Replacement of Gravity backboiler system -best way to go?

[Digiteeruk]

I have a late 60's end of terrace 4 bed / 1 bath house with a Gloworm 56F backboiler Gravity feeding an elderly smallish HW tank (no diverter valve), 10 rads via an underfloor pump. It has 3 HW taps (the bath one with a feed to an old Showerforce 2000 power shower) and 4 CW taps.

According to Gloworm, the boiler is about 12 years old with a good chance of a reasonable extra life, but the rads and rest of the system look like they are 15-20 years old. The system is not at all well as discussed here: //www.diynot.com/forums/viewtopic.php?t=43500&highlight=weird

I have done some work for a CORGI heating engineer, and in return he has offered to renovate the system if I cover the cost of parts - a very good offer I think.

He has condemned 7 of the 10 rads and recommended replacing them with TRV fitted new ones, fitting a new HW cylinder & header tanks and repiping to make fully pumped.

The price for parts is very reasonable, but he THEN said "of course you are still upgrading to an old design - how about a Combi?" He then explained their pros & cons - although mostly pros. As we are in a very hard water area, he also recommends an electromagnetic water softener if a combi is fitted.

For not very much more, he can fit me basically a new system using the existing CH ring and increasing bore of the HW main.

Due to the house's design, he found enough points to allow fitting a conventional rather than a Condensing Combi and can get a very good deal on a Woucester 35cdi.

Guys, what should I do? I really like the idea of only using gas when its required and never running out of HW. From reading the forums here, as our mains pressure is good, a nice thermostatic shower off the combi will be nearly as good as the power shower, which quickly empties our current HW tank and takes ages to heat up again.

The downside is am I throwing away something that may be a very reliable boiler for something that is nowhere near as reliable in the long term and has no backup in the form of an immersion heater?

From looking at this forum, there seems to be Combi fans and pumped fans - given this particular situation, which would be best, please?

Finally, if I go the combi route, is it OK for the future to fit a non-condensing type and which thermostatic shower would you recommend?

Many thanks in advance - all advice gratefully received.

Kind Regards, D

 

[Agile]

If your system is converted to be pumped then the recovery time will be greatly improved, perhaps form 1.5 hours to 0.75 hours.

A larger combi such as a 35 kW would not be that bad but the gas pipework from the meter will probably have to be upgraded to 28 mm depending on the distance.

The pipework to a large combi could be 22 mm to the CW input but the output should only be in 15 mm although taking a short length of 22 mm and then splitting in two different 15 mm directions would be good.

Householders are often fooled by the installer saying they can get "a good deal" on whatever the installer wants to fit. Find out exactly what deal he can get and then compare that price with local merchants and off the internet. The reality is that you will probably get within £20 or less of his "good deal" or even better it ! There just is not enough margin to give good deals, all the usual prices are good.

Tony

 

[chrishutt]

Due to the house's design, he found enough points to allow fitting a conventional rather than a Condensing Combi and can get a very good deal on a Woucester 35cdi.

I'd be a bit sceptical of this. You're house, being end-of-terrace, is effectively a semi which would attract fewer points than a terraced house. If the installer fiddles the assessment in some way it might have repercussions for you. A condensing boiler isn't a lot more money and it will save you 15% or so on your fuel bills.

The price for parts is very reasonable

You should check these yourself on the internet or somewhere that quotes real prices, not retail prices. Most builders merchants will quote you much higher prices than those actually paid by the trade.

a nice thermostatic shower off the combi will be nearly as good as the power shower, which quickly empties our current HW tank and takes ages to heat up again.

If you have a new tank fitted, as proposed, it can have a larger capacity, as well as much faster recovery, so you needn't run out of hot water again.

 

[Paul Barker]

I have to agree,

condnesing regular boiler converted externally to sealed system (or system boiler), new 170 litre bs1566 cylinder, S plan, programmable roomstat on heating side, cheap timer and cylinder stat on hot water. Powerflush, Magnaclean, new lockshields trv's, autobipass, junk any dodgy looking rads.

 

[Digiteeruk]

Many thanks for the replies.
I realise that fitting the combi option means prob a lot less work for him, but he has mentioned that the existing elderly pipe work prob will not take the pressure of a direct system (although OK for a Combi) - does this sound right?

Am a bit concerned about the 'fiddle' bit now. He has mentioned that he has worked the system like this in the past to fit conventionals over condensings...

...Surely if a CORGI Engineer signs it off via the points system (aren't you all self-certifying?) then the certificate will hold for the future? Playing Devil's Advocate, it's not up to me as a householder to question his Authority, or am I missing something here?

Grateful for your thoughts on this, and many thanks in advance.

Kind Regards
Dig

 

[chrishutt]

he has mentioned that the existing elderly pipe work prob will not take the pressure of a direct system (although OK for a Combi) - does this sound right?

No, it doesn't sound right. The pressures applied via a combi boiler are the same or greater than an unvented DHW system.

...Surely if a CORGI Engineer signs it off via the points system (aren't you all self-certifying?) then the certificate will hold for the future? Playing Devil's Advocate, it's not up to me as a householder to question his Authority, or am I missing something here?

Good point, but the question is if he's fiddling the assessments, is he going to notify Corgi of the installation and the fact that he's made an assessment in favour of non-condensing? If he does notify Corgi they might well choose to inspect that installation and discover his fiddle.

