making condencing boilers more efficient tips please

aboard_epsilon

OK ...
Ive sort of made my decision on the boiler

well I've decided to go for a Bosch Greenstar 24RI

it's a system boiler that heats the tank in the loft ...but it is also condensing. 90.2 percent efficient.
90.2..........some of the time..which is why i write this

it has a lot less parts contained within it, than a combi boiler.
No expansion vessel
No motorized valves
No programmer.
No pump

All of these will be separate ..and cheaper to replace with generic when they pack up.

So, should make it a lot simpler for me, when it goes wrong or bugggers up ..which it definitely will do.

Figures from the Which magazine boiler test(your local library has them ) ..done over four years till September 09..suggest that the best boilers in the test "valiant" had a 26% failure rate in the first four years ...followed by Bosch at 29% ...cant remember the others ..at about half way down are "ideal" boilers with failure rate of 40%

it's a poor show .....as the old non condensing boilers could go on for 15 -20 years without fault.

Think there is a planned obsolescence going on ..like washing machines ..only boilers are not like washing machines ..as in most cases they require a gas fitter at megabucks per hour to fix.

So a lot of the sheeple out there will be paying out for a few fixes within 4 years and a new boiler every 5- 7 years ...adding thousands of pounds to their cost of living..eating up their retirement funds once past 60 or 65...
All this, in order to save the planet of 15 percent less co2.....which will no doubt be EQUALED by the plumber driving around fixing them , (and some) going on extra holidays around the world with the money,and the manufacturer of them making twice as many.

NOW THEN.

I've read on wikipedia

http://en.wikipedia.org/wiki/Condensing_boiler

That the more difference there is between the returning water temp and the temp going out ..the more efficiently it will condense .

Having not had or studied these before ..i find this hard to understand.

Having said that, if i do follow the above difference rule .......it says to me in my head, that i should :-

Monitor return temperature...with a thermocouple attached to the return pipe...and tune rad valves so that it happens.

will a variable speed pump help achieve this ? ..i have a four speed pump

Have it so that the hot water tank is at 80 degrees rather than 60. (bigger difference hopefully)

Have it so the tank is only heated for the minimum timed period to get to 80 .....monitoring return temp as its happening ..so to achieve best results by gradually altering timed period .

This would go on for a week or so until I'm confident I've achieved my goal ..obviusly this test would have to be done at different times of the year ........and settings that performed best ..noted so the programmer can be set up for each seasonal period .

Do i have this right (i do have the time to do this ).......or am i barking up the wrong tree .....

btw ..do the adverts here cover up some of my post....they do for me .

all the best.markj

noncom_2

I'll answer the bits of your post that I can, which is not much, but someone who knows a lot more than me will be along shortly......

No, in my browser the ads don't cover up your post, so that's one good thing.

I don't think the answer to your problem will be turning the water temp up. You may achieve higher efficiency in the boiler that way, but will be wasting a lot of energy with the heat escaping from the tank, so would almost certainly be worse off. Plus, water at 80deg coming out of your taps would be extremely painful. The key is getting the return temperature to your boiler lower, which I think means big radiators and underfloor heating being the best way.

However, I'm not at all sure of this, and as someone who's just about to move into a house with a condensing boiler for the first time, I'm interested in the answers you get.

aboard_epsilon

well the 80 degree tank gives your system more capacity .

as it is now my tank electric immersion is set to 80 degrees....comes on twenty Min's in the morning at 7:30...and twenty Min's in the afternoon at 4:30

this allows me to fill the bath with hot and cold to half full....14 inches...rince my hair ...and rinse the bath out after wards.

if it was 60 degrees .the bath would have only some 8 inches deep of water ......before i had to stop and leave the rest for rinsing my hair and the bath...........and would probably run cold before that....unless i switched the heating apparatus or what ever it be, on again.

saving money involves the hot water only being heated for a set period once a day.

the tank is very well insulated ..two foot of insulation ....takes several days to cool down if you don't use any...
I'm aiming for a less than £300 yearly gas bill.

which should be quite achievable .being here, on my own and no one to share it with.

