What's most powerful, unvented or vented and pump? Mira Plat

[danyeates]

Hi,

I'll give you a brief rundown of our nightmare! We had a new bathroom fitted and the bathroom fitter recommended we get a digital power shower, so I bought a Mira Platinum pumped digital shower. He fitted it to our system, which consists of a regular boiler, cold water tank in the loft (this JUST feeds the cold supply to the shower) and a hot water cylinder in the airing cupboard. This is fed from it's own cistern which is built into the hot water cylinder. It's very old!!

As a result, the heads aren't balanced, and the capacity isn't big enough, it runs out of water. Therefore, it just isn't working very well. Neither the cold water storage tank in the loft or the hot water cylinder are large enough.

Then the boiler packed in and rather than change the new Mira Platinum pumped shower, we went for another regular boiler, a new Vailant. This has been working fine.

Now however it's getting annoying only being able to have a 4 minute shower so we want to do something about it. The options are...

1. Change the cold water tank in the loft for the minimum required, 230 litres, allow this to feed both the cold supply to the shower pump and the new hot water cylinder to provide equal heads. Fit a new vented hot water cylinder in the airing cupboard fed from the cold tank in the loft. This needs to be quite large. We would also have to reconnect the old small cold water tank in the loft to the central heating system. This is currently fed from a small compartment in the hot water cylinder.

2. Change the old vented hot water cylinder for a new pressurised unvented cylinder. The old cold water storage tank in the loft will become the heating cistern. Easy job. There's already mains pressure to all the taps including the bathroom, mains pressure water supply in the airing cupboard and an overflow from the old hot water cistern which we can use for the pressure relief valve. With this option I would have to change my shower mixer to a pumped version as it's different. This is about £300+!

I'm currently getting 3.0 bar constant mains water pressure in the house. Flow from the big bath tap is 13.6 litres per minute.
I'm also getting 15 litres per minute from the Mira shower when on fully cold (so running off the cold tank in the loft only).

So, the question is, what option is best? Will I see a reduction in flow from the pressurised unpumped version, or will it be about the same, or better maybe? The pressurised unvented tanks seem to be regulated to 3.0 bar which is what I'm getting anyway. My pumped shower is fantastic for a while, but the flow soon drops off when the tank empties and can't refill quick enough.

Any and all help appreciated please as I'm aiming to order the tanks and/or new shower ASAP!

Thanks,

Dan

 

[danyeates]

Got asked for this info on another forums so I copied it over here too...

It's a 2 bed house, one bathroom, 3 people.

Boiler is a Vailant ECOTEC Plus 41, open vent 15kw.

The heating is open vented, fed from a reservoir in the hot water cylinder. The hot water is open vented, fed from a little cistern built into the hot water tank. Pic...

Top of the hot water tank, the front part with the float valve is the cistern, this feeds the hot water tank which is behind and underneath

There is a 3 way valve and central heating pump fitted in the airing cupboard.

Thanks.

Dan

 

[danyeates]

Also just checked the kitchen tap, it's flowing at 15.6 litres per minute, 3.0 bar.

 

[Googlyhead]

I thought the general idea of a pumped shower is to get the absolute maximum output possible! So I have the simple opinion that if you like your (pumped) shower, you should keep it.
As you have the room, I believe a header tank to be a useful feature. Plus there's the extra complexity, (hyped-up) dangers, and regular checks required for a pressurised tank.

If your cisterns are having a lot of trouble keeping up (and the float in the HW one looks pretty new), I'd have doubts about the shower output.

 

[danyeates]

The shower says the cistern must be 230 litres to keep up with the maximum 16 litres per minute possible flow, so the cistern simply isn't large enough. The cold tank in the loft must only be about 75 litres or so.

I had it set in my mind that I would go for an unvented cylinder, but I'm not sure anymore. On the other hand, it seems a lot of work to fit a larger cold water storage tank and the structure to support it, rig up the old cold water storage tank to become the heating header and fit a new vented hot water cylinder. My shower is very powerful, it just doesn't last very long!

 

[seco services]

If your cisterns are having a lot of trouble keeping up (and the float in the HW one looks pretty new), I'd have doubts about the shower output.

If the shower was installed correct in the first place then it would never of of had any issues.

 

[danyeates]

Absolutely. I'm very annoyed at our bathroom fitter. He recommended we have a digital shower and recommended the Mira pumped one. He then fitted it and didn't tell us that the current heads weren't balanced, and that neither tank was large enough.

Our boiler then packed up and we had a standard open vented one fitted as per a recommendation from a gas engineer as the shower was fairly new so I didn't want a combi.

If the bathroom fitter had told us our system was unsuitable for the shower, we'd have changed the tanks and/or boiler at the time and got a complete system that's all perfectly compatible.

I've been doing so much research over the past few months and know how all the systems, boilers, cylinder etc. all rig together and operate, it's now a case of finding out which is best for my circumstances and doing it all properly. I know so much more now than I did when the bathroom went in, but that's the benefit of hindsight!

 

[danyeates]

One thing I did notice last night was all the manuals for unvented cylinders say they require 22mm mains water supply pipe, the mains water supply into my house (and into the main stop cock) is only 15mm. Is this going to cause a problem if I go for an unvented?

