New Boiler Advice

jc86

Hi,

Just moved into a new house which has a really old boiler, no heating controls etc - we want to replace it with a new efficient one.

At the moment, its a vented conventional system. The expansion and hot water tanks are both in the loft, as there is no space on the upper floor level. Cold mains pressure seems pretty high compared to our previous homes.

House is a 3 bed (plus study), detached, currently has one family bathrroom with thermostatic shower. We are hoping to add an ensuite shower room in the next year or so. We dont run long baths, as 95% of the time we shower.

Plumbers have advised to go for a big combi, possibly with an electric shower in the new ensuite.

The alternative would be a replacement conventional system. But the plumber said that with two showers we would need a pump to have reasonable HW pressure, but apparently that would need to go under the bath (noisy?) or in the loft (which apparently means we need a more expensive pump?).

He did suggest we could also go unvented cylinder, but said the expense of that was likely to be significant.

We really arent wedded to either system, does anyone have any experience of similar situations?

Thanks!

CashStrapped

There are only maybe a few thousand posts on this subject, so read the backlog.

Basically it comes down to how you live and the size of the property.

Combi -
Ideal for small houses/flats with one bathroom (maybe an small en-suite at a push).

Pro:

1. Take up a small amount of space. (no need for any extra tanks)
2. Hot water on demand.
3. Very efficient for light users and small houses.

Downsides

1. Hot water pressure can be poor (especially if two people are using water at the same time). The flow may reduce to a dribble.
2. You have to wait for the hot water to come through. This can mean 30sec or running the (cold) hot water untill the boiler fires up.

System Boiler - Ideal for larger properties with more than one bathroom.


Pros:

1. You can run more than one outlet without a noticable drop in pressure. i.e run two baths at same time.
2. Highly insulated tank means you still have hot water on demand.
3. You have "mains pressure" hot water, which means good showers. You add pumps to the showers to make them even more powerful.
4. You can get a hot water tank that has an input for solar power if you are considering it in the future.
5. Tank may also come with an immersion element, so you have an electric back-up.
6. Modern storage tanks are highly insulated and have fast heat up times.
7. The tank can be put wherever you want. Only the plumber may want it somewhere easy to access. However, if you want it in the loft, it can go in the loft. You will just have to pay for extra pipework to it. Ensure all pipework is well insulated. In reality it is best to have it near the boiler itself but it is not a requirement.

Downsides

1. You need space for a tank. (although see point 7 above.)
2. There is the possibility of using all the hot water up in the tank. However this may only happen if you incorrectly size your tank for the property and number of occupents.

So that is a rough guide. there is no right or wrong answer. It depends on how you use the house and what your preferances are.

matelodave

I'd go for a combi myself - we had one for 12 years and it was fine, water pressure was OK for showers, it took a bit longer to fill a bath but you could have as many as you liked, one after the other. We had no problems with others in the house turning taps on or off - the thermostatic shower took care of that. Pressure was better than that from a loft tank.
You can also save on the space required for the hot water tank and the tanks in the loft. You can fit the boiler in the loft if you want to, ours was fitted in the airing cupboard where the hot water tank had been.

Both my daughters have changed their system boilers and tanks for combi's and neither of them would go back to a system boiler and tank.

We can't have one now as we are all electric and have a pressurised hotwater tank with a heatpump which was expensive to install but quite cheap to run.

CashStrapped

First and foremost you need a good plumber. They should do dynamic flow tests on your mains water pressure to ascertain if it is actually suitable for a combi.

A lot of the problems with combis come from poor fitting. Many times the mains supply pipe should be upgraded to improve pressure but this is often overlooked.

I have yet to be in a combi property with equivalent pressure to my old open vented system at around 20l/min from the hot tap.

However, as I said, you need to work out what your priorities are.

Most importantly, get a good pumber!

macman

Why not go through one winter and see how the existing boiler performs? Get it serviced now. 'Old' does not automatically mean 'inefficient', and even if it is, it will still take you a decade or more to recover the capital cost in fuel savings.
You can still upgrade the controls and fit TVR's and a digital programmer for a relatively small investment.

AlexMac

In a house identical to yours, but with 2 bathrooms, we already had a system boiler and storage tank, and liked this arrangement- but when, 6 months ago we had to replace the boiler, we also changed to new system boiler and an unvented (pressurised) storage tank. With fantastic improvement in the water pressure from the shower heads, and no messing about with pumps to increase pressure.

Miles better than the biggish Vaillant Combi we put into another place a few years ago, also with two bathrooms; that was OK but nothing special.

I ain't got hair so that's not an issue but 'er indoors says the new showers are great for rinsing- saving time (= money & energy?). Costs a bit more, but worth every penny IMHO