Megaflow Pressure and Flow Rates

[powell30]

Right, i work for Heateam. We carry out all warranty work on megaflow/heatrae products.

I can't obviously confirm your conversation but i can tell you that if you did as said engineer told you and it was audited and found to be the engineer who had said this then it would result in disciplinary action and almost certainly classed a gross misconduct.

Let me repeat removal of a safety device on a G3 product is illegal regardless of whether you think it prudent or not

 

[doitall]

As above, so far I've been told if i remove the PVR and replace with a double check valve:-
1. I'll kill everyone in the house.
2. I'll invalidate my house insurance.
3. No plumber worth their salt would recommend doing this.

Well I have been keeping this bit quiet whilst i listened to what you all said on this, but do you know who suggested it? The Heatrae Sadia engineer whom came to replace the PRV that broke! Admittedly on the basis that "I haven't told you this and we can't then service it but there's no danger in doing so as you still have the safety valve set over double the PRV anyway. Don't listen to stories of one of these blowing the side off a house there's too many other safety devices built in". Comments please?!

Nudge, nudge, wink wink, do what you like mate, but we won't go within a 100 miles of it if you do YEAH RIGHT and neither will any competent engineer.

 

[MLT]

And I say it's you that doesn't understand.

Sorry - I am trying to though!

The WB is a high flow combi, with a small store, at the flow/pressure rates you think you had an hot shower would last about 3mins.

However long it lasted it never went cold on us and was a pleasure to shower with.

The Megaflow is not even in the same league, it's that much better. Start reading the posts and understand what is being said.

As I have said, it's my opinion and i have stated why it's my opinion along with a possible explanation as to how i got where i am - so i am at least trying to explain why i feel like i do and perhaps why it may be so. Why do you say it's that much better in your opinion? I have read all the posts very closely, found the majority interesting and also answered various questions/points when asked/made and politely. I think i do understand pretty well - any chance of your take on my points 1 - 3 made in previous posting and idea of using megaflow pressure/flow rate just on HW to shower whilst taking CW just to the shower off the main and by-pass the megaflow as you haven't commented on either?

Time how long it takes to fill a 5Ltr bucket using the bath taps full on, and post the answer.

I will check and post.

You are also misinterpreting the available pressure.

You said you had 40Ltrs at 4 bar, that then equates to 20 Ltrs for the hot and 20Ltrs for the cold, not 80Ltrs/m

I don't think I did say 80 l/m anywhere - if I did I didn't mean to (sorry) - I did say "These were then mixed together, now i know that does not = 8 bar/40L, but on reflection I bet it was a dam sight better than the 2.8 bar/28L the megaflow is chucking out?!" The logic being that I thought the 40L flow rate would stay consistent divided by the 2 and the split 4 bar whilst not equalling 2 x 4 could have been more than 4 bar and certainly more than 2.8-3 bar.

Thanks for your continued interest in my circumstances.

Regards.
MLT.

 

[MLT]

Right, i work for Heateam. We carry out all warranty work on megaflow/heatrae products.

I can't obviously confirm your conversation but i can tell you that if you did as said engineer told you and it was audited and found to be the engineer who had said this then it would result in disciplinary action and almost certainly classed a gross misconduct.

Let me repeat removal of a safety device on a G3 product is illegal regardless of whether you think it prudent or not

Hi there

Thanks for your email - as i have said i was somewhat surprised to say the least. I note all that has been said and am certainly keen (to say the least) to find an alternative solution and provide me with a shower more like we had before. So do you have any take please on my idea to:

On just the shower have the CW feed to the mixer altered to by-pass the balanced megaflow so I'd have the full megaflow pressure feeding just the HW into the mixer and the CW mains feeding just the CW into the mixer?

Thanks in anticipation.

MLT.

 

[doitall]

As I and the others keep saying the problem is must likely with the shower.

I would certainly say it has restrictors fitted in the inlet ports, remove them and you may be surprised.

 

[MLT]

I still have this pressure/flow rate at my outside tap - hope that makes sense?

Pressure and flow are not the same !

