Common misconception that combis are cheaper for DHW, for whatever amount of usage really. They aren't in our experience. Definitely go for weather comp as Notch suggests. We have an ASHP now but regardless of what heats the water, with weather comp the house is much more comfortable. Would never go back to fixed outlet flow temp.
-
Looking for a smarter way to manage your heating this winter? We’ve been testing the new Aqara Radiator Thermostat W600 to see how quiet, accurate and easy it is to use around the home. Click here read our review.
New boiler - what to ask the plumber?
- Thread starter nic11
- Start date
Yes, it depends on usage pattern. Might be cheaper if the daily HW is drawn in one hit, so combi people base it on that.
Already had the manual (when we first moved in the boiler had a fault and diagnosis from the manual was a replacement control board. Did that and it fixed it, no problems since), but thanks
Forgive the naivety - heat only, as in just for CH? We would still some hot water?
My thinking is if a plumber is decent they'll give both quotes, but if they are pushing for a new boiler option only, that might be £££££.
My concern over a new system completely is whether it could cope. The gas is 22mm so should be okay, but it goes under a concrete floor so would rather not if that's the requirement. It's a pre WW2 house and today at work someone gave the anecdote of their parents getting a new combi and the house pipework not able to supply enough to it, which has got me wondering.
The boilers only job, is to heat the water, your valve(s), probably in the airing cupboard, then direct the heated water to either, or both CH, or to heat the HW cylinder. Basically, the same as you have at the moment, which is a heat only boiler.
Much depends upon the condition of what you have at the moment, but. Some boiler installer might try to push you to accept a combi, you need to make it clear you want quotes for just a heat only boiler swap, and installation of a combi system.
A few years down the line now, but 40+ years ago, we had our open-vented/heat only boiler system originally installed, and I have looked after it and maintained it since then. It ran fine with an odd few cheap repairs for 20 years, until I decided to have a new condensing boiler installed, the same boiler as you have now. That boiler was very unreliable, and expensive to repair - two pcb's, a fan, then the last straw - heat damaged wiring for the fan, up the back of the boiler, so I opted for a Vaillant heat only, which has been great since. I paid around £1800 for that, then another £100/150 for a fancy Vaillant optimising control system for it, to replace our old, very basic on/off system. The decision to add the latter, has been well worthwhile, more comfort, it makes life easier for the boiler, and saves gas.
That system, has an outdoor temperature sensor, indoor and cistern actual temperture sensors, so it knows the actual temperatures, and what temperatures it has set. From that, it can tell the boiler exactly how much heat it needs to generate, to achieve the set temperatures. My old controls, would have it simply running the boiler at full throttle, then stop. My new one gently trickles to temperature, and gently holds it there.
22mm is normally big enough, for a combi, depending on length of pipe and the bends.
Last edited:
There are pros and cons to any system.
Too many to list here as there'll be some missed.
A good installer should ask you as many, if not more, questions than you ask them.
Really, all you need to ask is what do they recommend and why.
We need to know your lifestyle, expectations and plans for future, in order to come up with a solution... And budget of course.
Main reason for people choosing combis these days is saving space, having hot water on demand (though limited to 1 outlet, 2 max), they're cheaper than other types (mass production) and most of the things that control the system are within the boiler and therefore under the warranty (with couple exceptions).
But you have no hot water backup, unless you fit a leccie shower... Which is daft if you only have one shower!
Ultimately you'll need to bite the bullet and make a decision yourself. Don't underestimate the importance of a good install over system type and boiler model.
You said no bath and only hot water to sink! How do you wash then?
Good luck.
Too many to list here as there'll be some missed.
A good installer should ask you as many, if not more, questions than you ask them.
Really, all you need to ask is what do they recommend and why.
We need to know your lifestyle, expectations and plans for future, in order to come up with a solution... And budget of course.
Main reason for people choosing combis these days is saving space, having hot water on demand (though limited to 1 outlet, 2 max), they're cheaper than other types (mass production) and most of the things that control the system are within the boiler and therefore under the warranty (with couple exceptions).
But you have no hot water backup, unless you fit a leccie shower... Which is daft if you only have one shower!
Ultimately you'll need to bite the bullet and make a decision yourself. Don't underestimate the importance of a good install over system type and boiler model.
You said no bath and only hot water to sink! How do you wash then?
Good luck.
I assume he has an instantaneous electric shower.
As Harry said, it provides heat for CH and HW. An alternative is a system boiler, which does the same, but has the pump and expansion vessel built-in. That might save space, but my preference is heat-only, as having the parts separate makes it easier to diagnose and fix any problems.
Yup, heats up the cold water itself.
Only me and the wife for the last 10 years, previous owners were an old couple who's lived here for 30+. So can't see the current boiler have had a lot of welly, but who knows.
Part of my thinking do I replace whilst I have the money now, or wait until it breaks. If combis are more powerful, could that strain an old house (gas and water supplies) and end up with more problems.
Maybe seeing what each suggests and using that as a guide.
A bit more pressure, in your radiators, and heating pipes, but it will not strain your actual gas or water supplies.
Post some photos of the contents of your airing cupboard, and some of the radiators, for a better opinion of what might be possible.
An argument against switching to a combi (or system) boiler in an older house, and this one is 40+ years.
An electric shower?! Yikes. They are awful. Only good feature is that they work when the combination boiler is broken!
You need to ask yourself:
1) if you would prefer instant/on-demand or stored/tank hot water. A combination boiler means no tanks, which saves space, but it is a single point of failure. It may also need an upgraded gas supply, as they have to gobble a lot of gas quickly to heart on-demand (whereas a tank is heated up much more slowly).
2) What is the flow rate and pressure of the cold water supply into your property?
You need to ask yourself:
1) if you would prefer instant/on-demand or stored/tank hot water. A combination boiler means no tanks, which saves space, but it is a single point of failure. It may also need an upgraded gas supply, as they have to gobble a lot of gas quickly to heart on-demand (whereas a tank is heated up much more slowly).
2) What is the flow rate and pressure of the cold water supply into your property?
Electric shower is a thermo regulated one that does constant temp. It starts to heat the water first and then turns the flow on.
I hear the boiler fire up in the morning and evening (but over the summer not for long). My obvious ignorance thinking it costs more that way.
What do people think of sealed verses vented Systems. The cold water pressure seems fine but hot water is just gravity fed, so part was thinking changing would improve hot water flow rate. Maybe moving to a sealed tank eliminated the loft expansion tank and improves hot water pressure.
Hot water usage - 2 kitchen sinks and washing of hands in the bathroom.
I hear the boiler fire up in the morning and evening (but over the summer not for long). My obvious ignorance thinking it costs more that way.
What do people think of sealed verses vented Systems. The cold water pressure seems fine but hot water is just gravity fed, so part was thinking changing would improve hot water flow rate. Maybe moving to a sealed tank eliminated the loft expansion tank and improves hot water pressure.
Hot water usage - 2 kitchen sinks and washing of hands in the bathroom.
Similar to mine, and yes, they are quite acceptable, much more useable than the early electric showers which many seem to base their poor experience on.
Why does the boiler need to reheat the hw on a morning? It should still be hot from the previous day.
We have our hw set to come on at 3pm, through to 8pm. That keeps the stored hw hot for washing up from dinner, baths, and it remains hot enough next day, to last until 3pm.
The timer is set that way, isn't usually on for long in the morning.
we probably use a quarter or less of the tank a day.
DIYnot Local
Staff member
If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.
Select the supplier or trade you require, enter your location to begin your search.
Are you a trade or supplier? You can create your listing free at DIYnot Local
