Near death boiler + replacing a boiler

[David Hearn]

Our hulk of a boiler (Baxi WM 531 RS) is nearing death. The heat exchanger is leaking and we're finding we're getting a funny smell now. Couple of months ago we had a different funny smell when I split the thermostat's capillary tube but after replacement that is still intact and the boiler is working, unlike before.

I believe the smell to be caused by the evaporation of the water in the boiler and coming out the hole for the thermostat probe. Not actually sure of the cause of the weird smell (X100 inhibitor, Fernox Boiler Silencer or just some sludge) but its related to the boiler being on, and the flames are burning nice and blue (though flares up orange sometimes - I suspect when liquid drips into the flame). When the boiler is turned off for an hour or so, there is water sitting in the hole for the thermostat probe and rust is getting worse around it.

Now, firstly, is this smell/gas likely to be dangerous? Obviously you don't want to be drinking the inhibitor, but what about the smell from it? We're making sure we ventilate the area well (because its not a nice smell!).

If its not dangerous, then I have a little more flexibility with when I replace the boiler (few weeks, maybe month or so rather than days). Longer is better as I can then fit around my Dad's availability etc.

My plan is to go for a cheap/cheerful Ideal Classic SE RS boiler. Current boiler is a 62,000 BTU (18.4kW) input with 44,500 BTU (13kW) output. I assume that if replacing like for like then I just go for one with a similar output (therefore the Ideal Classic 15kW version) rather than looking at the input rating.

My reasoning for this boiler is that I should be able to use the same hole in the wall with the current balanced flue for the new one (or with minimal work). Rather than having to brick it up and put in a fanned flue (among other things).

Also, I want one which I can install myself (with help from my Dad who did his boiler a year or so ago) and doesn't require any specialist gear to set up (ie. flue gas analyser). AFAIK, a simple boiler like that should just require adjustment to make the pilot flame a certain size and also to get the required pressure on the test point.

I know the benefits of condensing boilers - and unless you can install one without any serious test-gear, I wouldn't consider it. I have to be able to do myself as a number of large, unbudgeted costs have come along (like replacing 2 rotten bay windows which are causing the bay to drop - approx £4k) just as a baby is due and we go to one income. I'm not going to put our family in any danger by doing it myself - but also we cannot afford to pay someone £1.5k (minimum total cost for someone to supply/install it I've had suggested) when we can just about afford £600 for the boiler.

So - what do people think about the Ideal Classic SE RS series boiler? Reasonably reliable? Easy/straightforward to install? It'll just be a simple replacement of a pumped (S plan I think) system running off an old balanced flue boiler to another balanced flue boiler. Controls are up to date - programmable room thermostat, 2 channel programmer, boiler stat, 2 zone valves, TRVs, pump etc.

One final question - what is the "standard flue pack" that is separate to the boiler? Is this the balanced flue to go with it or is that something different? I realise there is a Fanned Flue version - but we're not after that - just the plain Balanced Flue.

Thanks,

David

[Andy Hall]

This needs to be pensioned off pretty quickly........

As long as you are happy with the heating performance, then match the outputs as you suggest.

It's really no big deal at all to put in a fanned flue. Most of them are a set of concentric tubes and the size is smaller than for unfanned units. I did the complete job from having removed the old boiler to having the hole bricked up and the new flue located in a couple of hours and I rarely lay bricks......

In any case, there is no guarantee that the dimensions of a new unit will put the flue in the same place as an older model, so at least check that.

On many of them you can. It isn't so much an issue of whether the boiler is condensing or not but rather the age and origin of the design. Some of the more sophisticated controls require the use of a flue gas analyser to set up max and min gas rates. However other boilers are set on burner pressure or on gas rate measured by reading the meter and timing. You would need a manometer anyway to do part of the soundness test and they are about £15.

In terms of installation, the only additional thing for a condensing model is to provision the condensate drain and that is trivial.

Considering that you would save 20-25% of energy costs and some quite inexpensive condensing models can be found, to me it seems a no-brainer to use one, even accounting for all your other expenditures and reduced income.

