Condensing Boiler Setup/efficiency

nxdmsandkaskdjaqd

Cardew wrote: »

In any case how could you measure the efficiency of the boiler in your property? You can obviously measure the energy input(i.e. the gas used) but the heat output??

It's been a long while since I studied physics, but I believe you can get flow rates from the differential temperature across the radiators/boiler.

I am currently working on the modelling exercise, but have hit a physics related question which I have posted in another thread.

lstar337

Andy_WSM wrote: »

The difficulty you have is keeping the boiler in condensing mode and maintaining those temperature differentials.

So you set it up today, a chilly day in Winter, but not cold. Then the weather turns a little milder - what happens to your set up then? Then we return back to the -7C nights of late and suddenly you find your house is cold through insufficent flow rates and radiator temperatures - yet, the boiler is condensing lovely.

You can only set up a happy compromise on the system - that's just the way they are - as Cardew states above, obtaining maximum efficiency outside of a laboratory is nigh on impossible.

That's not entirely true. Get a boiler with weather compensation via an external sensor, and it'll do all the hard work for you. You set the differential, and the weather compensation bumps the rad temps and flow rates up and down to maintain that differential.

The only problem you could run into is if you like to turn your rads up and down or off. Then it gets harder as the boiler is missing vital feedback. Of course in the future with rad valves that communicate back to the boiler and a simple algorithm, you can solve that issue too.

Cardew

lstar337 wrote: »

That's not entirely true. Get a boiler with weather compensation via an external sensor, and it'll do all the hard work for you. You set the differential, and the weather compensation bumps the rad temps and flow rates up and down to maintain that differential.

The only problem you could run into is if you like to turn your rads up and down or off. Then it gets harder as the boiler is missing vital feedback. Of course in the future with rad valves that communicate back to the boiler and a simple algorithm, you can solve that issue too.

If you read the comprehensive study by Strathclyde University into the 'Development of a Methodology for the Evaluation of
Domestic Heating Controls' (Link in post#10) it would indicate that you rather overstate the effect of weather compensation controls.


It is a complex study but below is a quote:

for condensing boilers the efficiency is adjusted up 2-3% if there is load compensation, weather compensation or under-floor heating.

lstar337

Cardew wrote: »

If you read the comprehensive study by Strathclyde University into the 'Development of a Methodology for the Evaluation of
Domestic Heating Controls' (Link in post#10) it would indicate that you rather overstate the effect of weather compensation controls.


It is a complex study but below is a quote:

I purposely didn't claim any efficiency percentage increase. I simply said it keeps the boiler in condensing mode.

Given that the study states a 2-3% upward adjustment (roughly the increase stated for condensing mode over non-condensing), the study seems to tie up nicely with what I said.

Estwing

I installed a weather compensator early 2014 to my ideal logic condensing boiler. It was an optional extra which fits nicely behind the panel, total cost £30. Other bits of kit (external trunking etc) brought the total cost to £50 all in. Its quite hard to calculate the savings accurately as i installed a solar immersion kit not long after, but both combined they have reduced my gas usage by 28% in 2014 to 2013 using degree day data and some regression analysis. My house now uses 26.8kwh for every degree day based on maintaining 22 Deg C, compared with 37kwh/DD for 2013.
Degree days are a very useful tool for analysing gas usage / heating performance - not perfect, but useful.
I used the regression to find out that the solar immersion has reduced my baseload (ie DHS which isnt affected by the weather) from 98kwh per year to 40kwh.
Get your local degree day data here www.degreedays.net and have a play around with it, all you need your historical monthly gas usage on an excell spreadsheet (if your a saddo like me) and your monthly DD figures from your local weather station. You can then divide the kwh by the dd each month to get a ....kwh/dd figure for each month. Mine hover between 4 & 5 kwh/dd each month, if your figures are more far apart each month it indicates a more erratic level of control.
As we've just had daughter No.1 10 days ago and the house is occupied during each day for the foreseeable, ive just changed to the programme to stay on from 6am-10pm each day, rather than the previous 6am-9am / 4pm-9pm, to see if the boiler just tops up the temp efficiently using the weather comp to kick in the condense mode, rather than let the temp drop down to 18/19 in between the two time intervals.
Once january is over I'll use the degree data to see what the increase is, and what the likely increase in annual bills would be if i keep it like that.

lstar337

Estwing wrote: »

I installed a weather compensator early 2014 to my ideal logic condensing boiler. It was an optional extra which fits nicely behind the panel, total cost £30. Other bits of kit (external trunking etc) brought the total cost to £50 all in. Its quite hard to calculate the savings accurately as i installed a solar immersion kit not long after, but both combined they have reduced my gas usage by 28% in 2014 to 2013 using degree day data and some regression analysis. My house now uses 26.8kwh for every degree day based on maintaining 22 Deg C, compared with 37kwh/DD for 2013.
Degree days are a very useful tool for analysing gas usage / heating performance - not perfect, but useful.
I used the regression to find out that the solar immersion has reduced my baseload (ie DHS which isnt affected by the weather) from 98kwh per year to 40kwh.
Get your local degree day data here www.degreedays.net and have a play around with it, all you need your historical monthly gas usage on an excell spreadsheet (if your a saddo like me) and your monthly DD figures from your local weather station. You can then divide the kwh by the dd each month to get a ....kwh/dd figure for each month. Mine hover between 4 & 5 kwh/dd each month, if your figures are more far apart each month it indicates a more erratic level of control.
As we've just had daughter No.1 10 days ago and the house is occupied during each day for the foreseeable, ive just changed to the programme to stay on from 6am-10pm each day, rather than the previous 6am-9am / 4pm-9pm, to see if the boiler just tops up the temp efficiently using the weather comp to kick in the condense mode, rather than let the temp drop down to 18/19 in between the two time intervals.
Once january is over I'll use the degree data to see what the increase is, and what the likely increase in annual bills would be if i keep it like that.

I have the logic+ too and it explains in the manual how it uses the weather compensation add-on to keep the boiler condensing and working at its highest efficiency.

I can't say how much it might save, it could be very little. Above I was only explaining how the system works.

I don't have the compensator, I just turn it up or down a bit depending on external temp.

Pincher

From a user interface point of view, all we really need is a mode switch, which could be an ECO/TURBO button, or just something in a menu that you configure.


I assume all condensing boilers can measure the water temperature of the outgoing flow and return flow. In TURBO mode, you don't care about condensation, and just try to catch up to the set point as quickly as possible. In ECO mode, the boiler will monitor the return temperature, and turn down the flame to ensure condensation.


There should be an AUTO mode as well. In AUTO mode, if the house is cold, it should go full blast to catch up, but when the difference is only 2 degrees ( set point 20, room sensor says 18), it can go into ECO mode to go slow, but eventually get to 20 degrees. I expect this is what decent condensing boilers are already doing, but having the ECO/TURBO modes will give the compulsive fiddlers something to do.

lstar337

Pincher wrote: »

but having the ECO/TURBO modes will give the compulsive fiddlers something to do.

My fingers are positively twitching at that thought, due to my compulsive fiddler disease. The boiler is currently easing my symptoms somewhat, but when it warms up I'll have to find something else to fiddle with or risk insanity!:eek: