Worcester boiler central heating temp

JSHarris

gazb_2 said:

How much of a saving would it be lowing the flow temp to say 40degrees from 60?

TBH I don't know, but I do know that turning our old boiler down from the 65 it needed to be at to keep the house warm with the old rads to the 50 that worked fine with the new rads saved about 20% off our bill, so well worth doing.  Other benefit I hadn't thought about was the more even room temperature.  Not really sure why, but the living room no longer seemed to have warm and cool spots.  I can only assume it was something to do with more powerful convection creating a draught with the higher rad temperature.

FreeBear

gazb_2 said: How much of a saving would it be lowing the flow temp to say 40degrees from 60?

According to Which?, you could save 8-13%. In reality, going from 60°C down to 40°C will probably only save you ~2%. But you will need to ensure your radiators are properly balanced and set for the correct temperature drop*. At 40°C, it is quite likely that the radiators are no where near large enough to heat the property - Do a heat loss calculation and plug in different ΔT - https://www.stelrad.com/basic-heat-loss-calculator/

Delta T (ΔT) = (flow temp - room temp)

Radiator temperature drop = (flow temp - return temp) * 0.3

So for a flow temperature of 40°C, and a target room temperature of 20°C, the difference in flow & return across the radiator needs to be set to 6°C - You may well need to turn the CH pump up for a greater flow rate to ensure that all radiators are being fed with water at 40°C.

gazb_2

We’re in the process of completing gutting our home. I was planning on doubling the size of the rads we need going off a BTU calculator, do you thing this would be sufficient or do we need to go bigger? The house is having 4” celotex on all exterior walls (on inside) and 6” in all ceilings

QrizB

gazb_2 said:

We’re in the process of completing gutting our home. I was planning on doubling the size of the rads we need going off a BTU calculator, do you thing this would be sufficient or do we need to go bigger? The house is having 4” celotex on all exterior walls (on inside) and 6” in all ceilings

Ideally you'd do the heat loss calcs to work out what heat input each room needs, then size your rads to match.

Anything else risks either over- or under-sizing them.

FreeBear

gazb_2 said:

We’re in the process of completing gutting our home. I was planning on doubling the size of the rads we need going off a BTU calculator, do you thing this would be sufficient or do we need to go bigger? The house is having 4” celotex on all exterior walls (on inside) and 6” in all ceilings

Is the heat loss calculation based on having the extra insulation or without ?

Doubling the size of all the radiators regardless of insulation levels will mean you can run a gas boiler at a much lower flow temperature - This will translate in to higher efficiency and a reduced gas consumption. It also puts you in a better position to install a heat pump at a later date... If you are currently looking at a gas boiler, do give some thought as to where a heat pump might be situated and plan the plumbing around that. Also don't use micro bore pipes and go for 22mm or even 28mm for the bulk of the feed & return with short lengths of 15mm to the radiators.

Assuming you are also fitting high performance double/triple glazing, there is no real need to hang the radiators under windows - Placing them on internal walls can help to reduce the amount of pipework needed and simplify routing.

With 100mm on the walls and 150mm in the ceiling, your floors will (most likely) be the biggest source of heat loss. You might want to put some more insulation down below your feet. But digging up a concrete slab or ripping up a timber floor could push you well over budget.

Tip when you come to do the walls above doors & windows - Rather than using plasterboard over the reveals, use a strip of 12mm plywood. This will give you a solid surface to fix curtain rails to.

gazb_2

That’s a good tip, thanks. I forgot to say, we’re taking all the floors up and putting 4” kingspan and new concrete floors with underfloor heating