MegaFlo CL250HE - discharge from PRV

[coopersim]

Hello,

I have a MegaFlo hot water cylinder model - CL250HE

The copper over flow pipe from the PRV runs to the outside of my property, and recently I have noticed that it has been discharging, notably when the hot water timer on the boiler has been on, but we no hot water has been run.

As a matter of interest, also, when first turning the hot water tap on the tap feels almost "stiff" then after the tap has been running for a few seconds the flow rate slows

I am pretty sure that this is all related to the pressure setting on the PRV (a small brass type screw?) But I am unsure how, if at all, I should adjust this.

This is a brand new house <12 months old, should I call the builder back in? (as the house and it's appliances are covered by a 2 year warranty)

Also, the instruction manual for the MegaFlo advises the end user to switch the appliance off and discontinue use until this has been looked at, is it something to worry about?

Thanks.

 

[ollski]

Have you recharged the bubble as described on the sticker on the cylinder?

 

[coopersim]

Right o, thanks for the info, I have just given this a go trying to follow the instructions - but... I can't turn the isolating lever on the Cold Water Combination Valve as advised in section 7.4 of the instructions - it won't budge!

I thought it might be backed up pressure as we haven't run any water, so I gave the hot and cold taps a run then tried again, but I'm still not able to move it at all

Also, this 4 foot length of pipe it is attached to is very loose so I don't want to go hammer and tongue and have a flood on the inside of the house as well as one outside the back door!

Any ideas?

 

[Agile]

"""The copper over flow pipe from the PRV runs to the outside of my property"""

This is not an overflow pipe ! Its a pressure relief valve vent and should be installed according to specific requirements.

The air bubble absorbs expansion and needs to be restablished. You can do this yourself. If you cannot close the isolating valve at the cylinder you can turn off the cold water supply at the main stopcock.

You should also get someone who holds the Unvented Certificate to check it as they can be installed wrongly and explode quite violently. We do this in our local area for only £25 extra when we do a gas boiler service.

Tony

 

[oilman]

These require an annual service (£60-100) by a BBA aproved fitter - most are not. I advise you to get it done.

So far, so good.

Better still fit in a Pandora heat bank from DPS and then no drips ever - or £60-100 a year, or a potential bomb in your house.

This "heat bank" is no more than a thermal store with an expansion vessel instead of a header tank. In practice they DO require maintenance. The expansion vessel will not last forever, and the diaphram will give up at sometime. The heat exchanger will scale up unless the system is configured correctly, which will be unlikely in many installations. A thermostatic mixing valve will frequently cause problems as a result of limescale. As for a potential bomb?

You should also get someone who holds the Unvented Certificate to check it as they can be installed wrongly and explode quite violently.

Explosions are unlikely on a gas or oil heated system, as there are two thermostats to prevent overheating, and in your case (with the dripping vent pipe) the valve is open and so cannot reach the conditions required for an explosion.

The design of pressure relief valves now make it unlikely the valve will stick closed, and so give the conditions.

 

[HarrogateGas]

These require an annual service (£60-100) by a BBA aproved fitter - most are not. I advise you to get it done.

So far, so good.

Better still fit in a Pandora heat bank from DPS and then no drips ever - or £60-100 a year, or a potential bomb in your house.

This "heat bank" is no more than a thermal store with an expansion vessel instead of a header tank. In practice they DO require maintenance. The expansion vessel will not last forever, and the diaphram will give up at sometime. The heat exchanger will scale up unless the system is configured correctly, which will be unlikely in many installations. A thermostatic mixing valve will frequently cause problems as a result of limescale. As for a potential bomb?

You should also get someone who holds the Unvented Certificate to check it as they can be installed wrongly and explode quite violently.

Explosions are unlikely on a gas or oil heated system, as there are two thermostats to prevent overheating, and in your case (with the dripping vent pipe) the valve is open and so cannot reach the conditions required for an explosion.

The design of pressure relief valves now make it unlikely the valve will stick closed, and so give the conditions.

At last, someone talking sense. Whats was not thought out by WS is the fact that this is only 12months old and under builders guarentee. Do we think this customer really wants to be shelling out for a heat store when what he has is perfectly good and a decent hot water system.


I agree oilman regarding the mixing valve. ive lost count of the number of oventrop blending valves ive changed on a Gledhill. They are not a cheap component either.

 

[oilman]

HG Have you considered service kits for the valves? On 15mm valves it's rarely worth it, but for 22mm valves it might be, unless they are replaced using Plumb Center's cheapies (which then probably raises some non compliance issue ) I have fount the problem is the O-rings going flat and sticking. Once these are replaced and greased, they are ok.

I used to think thermal stores were a good invention. In reality, where there is hard water they are a good money spinner.

 

[Agile]

I used to think thermal stores were a good invention. In reality, where there is hard water they are a good money spinner.

I see the problems as virtually all due to a lack of maintenence. In reality they DO need annual checking and reinstatement of inhibitor to the correct strength which is rarely ever done on installation.