.andy

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[David Hearn]

Plans are underway for a few weeks time.

Sedbuk's 'whole house' checker estimates about 10.7kW, so maybe I could go for the 12kW version, though the 15kW one is closest to what I've got, and that works well enough.

In our case the wall is rendered (with a Tyrolean finish?) and is quite old. I would prefer to have as little rendering to do, matching paint is another problem - and no plans on re-painting the house!

Yup - I'm aware of that, though I'm hoping that one balanced flue is pretty similar in shape to another. Due to the size of our current boiler (wide - width of flue and then another 6 inches) and the shape of new boilers (narrow - about width of balaced flue) I expect there'll be quite a bit of work inside to make good etc. Trouble I have is that there's a hole in the ceiling for the plumbing and a hole in the wall for the wiring - both within the casing area of our current boiler, but outside of the casing area of the new one - so a bit of work will be needed to make it look tidy - though we do have some spare 50cm kitchen cupboards which may well allow us to hide it away subject to manufacturer guidelines.

Don't suppose that you know of which boilers don't *require* flue gas analysers?

But I'll already be saving fuel costs by using a new boiler compared to a

15/20 year old one - I wouldn't get 20-25% extra by going with condensing over standard.

The Ideal Classic SE RS has a SEDBUK efficiency of 79.9% which is low compared to 91% for the better condensing boilers. Some condensing ones go as low as 85-86%. SEDBUK claim that large old heavy weight boilers (which I would say the Baxi WM 531 RS we currently have is) is only 55% efficient. Even if it was a lightweight one it would be only 65%. Currently we pay about £30 a month for gas I think, £360 a year (which is between SEDBUK's heavy and light weight estimates for a semi).

Assuming currently 65%, then if we went to 100% efficiency, we'd spend £234 a year (£126 pa saving). 90% efficiency would cost £260 (£100 pa saving),

85% cost £275 (£85 pa saving) and 80% efficiency £292 (£68 pa saving).

So, going with a condensing boiler I would save between £85 and £100 per yead and with the Ideal Classic I save just £68. The savings over the Ideal Classic would be about £17 to £32 a year.

Ideal Classic SE 15kW £582 inc VAT. Ideal Icos HE 15kW £675 inc VAT.

Additional cost of condensing, £93. Best case it would take 3 years to pay for itself, worst case 5 years. Might be worth a look depending on cost, and how long we expect to live here.

Something I did fail to mention is that the system is currently vented - and I don't want to convert it to a sealed system (work, plus chance of leaks - at least 1 part weeps currently).

So - can anyone suggest (and recommend!) a condensing boiler that meets the following requirements:

Suitable for vented/unsealed system (and not a system boiler). Definitely does not require a flue gas analyser for installation/comissioning - just pressure checks. Does not cost more than £700 including VAT/delivery (any more is too expensive/too long to recoup additional cost). Reasonably easy installation.

[Andy Hall]

I wouldn't go lower than you have already.

Are you sure that the vanilla SE is still available? I can only find price references for the fan flue version and I believe you have to add a flue kit for that.

I was going to raise that point.

Not quite at your budget, but it might be comparable once all the bits are accounted for, would be the Keston Celsius 25. Discounted Heating have this for £797 inc.

I considered this one for my installation the year before last so researched it thoroughly. Ed Sirett and Andrew Gabriel have this one and as far as I know are pleased. Tont Bryer fitted two in his church.

It is a system model, in the sense that the pump is integral, but that is a good thing because the pump is switched between settings according to heat output which matches flow, temperature drop and output more effectively. Using this is trivial, because you simply take the old pump out of circuit.

The flue design is good and uses high temperature 50mm plastic waste pipe which can be obtained from plumbers merchants very cheaply. You can run long lengths of flue if it helps or just straight out. The boiler comes with the flue terminal bits so no extra cost there.

This is a pretty compact boiler and does not require a flue gas analyser for setting - there is a check by timing the meter.

It will run with sealed or vented circuits.

