Any advice on doing this?

I've bought a 70's built town house (yes I can drive into my house :D) with gas fired brick warm air heating and I assume theres a boiler for the hot water.

The layout of the place at the mo is a joke (access to the garden via a downstairs bedroom!) and needs total redecorating, so I'm going to put in GCH and relocate the kitchen to the downstairs bedroom.

Now then, am I right in thinking that if I get a combi boiler then I don't need a hot water tank?. Also do I need a cold water tank - can I just run everything off the mains?

I take it theres no problem with pumping water round 3 storeys either?

Any recommendations on a good Combi boiler?

Thanks

Justin

I'm plotting a similar scheme myself. (Again in a 3 floor town house)

You won't need a hot water cylinder with a combi. I am, however unsure of how the pressures work out. I think you will have to talk to your waterboard to find out what they will supply.

I'm sure there are some experts lurking here somewhere!

My main concern would be pressure related, you may need helper pumps, depending on the water pressure. The boiler you get will have a big influence as well, in other words, some small boilers will not be able to heat the water at such pressures.

Check out mrcentralheating.com for ch packages

Clickable (http://www.mrcentralheating.com/)

Does not look too bad

HA HA HA stick to the cars people and leave the plumbing to us professionals!! :p:p:p

Why not contribute some of your knowledge instead of taking the michael;):D

sorry mate, just a bit surprised to see plumbing talk on here.

You won't need a hot water tank the combi will do the hot.If you put the entire house on the watermain it will be fine, 3 storeys is no worry, 10 storey blocks of flats don't need 'helper pumps?'. In my opinion the best Combi available is the worcester 28CDi. Mr central heating is indeed cheap but the boilers they have are not that great. (combis vary greatly in hot water flow rate!) Get your rads from mr central heating and your boiler from a local supplier. Remember though you will actually be breaking the law if you fit a gas appliance yourself!!!

Scott

Thanks chaps

What about the cold water tank? In the last block of flats I lived in I had a combi and no cold water tank (I think). I'm sure that my new house has a water tank but I want to get rid of it. Can I run all cold water off the mains and not via a tank? Or are there some rules about this?

Justin

Our 3 storey house is on mains only and uses a combi, no probs with central heating pumping

There are regs for connecting direct to the mains - the water board want to make sure that you can't contaminate the drinking water supply.

I've always found plumber's merchants helpful, provided you go in when they aren't busy.

Having no tank can be helpful as you've got equal pressure for the hot and cold water, useful for thermostatic showers as some thermostats require equal pressure.

The only issue with combis is if you have multiple bathrooms ie lots of similtaneous hot water use the flow rate drops, as the output of the boiler has to be split across all the taps.

The only issue with combis is if you have multiple bathrooms ie lots of similtaneous hot water use the flow rate drops, as the output of the boiler has to be split across all the taps.


That's my worry as well. I understand that some combis have a small "thermal store" of hot water for peak demands like this.

Hi mate
you need to take a look at the house and the people in it.Sometimes combis are the worst thing to have.Yes they are a doddle to install but in the wrong house enviroment they could be the worst thing.

take into account
1:how many bathrooms?
2:what is the water pressure like?
3:is it a recently renewed water main?
4:how many people in the house?

Dont forget that a combi can only do one thing at once.So if there is 3 teenage girls plus mr and mrs then thats 8 or 9 showers/baths a day.So all the time its feeding the bath or a shower(unless its electric)the heating is off:(

Your best bet is to ask some friends if they can reccomend a good heating installer and ask their advice.Most probably would say we'll put a combi in for ease of installation but they wont come back when it isnt working right!!
If you do go for a combi get a good one not some cheap b+Q crap.
We only fit Worcestor boilers now because we feel they are the best on the market and rarely go wrong.Also sourcing spares for the older worcestors 15years+ is easy.

SN

If you have space for a tank, why not look at converting the system to use an unvented hot water cylinder, heated by a conventional (non-combination) Boiler?.

One of the problems with most Combination boilers is that they can't heat the water fast enough for a high flow shower (if you want one) unless you go for a woucester high-flow, or similar, which are quite expensive.

The installation of an unvented system is straight forward, and you get a balanced hot/cold water feed at mains pressure, and the recovery time is very quick (i.e. 15-20 mins to heat up again if you empty the cylinder). You also don't suffer from the either/or situation with heating and hot water services.

Given that I reused our existing boiler, the cost was less than a suitably rated combi boiler as well. You also don't need an expensive shower pump, which need replacing every few years.

You do need sufficient pressure from the main (2-3bar), and a decent diameter cold water feed as it needs sufficient flow to supply both hot and cold supplies at once - I have a 1/2 inch lead cold water feed, which is marginal.

The shower pressure / flow is very good, but pressure drops if someone turns on an additional tap or flushes the loo. The cold water feed needs to be at least 22mm, preferably 28mm.

You also don't have stored cold water, but you probably wouldnt with a combi either.