 

[heatingeng]

Hi,

I'll give you a brief rundown of our nightmare! We had a new bathroom fitted and the bathroom fitter recommended we get a digital power shower, so I bought a Mira Platinum pumped digital shower. He fitted it to our system, which consists of a regular boiler, cold water tank in the loft (this JUST feeds the cold supply to the shower) and a hot water cylinder in the airing cupboard. This is fed from it's own cistern which is built into the hot water cylinder. It's very old!!

As a result, the heads aren't balanced, and the capacity isn't big enough, it runs out of water. Therefore, it just isn't working very well. Neither the cold water storage tank in the loft or the hot water cylinder are large enough.

Then the boiler packed in and rather than change the new Mira Platinum pumped shower, we went for another regular boiler, a new Vailant. This has been working fine.

Now however it's getting annoying only being able to have a 4 minute shower so we want to do something about it. The options are...

1. Change the cold water tank in the loft for the minimum required, 230 litres, allow this to feed both the cold supply to the shower pump and the new hot water cylinder to provide equal heads. Fit a new vented hot water cylinder in the airing cupboard fed from the cold tank in the loft. This needs to be quite large. We would also have to reconnect the old small cold water tank in the loft to the central heating system. This is currently fed from a small compartment in the hot water cylinder.

2. Change the old vented hot water cylinder for a new pressurised unvented cylinder. The old cold water storage tank in the loft will become the heating cistern. Easy job. There's already mains pressure to all the taps including the bathroom, mains pressure water supply in the airing cupboard and an overflow from the old hot water cistern which we can use for the pressure relief valve. With this option I would have to change my shower mixer to a pumped version as it's different. This is about £300+!

I'm currently getting 3.0 bar constant mains water pressure in the house. Flow from the big bath tap is 13.6 litres per minute.
I'm also getting 15 litres per minute from the Mira shower when on fully cold (so running off the cold tank in the loft only).

So, the question is, what option is best? Will I see a reduction in flow from the pressurised unpumped version, or will it be about the same, or better maybe? The pressurised unvented tanks seem to be regulated to 3.0 bar which is what I'm getting anyway. My pumped shower is fantastic for a while, but the flow soon drops off when the tank empties and can't refill quick enough.

Any and all help appreciated please as I'm aiming to order the tanks and/or new shower ASAP!

Thanks,

Dan

I would just add bigger tanks in loft ,this should solve all your problems

 

[heatingeng]

One thing I did notice last night was all the manuals for unvented cylinders say they require 22mm mains water supply pipe, the mains water supply into my house (and into the main stop cock) is only 15mm. Is this going to cause a problem if I go for an unvented?

If you get unvented you will need to change the shower. No need. just get the shower you have had fitted correctly and it will be very good.

 

[Googlyhead]

If your cisterns are having a lot of trouble keeping up (and the float in the HW one looks pretty new), I'd have doubts about the shower output.

If the shower was installed correct in the first place then it would never of of had any issues.

I actually meant doubts re. the ability of a mains pressure shower. But see the point!

And I'm no expert on mains water supplies, but 15mm would seem small for most properties these days. The best question would be; do you notice when a second tap is turned on? The pressure/throughput isn't going to change if you do get a pressurised cylinder; what you get at the tap now is what you'll get after.

 

[Googlyhead]

Do you know how old, or any other details of the supply pipe?

I'm presuming as the hw tank is so old, the property is too. And if it's a lead pipe, there's usually a possibility of getting it replaced (hence, upgraded, hopefully!) free.
Might be a good first step to see if it helps the smaller tanks keep up, and if nothing else, will only benefit any replacements.

 

[danyeates]

would just add bigger tanks in loft ,this should solve all your problems

Read more: //www.diynot.com/forums/viewtopic.php?p=1943034#1943034#ixzz1HnsCd8hb[/QUOTE]

Thanks for your replies. I'm swaying that way I must admit.

Is there a way I can get the tanks to fill up quicker? At the moment they're filled by a floating valve but the flow is so slow it can't keep up at all. Any way I can get them to fill up quicker?

Obviously larger tanks will help, but I'd like them to recover quicker. There is 3 bar of pressure from the mains, but it seems very slow flowing into the tank through the flat valve. Is there a float valve which will allow for a fast flow?

 

[heatingeng]

Thanks for your replies. I'm swaying that way I must admit.

Is there a way I can get the tanks to fill up quicker? At the moment they're filled by a floating valve but the flow is so slow it can't keep up at all. Any way I can get them to fill up quicker?

Obviously larger tanks will help, but I'd like them to recover quicker. There is 3 bar of pressure from the mains, but it seems very slow flowing into the tank through the flat valve. Is there a float valve which will allow for a fast flow?

You could fit a 22mm valve or maybe the valve you have is a bit blocked up .
High pressure showers empty tanks very quickly i would say bigger tanks is the only way.

 

[danyeates]

Do you know how old, or any other details of the supply pipe?

I'm presuming as the hw tank is so old, the property is too. And if it's a lead pipe, there's usually a possibility of getting it replaced (hence, upgraded, hopefully!) free.
Might be a good first step to see if it helps the smaller tanks keep up, and if nothing else, will only benefit any replacements.

House is probably 1970's. Cheaply built 2 bed terrace on a housing estate full of the same houses. Pipes are copper, I'm sure.

Flow at the downstairs kitchen tap (all on 15mm pipe) is 15.6 litres per minute. Pressure is 3.0 bar with no taps on. Drops by 1.5 bar when a tap is fully opened.