Boiler house condensing boiler-any advice as regards brands?

anotherquestion

Hi folks,

I'm in the initial stages of researching an oil filled boiler house condensing boiler to replace an old 30 year cast iron boiler (burner was replaced about 20 years ago) all working well at the moment, but as I understand it, will probably use a fifth more oil, and oil as you know is not cheap at the moment.

Lots of ads  on tv for Grant boilers, but plumbers and the service guy have mentioned Warmflow and Firebird to me. How do they stack up against the Grant brand? Just don't want to buy and probably pay more for hype alone, and it has probably worked in my case seeing all the ads as I am swayed towards the Grant brand.

Idea's and any advice gratefully appreciated.
Many thanks.

Rodders53

What is the efficiency of the old oil boiler?  Brand and model?  Do you have the service or operators manual with that sort of info in it?

Grant utility boilers claim up to 93.3% efficiency... as do a few other brands?  If yours is 75% efficient then you'll use 100 x 75/93.3 = 80% of the oil you currently do = 1/5th saved (the figure you mention).  But your 'payback time' in reduced Kerosene use may be very long - even at the current high prices.  

If the new boiler is £3.6 k to install and you use 2000 litres per annum at say £1.50 (today) then its £600 per annum saved = 6 years at £1/litre it's £400 and 9 years. If prices drop back to 50p/litre it's only £200 and 18 years.  The new boiler may or may not last that long?

Brands: you'll have to do your own research and read the plumbing forums for installer experience and seek advice from a few local installers. 

BTW this is probably better in the energy forum https://forums.moneysavingexpert.com/categories/lpg-heating-oil-solid-other-fuels ??

anotherquestion

Hi Rodders33, 

Thanks for reply, just had a look and took a few pics, looks like an Neca Midy, as house was built in 1988, boiler has probably been here that long, as I moved in in mid nineties.
no manuals or very little info on net

Years ago , service people were quite impressed with it when they saw it, one even remarked it was the kind of cast iron boiler you would see in a guest house. Not so much impressed these days. Temperature guage on boiler needs to be turned up to max to get it to fire properly.

Boiler itself has never gone wrong, replaced the burner about 20 years ago with a sterling burner. Also replaced pump and that's about it. HAs served me well really.

Efficiency is high as regards it being an old boiler I am told, but still should save a fifth on oil, so the service guy says with a condensing boiler.

Taking a grant I could get I should be able to install a new boiler for about 2k.

gm0

Unless they have improved build quality in the past 20 years (and a lot of manufactured goods are on the opposite trend)

I wouldn't do payback calculations over >15 years or so.  Our Grant is about that vintage and we have replaced a fair number of parts already to keep it going. Burner fine so far.

But expansion vessel, prv, cold fill hose work, pump and electrical switches have all caused failures within that period.

If the actual heat exchanger boiler vessel starts leaking badly due to corrosion or the burner unit goes then it's probably junk at that point.  I very much doubt it will see a 20th birthday.

Rodders53

If your boiler man is right (and there's no promise on that as he's trying to sell you a new boiler I'd guess)... then you can alter the calculations I gave above for your oil use volume, remembering to use your crystal ball for future oil prices also.

But as the boilers is starting to give issues (max boiler water temp needed to make it run), then replacement over one Summer in the next few years would seem logical.

Due as much due diligence as you can by reading forums here (the LPG, Heating Oil one especially) and Plumbers/Heating ones as well, when selecting a brand to go for.

Moss5

https://www.inspiredheating.co.uk/mistral-outdoor-utility-standard-oil-boiler

https://www.inspiredheating.co.uk/warmflow-agentis-boilerhouse-condensing-boilers

I have the Mistral outdoor, it comes with its own boiler house.

I particularly like the blue-flame burner, also available on other boilers.

Return temperature would need to be less than 47C for an oil boiler to enter dew-point and create condensate.

When a Natural Gas boiler is run in non-condensing range, 11% of the energy is wasted.

(The maximum gain with the use of oil fuel is 6%)

When return temperature exceeds 47C, the boiler is running in non-condensing mode (like your existing boiler).

