Anyone fitted Valliant with 430 weather compensator

[Plucky]

Got a customer who wants one fitted and havent done one before. Had a quick look on the net and looks fairly simple all bar one thing.

Am I correct in thinking that the control panel which plugs on the front of the boiler has the room stat built into it? If this is the case what good is that if, say for example, the boiler is in the loft or another unsuitable part of the house.

Does the control panel get fitted remotely to the boiler, can you use auxillary stat or what?

many thanks

 

[doitmyself]

Click this link: 430 Installation and Operating Instructions

The controller can be installed in either the boiler or on the wall.

If it is in the boiler, it does not act as a room stat - for obvious reasons. Heating is controlled by the outside temperature sensor, so getting the heating curve right is essential.

If the controller is wall mounted it will display the temperature in the room as well as taking the temperature into account when controlling the boiler output.

 

[Plucky]

Click this link: 430 Installation and Operating Instructions

The controller can be installed in either the boiler or on the wall.

If it is in the boiler, it does not act as a room stat - for obvious reasons. Heating is controlled by the outside temperature sensor, so getting the heating curve right is essential.

If the controller is wall mounted it will display the temperature in the room as well as taking the temperature into account when controlling the boiler output.

How can the heating inside be controlled by the outside sensor?

The ouside sensor has no way of monitoring the temp inside the house?

 

[doitmyself]

How can the heating inside be controlled by the outside sensor? The outside sensor has no way of monitoring the temp inside the house?

There is no need for the outside sensor to know the internal temperature, it's done via the heating curve. This determines the relationship between outside, inside and flow temperatures. The attached chart shows the heating curves for the VRC430; the default is 1.5. This means that to achieve a room temperature of 20°C the boiler flow temperature will be 57°C when the outside temperature is 0°C. If it is found that the room temperature is too low a higher number will be selected. It is really up to the installer to do this. The room temperature set on the control unit determines the origin of the chart.

There is more info in the VRC430 Operating Instructions

 

[Cds]

doitmyself is correct about the outside temperature controlling the boiler flow temperature.

Looking at the instructions it is possible to fit the VR81 remote control device when the VRC430 is plugged into the boiler front. This allows for setting of operating mode and target room temperature.

 

[Plucky]

doitmyself is correct about the outside temperature controlling the boiler flow temperature.

Looking at the instructions it is possible to fit the VR81 remote control device when the VRC430 is plugged into the boiler front. This allows for setting of operating mode and target room temperature.

I understand that the outside sensor will determine flow temp and working rate of the boiler. But there must be a room stat to detect temperature inside the house to tell boiler that inside temp has been satisifed and shut off the boiler?

 

[doitmyself]

I understand that the outside sensor will determine flow temp and working rate of the boiler. But there must be a room stat to detect temperature inside the house to tell boiler that inside temp has been satisfied and shut off the boiler?

Why? You would need a thermometer to measure the room temperature while the correct curve is being determined, but once that is done, the system takes care of itself.

Let's assume that the radiators need to be run at a temperature of 60C to maintain the required room temperature of 20C. If you have a room stat, it will turn the boiler on and heats the water to, say 75C, and keeps the water flowing at that temperature until the house temperature has risen to 20C. The boiler then turns off and the water in the boiler cools down. When the room temperature has dropped, say 2C, the boiler starts up again and the cycle starts again. The average temperature of the water will be below 75C, approx 60C.

If, instead of turning the boiler on and off, the water is maintained at a constant temperature of 60C, the house will also maintain the desired temperature of 20C.

By measuring both flow and return temperatures, the boiler can tell how close the room temperature is to the desired temperature and adjust the output accordingly. If the boiler has modulated as low as it can and finds the return temperature is still rising, it will go into on/off mode. But, provided the boiler is properly sized, this should only happen when the outside temperature is 10C or higher.

Going back to your customer for a moment, is he asking you just to install the controller or is it part of a boiler swap or or is it a complete package, i.e including radiators?

If it's a swap or just a new controller, you may find that the existing radiators are undersized. This is because radiators running with a 20C differential give of about 15% less heat than those running with an 11C differential.

If you are installing new radiators you just up-size them by 20%.

 

[Plucky]

It is just a straight boiler swap so using existing rads. I am starting to understand the idea behind the compensator.

If you were not running the system with a room stat would the boiler not just be on the whole time when heating is on?

 

[billybongo]

Plucky i had a similar debate on this forum ragarding my own 430 and personally i am not convinced its as good as ye olde room stats flicking on and off when satisfied .
My house is ok when its cold outside but when its mild it quite often seems to warm which i guess is wasteing fuel , just my two peneth ... mark

 

[doitmyself]

If you were not running the system with a room stat would the boiler not just be on the whole time when heating is on?

That is possible, but the amount of gas used over the day should be less than if running in on/off mode.

It also depends on how low the boiler can modulate. For example, if you need 16kW to maintain 21C with an outside temperature of -1C, you will only need 8kW when the outside temperature is 10C. If your boiler can only modulate down to 8kW, it will go into on off mode when the temperature is above 10C.

If it's just a boiler swap, have you determined if the existing rads will still provide sufficient heat when running with a 20C differential?

Have you sized the new boiler taking into account changes such as loft and cavity insulation etc.