If he doesn't notify you wouldn't receive the appropriate building regulations compliance certificate from Corgi, which might cause you problems, for example with the guarantee. I can't see how it can be worth the hassle of fiddling the assessment myself. Perhaps he's not competent to install condensing boilers?

 

[Digiteeruk]

Wow, now you've got me worried!

When I challenged him on the ponts system, he stated that he can justify a sufficient number of points and is thus not fiddling (he acted a bit insulted actually) -hmmmmmn.

He stated that all the Fitters he knows fit condensing because they have to, but fit high efficinct conventionals for themselves! To back this up, he took me to his house (similar to mine) where he has indeed fitted a Worcester 35cdi conventional combi system last year, after April.

Should I go for the pumped option with my existing boiler instead then?

BTW, he will confirm on Monday, but is looking at an extra £300-£500 for a full combi system with new conventional boiler on top of the cost we agreed for fully pumping the existing back boiler blus new HW cyl & header tanks -does this seem fair to you?

Regards
Dig

 

[Paul Barker]

I could take you to a flat I own with Buderus condensing combi 500-28c with a magnaclean and a combimate.

So he believes in what he preaches and I believe in what I preach, you have to decide if I am right to move with the times, not to mention stay legal.

 

[Digiteeruk]

Paul,
Again, many thanks.
BTW, what is a magnaclean and combimate please?
What are your replenish times with this sytem's HW if you run out and how do economics compare against a combi as you're keeping a large tank of HW always hot?
Finally, could your suggested system be modified to use my existing back boiler which is quite adequate to keep the house hot currently, and only installing a new boiler when the old one gives up the ghost?

Regards
Dig

 

[Paul Barker]

In reverse order, keeping your boiler but safely converting it to fully pumped would be my first choice.

New cylinders are all less than 20 minutes recovery time, you can buy special fast recovery cylinders that take 10 minutes.

Magnaclean is a magnetic trap which catches magnetight before it goes into boiler. Magnetight is otherwise known as sludge. It works terifically, no mumbo jumbo.

Combimate is only applicable to combis, it's a mumbo jumbo device that inhibits scale, or doesn't depending whether you are a believer. I bought 10 to get 1 free so thought I'd better use one, but haven't made a very good job of selling them to my punters. Spose it's cause I don't believe in them.

I don't think economics come into play, combis will cost you so much in the future any minor savings on water heating (which haven't been proven by research) would be swamped in the decision making process.

The advantage of a combi is space saving and easy install.

Since my flat needed a boiler pronto and it was our busiest time I just through in a combi. I don't recommend this aproach, but at least it's a quality boiler. To spend less would cost much more.

 

[chrishutt]

Combimate is only applicable to combis, it's a mumbo jumbo device that inhibits scale, or doesn't depending whether you are a believer.

Paul, Combimate is based on proven technology using a chemical siliphos. It is not like the magnetic or electronic inhibitors which remain unproven. You can sell it with confidence!

 

[Paul Barker]

Oh great a reason to believe in it, thanks Chris. I can easily sell what I believe in.

 

[Digiteeruk]

Many thanks to Chris for posting the link to the Combimate product doumentation.

Interesting comment on the Secondary effect of coating pipes with a "non-residual microscopic protective coating". I know its probably semantics, but if its non-residual, surely it ain't gonna be protecting for too long!

Don't know about the health effects of polyphosphates such as this releases, the WHO class them a ssafe for human consuption I suppose.

There is the issue of annual replacement of the crystals - I note a bottle costs £20 + VAT, but I would be more worried that the company will still be around in the future to supply the chemical.

How about magnetic systems - has anyone had any experience with their success rates?

Magnetic IC Engine fuel combustion enhancers claim to work in a similar way, but noone really knows, "straightening out hydro-carbon chains to burn perol and deisel more efficiently" is often quoted. That said, strong magnets were strapped around fuel line to Spitfires flying over Russia in WWII. Ran OK on very poor Russian fuel with 'em, ran like dogs without them - something good is happening!

 

[Digiteeruk]

In reverse order, keeping your boiler but safely converting it to fully pumped would be my first choice.

I don't think economics come into play, combis will cost you so much in the future any minor savings on water heating (which haven't been proven by research) would be swamped in the decision making process.

The advantage of a combi is space saving and easy install..

Paul, why will combis cost much more in the future against stored-water system boilers please?

Thanks in advance,
Dig

 

[Paul Barker]

Ducks bellow parapet!

Oh alright but there will be a load of mud slinging to follow.

The short answer is they are crap. I don't feel like going into details, some here will say I am crap for saying so some will agree with me and some will keep out of the argument.

Let's put it this way, I fix a lot of combis which wouldn;t have gone wrong if they weren't combis. Secondly people's voices tend to sound much more strained on the phone when their combi is broken down that the voices of those folk who have a back up plan.

Now you might know that you aren't one of those folk whose going to get all wound up when his combi won't work, Only you can know that. All I know is folk with combis get all uptight until it's fixed.

I can only speculate that there must be some inconvenience to having no heating and hot water, oh and they also think they get more sympathy points for having a baby. EWell you're telling it to the wrong bloke mate, if you'd asked my opinion I wouldn't have told you to buy a combi!