Ive heated my whole house to a very comfortable temp 24/7 with paraffin this winter and several winters before .....usually use about 600-700 litres a year...at a cost of this year £440...if i can do that with paraffin ..which costs about three times per kilowatt ..as gas.......i can do it with gas far cheaper...well i hope too.

all the best.markj

Cardew

Couldn't agree more with the first part of OP's post.

It is am absolute disgrace that modern condensing boilers are so unreliable and we have no option but to buy one when our old boiler finally dies.

Like many others on this forum, my boiler is 22 years old and has had one thermocouple in that time - an easy DIY task.

Any savings from a new boiler costing £thousands to fully install will be wiped out paying for the first repair.

Jon_Tiffany

I've looked into this subject myself as the owner of Bosch condending boiler, from memory this is what a found out when I researched the subject.

Condensing boilers only condense when the return flow of water is 50 degrees or below.

For the most efficient heat transfer you need the biggest possible temperature difference between the boiler and the water flow, so either colder water of hotter boiler. Hotter boiler means it doesn't condense and there goes the efficiency.

Some plumbers say to get the best from a modern boiler you need oversize rads and piping - its a balance between the extra installation cost and the energy savings.

Just my thoughts, I'm no expert, but hopefully you will find it useful.

aboard_epsilon

maybe a a myson hydronic heater in the hall will do the task .

all the best.markj

claire_parker

Mark

A few points:

1. Please do not control your cylinder temperature at 80 deg C. It would be potentially very dangerous. People (particularly the elderly, infirm and children) would be at risk of severe scalding and even death. The cylinder should be sized to provide an adequate storage of hot water for your property, at 60 to 65 deg.C. The new boiler and also the system controls will enable the cylinder to heat up very quickly and you are most unlikely to run out of hot water unless you are very extravagant. One way of cutting running costs 365 days a year is to ensure you do not waste hot water. Don't leave taps running, don't overfill baths, basins and sinks, ensure shower heads are of a low water flow type and fit water flow regulators (eg Robert Pearson type). The cylinder would also scale up considerably quicker storing water at 80 as opposed to 65, if you live in a hard water area.

2. Bosch boilers are overall one of the best designs and quality. It should last you 12 to 14 years. Make sure though that the water quality is checked periodically and chemical inhibitor / biocide levels are maintained correctly. Modern boilers have more moving parts and require closer internal monitoring and control. They therefore will inherently require a higher level of maintenance and replacement of parts compared to their older counterparts. It can therefore be expected that they will break down more frequently. That is logical. The heat exchangers in condensing boilers do not last as long as non-condensing due to the high efficiency design.

3. Even when a condensing boiler is not operating in condensing mode, the efficiency will still be relatively high. There is no need to consider putting control devices (thermocouples / temperature detectors) on the return and even if you did there is nothing they could achieve without adding further complicated components into the system.

4. Your control system will incorporate a room thermostat and a cylinder thermostat. If you have a large property consider also having separate control zone (with motorised control valve) for downstairs and upstairs and possibly been other areas. Also consider having TRV's throughout except in rooms provided with room thermostats. (There is generally no point though in providing more than one radiator in a room with a TRV).

5. Ensure you only have the boiler set to heat the cylinder for the minimum time necessary. There is little point in heating the whole cylinder unless that hot water is needed.

6. Ensure the primary heating pipes (between the boiler and cylinder, including in the airing cupboard) are thermally insulated to a high standard. This will reduce considerable waste of energy, particularly during the summer period.

7. I would really recommend one of the modern low energy and variable speed pumps. They cost more than constant speed but consume far less electricity and theoretically should last much longer as wear is reduced. Have alook at http://net.grundfos.com/doc/webnet/poweredby/gb/alpha2_explorer.html and press the arrows, etc. A VS pump will also reduce water flow through the boiler under part load conditions which will therefore reduce the return water temperature and increase boiler efficiency slightly.

