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That's what I understand, that as a fixed appliance a heat pump does not have to have an RCD. Does this change if its a TT supply? Design of the circuit I leave to the sparkies!

Hi. I'm looking for some guidance on RCD/ RCBO selection for heat pumps. The heat pump manual states: The RCDs follow the standards and regulations but may be not applicable for heat pumps that have high frequency ampere peaks caused by the inverter technology. Therefore, RCDs need to be...

There is no benefit in significantly oversizing a boiler. It will increase the minimum output of the boiler and you can end up with a boiler that cannot modulate low enough in mild weather.

The water flow rate is irrelevant to the size of the coil. You can have an unvented (mains pressure) cylinder, or a vented (tank fed) cylinder with a large coil hat will heat quickly. Agreed, if your pressure/ flow rate is poor then a combi or mains fed cylinder would not be great.

The new Ecotec plus (system) has a stainless steel heat exchanger, as did the previous one. The open vent version has an aluminium heat exchanger.

Is there any reason it must be a heat only boiler rather than a system boiler? That would open up more options. If you plan to pressurise (seal) an open vent (heat only) boiler you might as well have a system boiler. If you use controls to make the system HW priority you don't have to add the...

The fundamental with a heat pump is the flow rate. If too many zones are closed, or the system is restrictive the flow rate will drop. Slightly too low will lower the COP (efficiency), if its too low the heat pump wont run at all. This can be mitigated with a header or buffer, with some loss of...

A large output Combi boiler is often massively oversized for the heat load of a house. Particularly if it is of modern construction. The ideal place for a boiler isn't always where the hot water is used. A cylinder can be placed to minimise hot water wastage. A boiler needs to go where the...

One of the problems with big output combi boilers is the minimum output in heating mode. This will often be above the minimum required to heat the building so causes cycling (switching on and off in short bursts) and loss of efficiency. It would be worth getting a proper heat loss survey done to...

Have you got vaillant controls? (The bit you set your timings on.) If you haven't then altering the temperature on the boiler will have no effect. The hot water temperature will be controlled by a thermostat on the hot water cylinder. If you don't have a full Vaillant system the boiler doesn't...

Sounds like the diverter valve or diaphragm needs changing.

It is in this case as Vaillant boilers do not have Opentherm. There is an ebus to opentherm adapter but it is not supported in the UK and will invalidate the boilers warranty. @fezster how are you switching the boiler off when you're not heating the radiators? Do you have switched live into 4...

The biggest difference between Ebus controls and Nest is that Ebus controls the flow temperature and boiler modulation (power output) Nest is a dumb on off control with a fancy interface. Your controls may just need commissioning properly.

You have a passing fill valve. You can pull the clip out of the right one and remove the non return valve (brass bit attached to braided hose). Make sure the fill taps are closed first. If there's a drip the valve needs to be replaced. Sometimes the handles are loose and don't turn the valve...

Try twisting your knob. In the picture its set on minimum.

Two things to note. Use the P0 purge program if you have drained any water. This will pulse the pump on and off without firing the boiler to help clear air locks. If you overheat this boiler it will go into protection mode and will not fire for 30 mins. This cannot be reset.

Yes. The 350 receiver in the front panel is directly connected to the PCB. Removing the 24 volt link will not disconnect the receiver.

The only way to stop the receiver for the 350f affecting the boiler is to disconnect the wiring (if external) or remove it from the front of the boiler if it's fitted there. You cannot have two controls connected to the boiler at the same time. Hopefully your installer left the blanking plate...

Cheers chaps, what I was expecting. I'll stick with standard sockets.

I'm thinking of changing some of my sockets for ones that include USB sockets. Are there any available that allow the USB outlets to be switched off when not in use?