Weather compensation - pump runs all the time?

[Rory]

Just had a WB combi installed and went for their Wave controller, a feature of which is weather compensation.

Enabled weather compensation during the day yesterday when the temp setting was 14C. Actual inside temp was 19C, and outside was 11C.

I understand (well, perhaps that's over-stating it a bit) that it works by monitoring the water flow temp vs outside temp, but was a bit bemused that the combi's pump runs all the time, with the boiler firing so infrequently that it's basically circulating cold water.

Is that how it's supposed to work - will the pump run 24/7 with weather comp enabled? Seems a bit of a waste of 'leccy.

 

[Ermintrude]

No it's not set up correctly

 

[Jay Jay]

Just had a WB combi installed and went for their Wave controller, a feature of which is weather compensation.

Enabled weather compensation during the day yesterday when the temp setting was 14C. Actual inside temp was 19C, and outside was 11C.

I understand (well, perhaps that's over-stating it a bit) that it works by monitoring the water flow temp vs outside temp, but was a bit bemused that the combi's pump runs all the time, with the boiler firing so infrequently that it's basically circulating cold water.

Is that how it's supposed to work - will the pump run 24/7 with weather comp enabled? Seems a bit of a waste of 'leccy.

Hi make sure set up of control is correct,not being wb fan, but it could be faulty flow switch on boiler causing pump over run,or software fail causing pump over run,it depends on how wb flow sensor works,I might be off target but that's what can happen on certain brands of boilers,also check set back temps on control but like last post prop needs setting up
Let us know how u get on

 

[Rory]

Thanks - you both may well be correct, but there isn't an awful lot of options in the set-up.

There also isn't much on the Internet about weather comp, and some forum discussions end up in fierce arguments! They do talk about things like "constant circulation" which appears to be what's happening in my case. I can easily visualise how it would work well with underfloor heating, but not so with radiators.

Maybe the system learns over time and I just need to leave it alone. In the meantime I've email WB for their comments.

 

[Rory]

Well, response from WB is exactly as I'd garnered from various web sources - "during weather compensation the pump will run all the time so that the boiler can monitor the temperature coming back from the rooms and maintain the calculated flow rate."

Perhaps I'm missing something but when the current programmed room temp is way below the actual temp, it's not cold outside and the outside temp is steady, it seems a bit ridiculous to be circulating cold water. I wonder how long the pump will last? 🙂

 

[doitmyself]

Has an external temperature sensor been installed?

If it hasn't turn weather compensation off.

 

[Rory]

Has an external temperature sensor been installed?

No - but...the Wave unit is connected to the internet and it looks up the external temperature from a local weather station. Seems accurate enough - it knew it was 11C outside on Saturday when I was trying it.

 

[lame plumber]

probably find the internet and real life dont agree all the time, most inefficient way of monitoring outside temp you can possibly think of, swap it for a sensor on the wall of your house, then things may start to work better.

 

[Rory]

probably find the internet and real life dont agree all the time, most inefficient way of monitoring outside temp you can possibly think of, swap it for a sensor on the wall of your house, then things may start to work better.

Checking your local weather station My Local Weather - Your local UK weather page is probably as good as any other way to be honest. I've got a wireless thermometer using an outside sensor on my desk and that over-reads by 2C compared to an outside thermometer.


Anyway, that doesn't appear to matter in the way the system works - WB say the pump will run all the time.

 

[Ermintrude]

Checking your local weather station My Local Weather - Your local UK weather page is probably as good as any other way to be honest. I've got a wireless thermometer using an outside sensor on my desk and that over-reads by 2C compared to an outside thermometer.


Anyway, that doesn't appear to matter in the way the system works - WB say the pump will run all the time.

What? How the hell is that compliant? Yes it's an A rated boiler it's hot weather comp and yes the small energy savings we make are almost instantly eaten by the pump running 24/7

 

[Rory]

..the small energy savings we make are almost instantly eaten by the pump running 24/7

There is a mode where the pump will turn off overnight, but oddly, not at other times when it would seem not to be required.

