Boiler broken - Combi vs Unvented

[busydad]

Morning all,

I called our home emergency cover yesterday and a heating engineer came out to basically say he think's our boiler is beyond economical repair. I also have a Gledhill Systemate 2000 which has two leaking pump valves and he advised I get rid of this also (it, like the boiler, is 14 years old). I should add, we've only been in the property a couple of weeks, so is typical of my luck when it comes to plumbing.

I've got a 5 bed, 3 storey house with 2 ensuites and a main bathroom. I've obviously put out some calls to get some quotes as it needs sorting quickly once the insurance confirm its beyond repair.

Question is, will a combi cut it? My usual plumber previously recommended a 40kW Baxi Duo tec and said overall this should be fine for our needs and would only cause a problem if we had 2 showers going, with other things like the washing machine. My 2 kids are both under 5, so I don't see this being an issue for the next 7-10 years. Basically our hot water demands at the minute are no higher than our last house which was considerably smaller.

The other option is an unvented cylinder, with a system boiler, obviously a bit more expensive/time consuming but potentially better hot water reliability/flow?

Just to add we have good mains pressure, so much so there is a pressure regulator attached to the stopcock, current pressure 3.25bar if that makes any difference? The pressure in the shower on the top floor is very good indeed (I will probably convert it to an electric shower in the future in case boiler breaks again).

 

[GasElectricalRepairs]

You may need to upgrade your gas supply, but a big ish combi sounds like an economical solution. What dia is the water supply pipe.
Measure the flow rate of how long to fill a 20 litre bucket, you need flow as well as pressure.

 

[bernardgreen]

Question is, will a combi cut it?

Be wary of claims for spectacular efficiency which are based on test results but then "adjusted" by the application of "proven" formulas.

This from the Building Research Establishment makes for informative reading.

https://www.bre.co.uk/filelibrary/.../STP10-B08_Lab_Tests_Gas_Oil_Boilers_2010.pdf
https://www.bre.co.uk/filelibrary/SAP/2012/STP10-B08_Lab_Tests_Gas_Oil_Boilers_2010.pdf <corrected by mod

Especially the vast differences in efficiency for the same boiler between the various ways that hot water is used

 

[Dan Robinson]

Blowhardgreen will you stfu! For God's sake no one has mentioned efficiency and the boiler you have a hard-on for isn't even on sale yet!

OP, I wouldn't advise a combination boiler for you at all. Other than from the context of adding a cylinder to it later, but then it would be mental to install a 40kw boiler for instant hot water performance when an 18kw boiler is all that would be needed with a cylinder. As GER mentioned too... You will almost certainly need to upgrade your gas supply too if you go down the combi route.


BTW..... Ignore Bernie. Most of his advice is poorly informed drivel.

 

[dilalio]

@busydad (with a nod to your other thread) as it now seems that your thermal store is also now in its death throwes and needs outing, I would advise that you have an unvented installed with a new low kw system boiler. If space is not an issue in your property (the main reason people opt for combi’s) then this would be the way to go. If properly designed and installed (& good products), it will give you complete comfort and usage and will be future proofed for when the kids are older or for when you sell the house to a family that does need the extra oomph of 250 odd litres of DHW at mains pressure

 

[busydad]

Many thanks for the replies and advice so far. I'll get some quotes tomorrow. I must admit I am leaning towards the unvented option.

 

[bernardgreen]

BTW..... Ignore Bernie. Most of his advice is poorly informed drivel.

So are you saying the Building Research Establishments independent testing of boilers is incorrect or un-informed

no one has mentioned efficiency

Are you suggesting that actual efficiency is not an important factor in the decision about which type of equipment to install for heating and hot water supply ?

the boiler you have a hard-on for isn't even on sale yet!

Did I ( or the BRE ) mention that boiler ?

 

[Dan Robinson]

So are you saying the Building Research Establishments independent testing of boilers is incorrect or un-informed

Even a stopped clock tells the right time twice a day.

Are you suggesting that actual efficiency is not an important factor in the decision about which type of equipment to install for heating and hot water supply ?

I'm suggesting that it is irrelevant to the thread.

Did I ( or the BRE ) mention that boiler ?

You know full well where you were heading.


BTW having worked at the BRE on a project, I wouldn't necessarily trust their data as far as I could throw it.

 

[FiremanT]

I am with Dan on every sentence. In both his heating and BurnieBoy comments.

I git "talked" into a 42Kw Worcerster for similar reasons. (3 showers/1 bath/4 Occupants). Biggest waste if money ever. Just ripped it all out and fitted System
boiler with UV..

 

[bernardgreen]

I git "talked" into a 42Kw Worcerster for similar reasons. (3 showers/1 bath/4 Occupants). Biggest waste if money ever. Just ripped it all out and fitted System boiler with UV..

Which is my point. Too often a Combi is sold to the customer whose needs are best satified with a non combi boiler and a cylinder for hot water.

 

[FiremanT]

Burn, I was talking about you. Not to you. You boil my p*ss.

 

[ianmcd]

+1 for system boiler and UV, an expensive project so do it right first time.

 

[GasElectricalRepairs]

If you have a nice south facing roof and some money in the bank that is losing value, get an unvented cylinder with a solar coil and fit a solar thermal panel.
I'm in the middle of fitting one at the minute. I dont expect to save mega dosh, probably around £200 a year from my calcs, it's a bit of an experiment to see what these things can realy do. The gear new, not inc the cyclinder is about 2k and say £1.5 k for bits and fitting. So for 3.5k you save £200 pa. Roughly 6 percent return and thats at current gas prices.
Just a thought before you buy your cylinder.

 

[FiremanT]

If you have a nice south facing roof and some money in the bank that is losing value, get an unvented cylinder with a solar coil and fit a solar thermal panel.
I'm in the middle of fitting one at the minute. I dont expect to save mega dosh, probably around £200 a year from my calcs, it's a bit of an experiment to see what these things can realy do. The gear new, not inc the cyclinder is about 2k and say £1.5 k for bits and fitting. So for 3.5k you save £200 pa. Roughly 6 percent return and thats at current gas prices.
Just a thought before you buy your cylinder.

Not really arguing, GER, or decrying the value of roof panels, but quoting a 6% return is a bit misleading. With an investment return, you expect to receive x% "return", PLUS the retention of the capital. Whereas in your case the equipment is a depreciating asset, and not in a liquid form.

Have you been a double glazing salesman?

 

[GasElectricalRepairs]

Not really arguing, GER, or decrying the value of roof panels, but quoting a 6% return is a bit misleading. With an investment return, you expect to receive x% "return", PLUS the retention of the capital. Whereas in your case the equipment is a depreciating asset, and not in a liquid form.

Have you been a double glazing salesman?

LOL,

Made to feel like one at times!

Agree a lot depends on where you live, for how long , roof orientation, water use and expected increases in gas as to how you decide if it stacks up. I just like the idea of free hot water and it is an experiment for me. When it's up and running I will know first hand what the score is.

Unless you have plenty of cash in the bank earning nothing or you are environmently minded, I agree It's expensive and a long payback.

Does that sound fairer MR T?

I would prefer to lose money than reputation!