Cheers,

Alex

[Edited by AlexM - 12/12/2002 2:07:14 PM]

[Edited by AlexM - 12/12/2002 2:08:51 PM]

hmmm excuse me if this is grandma and egg sucking time but i think theres some confusion hear about Tanks in the loft
a traditional central heating system and hot water tank (lagged tank usually in airing cupboard)require two tanks in the loft

Neither of these tanks supply cold water to your taps as this comes direct from the mains supply in almost every case bar huge blocks of flats.

The large tank in youre loft provides the water pressure to your hot taps and feeds directly into the lagged hot water tank

the smaller tank is a header tank for the radiators and makes sure the rads and connecting pipes remain filled with water it also has an expansion pipe which will allow the heated expanding water to run off into the tank and acts as a kind of safety valve.

Combi boilers require no tanks in the loft and some insurance companies will look kindly on this for obvious reasons.
they are fine as mentioned already for smaler properties with up to two bathrooms three at a push after that .

If you want a really good system with loads of hot water pressure then a mains pressurised system works wonders I dont know the fine details but basically you get a large hot water tank which can be stored on any floor level(as its not gravity fed)which is fed direct from the cold water mains and makes your hot taps run as fast as the cold
this is heated by a farly traditional boiler and is more fiddly to maintain but it gives superb showers on a par with a decent power shower.

Bit of a sweeping statement about water pressure Scott?

Water companies have to provide minimum of 15m Head outside the property in their own pipework and 10m at point of supply at the stop cock. Give some further pressure loss due to fittings, bends etc then a town house could have mains pressure problems if a combi is used in an area that has a PRV fitted.
A 10 storey building is going to need approx 30m Head of mains pressure to avoid booster pumps and that is pushing it. Many ater companies use timed PRVs to reduce pressure at night (to reduce leakage) and will aim at 20/25m Head during the early hours.


Justin...

Get your plumber (or contact your Water Company) to find out what the mains pressure is during the day and more importantly the night. Ask if a PRV is fitted in the distict. Don't rely on mr. plumber taking a quick pressure reading during installation.

You can ditch the cold water tank but must install backflow/back pressure fittings that meet the Water Supply Regs 1999 to avoid complications, but qualified plumbers should know what to buy.

Avoid plumbers talking about fittings meeting Water Byelaw approval as they are not up with the times and will be supplying items that are not approved.

Nick

Nick I assume you work for the waterboard?

Nick, almost word for word what my local water co. told me...

Based on this, I think we will need a booster pump of some kind for our system.

I used to Scott. Now I work against water companies.

I run an industrial water/effluent consultancy - dealing with reducing water co. charges for large water users, but I dabble in water supply problems such as pressure, leakage, Water Regs and Legionellosis issues. Also environmental issues (ISO14001 & IPPC) for same type of clients.
Best not go to far otherwise I'll have to rent a banner :)

Nick

I had a combi boiler fitted a couple of years ago and am on the whole happy with it. Howevewr, I have experienced many of the niggles described here. The hot water supply just does not cope with a second tap running (either hot or cold) and the shower pressure/performance varies greatly depending on the time of day/year and whether the heating has been switched on.
To explain, you get a better, hotter shower in winter because if the heating is on the heat exchanger is already up to temperature to heat the hot water supply.
In the summer when the heating is off and 3000 locals are running their sprinklers, the water pressure drops in the area causing a poorer flow rate and the heat exchanger is starting from cold.

I reckon that the capacity of the one I have fitted is probably marginal for my house and mixed with a poor mains supply (1.7 bar max according to the gauge on the boiler when I filled the system) I get good performance if I'm aware of its limitations. As one guy said, if I had a housful of kids I would have to look for either a higher capacity combi or a tank system.

Can anyone describe the effects of running a lower pressure in the system (less heat?). Also, what is the max pressure (at full temp) that you think you should see?

Neil.

Neil..I'm a little confused about your interpretation of your mains water pressure coming into the house and reading it from the gauge on the combi. The gauge is purely an indication of the pressure within the heating system and has no bearing on the hot water performance of the boiler whatsoever. The gauge should allways be read when the systen is cold to get consistant readings, a new system should be filled to about 1.5 bar (cold) and this will probably rise to 1.8/2.0 bar when hot. However when an existing heating system is coverted to a combi type then the filled pressure should only be .5/.8 bar (cold),the position of the boiler/gauge in the house is also important as if the boiler is fitted in the loft and reading 1.0 bar then the downstairs pipework/rads will be subjected to 1.5 bar. Water pressure is also secondary when specifing combi boilers as you can get 3.0 bar through a pin hole and zilch litres per min which is important.

Mog

Mog. What I meant by that was that when I pressurised the combi system after a drain down I could only get that amount of pressure into the system and as you fill the system from the mains via the filling loop, I assumed that I would be reading the maximum mains pressure. I guess the actual reading must be higher judging by what you say as the boiler is located upstairs which would sap a couple of bar I suppose?

Neil.