Low pressure on Mira Combiflow shower

[Madrab]

The Grunfos needs a break tank, can't be connected straight to the mains without prior approval which would be hard to get, too high a flow. Yes, it could be connected to a combi

The Salamander is the better choice and boosts pressure by up to 1.5bar and but tops out the flow at the regs limit of a pump connected to the mains @ 12L/Min. It's pricey though.

I do feel I am repeating myself a little though. You need to know what you are starting with and what end result you want, before you can design an effect solution.

 

[richardc1983]

Yes I need to check the flow rate but I was also led to believe that the grundfos could be connected directly to the mains as per the below link it says it is ok. There are two versions one has a built in tank.

http://www.prestigepumps.co.uk/uploads/files/Grundfos_1/UPA_15-90.PDF

Tje pump is also limited to 12l/m so you don't need permission from the water board as I already know from them that you can pump upto 12l/m.

 

[Madrab]

You know the flow rate, it's the pressure you need to know now!!

There is nothing in the linked doc thats states the grundfos is limited to 12L/Min it actually states it can supply up to 0.3L/Sec x 60 which is 18L/Min.
Also there couldn't be a version that has a built in break tank. If you realised what a break tank was you wouldn't have said that. A break tank is like the size of a Cold Water Storage Cistern able to supply a pump like that without running dry. It, quite simply, couldn't be 'built in'!!

As that Grundfos pump can deliver more than 12L/min it needs permission from your supplier for mains connection to avoid possible delivery drops to other customers, As I said before

The only pump you have suggested that is limited to 12L/Min is the salamander home boost - As I again said before.

 

[richardc1983]

http://uk.grundfos.com/products/find-product/home-booster.html That is the one I was referring to. It's s new version and states has an inbuilt tank.

Regarding the one I linked to I had read from another post on here others who had used them you see.

I might contact the water board and ask them but first gonna find out the pressure.

 

[Madrab]

lol...that's better, now I can go with that one. That's basically a big tank with an in-built pump and controls, not a pump with a built in tank
Only issue with that one is it's over £1.3K!! not something I would have considered for you give your situation, a bit overkill surely?

This is all getting a bit silly now tho. All that to cover an extra couple of L/Min for your shower?? Where would you put it? It's a really significant installation!

Compare that to the salamander home boost at £350

 

[richardc1983]

Yes I agree, it seems silly but the extra 2l/m would really improve the sjower experience. Like you say its pressure that also contributes so I need to find out what the score is there.

The other pump you mention the £350 is much better, the main reason o was going for the grundfos though was it only costs £140. I wonder if water board would give me permission to use that one?

 

[Madrab]

Of course, All you can do is ask though I have seen those requests refused in the past.

The pressure is the key though, not necessarily the flow

 

[richardc1983]

Of course, All you can do is ask though I have seen those requests refused in the past.

The pressure is the key though, not necessarily the flow

Wonder if there's a way they could increase pressure for me?

 

[Madrab]

Do a pressure test, take it from there!

 

[richardc1983]

Bit of an update...

As this is a pressure differential valve it balances the temp by adjusting the pressure. We have the hot water on our boiler set quite low so that can wash hands at hot taps without having to have the cold on.

Today I tried something I haven't tried before. Turned the boiler up to the Eco setting which is what glow worm recommend for decent hot water temp/economy. We them were able to have the shower valve bang on halfway which means the valve will have been mixing water 100/100 on both sides. A slight tirn to the right keeps the flow to just short of 12l/m and produces a hotter shower. Having it bang in the middle is still a warm enough shower but when it was on the lower boiler setting meant we had to have the dial turned further to the right which means the valve shuts off the cold rather than a mixer shower that will mix more hot. There is a fine level on the valve where you turn it too far to the left/right as in hot or just cold and you reduce the flow down by 2/3l which was producing the issue we had. Having the boiler set too low was the issue.

On this valve a slight turn to the left or right should be cool or hot enough for each person, not having the boiler hot enough means that you turn it beyond the optimum flow setting so it starts reducing water through the cartridge when in reality having it this far round with the correct boiler temp means the shower would be too hot.

Shower flow now is pretty much the same as the taps in the house.

 

[Madrab]

Bit of an update... As this is a pressure differential valve it balances the temp by adjusting the pressure. We have the hot water on our boiler set quite low so that can wash hands at hot taps without having to have the cold on.

Some information we didn't have at the start, you didn't mention you had the boiler hot water setting turned down

Oh and as a footnote - hot water to cold water ratio, for a comfortable shower is usually around 2:1 hot to cold

 

[richardc1983]

Bit of an update... As this is a pressure differential valve it balances the temp by adjusting the pressure. We have the hot water on our boiler set quite low so that can wash hands at hot taps without having to have the cold on.

Some information we didn't have at the start, you didn't mention you had the boiler hot water setting turned down

Oh and as a footnote - hot water to cold water ratio, for a comfortable shower is usually around 2:1 hot to cold

Yes sorry about that. I turned it down as we didn't have mixer taps on the other taps or kitchen but now they are all mixers I never adjusted the hot water you see. Just left as it is as we checked other taps and it didn't matter as flow was still 12l/m out of them. So it's the shower that restricts it down.

 

[richardc1983]

Yorkshire water came out to check the pressure, they said that there is 5 bar of pressure at the outside tap which is fed off the stop cock in the kitchen. There is a flow rate of 18l/m at the outside tap apparently but I think he was being optimistic as the kitchen tap which is closer he was saying got 15l/m.

He then measured the shower for me and said it was 8l/m which is completely against what my bucket test showed and my bucket has measurements along the way! The bath taps were showing 15l/m apparently.

Anyway ive been reading up about removing the flow restrictor in the boiler. Apparently my boiler is only capable of 12.3l/m and has a 12l flow restrictor in place. I removed this yesterday as I do believe that these things especially in shower heads there is natural pressure loss through the boiler/shower itself. if I want really hot water for washing up then ill turn the flow of the tap down. The shower is a little more powerful now and the temperature is the same as before, nice and hot.