Underfloor heating question (specifically Wunda)
Discussion
As winter is approaching I'm looking at my UFH system and making sure I've got it setup correctly etc as it was installed in Spring so we've never really used it.
One of the many setting in the app seems to offer the ability to delay the pump on or off time from 0 up to 10 mins. Does anyone know why you'd ever want to do this? Surely as soon as you call for heat or the thermostat hits the temp needed for the heating to come on, why on earth would you want a delay to occur?
Also, the switching differential can be set between 0.2 degrees up to 2 degrees. Am I right in assuming this is saying that this is indicating you could have the heating start 0.2 degrees before it hits your set temperature (up to 2 degrees if you really wanted). I sort of understand this one, but the delay question above baffles me.
Screengrab below of my app showing these options
One of the many setting in the app seems to offer the ability to delay the pump on or off time from 0 up to 10 mins. Does anyone know why you'd ever want to do this? Surely as soon as you call for heat or the thermostat hits the temp needed for the heating to come on, why on earth would you want a delay to occur?
Also, the switching differential can be set between 0.2 degrees up to 2 degrees. Am I right in assuming this is saying that this is indicating you could have the heating start 0.2 degrees before it hits your set temperature (up to 2 degrees if you really wanted). I sort of understand this one, but the delay question above baffles me.
Screengrab below of my app showing these options
Pump delay on/off is so that you can keep the warm water circulating after the boiler stops firing (or the room stat turns off the UFH) so you can get the heat out of the water and into the room - and also if you have a boiler heat exchanger with a high thermal mass (old boilers) that might otherwise "waste" some heat.
Pump on delay is similarly about getting the system up to temperature (not the room, the system/water) before you get it pumping round under the floor.
Pump on delay is similarly about getting the system up to temperature (not the room, the system/water) before you get it pumping round under the floor.
Heroin chic said:
Pump delay on/off is so that you can keep the warm water circulating after the boiler stops firing (or the room stat turns off the UFH) so you can get the heat out of the water and into the room - and also if you have a boiler heat exchanger with a high thermal mass (old boilers) that might otherwise "waste" some heat.
Pump on delay is similarly about getting the system up to temperature (not the room, the system/water) before you get it pumping round under the floor.
Ok that makes a bit more sense. I think originally the setting was 2 min delay for pump on but I changed it as it made no sense to me at the time. I should probably put it back to what it was set to then I imagine.....? Pump on delay is similarly about getting the system up to temperature (not the room, the system/water) before you get it pumping round under the floor.
Up to you really, as you probably have a relatively modern system then no delay at all is probably fine - my ancient oil boiler takes about 20 minutes for the whole system to get up to temperature I'd have a delay on mine both pump on and pump off. It's not going to make a massive difference - see how it goes.
Heroin chic said:
Up to you really, as you probably have a relatively modern system then no delay at all is probably fine - my ancient oil boiler takes about 20 minutes for the whole system to get up to temperature I'd have a delay on mine both pump on and pump off. It's not going to make a massive difference - see how it goes.
Ok thank you. My system is nearly brand new, although the boiler is old, not sure how old, but certainly looks like it's been here a while. Not sure as we didn't go with the Wunda controls but I suspect the switching differential is the difference between the set room temperature and when it switches back on to heat. For example if you set the room to 20c and the differential to 1.0c then when it's hit 20c temperature and turns off, it won't come back on until the thermostat drops to 19c, but if you set it to 0.2c then it would come back on as soon as the room drops to 19.8c. If you set it too small then it will keep the temperature more constant but at the expense of the boiler switching on and off more often.
CharlesElliott said:
Worth experimenting but I think 1 degree will be far too wide for wet UFH where the whole floor slab is the heating medium. I expect it will overshoot significantly.
This is retrofit UFH using high density polystyrene tiles so there's very little thermal mass unlike UFH buried in the slab on a new build.LocoBlade said:
CharlesElliott said:
Worth experimenting but I think 1 degree will be far too wide for wet UFH where the whole floor slab is the heating medium. I expect it will overshoot significantly.
This is retrofit UFH using high density polystyrene tiles so there's very little thermal mass unlike UFH buried in the slab on a new build.LocoBlade said:
Not sure as we didn't go with the Wunda controls but I suspect the switching differential is the difference between the set room temperature and when it switches back on to heat. For example if you set the room to 20c and the differential to 1.0c then when it's hit 20c temperature and turns off, it won't come back on until the thermostat drops to 19c, but if you set it to 0.2c then it would come back on as soon as the room drops to 19.8c. If you set it too small then it will keep the temperature more constant but at the expense of the boiler switching on and off more often.
Cheers Chris, exactly as I’ve now understood it to be as well so good to have it confirmed. I’ve decided to drop it to 0.2 rather than 1 (might change that in depth of winter) as at the moment I’m just trying to get the living room to be a bit warmer when I come down in the morning. Once it’s colder and I’ve got all zones running it might make sense to go back to 1.
Appreciate this is an old thread sorry, but think it’s worth mentioning what the delay is for.
The actuators seem to use some sort of solid wax to keep the valves compressed, when activated, they heat up, the wax melts and valve opens. This process takes a couple of minutes, and even longer to turn off and cool back down to close the valve.
I’m using a third party Heatmiser controller where I can’t add pump or boiler delay, so the boiler is locking out whilst it waits for the valves to open and the pump and mixing valve are under a lot of stress at the same time which seems to be damaging them.
After a lot of googling, I found Wunda do actually sell a pressure/valve bypass to address the issue with third party controllers that don’t have pump delay. I’m fairly annoyed their team didn’t make me aware though, nor is it in any of their documentation.
The actuators seem to use some sort of solid wax to keep the valves compressed, when activated, they heat up, the wax melts and valve opens. This process takes a couple of minutes, and even longer to turn off and cool back down to close the valve.
I’m using a third party Heatmiser controller where I can’t add pump or boiler delay, so the boiler is locking out whilst it waits for the valves to open and the pump and mixing valve are under a lot of stress at the same time which seems to be damaging them.
After a lot of googling, I found Wunda do actually sell a pressure/valve bypass to address the issue with third party controllers that don’t have pump delay. I’m fairly annoyed their team didn’t make me aware though, nor is it in any of their documentation.
Having had my system for over 4 years now, I'm happy with it. Got used to its little quirks, does the job very well in terms of timings etc
Only issue is that this poorly insulated house means the whole system struggles to hold temp when outside is below freezing. But not sure that's an UFH fault, more a fault with the insulation situation.
Only issue is that this poorly insulated house means the whole system struggles to hold temp when outside is below freezing. But not sure that's an UFH fault, more a fault with the insulation situation.
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