How much energy does a condensing boiler save? is it worth worrying about?

[vulcancontinental]

Have you any calculations to reinforce your claims? A calculation of the inefficiency due to ON/OFF cycling for example (there is one of course).

Manufacturers promote their products not their limitations; it's the installers job to look investigate the viability of claims rather than to soak up and repeat marketing blurb. Remember you're dealing with people who with a straight face can show you certified figures for their products of 108% and 127% efficiency while the appliance case is warm, the flue is warm and there is a plume at the terminal or where one brand will claim a flue to return water temperature differential of 5 degrees and another of 7 degrees yet both have the same space heating efficiency figures.

One thing to start with is to differentiate between combustion efficiency, fuel efficiency and system efficiency.

It's quite possible now with ultra high modulation of the burner to reduce fuel efficiency of the appliance.

Similarly with an ON/OFF thermostat it is perfectly possible to operate a boiler with lower modulation cycling cheaper than continual running and still maintain comfort levels.

 

[hard-work]

Have you any calculations to reinforce your claims?

Oh no attempting to duck to one side. From someone who dealt with commercial HVAC control I am dismissive of most of what you wrote. This was pretty well incorrect: "It's quite possible now with ultra high modulation of the burner to reduce fuel efficiency of the appliance".

When a boiler is injecting into a building pretty well the exact level of heat equating to the building's heat demand, efficiency and comfort levels are high. Unless the boiler is so badly designed of course in which what you mentioned about combustion, flue, etc efficiencies is true.

 

[vulcancontinental]

It doesn't matter if you dismiss it. You haven't substantiated anything with any evidence, what is the efficiency loss through the appliance cycling?

The second paragraph is true but of course it's not germane to the thread. What efficiency is affected with this balance, system, fuel or combustion and more importantly why and how?

 

[hard-work]

It doesn't matter if you dismiss it. You haven't substantiated anything with any evidence,

Neither have you. From extensive experience working for Honeywell and Siemens on HVAC control, I know what I am on about.

 

[ianmcd]

Multiple zones on OpenTherm

Why do I think you and him are the same person ?

 

[ianmcd]

Neither have you. From extensive experience working for Honeywell and Siemens on HVAC control, I know what I am on about.

Well your time was obviously wasted there , and that is why you USED to work for them , you havent a clue ,I would take advice from @vulcancontinental , before you any day of the week

 

[ianmcd]

I do not know how Scotsmen think. As I am 6 foot, slim and not having a Yorkshire accent I assure you he is nothing like me, although a nice guy he is.

But he is a genuine source of advice about boiler problems, you are no where near

 

[ianmcd]

You are an uneducated workman. Work on it mate. And stay off the single malt.

Ha ha Love that , yet again you know nothing about me , I can assure you I have forgotten more than you will ever know

 

[ianmcd]

You have nothing to contribute to in this thread so GO AWAY!

Says it all really, I have worked in many countries and have worked with many boiler maufacturers , but you have ACS , so you can advise better than I can , you total clown

 

[dilalio]

You have nothing to contribute to in this thread so GO AWAY!

I'd love to see you try and get away with your rudeness in a face to face encounter with those who you disrespect on this (and I'm guessing) many other forums... Unfortunately social distancing prevents that at this time... Lucky for you eh!

 

[ericmark]

Thank you @hard-work the video was very interesting, I have been giving false information, I did not know you could have multi-opentherm devices, that is a great improvement. And not too expensive either, so once this is all over that seems the correct control system.

So now how about second question, can you use a fan assisted radiator with a condensing boiler? I assume it will need some modification? so water flow is controlled as well as fan speed, would it need a new iVector or can I convert the old Myson with some add on.

 

[hard-work]

Thank you @hard-work the video was very interesting, I have been giving false information, I did not know you could have multi-opentherm devices, that is a great improvement. And not too expensive either, so once this is all over that seems the correct control system.

So now how about second question, can you use a fan assisted radiator with a condensing boiler? I assume it will need some modification? so water flow is controlled as well as fan speed, would it need a new iVector or can I convert the old Myson with some add on.

Fan assisted radiator? No problems, just make sure it has adequate flow. Most of them have an internal thermostat that brings on the fan when the heat exchanger is above ~38C. So if a condensing boiler is dropping the flow below say 38C, it will not work. The slope graph of weather compensation can be set to avoid such a flow temperature drop. Load compensation may drop the temperature below 38C, but by the time that occurs the building is about up to temperature anyhow.

 

[vulcancontinental]

Neither have you. From extensive experience working for Honeywell and Siemens on HVAC control, I know what I am on about.

I haven't, you are right in that, what a great opportunity for you to shoot me down... but you don't. Saying who you worked for without some solid figures which should be at your fingertips is meaningless.

What I will say, as the calculations I speak of are being verified by others at the moment, is that the inefficiency of cycling (stop/start, sensible heat leakage, wasted energy etc) would have to exceed 17% to impact overall fuel efficiency and that is just not going to be the case.

 

[hard-work]

I haven't, you are right in that, what a great opportunity for you to shoot me down... but you don't. Saying who you worked for without some solid figures which should be at your fingertips is meaningless.

What I will say, as the calculations I speak of are being verified by others at the moment, is that the inefficiency of cycling (stop/start, sensible heat leakage, wasted energy etc) would have to exceed 17% to impact overall fuel efficiency and that is just not going to be the case.

Your claim is that a boiler cycling can be more efficient than a boiler modulating the burner to input heat into a building to match the building's heat demand. No one will take that seriously. Until you come up with calculations proving that a cycling boiler is more efficient over a heating season, and does not reduce the controls longevity, no one will take you seriously.

 

[vulcancontinental]

Your claim is that a boiler cycling can be more efficient than a boiler modulating the burner to input heat into a building to match the building's heat demand. No one will take that seriously. Until you come up with calculations proving that a cycling boiler is more efficient over a heating season, and does not reduce the controls longevity, no one will take you seriously.

And quite right too. Don't take me seriously, it doesn't matter. Things need to be verified but I'm happy with them and confident they stand up. You might be a little more careful in choosing your words though, I am. I say that an average modulation boiler cycling (1:5 -1:8) with an ON/OFF room thermostat can be more fuel efficient and have calculations to prove it. Of course I designed a construct to prove this but it's a construct that most of the housing stock in the UK would fit into with occupation patterns that also would be in the majority.

I emphasise not more efficient in the combustion of the fuel, but in reducing the cost of operating the appliance without any discernible reduction in the comfort levels for the occupants and Eric's OP was a question regarding actual economies.

Lastly, even if I am wildly off the mark, a simple condensing boiler operating on a time switch and thermostat would over lifetime cost less than a system with a low loss header, three smart pumps and a multi zone OpenTherm system with a relay switched weather compensation. (Incidentally I have written months ago to EPH who were unable to confirm the layout mentioned in the video. Maybe in the future is what the reply was). It is also uncharted territory changing analogue switching of a boiler via a relay to a digital protocol and back and the long term effect that may have on the software of the boiler. I personally would shy away from that. KISS.

Buy a boiler set up for a four pipe system or an Intergas arrangement. Domestic LLH and CST's tend to operate at higher non-condensing temperatures and closer delta T's so any savings are system savings only and they form the greatest expense in implementation but minus condensing efficiencies available to pay for them.

The average heating bill in the UK according to DECC is £850 ish. The EU determine an ON/OFF room thermostat saves 1% (£8.50p). Weather comp offers a 2% saving (£17). WC + OT 4% (£34). Multi zone OT, minimum 3 zones, 5% (£42.50).

The math is straightforward.