off.

Is there a way to have the pump working only when it needs to? Viessmann say no, but surely that cannot be the case.

Thanks,

Rex

 

[DeltaT2]

Seems a bit daft Rex!! Sorry, without knowing your system control set-up I'd be unable to comment further.
Why not post up the control system details or link etc?

 

[igotalake]

can viessmann explain to you what the logic is behind the continuous pump operation? i've got a similar problem with a viessmann vitotronic 150 controller which has the pump running all the time even when the boiler water is cold. if i change the reduced room temp to the lowest setting it stops the pump running unnecessarily but then it means the pump stops immediately when the heating cycle is over so the 70 deg water left in the boiler stays in the boiler and ultimately warms up nothing but the boiler shed. i have tried recoding and asking viessmann professionals and others but get no sensible answers.
it seems like a good quality boiler to me but without an explanation that makes sense, i'm struggling to accept that there's any benefit in this pump operation

 

[Rekusu]

No, Viessmann have only given me their 'standard' reason, which in my opinion, does not seems very reasonable.

They say, that the combination of weather compensation, flow and return temps and the 'Normal Room Temp' set on the boiler, gives the electronics all the information that it needs. But to get the correct flow and return temps, the pump has to be running, otherwise, those temps will be static at the time the pump switch off.

What I don't understand is; given all the sophisticated electronics, surely it must be possible to arrange for the pump to overrun by 'X' minutes when there is no call for heat, and then, start the pump every 'X' minutes to 'sample' the water temp to provide that information.

Even my plumber, who is Viessmann expert, does not have answer apart from winding the pump wattage to the lowest setting to conserve electricity costs.

Viessmann also say the the costs benefits of weather comp controlling the way the boiler operates, will more than off-set the cost of the pump running continuously. Seems to me that with the pump not running, I would have even better cost benefits!

Rex

 

[igotalake]

i agree. i doesn't seem that difficult to arrange a regular sampling of heating water or even memorise the last temps recorded and using the outside temperature and some algorithm or other i'm sure the controller could ascertain when it may be sensible to run the pump to re-sample the water temps or indeed fire up the boiler if that's what the customer has programmed.
for me the constant water flow is even more useless as i have wood burners downstairs so they are effectively heating the rads which then tells the boiler control everything is alright anyway. in the right circumstances it sounds like a good enough system but not if you do not have unlimited fuel supplies and therefore wouldn't have the boiler come on when 'it' believes it is necessary. and not if you have alternative sources of heat which are being absorbed by the viessmann and dissipated into the atmosphere via the shed...just so that the boiler knows how warm your house is. must the most expensive feedback loop in domestic home heating.

 

[Rekusu]

When I was talking with the plumber regarding the pump running continuously, he did say that this time of the year, weather compensating is of debatable usefulness. The external temp is neither too hot nor too cold.

He said, and Viessmann have more or less told me the same, that in the winter, when weather comp is set as I want it, it is very much, just leave it to do its own thing and the house will never be cold or hot. Seems to be a question of hitting the correct balance of the heating curve, when it has been found, just leave well alone.

Rex

 

[igotalake]

the reason this problem came to light at my house is that i would be woken in the night with the sound of water running through my rads, that's another downside to the contant pump operation.
i think the outside temp compensation is a fine idea but it's a shame it doesn't achieve its purposes efficiently by having the pump running 24/7. a room stat would surely do the same thing without losses.

i have only had the explanation that 'yes, in extended economy mode the pump will run constantly' as if that helps.