To achieve the target 47C, you may have to run radiators at 60C. I run my radiators at 75C and return at 55C, so not condensing.

To achieve high efficiency, you may have to live in a cold house. Is it worth it for 6%?

BikingBud

Moss5 said:

https://www.inspiredheating.co.uk/mistral-outdoor-utility-standard-oil-boiler

https://www.inspiredheating.co.uk/warmflow-agentis-boilerhouse-condensing-boilers

I have the Mistral outdoor, it comes with its own boiler house.

I particularly like the blue-flame burner, also available on other boilers.

Return temperature would need to be less than 47C for an oil boiler to enter dew-point and create condensate.

When a Natural Gas boiler is run in non-condensing range, 11% of the energy is wasted.

(The maximum gain with the use of oil fuel is 6%)

When return temperature exceeds 47C, the boiler is running in non-condensing mode (like your existing boiler).

To achieve the target 47C, you may have to run radiators at 60C. I run my radiators at 75C and return at 55C, so not condensing.

To achieve high efficiency, you may have to live in a cold house. Is it worth it for 6%?

@Moss5 Define cold house please.

I would offer it may not be a direct replacement and that other works are required to change emitters etc that would incur extra expense but why would you change a boiler and then be living in a cold house?

BUFF

Moss5 said:

Return temperature would need to be less than 47C for an oil boiler to enter dew-point and create condensate.

Why would an oil boiler have to run lower than a gas boiler to condense - it's the same air & therefore same dewpoint?  Or is it a typo (but you repeat it)?
Indeed, afaik Grant say between 40C & 55C e.g. https://www.grantuk.com/media/1278/grant-vortex-eco-utility-installer-doc-0080-rev-21-january-2016.pdf

Moss5

https://www.heatgeek.com/condensing-boilers-efficiency/

• Condensation: releases 2,500,000 J/kg latent heat

That's a theoretical maximum of 690 Watts of energy for every litre of condensate created.

That is like free electricity from an air-source heat pump.

 All of the efficiency calculations are based on the boiler operating in the condensing mode at all times. (Flow 60, Return 47).

My radiators are sized for a 36-year-old system with flow temperature 75.

If I want to see what it feels like at flow 60, I can turn the boiler down to 60.

Feels like a cold house.

I also have a ‘Dunsley’- style mixing tank to enable me to choose heating from a multi-fuel back-boiler. To take advantage of the condensing boiler would require me to fit larger radiators/under-floor heating and remove the integration with the coal/log burner.

Hopefully, I won’t live long enough to see the pay-back on that disruption.

"it's the same air & therefore same dewpoint?"

But gas contains water. 

in_my_bumble_opinion

anotherquestion said:

Hi folks,

I'm in the initial stages of researching an oil filled boiler house condensing boiler to replace an old 30 year cast iron boiler (burner was replaced about 20 years ago) all working well at the moment, 

I got as far as this.....
If it ain't broke, don't fix it would be my advice because they don't make 'em like they used to when it comes to boilers. 
I'm a bit of a sceptic about claimed efficiency of new boilers v old, too. Salesmen don't know the efficiency of your old boiler.

All that being said, if I was buying new today it would be a Grant.

I know a couple of oil boiler engineers. They both tell me the same thing: in terms of callouts to newer boilers with problems, they rarely get called out to a newer Grant boiler but get lots of callouts to newer Worcester Bosch models. The reverse is true for older boilers: the older Worcester Bosch are bulletproof and the older Grant boilers have more problems.

Do your own research of course.

coffeehound

BUFF said:

Moss5 said:

Return temperature would need to be less than 47C for an oil boiler to enter dew-point and create condensate.

Why would an oil boiler have to run lower than a gas boiler to condense - it's the same air & therefore same dewpoint?  

Presumably the combustion products also have an effect

Unit for unit, oil is a more efficient fuel source than natural gas, with about 40% more energy per unit. However, when installed correctly, a gas condensing boiler can be more efficient than an oil boiler at approximately 95% vs. 87% AFUE efficiency respectively.  Per unit of fuel, a gas condensing boiler can provide a better heat output. 

https://blog.viessmann-us.com/blog/oil-vs.-gas-heat-whats-the-difference