Change my old CH boiler for a new one?

ming60

[FONT=Verdana, sans-serif]Hi all.
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[FONT=Verdana, sans-serif]We're thinking of updating our central heating boiler. We have a 20 year old Gloworm Hideaway 50B boiler, with a gravity fed CH/HW system, with a Danfoss 103 programmer, and a room thermostat. My service guys tell me the boiler itself is in very good condition for its age, and so far it hasn't broken down in the 14 years we've lived in the house (apart from a new pump, and a new 2/3 way valve). Our house is a standard Jelson built, 1965, 3 bed detached in Leicestershire, with all the normal insulation – loft, cavity wall, 8yr old double glazing etc. However, I'm getting more and more frustrated every year, with the fact that on these increasingly chilly mornings, we have to wait 40 minutes for the boiler to heat up the water, before the radiators then kick in. Also, when we draw off hot water during the day or evening for, say, a load of pots to wash up, or a bath, it takes the water away from the radiators, and we have to wait at least another 40 minutes for the water to heat up and the radiators to kick back in.[/FONT]

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[FONT=Verdana, sans-serif]We are both 70 years old, and are home all day a lot of the time, so in the winter months, we have the boiler on from 7.30am – 12.30pm, and 2.30pm – 10.00pm, but during the summer, something like 7.30am – 10.00am, and 4.00pm – 9.00pm[/FONT]

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[FONT=Verdana, sans-serif]My question is, we are unsure if a new combi boiler is going to give us better economy, and with enough of a saving each week/month/year to warrant the initial expense. I understand that a combi boiler gives instant heat to the radiators, so there's no 'waiting time' in that regard (that will be a nice benefit!). Is a combi boiler the right option for us? Is there a formula, or some way of working out the efficiency comparisons, and therefore the savings, of our existing boiler, to a new one, whatever type that is? I know how much gas we use each week, month, and year, so I can input figures if necessary. Basically, over the last 6 years or more, we've averaged out around 23,000 kWh/yr in gas, and 2,400/kWh/yr in electricity. I think this is well above the average, probably because we are home a lot more.[/FONT]
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[FONT=Verdana, sans-serif] Is there anybody out there that can give us some guidance? I would really appreciate some help.[/FONT]

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[FONT=Verdana, sans-serif]Many thanks, in anticipation.[/FONT]

System

There are a myriad of issues here which need to be thought though. A new condensing boiler will save you money year on year; however, ...........

HW versus CH. Cylinder systems are usually configured for HW priority or both CH and HW. I suspect that you are in the former category. The answer to HW priority is to use a timer to turn on HW heating ahead of your CH start time. A combi boiler might well suit a 3 bedroomed home.

Sludge. A 20 year old system will undoubtedly be filled with sludge. It would be madness to fit a new boiler on to a dirty system. You would be asking for heat exchanger problems. A powerflush might well cost you upwards of £500.

Combi boilers now have to comply with Boiler Plus 2018 Regulations. Boiler Plus requires an energy efficient boiler plus one of 4 extras.

Gas boiler performance: space heating efficiency of the new boiler no less than ErP 92%
Time and temperature control required for all gas and oil boiler installations
Combi boiler installations must also include one of the following: Weather compensation, Load compensation, Flue Gas Heat Recovery, Smart controls.

You will also need updated boiler controls and TRVs on the radiators. The latter may require new TRV bodies.

Finally, you are a very high energy user. My wife and I live in a 4 bed detached house with the heating on from 7am to 9pm, and we use less than 10000kWhs of gas a year. I mention this not to brag but to highlight something that a new boiler cannot change: that is, an apparent lack of insulation in your home.

In sum, a new boiler will undoubtedly save you money; however, I doubt that you will get a return on your investment given that modern boilers are unlikely to last as long as your present boiler.

Worth a read: (NB table at bottom)

https://www.greenmatch.co.uk/blog/2015/09/how-efficient-is-a-condensing-boiler

ming60

Thanks for the reply Hengus. Some interesting, and enlightening points to consider!

I think my existing Gloworm boiler is F rated. I guess new combi boilers are A rated? Is there any way of finding out what the monetary difference, in efficiency terms, there is in these ratings? In other words, if both boilers were on for 10 hours, which would be the most efficient in terms of kWhs? Is there a formula? Have the industry bodies come up with comparisons like these? Or am I asking an impossible question?!

chrisw99

Hengus wrote: »

Sludge. A 20 year old system will undoubtedly be filled with sludge. It would be madness to fit a new boiler on to a dirty system. You would be asking for heat exchanger problems. A powerflush might well cost you upwards of £500.

