IMM, Andy, Nat Philiso, John, etc, some more advice please

[Suz]

Still chewing over with hubby what way to do CH and DWS.

Learnt a lot from all of you boys in the last few weeks - thanks. Reading with interest the "Thermostatic or electric shower from combi" thread posted by Eno. Makes a lot more sense when you understand the terms without a dictionary of gas and plumbing terms!

The latest brainstorm from us is thus: Replace oil boiler and all tanks with condensing gas combi. Leave crappy water supply of 15mm as is - (11 litres per minute) and plumb it to all kitchen equipment - sink, dishwasher etc. Bring in new 35mm water supply and plumb all "upstairs" stuff with new water supply through combi (and kitchen hot tap). Will feed 2 loos, 2 showers and

1 bath. This is after friendly plumber's advice that just upgrading the supply as is mightn't be enough for our needs as a family of five. Combi will do CH and one large underfloor heating area and bathroom stuff.

Big story, one small question: To avoid digging up lovely new tarmac drive, we would like to bring it through grass to near the front door and then dig across paved step area which would be relatively simple to re-lay, in under door area and straight up the hall (needs levelled anyway to tile, its like a dog's hind leg at mo). But can we? Is it silly to bring 35mm water supply through a hallway in case of leaks etc? Is it stupid to put a gradual bend in the pipe just to save a drive?

Like John's idea of the Mira 415 shower valve. Avoids Bart-Homer-esque moments in the shower, and singed kiddies. Any drawbacks?

Ok that's 4 questions, I'll stop now.

Many thanks Suzanne ¦^D

[Grunff]

But why? Oil is cheaper and (IMO) nicer to work with. Why do you want to switch to gas?

I don't see a problem with that.

[IMM]

35mm will not be enough? See the water company, and see what they will deliver in flow and pressure.

No it is not. See the water company first. Some only allow the shortest route from the water mains to the house.

Suzanne,

If you are bringing in a new 35mm water main, then why are you leaving the existing 15mm main? The water company will charge you extra for two mains entering a property. 35mm will be fine, assuming you will have the pressure and flow, which most 35mm pipes do. See the water company.

2 showers, one bath, 5 people. I would go for a heat bank and a gas condensing boiler. See Christian McArdles posting on the current thread Hot water System. He has bought a new DPS Pandora heat bank and is fitting it in his loft. The same price as a Megaflow unvented cylinder and no overflows. This will do all you want in a hot water mains pressure system and no cold water storage tank. Then fit a condensing boiler. The UFH side is easy enough. See the Polyplumb or Speedfit web sites. combi will do what you want, but it will be a top of the range state-of-the-art very expensive job. It may work out cheaper though and you save space.

Yes fit the Mira 415 shower, or the Screwfix job - I posted the details. I fitted a 415 for a friend 13 years ago. I have used it occasionally and it operates very well. It reacts very quick to pressure fluctuations in the system. You notice a pressure change rather than a temperature change.

Another suggestion will be to install a pressure equalising valve at the main stop c*ck. One pie directly to a heat bank, or combi, and the other, to the cold outlets. Then cheaper shower mixers can be used. The equalisation valve will do all the house, inc the two showers. You will have to price up two 415s and two shower mixers and a 22mm equalisation valve. The valves are available from Plumb Center.

[Andy Hall]

My only concern here is whether even a large combi is going to give you a fast enough production rate of hot water if you want to use the showers and bath simultaneously.

Consider that in effect in cold weather the specified flow rate of the combi will be all that you will get at shower temperature. If the mains supply is (say) 8 degrees and the shower 40, then at the standard 35 degree uplift temperature by the boiler you will not be mixing much cold in with this and the combi flow rate becomes the total rate.

Check out the flows that you want for the showers (personally I wouldn't accept less than 15 litres/min each) plus the bath and you may be in trouble with a combi - even a large one.

You may find that you need to have some form of heat storage, whether it be a pressurised cylinder or a heatbank. There is nothing to stop you heating one of these from a combi using its CH side and motorised valves (effectively like a non-combi), then using the hot water production from the combi to run some of the hot water services and the stored water the rest.....

.andy

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[IMM]

The Screwfix Pressure Balance Shower Valve is rated at 7 litres/min, and that is mixed water, so drawing less from the combi than 7 litres/min. Most showers are around this. This makes a 13 litre/min combi adequate for two simultaneous showers.

In this case, as liberating space is important, two combi's might be the best approach. One large (13 litres/min), for the bath, and one smaller, around 10 litres/min.