Power output modulates from 7 - 25kW so matches your needs comfortably. One other benefit out of this is that it may heat the hot water a little more quickly. If you replace the cylinder at some point with a new one, you can use a fast recovery type and it will heat very quickly and have the power available to do so.

.andy

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[Ed Sirett]

I'd be tempted to fit a fanned flue boiler of a non-condensing type, the old balanced flue boilers are generally much less efficient than a fanned model. Most new boilers you can get the instructions for online so you can check out where the flue and mounting points would come. Don't go below 15kW since you need to have some HW capacity and you might replace the cylinder with something faster during the life of the new boiler. Most boilers are sold with a 'standard flue kit' which will usually let you mount the boiler on or adjacent to an outside wall. I believe that you can still get balanced flue boilers but other than for the cheapest and quickest like for like replacement I can't think why anyone would want one.

A boiler like the Potterton Profile 50eL would also be good if the price was not too high. If you could fix the leaks then I'd strongly recommend you go for a sealed system in which case A Vaillant Thermocompact 615e or a Glow Worm Compact 60 would be on the shortlist.

If you go for a condensing model then the Keston Celsius 25 would be a good choice.

[andrewpreece]

I recently fitted a new combi on my own, a Vaillant Turbomax, and this did not require a flue gas analyser, so I presume neither would the Thermocompact boiler. The job was lengthy ( especially so since I resited the boiler from an upstairs bedroom to an outside toilet ), but within the scope of a competent DIYer with a bit of common sense and technical aptitude, so a straight replacement of a boiler in the same position should be within your capabilities. The Vaillant Turbomax comes with all gas settings factory preset, so unless you're keen to "tune" your gas boiler to your particular system requirements, no adjustments are needed ( I presume all Vaillants are like this )

I found the only "special" tool needed was a u-tube manometer, but you can make one yoursely with clear plastic tube, a ruler and a bit of wood if you're hard-up. The only vaguely hairy work is the gas side of things, but Ed Sirrett has written an excellent FAQ on leak-testing etc. Do the ground-work first and down-load the boiler and flue installation pdf files for your chosen boiler before you buy so you know what you need to do. Vaillant certainly has these available on its website, some other manufacturers do too. If you do the gas side of things your guarantee may not be valid, so buy a decent make, and also bear in mind that a boiler fault that causes damage may not be covered on your insurance ( so make sure you do it right! )

Andy.

[IMM]

That is cheap and nasty. Well not so cheap for what it is.

Go for a Glow Worm condensing boiler. They are good and can be sealed or open system. Don't mess about with outdated inefficient crap.

[John Stumbles]

Is Tyrolean the one where they spatter render with gravel? I recently had to make good that sort of finish (in this case, unpainted) after chopping out a couple of bricks for a waste pipe. After blocking up the hole with brick fragments and mortar I simply stuffed handfulls of gravel (from the gravel drive) onto the wet mortar finish: job done! In your case you'd want to get some reasonably matching paint on top of it: I don't know what colour the existing finish is but I'd imagine a bit of an appropriate colour 99p sampler pot mixed with white masonry paint should get you close enough for jazz :-)

John S

[David Hearn]

This one does look nice, though I think its a little pricey (though good for what it is) and the problem I would have with it is that its a twin flue arrangement (minor point) but also that the expansion tank MUST be connected to the return. Currently we have it connected to the flow - which fits in with the Ideal Classic's requirement. Also the Celsius takes the pipes in at the bottom - whereas we have the pipes coming down from the ceiling in our case and would be a bit messy to route the pipes around (and don't want the additional cost of the box which brings it 5cm out from the wal).

Nice boiler - though also very complex - number of PCBs etc. I must admit I like the nice and simple design boilers where there's less to go wrong, and less reliance on black boxes (ie. PCBs) - though I do speak as a Electronic Engeering graduate.

Thanks

David

[David Hearn]

Yes, the standard SE RS rather than the SE FF is available still:

I expect I'll need the standard RS flue kit @ £40.

Surprisingly, the fanned flue version claims 78% efficiency in the manual whereas the balanced flue version claims > 80% in the manual. Though I'm sure there's a degree of error/variation anyway.

Thanks

David