8. Keep the boiler thermostat at maximum, which will ensure the system heats up as quickly as possible, thus reducing cycling.

9. Keep the room thermostat and TRV's as low as possible but at the same time make sure occupants are adequately warm, as this will reduce energy consumption considerably.

10. Turn off the heating system whenever possible - when you go out, probably when you are in bed and at any other times. If you need the heating operating during the night then consider turning down the room thermostat / TRV's. Where possible turn radiators off or down in unused rooms.

11. Satisfy yourself as far as possible that the person who is carrying out the work is experienced and competent. If you cannot judge this then I would suggest you use an Institute of Plumbing and Heating Engineer Registered Plumber. There is no guarantee that they will be competent but they will have had to demonstrate that they have undergone adequate training and have adequate qualifications to carry out the class of work in which they are registered. Also there is a system for complaints and investigations should a dispute arise. They MUST also be Gas safe Registered.

12. The 24RI is not a system boiler. A system boiler would contain the pump and expansion vessel but not the motorised valves. A point to consider is that a system boiler may provide a neater more compact installation, may be cheaper to install and may be cheaper to purchase than separate items.

13. How do you know that you need a 24 kW boiler? A smaller output boiler, if adequate in size, would most likely be cheaper and also overall more efficient.

I don't think you are going to be disappointed with your new boiler if you have an old boiler, possibly also with poor controls. Carry out a comparison of before and after gas consumption. I have been doing this in my own house for about ten years using a simple spreadsheet program, over which time i have had wall insulation, roof insulation and a new condensing boiler. Each has shown a considerable annual energy reduction.

Claire

aboard_epsilon

Hi Claire , thanks for the very informative reply

answer to (3)

The thermocouples are type "k" monitoring ..hand held affair ..no control... just monitoring ..it's just a wire coming from a meter that you tape onto the pipe ...so will give you info on whats going on ..and by then fiddling with the program controls and rad valves will help me keep returning temp at below 50c

answer to 1

There are no old or young people here ..and Ive had my tank at 80 for 25 years ..

Yes, "system" was typo..me not thinking ..its called a regular condensing i think.

I've no idea what boiler output i require..i don't know gas boilers, how they are calibrated to suit house size

I can tell you precisely how many kw I need to heat the house though ..with paraffin. NB 24/7 kw

Info gleamed from using paraffin for years ..

When you heat with paraffin heaters ..you must leave them on 24/7

or you will not catch up ..and will encounter condensation..
i never ever had condensation ..24/7 is the key.

modern Paraffin heaters are over 99% efficient.

it's quite easy to work out the KW of them because all 99 % efficient ones use round about, or near enough 0.1 litres per hour for each KW produced

Anyway ..

Results with paraffin.

Ambient outside temp 5- 10 degrees ..no wind... constant 2.5 kw required to keep house at 19- 21

Ambient outside temp 5-10 degrees and windy.......constant 3 kw

0 -+5 degrees ...3kw.......with supplementary 500 watt in the bedroom at night. (sometimes)

Coldest day of the year probably 4 kw

As you can see ...all this experimenting, i did with paraffin ..alerted to me to the best way to heat a house ...and that is with a constant low wattage.

so why dont i carry on with paraffin

it's become too expensive
its' become dodgy in its make up ..with dies that ruin wicks.
and cant be that healthy .
yellows paint work in short order of time .,

SO...time to move on .
was a stop gap that lasted many years ..


to carry on ..
Trying to heat anywhere quickly playing catch up ..with any fuel ..in my opinion, wastes fuel....its like going from 0- 70 in a car at full throttle ..wastes fuel

That's what i don't understand about these gas heaters ...
if they made one that you could leave ticking over giving out 2.5 kw 24/7 or 4kw 24/7 when its severe..to my mind that would be a better way to heat a house.