Most new boiler installations should have a magnetic filter installed just before the boiler to stop any of the sludge getting into it.

System

chrisw99 wrote: »

Most new boiler installations should have a magnetic filter installed just before the boiler to stop any of the sludge getting into it.

True - but in my experience reputable installers would not recommend adding a filter to a 20 year old system without cleaning it first. I have just watched my neighbour getting a new boiler installed. The installer took out all the radiators and pressure flushed them outside because he was concerned that power flushing might result in blocked pipes.

To get back to the OP's question. There is no definitive guide to the savings that you will achieve with a new boiler and better heating controls. Having just been in an exchange with the Building Research Establishment (BRE) about smart heating control efficiency savings, they do not accept ErP efficiency ratings (as these are produced by the manufacturer) and so on. Various websites quote savings as high as £340 per year (unlikely in my view) down to very little (also unlikely in view).

A quick check of Help Link shows a potential £18 per month saving on a monthly payment for gas of £60. (£60 per month is roughly what I would pay for your usage in my postcode).

Given that a new boiler with controls and a flush could cost you, say, £3000 then at £200 saving per year, the payback period would be 15 years. By then, you would probably be looking at another new boiler. That said, the payback period may be reduced by savings on repairs.

All that said, we still come back to the elephant in the room. Your usage is high either through choice or the fact that your home is not particularly well insulated. It is the latter that needs to be looked at first in my opinion.

tacpot12

Hengus wrote: »

True - but in my experience reputable installers would not recommend adding a filter to a 20 year old system without cleaning it first. I have just watched my neighbour getting a new boiler installed. The installer took out all the radiators and pressure flushed them outside because he was concerned that power flushing might result in blocked pipes.

It is also possible to fit a plate heat exchanger between the new boiler and the old heating system, to reduce the likelihood of contamination in the old system damaging the new boiler. The heat exchanger creates a complete separation between the old and new systems. Powerflushing would be necessary even with a heat exchanger.

I did the calculations for our Glowworm Spacesaver KFB boiler (G-rated) and worked out it would save us about £300 a year. We pay about £800 per year for gas, so it will take use about 10 years to recover the cost of a new boiler.

misterbarlow

Hengus wrote: »

Various websites quote savings as high as £340 per year (unlikely in my view) down to very little (also unlikely in view).

When we moved in here 12yrs ago there was a baxi bermuda back boiler that looked from the 70 or 80s..
It was all working ok though and we were skint from the move etc, so I just re-lagged the tank and bought a better controller with digital timer, and kept it going..
For last few years I had been paying £40pm and annual statement was usually correct to within £10-20 either way..

Early last year we came into some PPI so decided now was the time while we had the cash to get rid, and had a new Worcester combi fitted..

Left my DD at £40, and in the last 18 months since, my gas usage has barely changed from before...
I was expecting a nice refund and was only £18 in credit at end of year!!
We are not really saving anything at all.. maybe £1-2pm!!

AndyPK

If you have 2 bathrooms I understand combi's aren't suitable.

I wouldn't change the boiler if I were you.

Maybe some LED lamps and insulation would be a good idea

Mister_G

Yes, very similar situation with us.

We had a Baxi Bermuda backboiler installed in 1982, so it's now over 36 years old. I believe that it's only about 65% efficient but has been absolutely reliable with only a replacement gas valve (£40) a few years ago and a regular annual service (£50).

I have thought about replacing it, but like other have said, the payback would be at least 10 years. Also I know that the replacement will not be as reliable!

Marmaduke123

Set the water heating on a timer to be on only at night, when there is no requirement for the radiators to be hot. I assume you have got a timer which can determine the hot water periods, as you obviously have one for the central heating

macman

Your existing system does not 'take heat away from the radiators' when you draw off hot water. They are two completely separate circuits: your hot water is stored in the hot water tank.
With a combi, you will have hot water on demand, but while you are producing hot water, no heat will be sent to the CH circuit.
I think you are confusing a combi with a condensing boiler. All new domestic installs are condensing, whether combi or conventional.
I agree with the comments that suggest that the existing system may be heavily sludged and could benefit from a powerflush (which you'll need to do anyway prior to a new install).
Either type of boiler gives instant, or near instant, heat to the rads. But only a combi gives hot water on demand.