Is there something wrong with our new combi gas boiler and plumbing?

Boilertrouble

We just got an all new gas combi boiler, with new radiators and all new piping maybe our expectations were too high but I thought the point of getting a combi boiler was near instant hot water?

It takes two minutes and twenty seconds to get hot water to the kitchen tap and even then it goes cold quite a lot.

We have a Greenstar I in the loft that hovers around 15mbar pressure there's four radiators upstairs and five downstairs. There are two pipes going downstairs one goes to three radiators that heat up quickly but the other one goes to two which take a long time to heat up and I assume this pipe is also for the hot water in the kitchen.

Should we ask the plumber to have a look or as a lot of people online are saying this is normal?

Thanks

C_Mababejive

Assuming you have your heating on, as soon as you turn on your hot tap, your boiler stops supplying the heating and revs up to max output to heat the water. The water is drawn direct from the cold incoming water service,is slowed so that it picks up more heat as it passes through a heat exchanger. It then flows to your tap. This all takes time. The output at the tap can be measured using a flow measuring device and thermometer. If it matches the spec in the boiler booklet then its doing its job.

societys_child

You're mixing your pipes up.
The heating is a circuit, which carries hot water around all the radiators and back to the boiler to be re-heated (Flow and Return) The first radiator on the flow pipe will normally heat up quicker than the last one on the circuit.

The hot water is entirely separate, it doesn't take water from the heating system. The cold water is heated by the boiler when a hot tap is opened, and has quite a distance to travel from the loft. It shouldn't keep going cold whilst the the tap is running.
They do give "instant" hot water as opposed to switching on an immersion heater and waiting 30 minutes or more for the tank to heat up.
15mbar? Are you sure?

Boilertrouble

Just checked and it's even less imgur.cxm/a/YejnR

Replace x with o

Boilertrouble

Society's child there are two pipes that go down the side of the wall one gets warm when three of the ground floor radiators are on and the other gets warm when the hot tap is on or when the radiators are on.

Why would the water not stay hot? Low water pressure?

Alex1983

That your water pressure anywhere between 1-2 will be fine, Worcester recommends it set at 1.5bar

Alex1983

Could be flow rate, try slowing the flow and leave it a while to see if it stays hot.

daveyjp

Was the boiler sized for your cold water pressure? If the water pressure is too high the boiler may not be powerful enough to heat the volume of water running through it, hence why it runs cold.

Boilertrouble

I beginning to think it might be the flow rate.

Alex1983

What model Worcester is it? The flow rate most do is roughly between 11-13 litres per minute with a 30-45 degree rise. Tell me the model and I'll give you accurate numbers.

Boilertrouble

The stop value is fully open which is the only way I know to fix it.