Poor pressure on a megaflo??

[ChrisR]

What you're doing is the same thing. The time you have to wait for the water to come out(under gravity) depends on the configuration, and how much water there is to come out.
It sounds like one of your safety valves is leaking - ie letting water pass, below the pressure at which it's designed to. There are two and they will both widdle through the tundish. You can tell which by undoing the union (usually just a compression nut) on the valves and seeing which one is wet inside. If you twist the knob on the valve water will rush out and the valve will snap shut, which just might be all it needs.
Obviously this should still be covered by the warranty, so the installer's problem.

 

[davecon1]

Cool.

Thanks for that. Megaflow did mention that one of the valves might be blocked/broken or leaking (there has been alot of dust and debris in the room) so when the engineer comes he'll be looking into that.

I'll also have a list of other questions to ask him (and the plumber) when they arrive (static water pressure, flow rate, use of an accumulator etc).

Cheers

Dave

 

[doitall]

Your getting there Davecon 1

Don't do anything untill you have the standing pressure, and the flow rate, L/min.

If you can also getting the operating pressure so much the better.

 

[ChrisR]

A pressure gauge screwed in to the multifunction valve can be illuminating. You can watch the P dropping when the tap's turned on. I think there's a spare hole, they changed the casting.

 

[simond]

Any of you chaps had

- leaking immersion heaters
- rattling combi valves

On megaflos? Just wondering......

 

[davecon1]

OK. So the megaflow engineer came back and the dripping was caused by the air gap (or lack of it). Either way he regenerated it slightly differently to the way they tell you to do it (using a hose) and it gurgled for a few minutes. Hopefully that's all back to normal now.

I was also able to find out the flow rate- it's 17 litres per minute. He reckons I only have a 15mm mains cold leading into the house which would be a surprise as I think it's 22mm. If that were the case it might be an option to dig up the pipe and replace it with a 25mm one.

The plumber is supposedly due over later on today and I'll ask him about the standing pressure etc. If he turns up of course.

Incidently does anyone have recommendations for underfloor heating. I'm thinking of using devimatt and it will be on the second floor under tiles. I had heard that if you use that sort of system on suspended floors it you can lose a fair bit of heat downwards instead of into the tiles.

 

[doitall]

Yes Davecon 1, but what is the pressure.

You cannot expect good advise without the pressure.

its the singular most important bit of imformation.

 

[Gasguru]

This problems going nowhere fast - useless plumber and even more useless Megaflow engineer.

 

[davecon1]

Unfortunately the pressure is still unknown. Whilst the plumber did fit the disharge pipe correctly he did not bring a pressure gauge. You're right they are useless the pair of them although I have to point out that the shower seems to be more powerful now the air gap has been regenerated (unless I am imagining it)

Anyone know of a good plumber/bathroom fitter in the wimbledon area?

I'm off to have a beer and forget about it all for a night. I appreciate all the feedback everyone is giving me.

Cheers

Dave

 

[simond]

Faced with the task of keeping air and water separate, which is critical in an unvented cylinder, the design engineers have two choices.

First one is to separate the air and water by a neoprene bag (a expansion vessel).

The second method is to allow the air to occupy the top of the cylinder but recognise that over time the air gap will deplete by water absorbing oxygen.


Most manufacturers take the first route and the expansion vessel is normally good for 7 years or more. Two manufacturers take the second route, one of which claims to have solved the problem with a baffle. Amusingly, having made these claims this is the manufacturer who prints instructions on the side of their cylinder how to periodically refill the air gap.

DaveCon1, I guess you know what I am talking about.

If you are in Wimbledon, we can measure your standing pressure and we can solve your problem of poor flow. Operating pressure at the moment will be crap at 17 litres per minute. Whoever put in your unvented cylinder could have achieved an identical performance with a modest combi.

And yes, if our solution doesn't allow you to run appliances simultaneously we will take it out at no charge. No one has claimed so far.......

 

[chrishutt]

the air gap will deplete by water absorbing oxygen.

Operating pressure at the moment will be rubbish at 17 litres per minute. ...

Firstly only 20% of the air gap will be lost through oxygen absorption. You mean air absorption? Secondly 17 litres/minute is flow rate, not pressure. Minor points but we might as well get them right.

By the way, I don't think you've mentioned how much your accumulators cost. Just a steel cylinder with a rubber bag in it, I know, but must be a fair few quid? This 200 litre one is £200.

 

[simond]

Chris

Please stop nitpicking.

The operating pressure at 17 litres per minute would be almost nil if you were running 17 litres off - that was my point. I was not saying that pressure and flow are the same thing.

Would you be irritated if I nitpicked that (its only a minor point but) oxygen is 21% of air, not 20%? I thought so.

Anyway, putting your criticism to one side, our company does not sell accumulators, we are a local specialist installer. Any prices we quote will include installation and be dependent on how difficult it is.

As you know only too well yourself, many customers endear themselves to heating engineers by telling them how much they can get the boiler/cylinder/valve etc on the internet themselves. So there is little point in quoting pricing. If a customer wants a solution that works, our experience will pay dividends.

Best regards

 

[chrishutt]

Would you be irritated if I nitpicked that (its only a minor point but) oxygen is 21% of air, not 20%?

Not in the least. Thanks for pointing that out. I pleased to see that I'm not the only nitpicker.

I thought you might be rather coy when it came to discussing the price of your accumulator installations.

 

[ChrisR]

Any of you chaps had
- leaking immersion heaters
- rattling combi valves

Yes. Former just one, was ancient, and they've changed the latter recently - again.
Also had the NRV letting by - so HW coming from CW tap.
Megaflo tech support is pathetic, if you get the girl.

I've measured 0.8 bar and 8 bar in different parts of Wimbledon, too. Most of the high bits, with lower pressure, are posher, so it serves em right.

Curious about why the guy used a hose to regenerate the air gap. If the normal method didn't work, something must be wrong?

Btw nitrogen dissolves in water too!

 

[doitall]

Can only think he used it to drain some water from the cylinder Chris.

Unless he stuck the hose in the tank and blew it up