I’ve been reading some advice here on other things, and there seems to be a great deal of knowledge and helpfulness amongst members, so hope it’s ok to ask.
We’re going through a house refurbishment, and one of the choices I have to make is to choose a boiler.
I’m ok to pay a bit more for a better boiler but a bit confused about a couple of things.
House is a small Edwardian(solid walls) 3 bed+loft conversion, which will have 1 bathroom and an en-suite shower. We have 2 small children who will eventually get to become teenagers, so maybe the need to run 2 showers at the same time(though I’m sure we could work around that)
Under floor heating donwstairs and normal radiators on the 1st floor and loft
Companies offer a water storage within, but I can’t work out if you always need to pre heat the water, or have the option to just run the water without it going through the storage unit.
I’m not convinced we need the water store. The current boiler(at least 15 years old) will run the heating effectively, and allow washing up to be done while showering the children with a very slight drop in water pressure.
Initial thoughts are the vaillant 838 or 938.or weissmann equivalent, but open to suggestions and appreciate advice.
I think the first question installers always ask is "what size is your gas main" as that limits your options.
The 838 would be more than adequate for the property I imagine... Whether you can run hot water and a shower at the same time is partly down to the actual water pressure to the house rather than the model of boiler in my understanding.
Thank you.
The boiler location is being moved.
Not sure if that means that we’d not be restricted with the gas supply.
Water pressure is very good. Not sure what that means in litres per minute, but it’s been commented by the 2 seperate people that measured it
From experience I would go for a Worcester or vaillant every time.
Is the current boiler a combi?
Currently a combi, which is actually perfect, but very old and probably not very efficient.
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Personally I would go for a 40-42 kw boiler as it's always better to be over rather than under on kw's required.
A magnetic filter will also be required.
Veissmans are a good idea at the time but parts are very expensive and most heating engineers avoid them like the plague, your installer is probably getting a bonus from veissman for installing their boilers.
Is that still the current thinking for boilers?Originally Posted by CaptainSlow
The reason I ask is I have just been told the opposite by a boiler installer who suggested that a smaller (ie correctly sized rather than undersized) boiler working harder is better than a larger boiler working 'less hard'. Reason given was that it keeps the boiler working in condensing mode more often due to the longer burn cycles, so it ultimately uses less fuel for each KW energy produced.
Obviously you don't want a boiler which is to small for the task though!
I should add that the above advice was based on a stored HW solution, so was NOT for a combi boiler. Not sure if that makes any difference?
Last edited by Maysie; 26th October 2018 at 12:47.
This is where it gets confusing.
I’ve also heard the same, but had a too small boiler fitted in a last property, which meant the bath took a long time to fill.
More than happy to pay a fair bit more for one that exceeds the job that it needs to do, but concious of the fact that gas prices are only going one way.
You have to have some overcapacity. But what gets me - is how Combi-boilers are ever recommended for anything other than the smallest of property.
The short-cycling element of their operation day to day - negates their cheap installation benefit.
if not mentioned already you might want to consider including a ground source heat pump.
http://www.energysavingtrust.org.uk/...rce-heat-pumps
Rob.
I guess if you are a landlord (and looking after your own interests and not the tenants) it makes sense.
So is the other option a conventional boiler with storage tank?
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Very true. But look at the number who have installed them in owned houses - it amazes me.
all the 2-5 bedroomed new builds that I'm going to nowadays have Unvented storage systems so it looks like that Is the demand now, its a bit ott for a 2 bed house though.
thats what my 4 bed has and its a cracking system delivering piping hot water and is cheaper to run despite recent price hikes than our very old system at my old 3 bed end of terrace.
If I were doing it from scratch I would definitely go for the heat pump though. Seems too good to miss out on especially with the Renewable Heat Incentive.
Are you referring to a “Mains pressure Hot Water tank” system? (Whereby all hot and cold outlets are at mains-pressure?)
Or - is there anything additional to your system?
I’ve recommended the mains-pressure system for a long time - even on small apartments.
I believe he is referring to this type of system https://www.thegreenage.co.uk/tech/h...ented-systems/
Yeah - that’s what I described/have - a Megaflo tank.
Great system, which allows for balanced full-flow to all mixer taps/showers, usually meaning that “power-shower” pumps can be avoided.
They aren’t cheap tanks, but if you get the largest you can afford/fit - it should sort all consumptions.
I wanted a ‘megaflo’ hot water cylinder for my flat, the plumber turned up with a gledhill unvented cyclinder with a small expansion vessel, was a bit miffed at first as I wanted Rolex but he turned up with a Tudor
Turns out you don’t have to do a drain-down and recharge with these and people ask for a megaflo as that’s what they think they want (me included).
i thought I wanted a Megaflop, but the installer recommended and put in a 250 litre Worcester Bosch unvented cylinder. It has a ten year guarantee, and works brilliantly. Mains pressure here is a touch over 4 bar, so there is a pressure reduction valve fitted that limits hot and cold pressure to 3 bar. Showers are fabulous with no need to have pumps. I’m happy.
Water pressure and flow are 2 different things as you point out. If you have poor flow you will need some sort of stored water system if you have good flow you can look at a combi.
The heating a small boiler will be adequate you just need the kWh and gas main for high flow showers via a combi.
The need for the small hot water store in a combi is to avoid the wait for hot water this will depend on how far from the boiler your outlet is and how often it is used.
You can get very good combi installs and bad ones - a lot depends on the site and then the boiler.
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I have an IVT GSHP in Addick Towers.
The installation costs are likely to be 7 times that of the boilers the OP is considering.
Much the same but ours is a vaillent tank, wish I’d gone a bit larger than we did.
We also had a pumped hw loop installed, not for pressure but to avoid the wait for hw to make its way from the tank to tap. The hw is constantly pumped from the tank around the hw tap loop and back to the tank, via a pump on a timer.
What are the typical timer settings? Is it set for notional consumption periods? (Off overnight)
I would guess it is a large house with long pipe-runs.
Three bed detached 2 bath. 7-22hrs
We work from home hence the longer than average run time.
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