You've hit on the key question though: Would the gas saving by using weather comp be wiped out by the extra electricity cost (and maybe replacing pump if it wears out 🙂 ).

I have no idea of the answer to that. Viessmann, who seem to be regarded as something of a reference point in these matters, talk about a 20% saving.

 

[solutions]

There is a mode where the pump will turn off overnight, but oddly, not at other times when it would seem not to be required.

You've hit on the key question though: Would the gas saving by using weather comp be wiped out by the extra electricity cost (and maybe replacing pump if it wears out 🙂 ).

I have no idea of the answer to that. Viessmann, who seem to be regarded as something of a reference point in these matters, talk about a 20% saving.

That makes no sense to me there is no need what so ever for the pump to run continuously in order to take advantage of weather compensation as the boiler should only have to moniyor the return temperature when the room thermostat says there is a heating demand. At which point as I understand it it will set its modulation point based on the external temperature the intended room temperature and the returning temperature from the circuit. Surely the minute the room stat is at temp the boiler ceases to give a $hit what any temperatures are.

 

[Rory]

That makes no sense to me there is no need what so ever for the pump to run continuously in order to take advantage of weather compensation as the boiler should only have to moniyor the return temperature when the room thermostat says there is a heating demand.

It doesn't make sense to me either - I can only guess that the idea is that the building doesn't get too cold so when there is a call for heat it recovers fairly quickly. The way it works makes sense with underfloor heating where the response time would be slow, but not with radiators.

 

[solutions]

It doesn't make sense to me either - I can only guess that the idea is that the building doesn't get too cold so when there is a call for heat it recovers fairly quickly. The way it works makes sense with underfloor heating where the response time would be slow, but not with radiators.

Is the burner actually lit during the pumps running? It could be that its actually still circulating water through the system as long as it is still warmer than the room temperature. I would still suspect it to either not be set up appropriately or actually have sone kind of fault. The problem however is how on earth are you meant ascertain if its operating correctly. I am all for this kind of sophistication but giving the boiler tge ability to decide for itself what it needs to be doing is going to make diagnosis of sofware or component faults almost impossible without car style idb diagnostic data connections.

 

[doitmyself]

Weather compensation with constant circulation is standard practice in Europe, particularly Germany. It is also becoming popular in the USA.

 

[Rory]

Is the burner actually lit during the pumps running? It could be that its actually still circulating water through the system as long as it is still warmer than the room temperature.

In the time I tested it - a few hours on Saturday afternoon - it fires the boiler very occasionally. Whether that's as a result of some clever calculation it's doing, or it's merely to maintain the minumum flow temp (which I think is 20C) I have no idea.

 

[Rory]

Weather compensation with constant circulation is standard practice in Europe, particularly Germany. It is also becoming popular in the USA.

That's my understanding too. After some heavty duty Googling. I've found that the WB Wave controller, while new in the UK, has been sold in Europe for some time.

As I mentioned earlier, the way it works (constant circulation) makes sense with underfloor heating - maybe that's more common elsewhere. It does have a setting to choose your type of heating though - have that set as radiators.

 

[Ermintrude]

There is a mode where the pump will turn off overnight, but oddly, not at other times when it would seem not to be required.

You've hit on the key question though: Would the gas saving by using weather comp be wiped out by the extra electricity cost (and maybe replacing pump if it wears out 🙂 ).

I have no idea of the answer to that. Viessmann, who seem to be regarded as something of a reference point in these matters, talk about a 20% saving.

Really based on what?

 

[Gray0689]

Weather comp in domestic is no saving when you factor in cost of installing and cost to run

 

[Silent Dancer]

Sounds like it's working how it should do. With an outside temp of 11℃ and indoor set of point of 19℃ it has calculated that you only need a low flow temp to maintain the house temperature so the pump will run and the burner will fire only occasionally to top up the heat but the pump continues to circulate. Note that if you switch off the weather comp the control is load compensated so it continue to perform similar calculations using the indoor temperature.