Whats important is the dynamic flow rate.

I am assuming you had 4 Bar STATIC and 40 li/min OPEN PIPE which means at NO pressure.

Whats relevant in your case is the DYNAMIC pressure.

See what flow rate you can get out whilst leaving 2 bar in the pipework. It will hardly be 20 li/min and thats probably why it does not meet your expectation.

Presure and flow should be GCSE science but its surprising how many plumbers dont understand the terms and their interrelationship.

Tony

Thanks for your post

I understand the difference between pressure and flow rate and how you can have one good but the other poor. But nothing at all about DYNAMIC pressure - anywhere i can read up on it in greater depth please Tony?

Thinking about it though, this still would not explain why the shower was great on the old system but nowhere near as good after the megaflow was installed with exactly the same pipework in situ and still nowhere near as good once all pipework renewed and upgraded in size.

Cheers.

MLT.

 

[MLT]

As I and the others keep saying the problem is must likely with the shower.

I would certainly say it has restrictors fitted in the inlet ports, remove them and you may be surprised.

As I have said - I had the benefit (thank goodness) of experiencing the same pipework and mixer set up on one shower before and after megaflow installation so am comparing apples with apples. Otherwise you'd have me questioning my own sanity.

I have however spoken to Hansgrohe, downloaded the assembley instructions of the mixer and note there are non return valves - I pressume these are the restictors you suggest removing? If this works it would be great thanks. Even if it got to halfway between what we had before and what we've got now it would be progress. I will let you know - might not be till the weekend though!

In the meantime still no thoughts on my idea re separate CW supply to mixer?!

Cheers.

MLT.

 

[doitall]

They're little plastic disc that go in the inlet pipes, there's also a filter in there that could be checked whilst you have it off. the bucket test will tell you a lot, you could even take the rose off, if it's a hand set and do the same test with just the hose in the bucket.

A direct cold to the shower will make no difference.

 

[electronicsuk]

So now what I'm trying to do is see whether there is a relatively simple fix for just the shower, hence my idea:-
On just the shower have the CW feed to the mixer altered to by-pass the balanced megaflow so I'd have the full megaflow pressure feeding just the HW into the mixer and the CW mains feeding just the CW into the mixer? This might then be more akin to how the set up was before with the WB combi. Any comments on this idea - I will also ask Heatrae Sadia what they think about that idea.

You could certainly try it. If the PRV is indeed causing a severe flow restriction (which it should not, but I understand you want to prove this) then you should see some difference in taking the shower's cold feed from the mains pressure inlet side of the PRV.

However, if you like your shower particularly hot then you may not be mixing in a huge amount of CW in the first place. You may also find that if the shower mixer is intended to be used on a balanced supply, having the DHW and CW at different pressure may cause even more problems.

It may in fact be easier to purchase yourself a pressure reducing valve, set it to 3.0bar to match the one fitted to the megaflow, attach to your outside tap where you're getting 40l/min, and then see what flow rate you get at the outlet of the PRV. This will help you establish exactly what affect the PRV has on flow rate, and will avoid the need for replumbing the cold supply to the shower which may or may not make any difference.

 

[ChrisR]

As I have said - I had the benefit (thank goodness) of experiencing the same pipework and mixer set up on one shower before and after megaflow installation so am comparing apples with apples. Otherwise you'd have me questioning my own sanity.

Oh no you aren't. You now have the plumbing to and from the unvented cylinder in the way.

 

[ChrisR]

I was not refering to all the shower mixers in the UK, I was refering to the hans grohe ones, so either you haven't noticed it or you haven't seen any.

I 've seen a few dozen HansGrohes, and have one on a bathroom of my own.

 

[MLT]

As I have said - I had the benefit (thank goodness) of experiencing the same pipework and mixer set up on one shower before and after megaflow installation so am comparing apples with apples. Otherwise you'd have me questioning my own sanity.

Oh no you aren't. You now have the plumbing to and from the unvented cylinder in the way.

