boiler exchange

[honda]

hi, i have an old floor-standing boiler with gravity fed domestic and pumped heating. i want to upgrade the boiler and the h/engineer has given me two options.
1. install a modern conventional boiler with a fully pumped system, new cylinder and new controls.

2. install a modern combi boiler and do away with cylinder, loft tanks etc.

what are the pros and cons for each system and what would you as experts go for?

many thanks

 

[ChrisR]

The answer would fill a small book. It depends on water requirements, property size, space available, and on and on. There are many similar questions here, try a search.

 

[plummerman]

The top an bottom of it is 'wot ever the customer wants' within the constraints of the points raised by chris. But MOST requirements are possible. Speak to a good RGI and give him wot you require in terms of perfomance and he/she should be able to advise.

 

[Paul Barker]

Looking 10 years hence; the former when things go wrong it will be repairable using van stock. In the latter you will wait for a second visit, and quite likely more frequent costly visits.

When I was a manufacturers service agent the calls to combis were most of the work. Seldome required for a regular or system boiler.

When I sub contracted to British gas repair man I changed or repaired a lot of external motorised valves the occasional pump TRV's, and also combi diverter valve parts aswell as attending many combi conundrums where they had been visited on many occasions but nobody had got to the bottom of the trouble. I think on the whole I got to the bottom of it as
I was only one of the 4 out of 80 in my area who achieved bonus and the only contractor. But for that reward I spent a minimum of an hour on evry such job and sometimes 2 to fully investigate the boiler and ensure I had truly nailed it. It isn't cover off bang a part in naff off as quick as you can, which it seams 76 times out of 80 is what you will get.

In short unless you have a very rare breakdown engineer, or unless you don't mind leaving the key under the mat for the engineer on a regular basis; avoid combis.

ps I still sub to bg but don't do breakdowns out of principle. The wages even after bonus are less than the simpleton who does servicing only, and though i am capable i am human. why work harder for less money?

 

[Paul Barker]

that said i have a combi at home, but that's an energy efficiency reason. I have emulated the Alpha solasmart design with a cheap second hand single coil unvented cylinder heated solely by solar
(though if there was no sun and a gas shortage I could heat it with electricery) the output of which is diverted through the combi only if it falls below 42 degrees. therefore i always harness the maximum of the sun and always benefit from it. So a combi is fairly essential to maximise the benefit of solar.

The combi like the cylinder came cheap from ebay and was ever so easy to fix.

i think it is extremely green to put to good use once more an item someone else has discarded.

in the case of the cylinder it was a solar installation company whi ripped out a perfectly good single coil cylinder because they haven't sufficient imagination or care about client's money or the planet's resources to incorperate it into the solar system. Their's and their client's and the environment's loss, my gain.

the combi courtesy of a council who when renovating buildings trashed by the ungrateful opccupants rip out perfectly good kit and renew it without a bye your leave as to how wisely they are spending tax payers money on behalf of leaches.

 

[D_Hailsham]

The problem with combi, (or should it be conbi?) boilers is that the size of boiler required for an acceptable hot water supply may be so much larger than that for heating on its own that the boiler will not be very efficient when heating.

As an example, the hot water may need a 42kW boiler but the heating may need only 20kW, so you buy a WB Greenstar 42CDi. This gives you the 42KW for hot water and a heating output of 9.8-30KW. The hot water is fine and when it is -1 outside the heating is fine as the boiler will be giving out 20kW. But when it is warmer outside, say 10C, the boiler now only needs to produce 10kW, which is still OK as the boiler can modulate down to 10kW. But any warmer than 10C outside and the boiler can't modulate any lower so it goes into on-off mode and the efficiency goes down.

It would be worth checking what size heating boiler you need using the EST online calculator and also find out the heat output of your radiators using the Stelrad Elite Catalogue

 

[honda]

thanks to the last two contributors to this thread for your very helpful and involved replies. spoke to the engineer today(a neighbour) asking him which is best to go for and he recommends a combi for the 'simplicity of the system' and 'parts are cheaper' so obviously he has different opinions.
basically i think the decision comes down to me and what i think would be best from knowledge so far gained from searching on here

 

[honda]

any other opinions or thoughts?

 

[gas4you]

A combi is more space saving, but all your eggs are in one basket if it breaks down. No HW or heating till it is fixed.

It can be cheaper to install when comparing to having a new cylinder along with a conventional boiler and with a cylinder you always have the back up of an immersion heater, but a combi will probably need a larger gas supply from the meter.

Unless you live in a very small dwelling, the heat requirement for your property is going to fit well within the range rating parameters of a combi's heating side.

90% of what I am asked to quote for and fit are combi's and all my customers are happy, but I do spend a while asking about their HW usage etc, before I advise anything. Would I have one in my house? I don't think so, but never say never

I would disagree that combi parts are cheaper, there are more of them so more to go wrong in theory and most are expensive to repair once out of warranty.

Personally I have not come across a customer who needs more than a 37Kw combi to date.

 

[swbjackson]

I've got a 40Kw combi in my place but, given the room, would have fitted a stainless steel unvented and sealed system.

 

[honda]

many thanks for advice received so far. i feel i should say that the installation and alteration costs do not(although i'm not loaded lol)particularly worry me as they are a one-off, my concern is the running and maintainance costs in the future being now retired after a lifetime of graft.

 

[corgiman]

. 'parts are cheaper'

EH??

Cheapers parts???


you gotta be kidding?

 

[Paul Barker]

If you have the space and the money and are geting old regular boiler and unvented cylinder every time.


Combis are simple (to install) and easy (for ignorant installers) to understand how to fit.

Reglur boilers and unvented cylinders are hard (to install) and difficult (for the ignorant) to understand how to fit.

Combis are trecherous to fix which will occur when you are old and grey and don't really want incompetent medlers trapsing in and out of your house while you shave with a kettle yet again and huddle in front of the fan heater..

 

[honda]

so what would be the benefit of an unvented cylinder as apposed to a vented one paul? by the way i like your sense of humour!

 

[kevplumb]

Reglur boilers and unvented cylinders are hard (to install) and difficult (for the ignorant) to understand how to fit.

and they explode