The failures are not usually noticed until they become total. A friend had one with a seized F&E float valve but when I went to have a look I found that it was leaking from the base seam.

It turned out that after 10 years, already three out of the 22 flats had had their stores replaced, ALL with combi boilers !!!! Not much contentment with stores there!

Tony

 

[coopersim]

Hooray, I have managed to budge the service valve and complete the re charge as per section 7.4

The problem is that the builder has routed the pipe work too close to a partition wall, and the valve could not be turned off without pulling the pipe work away from the wall !!!

Anyway, I will wait for dry weather and monitor the discharge pipe for signs of water

Thanks for the advise

As a foot note, I have been very happy with the MegaFlo, you can easily have two people using seperate showers with no noticeable loss of pressure - unlike my last house that had a BAXI 105 instant - useless combi boiler !!

 

[Agile]

Wow, WS has missed commenting on a dodgey statement!

"""Explosions are unlikely on a gas or oil heated system, as there are two thermostats to prevent overheating, and in your case (with the dripping vent pipe) the valve is open and so cannot reach the conditions required for an explosion."""

The problem is that on an unchecked builder's installation, unless you have a benchmark certificated signed by an identifiable person, you cannot know that it has been correctly fitted and those two thermostats have been fitted or wired up.

Furthermore, with a gas or oil heated cylinder its still usual to have an electric immersion heater and its that which usually causes the explosions.

Tony

 

[kevplumb]

same old song salesman

everybody with an unvented cylinder is sitting on a bomb

ohh excuse me what you need is a vented thermal store

 

[coopersim]

I guess I will be chasing the builder in this case then!

I checked the link, the cylinder seen clearly flying through the air looks nothing like mine, so I'm sure it will be fine.....

 

[Agile]

It turned out that after 10 years, already three out of the 22 flats had had their stores replaced,


Probably by some of the numpties about who haven't a clue how they work.

Actually they were all replaced because they were leaking at the bottom seam!

The one I removed had about 2 kg of calcium and copper carbonates in the bottom!
++++++++++++++++++++++++++++++++++++++++++
Aside from not adding any inhibitor, what aspect of the installation do you think would cause them to leak as a result of corrosion on the lower seam?

Tony

 

[oilman]

Wow, WS has missed commenting on a dodgey statement!

"""Explosions are unlikely on a gas or oil heated system, as there are two thermostats to prevent overheating, and in your case (with the dripping vent pipe) the valve is open and so cannot reach the conditions required for an explosion."""

The problem is that on an unchecked builder's installation, unless you have a benchmark certificated signed by an identifiable person, you cannot know that it has been correctly fitted and those two thermostats have been fitted or wired up.

Furthermore, with a gas or oil heated cylinder its still usual to have an electric immersion heater and its that which usually causes the explosions.

Tony

The two thermostats I was referring to are in the boiler. If you have an immersion heater you then have an electrically heated one and not a gas or oil one. In the case of a Megaflo, the immersion heater is part of the supplied package, and so is a factory fitted item.

Even if it is signed by an identifiable person, you cannot know that it has been installed correctly, and if as you insist it blows up, all the evidence has vanished.

Do stop this doom pedalling, and instead learn the complexities of using the

quote

tool in the row of buttons above.

Now please excuse me, I have to go and spread paronoia to some poor soul who doesn't realise the thing in the airing cupboard is more terrible than iran's nuclear program.

 

[Water Systems]

This "heat bank" is no more than a thermal store with an expansion vessel instead of a header tank.

No not at all. There is thermal storage. It can be pressurised, vented by an integrated F&E tank or remote F&E tank, Or have none at all like the Pandora. The water can be shared with the boiler and/or the CH circuit, or not shared at all, like some Gledhills and the Pandora.

The difference is by the heat transfer to the DHW. It splits into two types:

1. Thermal Store (uses an integral coil)
2. Heat Bank (uses a plate heat exchanger)

In practice they DO require maintenance.

Not a mandatory annual service. Only when thing go wrong, as in many appliances.

The expansion vessel will not last forever, and the diaphram will give up at sometime.

Yes, as needed maintenance, not an annual, service. In a vented heat bank this is not an issue. Pressurised heat banks a few and far between.

The heat exchanger will scale up unless the system is configured correctly, which will be unlikely in many installations.

Configured correctly? Uh? The large area flexible plate heat exchangers rssiust scale very well. The only places they have had any scaling is in "very" hard water areas, otherwise no scaling.

A thermostatic mixing valve will frequently cause problems as a result of limescale.

Only in "very" hard water areas. As TMVs are to standard this will be a general issue.

A thermostat valve restricting flow through the plate while sensing DHW outlet temperature does not scale up.

As for a potential bomb?

You are in unvented cylinder territory there, not venetd heat banks.

Explosions are unlikely on a gas or oil heated system, as there are two thermostats to prevent overheating,

Explosions are far more likely on unvented cyldiners than other appliances, that is why they stipulate an annual service.
http://www.waterheaterblast.com

To the nutter of a MOD: Do NOT change the content of the posts. It is NOT your business to change content. It is for the benefit of the original poster NOT you.

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