Old boiler advice - replace or not

bris

Ideal Mexico is practically bullet proof, I have only  replaced one a few years ago had to go because rust got the better of it and it couldn't be saved.  

The cost to replace it will take years to recover through efficiency so if it aint broke....

Jeepers_Creepers

It's not an easy call for Chaser. There would certainly be savings to be made, tho' just how much is debatable.

Let's assume it is the best part of £400pa. There are then two further issues to consider; one is, of course, the cost of replacing the boiler. This will hopefully be pretty reasonable since a system boiler is the cheapest to buy and also to install (compared to combis). It should almost be a like-for-like swap - no extra pipes apart from the condensate. Gas pipe should remain fine. The flue depends on how complex it is to replace - does it go straight out through a wall, for instance? So, how much? Dunno - but £500-£800 for the boiler, and almost certainly doable in a single day. Shouldn't, surely, be more than £2k all in? So, 5 year recoup at the most?

The other issue is, although system boilers are far less complex than combis and therefore far less likely to go wrong, they are still more fragile than the basic old workhorses. Chaser expects to be in his house for another 10 years - just about the time his beautiful new boiler will start to play up :-)    Ok, it hopefully won't, but in 10 years time it will be considered by many as 'getting on a bit'.

So, I think what I would do in Chaser's position is to wait a few years until the old boiler really does start to have issues, and then swap. This way he'll be selling his house with a 'newish' boiler installed (buyers love that) with hopefully no issues and a better energy rating.

grumbler

Jeepers_Creepers said:

That diagram you have also seems to suggest the cold water goes straight to the 'water-to-water' exchanger and out as DHW - no link to the combustion or flue other than via the main system's water.

Yes, you seem to be right, but it's beyond me why mains water doesn't go through the condensing part first.

FreeBear

Jeepers_Creepers said:  There are then two further issues to consider; one is, of course, the cost of replacing the boiler. This will hopefully be pretty reasonable since a system boiler is the cheapest to buy and also to install (compared to combis). It should almost be a like-for-like swap - no extra pipes apart from the condensate. Gas pipe should remain fine. The flue depends on how complex it is to replace - does it go straight out through a wall, for instance?

A quick look at the installation manual for an Ideal Mexico shows that the gas connection is 1/2"BSP, so probably a 15mm copper pipe. Many modern boilers need a 22mm for gas. So may need to factor in the cost of a replacement..

Regulations on flue location with respect to window/door openings may have changed since the old boiler was fitted. Something else to bear in mind when weighing up the cost of replacing a boiler.

ratechaser

Thanks again everyone, far more useful information than I could reasonably have hoped for so genuinely appreciated. 

So I'm going to leave well alone for the foreseeable future - understood that it may not be the most efficient boiler, but sounds like all being well it should give a good few more years service.

I'm also thinking back now to when the Megaflo system was put in and the loft fully converted - that added another 4 rads and a big bathroom to what we already had but clearly there were no concerns with the ability of the boiler to cope with the extra demand.

just one point in response to Jeepers comment about flue positioning - the boiler is against an external wall and it goes directly through so simple enough. Also, nearly all the pipework looks to be 22mm, with the exception of a little bit near the floor that is 15mm and could be the gas - I'm going by eye, not actually measured. If you're at all interested, here's a pic of the left hand side of the boiler (the 15mm pipe is a bit in the shade down the bottom) - you can also see some of the asbestos lagging!

Thanks again all
RC

twopenny

I had an old freestanding boiler for 40yrs, only had a small problem once. I kept being told it was expensive to run but I heated an enormous 3 bed Edwardian semi for £125 a quarter. It's trying and testing the best way to heat the house. Immersion tank lagged with 3 layers, foil behind the radiators in winter (I was told that would only be 2% but turned out to be 10% increase in heat), pipes lagged, thermostat turned down to 13 or so but on all day.

I now have a newer one and it heats a small 4 room bungalow for the same price. Working on the lagging etc now. Plumber just told me mines not worth changing

Keep the old but start checking where the new one will go and flow etc with the advice here . So many places  your not allowed to put them these days.

fred246

Regarding the Megaflo pressure there is a cartridge on the 3 bar inlet pressure reducing valve that should be cleaned regularly. It may be blocked or could have failed. You are probably better getting a person with the right certificate to do it.

mcplumb

First thing you need to check is whether this boiler has an overheat stat, I'm fairly sure its an add on accessory on this model. If you have a Megaflow cylinder, an overheat stat MUST be present 

coffeehound

Jeepers_Creepers said:

It's not an easy call for Chaser. There would certainly be savings to be made, tho' just how much is debatable.