[Owain]

"Suz" wrote | "Grunff" wrote | > > Replace oil boiler and all tanks with condensing gas combi. | > But why? Oil is cheaper and (IMO) nicer to work with. Why do you | > want to switch to gas? | We have been advised by a few different un-involved parties that the gas | bills are lower over time.

Also, no unsightly oil tank in the garden, and IMHO gas ch is more appealing to house buyers than any other type. I'm not saying it will add £1000s to the property compared to oil, but oil ch can be viewed as a slight drawback by some prospective purchasers because of the tank/smell/refilling - even if the energy itself is a bit cheaper.

Owain

[Suz]

No he meant one supply of 15mm would not be enough and to put in a 35mm in addition. Pressure is 5bar and flow rate with current old 15mm supply is

11litres a minute

The route won't be a problem as main connection is over the hedge at the point where grass meets driveway :-), just a groovy swerve at the bit near the door. Apparently it is our responsibility to choose route, they just inspect it to give it the OK

We thought we would leave the existing one and all the internal plumbing to kitchen stuff intact so there would be no unexpected dip in pressure from dishwasher etc. It would be a one off installation charge for new main of just over £100 at the mains (plus our costs of installation on our side). We do not have water charges in Belfast :-), just terrorists and stuff.

Will the pressure equalising valve reduce the flowrate at all?

[IMM]

No. the hot and cold supplies go through it. The hot supply can be on the cold feed side of a combi, unvented cylinder or heat bank. when one side of the valve drops in pressure (someone draws-off cold water) the other side drops its pressure to suit, so it is equalised. some are built into shower mixers, some hare 15mm and are to be fitted before a mixer, others are 22mm and are to be fitted at the stop-c*ck (one leg to all cold taps the other supplies the hot water appliance).

[Suz]

Yes, and my comment is "no point in having 2 bathrooms if you don't intend to use them both at the same time"

We had considered putting an electric shower in for the girls and hogging a brilliant one for ourselves, but we reckoned they would just hijack ours when they grow up.

We have been looking at the Megoflo brochure.

A couple of questions came out of this: Is it not a waste of energy to have hot water stored and therefore lose heat/energy before it gets used? If you are having a shower and hot water gets drawn off somewhere else, do you get frozen in the shower?

[IMM]

Give unvented cylinders a wide berth. Go for a heat bank. Look at the current thread about the Pandora. About the same price.

In theory yes. But the heat looses are not that great.

It depends on the flow rate of the heat bank, combi etc. Installing equalising valves reduces influences from one draw-off to the other. Also having large enough pipes and splitting them to hot and cold after the mains stopcock helps.

[The Natural Philosopher]

My tank don't smell, is a cinch to reill, and is nor covered with attractive climbing roses and creepers.

[Andy Hall]

It would do if you think that 7 litres/min for one was good enough. I don't. This is not much better than a crappy electric job.

.andy

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[IMM]

There is a big difference between 4 litres/min and 7 litres/min. I'm sure this mixer can take more than 7 litres/min though.

[Andy Hall]

Exaactly.

Electric showers are very disappointing. 5 litres/min if you are lucky. They won't thank you for that when they are washing their hair I can promise you.

As to hijacking, I can confirm that they will hijack both and will leave both in a condition other than that in which they would hope to find it.

They are great at hanging up the clothes that you just washed as well

- until they run out of floor space.

A permanent supply of bin liners is essential while they go through the teenage metamorphosis.

Not really. If you have good insulation the heat loss becomes tens of watts - i.e. less than a light bulb.

Not if the plumbing is designed properly. If you have either a stored hot water system where the water is used directly, having been heated to 60 degrees, or a heatbank where it is hotter, but the stored water is used indirectly through a heat exchanger then you are rather better isolated from the effects of temperature change in the cold water affecting the hot water production rate.

If you mix 60 degree hot water with some cold to produce 40 degree water for a shower, even if the cold water temperature varies over the year the effect is not as great as if you are using a combi and *all* of its production is used for the shower. Then you would be vulnerable. This is one reason why IMM is suggesting that two combis might be an option. The peak needs might not be met by one.

Having some form of storage would improve the overall system performance considerably - whether it's a pressurised cylinder or a heat bank.

.andy

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[IMM]

Or two combi's. Liberating space is one aim here. Combi's neatly fix to walls. Unless a heat bank is designed to be square and sit at the bottom of a cupboard taking up little space. Long thin cylinders take up space.

[Andy Hall]

There's a big difference between 50p and a pound as well, but neither will buy a large G&T........ :-)

.andy

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