I think I was comparing apples with apples as close as makes no difference; reasoning:-
Before - restricted CW supply to combi at ground floor with HW coming out through 15mm to bathroom shower about 10m away. CW supply direct to shower T off CW supply before combi.
After (before final instal) - megaflow installed at 1st floor with new blue 22/25mm CW supply to megaflow with HW supply coming out of megaflow in 22mm and T into old 15mm pipe about 6m from the shower and same with balanced CW. This then ran the old shower via the old pipework until we then renewed the bathroom and renewed all the pipework then. So in the intermediary period I reckoned we were as close as apples to apples as we could get - hope that may be clearer - what you reckon Chris?

 

[ChrisR]

There have been a few variants of the Raindance head (eg one lets air through) & I've fitted a few. They haven't have any restrictor or flow limiter (those things are NOT equivalent, by the way) in them - apart from the mechanism.
I have tested a couple for resistance. They were 20 - 30 litres/min installations, and didn't restrict the flow appreciably. SUggest you test yours., it could be full of crud!

The Ibox housed mixers came/come in (at least) two types. One is a simpler thermostatic mixer, two pipes in, one out, and the other is a two in two out, diverter, which you might use for a bath/shower mixer or a shower and body spray controller.
They both have non return valves in them which are quite small. It helps a bit if you remove them, but not as much as you might hope.
If you have the diverter style mixer, it has a very high internal resistance, much higher than the simpler one. The waterways in there are only about 6mm across in places.


There's been a lot of the usual claptrap in this thread. As Tony says, it all boils down to dynamic pressure, which is the pressure you get when the water is flowing. The only way you're going to know what that is, is to (calculate or) measure it. The pressure drops across every pipe and fitting on the water's way from the road to the shower head.
I'd try removing the non return valves, and I'd try taking the cold to the shower from before the pressure reducing valve. A thermostatic mixer will cope. But if you do both, you're in breach of water regs (possible backflow - though it's highly unlikely),
I'd also add £5 pressure gauges wherever you can.
You do need to measure everything - start with that flow rate.

There's a strainer in the inlet valve group on the Megaflo - you might check it isn't blocked. Also see how wee the non return valve in there is!

 

[MLT]

You could certainly try it. If the PRV is indeed causing a severe flow restriction (which it should not, but I understand you want to prove this) then you should see some difference in taking the shower's cold feed from the mains pressure inlet side of the PRV.

However, if you like your shower particularly hot then you may not be mixing in a huge amount of CW in the first place. You may also find that if the shower mixer is intended to be used on a balanced supply, having the DHW and CW at different pressure may cause even more problems.

It may in fact be easier to purchase yourself a pressure reducing valve, set it to 3.0bar to match the one fitted to the megaflow, attach to your outside tap where you're getting 40l/min, and then see what flow rate you get at the outlet of the PRV. This will help you establish exactly what affect the PRV has on flow rate, and will avoid the need for replumbing the cold supply to the shower which may or may not make any difference.[/quote]

Hi Matthew
Thanks for your posting. Reference your last paragraph, my idea for in taking the shower's cold feed from the mains pressure inlet side of the PRV was in the hope that the megaflow would still chuck out near enough the same pressure as currently and maybe even the same flow rate of very hot water, but then mix in some CW direct and the sum of the 2 parts might be considerably better than what the megaflow chucks out on it's own? Given i could get the alteration twin tracked with stop cocks in effect i could then switch back at the turn of 2 stop cocks if it made no difference and all i've probably lost is a day's labour and a few parts plus a bit of making good behind a wardrobe. In essence i'm trying to get a higher performance just to the shower than the megaflow seems capable of supplying.
Cheers.
MLT.

 

[ChrisR]

Any thermostatic mixer I've used/taken apart wouldn't be bothered by the difference between say 3 bar and 4 bar. They have an expanding springy thing which moves to restrict the flow, there's nothing very sophisticated about them. The dynamic pressures of hte H and C inputs will not be the same whatever you do.

Different story for NON thermostatic mixers, there balanced supply does help.

One variable not mentioned is HW remp , by the way.

The Ibox mixer has the NRVs in the back, I've never seen filters in one yet.