Unvented Cylinder

[Danv44444]

Hi Guys,

I would like to ask your advice on an unvented cylinder hot water system please. I think me and another plumber have made a mistake when installing the cold supply from the main to the cylinder?

We have installed 22m Speed Fit pipe from the cold main directly to the multibock on the cylinder without teeing off anywhere else the run is about 12 meters.
There are 4 mixer showers and when you try and run 1 shower and 1 hot tap or cold tap simultaneously the shower temperature goes hot or cold and doesn't stay stable it runs luke warm or scalding hot.

I am thinking maybe we should have run the cold supply in 28mm and maybe had an accumulator, but surely it should work ok with one shower and one tap on.
Its an Albion Cylinder and we have checked and all the minimum flow rates have been exceeded.

To replace the cold supply would be a major job as all the carpets and flooring has been put down.

Id appreciate your help please guys, Dan

 

[Linkyplumb]

Ideally it would of been prudent to have a balanced cold off of the combination valve, to the showers at least. I assume the flow rates are not an issue, ie min of 20litres per minute.

 

[Destroyer2813]

Shouldnt tee of before pressure reducing valve as you will then have unbalanced suppplies, what flow rates incoming pressures you got ?

 

[Danv44444]

Hi Linky, we took all the cold feeds off of the combi valve. Sorry I forgot to mention that bit

 

[Danv44444]

Hi Linky, we took all the cold feeds off of the combi valve. Sorry I forgot to mention that bit. The supply goes straight to cylinder then back out to everything else.

 

[Danv44444]

the flow rates are about 25l/min at 2bar

 

[Destroyer2813]

That static or woking ?

 

[Ermintrude]

Might have crud in valve. U cleaned combi valve ? Have u come off valve or After it? If after have u fitted nrv

 

[Danv44444]

That static or woking ?

Working

 

[Danv44444]

We have replaced the valve. Didn't make any difference.

 

[Danv44444]

We came off the combi valvevalve

 

[Ermintrude]

Up load a pic of install

 

[Ermintrude]

Have u had end off speed fit and measured flow / pressure? Sounds like you have a cross flow. Do all mixer outlets have nrv fitted

 

[Danv44444]

I don't have a pic but it's 22mm into combi valve then 22mm out of combi valve.

Other things i forgot or got to mention are that the cylinder has a secondary return with brass pump and single check valve, but that shouldn't make any difference

 

[Danv44444]

The speed fit is under the floorboards and comes up to cylinder in 22mm copper. I have checked at taps and there's 20ltrs/min. We haven't installed none return valves on mixers.

 

[townfanjon]

have you definitely used the correct ports out of the inlet control set ?
Just check with MI's

 

[Danv44444]

Yes definitely right. I have fit a few albions, I'm thinking maybe it's the size of the place. Does anyone else think an accumulator would fix it?

 

[Ermintrude]

Nope. Shut off pump valves. Fit some Nrvs on mixers then get back to us. Defo crossover.

 

[townfanjon]

had to ask pal, I have seen cylinders filled up through the expansion hose port before now.

 

[Danv44444]

No worries Jon. It's better to rule thins out

 

[townfanjon]

Albions are Tribunes in disguise and you pressure/flow is ok. I would not go down the accumulator path I am with Ermintrude on this - crossflow somewhere. Just one connection piped up wrong causes havoc.

 

[Danv44444]

Nope. Shut off pump valves. Fit some Nrvs on mixers then get back to us. Defo crossover.

the showers are obviously mixers but the taps were turning on aren't mixers. So you think putting nrvs on the shower feeds would help?

 

[Danv44444]

the showers are obviously mixers but the taps were turning on aren't mixers. So you think putting nrvs on the shower feeds would help?

So we would have to put nrvs on all the showers and any mixer taps.
I suppose putting an nrv on the hot supply from cylinder wouldn't solve it?

 

[Ermintrude]

Nope because it's a sneaky back route for that pesky cold water. If you have ISo fitted just close them.

 

[Danv44444]

Nope because it's a sneaky back route for that pesky cold water. If you have ISo fitted just close them.

Thanks for the help guys. The only trouble I have now is how to get to the shower pipework. It's all in walls or under carpets .

cheers,

 

[Ermintrude]

If exposed mixers just remove bars and fit 3/4 blank?

 

[chris watkins]

I am not having a go but this thread highlights why plumbers / heating engineers need to have done the Water Regs training course as well as the Part G.
It is a legal requirement that single check valves are install to any fitting where hot water (category 2) & cold water (category 1) mix to prevent cross (back) flow. Sometimes the fittings come with these built-in but others don't & they have to be installed to the supply pipework, it is our responsibly to check.
Had this been done this situation would not have arisen & the costly correction work would not now be required.
Sorry Dan
Please don't blame the messenger.

 

[Ermintrude]

Well said Chris. We fit double check valves on showers after a debacle with Bylaws inspector , 20 odd shower and no restraining ring on the hose, as the the head could back syphon.

 

[Megaflo-Experts]

I believe the op does have balanced hot and cold supplies (post #5), so it may not be cross flow.

Does this happen with all the showers?
Does opening one cold tap affect the flow of another cold tap?
Does the same happen with the hot taps in the basin or bath?
Are hot and cold flow/pressure rate similar at the basin or bath?

Probably investigating a little further before ripping things up!

 

[Danv44444]

I believe the op does have balanced hot and cold supplies (post #5), so it may not be cross flow.

Does this happen with all the showers?
Does opening one cold tap affect the flow of another cold tap?
Does the same happen with the hot taps in the basin or bath?
Are hot and cold flow/pressure rate similar at the basin or bath?

Probably investigating a little further before ripping things up!

hi megaflo,

yes it happens with all showers, three are the same type of shower one is different but there all mixers

yes the flow does change a bit when you open another cold tap

The same happens with basin and bath taps and the flow/pressure is similar

thanks

 

[Danv44444]

The supplies are definitely balanced. All the colds come from the port on the block

 

[Danv44444]

Mega flo are you thinking maybe the cold supply to cylinder isn't big enough? Or along those lines?

 

[townfanjon]

are the shower mixers of a reputable brand ie not Aldi quality.
Cartridges all in the right way up etc etc.

 

[Danv44444]

There Vado showers. Customer supplied them. They were all new though

 

[Danv44444]

I did try changing one of them for a bristan artisan but it still happened.