New boiler fitted - unhappy with hot water setup.

[fatplumber]

Thanks again.

Last night I turned the circulator speed down from 111 to 11. I reckon you can circulate the water too fast for useful heat transfer at both ends.

Yes you are correct. The example I always give is that of a kettle with the lid off, placed under a cold tap and switched on.

If the cold tap is running too fast, then kettle will never heat up/boil the water properly.

Not in central heating though as it is a closed system.

 

[Agile]

I dont agree with that suggestion.

The reason that a central heating system is designed to have a differential between the flow and return is so that the boiler can operate in accordance with its design criteria.

On non condensing boilers that has always been 11°. However, on condensing boilers its far more critical as the return should be around 50°C for efficient operation which then limits the flow to 70° C. That is 10°C lower than was the case previously, hence the suggestion that rads needed to be oversized. Thats no longer true now as rads are now rated on the basis of a 70° C flow temperature but it can be relevant for old systems. In practice improvements in reducing heat loss has more than compensated for that.

Tony

 

[D_Hailsham]

I understand your feelings about zoning but there are the Building regulations which we are expected to follow

It's what the regulations say not what you think they say which is important. It's all set out in the Domestic Heating Compliance Guide, which is the next official document down from the Part L Approved Document.

According to the DHCG, houses under 150m² floor area need two zones with separate temperature control, one being the living area. Houses over 150m² need two zones with separate time and temperature control.

It also says that temperature control can be achieved either by separate thermostats in each zone or by having a thermostat in the main zone and TRVs on the radiators in the second zone. So a house which is under 150m² which has a thermostat downstairs and TRVs on all the rads in the bedrooms meets the requirements.

As we do not know the floor area of the OP.s house we can't say if he need separate timing control on both heating zones.

 

[RigidRaider]

We have TRVs on all rads except one on each floor.

What would be a 150m2 house? Something like a 3 bed semi?

 

[Agile]

Its a house where the total floor area comes to more than 150m² !

A traditional 1930s three bed semi is usually under that area but a large semi could be.

Tony

 

[D_Hailsham]

What would be a 150m2 house? Something like a 3 bed semi?

If you have a decent length tape measure, you can work out the floor area of your house

Measure Overall Width (OW)and Overall Depth (OD), in metres
Multiply OW by OD, to give area of one floor in square metres
Multiply floor area by number of floors
This gives the total floor area.

My 4 bed detached house is under 150 square metres.