I know, they have made them modulating ...but most only go down to 6- 7 kw...perhaps it's something to do with keeping them condensing.

As regards components, all in the same boiler ...Im not into paying for genuine parts at huge prices, when you need them in a hurry.

Better to have quality parts outside the boiler .easy to get at ..easy to DIY ..and cheap to buy, and quicker to get.

all your other pointers are useful thanks ..im taking note .

oh .and i need the extra capacity to heat my workshop..im running a couple of pipes across to it ..its 26x26 with solid walls ...and needs 3.5 kw to heat

All the best.markj

Cardew

claire_parker wrote: »

Modern boilers have more moving parts and require closer internal monitoring and control. They therefore will inherently require a higher level of maintenance and replacement of parts compared to their older counterparts. It can therefore be expected that they will break down more frequently. That is logical. The heat exchangers in condensing boilers do not last as long as non-condensing due to the high efficiency design.

The electronics on modern boilers are their 'Achilles heel'. PCBs that cost up to £hundreds that a gas safe engineer has no option but to replace.

It is surely an oxymoron to talk of high efficiency design which means it is logical that they break down more often even with ' a higher level of maintenance'.

The RoyalInstitution of Chartered Surveyors stated recently :

The average cost of installing one of these modern boilers is £1,720, but saves on average just £95 off people's gas bills." See:

http://www.telegraph.co.uk/news/ukne...erts-warn.html

Progress? - I think not!

claire_parker

You are not going to be able to do anything productive or cost effective by monitoring the return temperature. There are only three adjustments which can be made to keep the return temperature at below 50 deg.C.:

1. Reduce the water flow rate through the boiler, which is risky and could lead to early boiler failure.
2. Increase heat output of the radiators at times of low demand, which will totally defeat your object.
3. Reduce boiler output which will lead to under heating.

In any event this would result in a temperature differential of 30 deg.C at peak demand which will have an adverse effect on radiator heat output, unless that is designed into the system from the start. The resultant water flow rate may also have an adverse effect on boiler life. I would suggest you stick to the industry design standard for condensing boilers of 80 deg C. flow and 60 deg. C return.

I repeat please do not run your cylinder stored water temperature at 80 deg. C. This is potentially very very dangerous. In addition this will decrease the overall heating system efficiency.

The required boiler output needs to be calculated. If the boiler is oversized, the efficiency will decrease and also the system will cost more.

You cannot readily compare the gross heat output (or input) of paraffin with the heat output from a boiler. The heat output of a paraffin heater combines two elements sensible heat and latent heat. The heat output from a boiler is only sensible heat. Therefore a smaller boiler could be used to provide the same useful heat compared to the output of a paraffin heater.

Paraffin heaters (and LPG room heaters, gas cookers, etc) are certainly unhealthy and will result in the human body absorbing increased levels of carbon monoxide, even with the recommended fresh air vents – witness your yellowing of paint. It is about time they were all banned.


Claire

aboard_epsilon

I don't know Claire ..
gas CH is new to me ..but i will quickly learn.

I may be totally wrong about this ..but , who knows, the massive water capacity rads i have in place ..may even help it .....meaning that they will continue to emit heat for longer ..so longer between fire ups .

i don't know a lot now ...but monitoring will help me understand a bit more about the characteristics of it all ..and what i have to do to make it run as efficient as possible without having to fork out too much.


BTW .....ive had every other form of heating in place but gas .......by far the cheapest (almost zero) was waste oil CH ....but the neighbours didn't let me get away with it ..not that it was making smoke or smell ..more of a jealousy thing ..and them knowing it was against the law and them paying through the nose and this and that.
if i was out in the sticks (isolated house) ...i would go out and out to perfect that form of heating....as i had it more efficient weight for weight than anthracite.

all the best.markj