Non-Condensing Boiler Flow Temperature?

paperclap

So after running the boiler for six hours at the previously mentioned parameters, the central heating averaged out at 30p per hour.

I was expecting there to be something of a downward curve. The first hour 30p, the second hour 28p, third hour 26p, etc, as the house had warmed up thoroughly, and therefore the boiler didn't need to click on as much. But, hasn't seemed to have been the case. Weird, frankly.

Now running another test. Same thermostat temp (18 degrees), but have changed the boiler flow rate, from setting 5 to somewhere between 3 and 4. Let's see.

shiraz99

housebuyer143 said:

paperclap said:

Don’t disagree with either of you!

But, the cost of a new boiler is a pretty penny. 

The efficiency (and therefore the cost savings) of a new boiler would be less than the cost of the new boiler.

Therefore, economy more wise to actually keep the older, inefficient boiler.

I'm thinking along the same lines as you. 20 yr old non condescending boiler. I am told the best saving I will make it £500 a year by changing it, based on the new tariffs (I am currently paying less than half of this, so saving is more like £200).
New boiler is £3500, so worst case it would take 7 years to recoup the cost. 
My boiler isn't as efficient as it could be but it's cheaper to keep it. 

In answer to your question, British gas advised me you save almost nothing turning it down. However what will happen if you turn it to less than 65-70 is that your hot water tank won't heat up very hot, if you have one 

If you wanted to take full advantage of a new, condensing boiler then it will it cost more than just the boiler itself, on an old system like yours you'd probably want to look at upgrading all of your radiators, get weather compensation controls fitted, decent thermostat system etc.

macman

Why would you change the rads, unless they're seriously undersized? Weather comp and a decent programmer agreed, they should come as standard spec, along with TRV's ,on any new install.

shiraz99

macman said:

Why would you change the rads, unless they're seriously undersized? Weather comp and a decent programmer agreed, they should come as standard spec, along with TRV's ,on any new install.

A 20+ year old system is likely to have radiators that will be undersized for running a new combi boiler at lower flow temperatures.

ThisIsWeird

paperclap said:

ThisIsWeird, this is great, thank you!

Today, as we speak, I'm running a little experiment. Central heating on all day. Thermostat set to 18 degrees. Boiler setting at 5. All radiator TRVs are set to Max.

Going to see how much on average, per hour, it costs.

Then on Thursday, I'll do the same text. But, drop the boiler setting to 4. And maybe, the TRVs to 5 or 4, too.

Surely too many variables adjusted at the same time?

When you say 'all' TRVs are on 'max', do you really mean 'all' or the ones in the room with the wall thermostat?

housebuyer143

shiraz99 said:

macman said:

Why would you change the rads, unless they're seriously undersized? Weather comp and a decent programmer agreed, they should come as standard spec, along with TRV's ,on any new install.

A 20+ year old system is likely to have radiators that will be undersized for running a new combi boiler at lower flow temperatures.

I wouldn't be getting a new combi.. New system boiler is my preference.

NannaH

My rads are all singles,  mostly 40 years old bar two,  my CH is perfectly efficient and warm with a vaillant 28kw combi running at 60° flow temp,  I keep meaning to check the return temp,  I only have 8 rads in my 3 bed house. 

I did have reservations about changing from a system boiler and tank but it paid for itself within 4 years.  It was fitted in 2015.    

It’s pointless having trvs on max if the thermostat is set to 18°,   Max is 25°.  

paperclap

Yeah, I really do mean every single TRV on max.

I do understand that TRVs are intended to allow for single room temperature control, but just wanted as few variables as possible.

Plus, I work in one bedroom. My partner works in the other bedroom. The thermostat is in the hallway with another rad with a TRV. Then there’s the living room and conservatory, both of which are prone to being cold, as north west facing. Bathroom doesn’t have a TRV… and bloody kitchen doesn’t even have a radiator!

ThisIsWeird

I'd think I'd focus on just saving energy costs, to be honest.

Hall thermostat set to whatever temperature keeps the boiler running to warm the two bedroom radiators. TRV on the hall radiator set to '5' (ie fully open)*, bedroom TRVs set to around 3 or whatever temperature you both want/need them), and every other TRV set to '1' or '2' just to keep the chill off the air and prevent freezing. 

Turn the boiler output down to what will still heat your hot water cylinder effectively - high 60s? - and forget about taking measurements, unless the physical exercise keeps you warm.

Any savings achieved by reducing the boiler's water temp (and hence its 'return') a small amount on a non-condensing boiler - and it's theoretical, but I think does make some sense - will be lost in all the other variables which will be far greater - changes in ambient temps, the sun popping its head out, doors left open, cooking, that sort of stuff.

Hang gloves and a warm outdoor coat on the door leading to the kitchen. :-)

ThisIsWeird

Oh, the '*' (can't edit post).

The hallway should normally be at around 18oC or so (personal choice), cooler than the living areas, but warm enough to welcome folk into your house. If you set the wall thermostat to that, say, 18oC, and find that the hall heats up too quickly so that the boiler is turned off before your bedrooms reach their new required temps (higher than normal since you are now working in there and not just sleeping, then there are two things you can do to sort this. One is to simply turn up the hall thermostat until the bedrooms heat up more, but that means you will also be heating the hallway more than you may want, so possibly be 'wasting' energy heating the hallway, but you may decide that this will be background heat for the rest of the house, for example, so you leave the hall doors open to the other rooms to let this extra heat trickle out, and the other is to reduce the output from the hallway radiator so it doesn't heat the hall as quickly. This is normally done by tweaking down the lockshield valve - on the opposite end to the TRV - but I would be tempted to simply drape a blanket over the radiator, so you won't need to fiddle with the radiator controls.