Let's assume it is the best part of £400pa. There are then two further issues to consider; one is, of course, the cost of replacing the boiler. This will hopefully be pretty reasonable since a system boiler is the cheapest to buy and also to install (compared to combis). It should almost be a like-for-like swap - no extra pipes apart from the condensate. Gas pipe should remain fine. The flue depends on how complex it is to replace - does it go straight out through a wall, for instance? So, how much? Dunno - but £500-£800 for the boiler, and almost certainly doable in a single day. Shouldn't, surely, be more than £2k all in? So, 5 year recoup at the most?

The other issue is, although system boilers are far less complex than combis and therefore far less likely to go wrong, they are still more fragile than the basic old workhorses. Chaser expects to be in his house for another 10 years - just about the time his beautiful new boiler will start to play up :-)    Ok, it hopefully won't, but in 10 years time it will be considered by many as 'getting on a bit'.

So, I think what I would do in Chaser's position is to wait a few years until the old boiler really does start to have issues, and then swap. This way he'll be selling his house with a 'newish' boiler installed (buyers love that) with hopefully no issues and a better energy rating. 

Where did the efficiency numbers come from Jeppers?  What I've managed to find indicates that the annualised efficiency rating which takes account of the reduced efficiency when heating just the DHW, seems to be taken as a reasonable indicator of real-world efficiency, e.g.

Due to its larger heat exchanger, a condensing boiler does not have to condense in order to be more efficient. Typically a new gas condensing boiler will have a seasonal efficiency of between 84% and 92% compared with a new non-condensing boiler at 78% or an older boiler at 55-65%. See table below for typical annual fuel costs for condensing and non-condensing boilers.

The SEDBUK (Seasonal Efficiency of Domestic Boilers in the UK) rating is the average annual efficiency achieved in typical domestic conditions and is quoted in a series of bands (from ‘A’ at 90% or over, to ‘G’ at below 70%).

That from a Building Research Establishment pub.  Another thing with the return flow temps is that it's a sawtooth profile with the temperature cycling between a peak value and a trough of perhaps 15 º lower, so despite a peak value above 55, much of the time it will be below that, and in the full condensing zone.

Given that the old boiler may well be below 60% efficiency now, think I'd be tempted to get it replaced now and enjoy the benefits for the next 10 years rather than having to replace it anyway nearer to selling up.  Also there's the chance that fuel prices might go up in coming years as the squeeze is put on fossil fuels.  

Ratechaser, have you looked into whether any grants are available?  E.g.:
https://www.moneysavingexpert.com/utilities/free-cavity-loft-insulation/#boilers
https://www.moneysavingexpert.com/utilities/green-homes-grant/

Jeepers_Creepers

coffeehound said:

Where did the efficiency numbers come from Jeppers?  What I've managed to find indicates that the annualised efficiency rating which takes account of the reduced efficiency when heating just the DHW, seems to be taken as a reasonable indicator of real-world efficiency, e.g.

Where did I get the energy efficiency figures from, Coffee? Why, I pulled them from there, of course (points to thin air above head).  

This is Chaser's call. I don't think anyone can claim to have a definitive answer; it's swings and whatsits.

I can cite an energy efficiency website which states the Mexico RS3 has a 'seasonal average efficiency' of 72.5%. I don't know where Chaser's RS3 example falls here. I also cannot comment on the true eff levels he'll obtain from a modern condensing boiler which will have to heat his existing rad system using what will likely be flat-out performance in cold weather, so not running at peak efficiency.

I can only give a stab. As, I also suspect, applies to others.

I suspect his maximum savings will be in the order of £400 per year. Armed with that, Chaser can make a decision.

No harm whatsoever in him getting some quotes for a newie now.

I'm absolutely not telling or suggesting that Chaser does not replace his boiler; I am suggesting what I think I would do in his position.  Tbh, I doubt it makes much difference either way. ~£2k outlay now, recovered in ~5 years. That's pretty cool. A much smaller, probably wall-mounted, boiler. That's also cool. Relax knowing it's unlikely to give any issues for a good while. That's triple-cool. Noticeably smaller monthly bills - fourble-cool.

Pros and cons; he's forked out ~£2k when he doesn't really need to. In 10 years time the new boiler might be starting to have problems.

(The RS3 has an output of up to 30kW - that's a biggie. If the existing gas pipe is 15mm and coping ok with no significant drop in pressure, that suggests - tho' the GasSafe will confirm - that it'll also be fine for the newie.)

Chaser, by all means call out a couple of GasSafes and ask their thoughts; recommended models, cost of conversion, likely savings to be had. Info info info - the more you have the better.