Conventional (compact) boiler replacement: suggestions/advice pls.

[Harry Bloomfield]

I have the EcoTEC plus 418 and when I was buying it, I asked what the difference was between the Ecotec Plus and the Ecofit pure (which was cheaper) and I was told that the pure was just a rebadged Gloworm.

That doesn't sound right, because as I understood it, the Pure was simply a version for mounting inside a cupboard, a more basic look to the casing. They are the same boiler internally.

 

[Laurence Harvey]

I have the EcoTEC plus 418 and when I was buying it, I asked what the difference was between the Ecotec Plus and the Ecofit pure (which was cheaper) and I was told that the pure was just a rebadged Gloworm.

Notwithstanding the price, does that suggest the Ecofit Pure is inferior to the rest of the Vaillant range?

 

[fixitflav]

i think you have misunderstood,

modern boiler are designed to be optimal across the range, however they will be most optimal when cruising at a low modulation (similar to driving your car at 55mph for optimal fuel consumption).

modern boilers are ecu controlled, again similar to a car, where for a given amount of air and comparing inlet and outlet temperatures etc etc it optimises the gas valve.

it is proven that using modern low temperature heating with controls such as opentherm or the boiler manufacturers equivalent does improve gas consumption, albeit only a few percent in some instances but can be as much as 25% in others, and therefore not a big deal on its own, but if everyone in the country done that it would be a massive deal.

Thanks for that. I was about to edit my post to the effect that modulation could be over a wide proportional band, start to modulate at say 60°, down to minimum gas flow at ~ 80°, rather than all at once at 80°-ish, which could give a potential advantage of more condensation. But you beat me to it.
Also that weather compensation might help, again because of more condensation. But whether the ecu control gives higher efficiency, or whether bernardgreen's point about optimisation at a certain output is correct, I wouldn't like to guess.
In addition, modulation and weather compensation result in the fan and pump running for longer, using more (expensive!) electric.

 

[vulcancontinental]

Condensing is a relatively small improvement but worth it if it doesn't cost too much. PDHW is a good efficiency improvement, possibly better than condensing. Weather compensation is a boon in responsiveness in my experience.

 

[Mottie]

That doesn't sound right, because as I understood it, the Pure was simply a version for mounting inside a cupboard, a more basic look to the casing. They are the same boiler internally.

Well as far as I know, no boiler is a work of art showpiece so if they are both the same internally, why offer a bigger casing at a higher price? Why not just make one size of casing? I very much doubt that people would look at the pure casing and say "Have you got it in a bigger size"?

 

[fixitflav]

PDHW is a good efficiency improvement

Assuming PDHW means priority domestic HW, that's interesting. If that's the case, the move away from W-plan with either/or diverter valve (and PDHW) to Y or S-plan has resulted in a lot of wasted gas over the years! I've always had W-plan and don't see any significant advantage in simultaneous CH and HW.
With weather compensation it must be PDHW with compensation bypassed when HW called, or the flow temperature might be below cylinder stat setting. With W-plan no problem, but there was a recent thread on here about how to modify S-plan to achieve it, most likely by adding a relay. Y-plan with mid-position 3-port valve would also need wiring mods, or replace the actuator.

 

[vulcancontinental]

Not quite as black and white as that though.

W plan was a cost exercise when introduced 50 years ago; it allowed smaller boilers to be installed (one load at a time) with cheaper valves (the mid-position was a very expensive option back then in comparison due to early electronics and needed a relay; 2 zone valves more so).

It also didn't matter too much when simultaneous space and DHW heating became possible because all boilers ran at high temperatures as there were no condensing boilers.

Run a cast iron or low water content standard efficiency boiler at low temperature and the condensate would destroy the boiler. Makes me smile when recalling servicing a cast iron boiler to see the customer had thought they were saving money by turning the boiler stat down low only for me to remove a dustpan full of rust from the heat exchanger and burner bar.

Now we have condensing boilers that can withstand the condensate we can take advantage of latent heat gains through condensing therefore differing flow temperatures between space and DHW reheat becomes an efficiency gain. It is small but worthwhile as space heating at lower temps is around 80% of a NG bill and better controls make adjustment automatic.

 

[fixitflav]

Not quite as black and white as that though.

W plan was a cost exercise when introduced 50 years ago; it allowed smaller boilers to be installed (one load at a time) with cheaper valves (the mid-position was a very expensive option back then in comparison due to early electronics and needed a relay; 2 zone valves more so).

It also didn't matter too much when simultaneous space and DHW heating became possible because all boilers ran at high temperatures as there were no condensing boilers.

Run a cast iron or low water content standard efficiency boiler at low temperature and the condensate would destroy the boiler. Makes me smile when recalling servicing a cast iron boiler to see the customer had thought they were saving money by turning the boiler stat down low only for me to remove a dustpan full of rust from the heat exchanger and burner bar.

Now we have condensing boilers that can withstand the condensate we can take advantage of latent heat gains through condensing therefore differing flow temperatures between space and DHW reheat becomes an efficiency gain. It is small but worthwhile as space heating at lower temps is around 80% of a NG bill and better controls make adjustment automatic.

OK, I thought (wrongly) you were saying in your earlier post that PDHW gave improved efficiency by itself, as opposed to it being there by necessity when weather compensation is used.

 

[Laurence Harvey]

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[sxturbo]

OP here,

Heating engr round today. He reckons an “Ideal Logic Max Heat” (heat only) 15kw boiler would suit. It comes with magnetic filter as standard,...7 year warranty & 10 year warranty on heat exchanger,...cupboard fit,... fully modulating down to as low as 4.8kW.

Any thoughts/comments please?

My parents and my brother have ideal logic plus combos, and they are quiet. And small, my brother has his in a cupboard.

The hot water side is crap but the heating side is fine. Both are 2 years old now with no problems this far.

 

[fixitflav]

My parents and my brother have ideal logic plus combos, and they are quiet. And small, my brother has his in a cupboard.

The hot water side is crap but the heating side is fine. Both are 2 years old now with no problems this far.

The OP asked about a heat-only.

 

[sxturbo]

The OP asked about a heat-only.

I know I was commenting on the brand.

 

[fixitflav]

I know I was commenting on the brand.

I just meant difference between HW and CH wouldn't arise with heat-only

 

[Laurence Harvey]

OP here with an update for anyone remotely interested.

Ideal Logic ‘MAX Heat’ 15kw boiler (heat only) was purchased: vat&del + flue kit + Ideal System filter + 10yr warranty = £1008 in total.

The boiler was installed yesterday by local GasSafe engr and is working perfectly.

Many thanks to all for the help/advice upthread.