Sudden pressure loss from unvented system

[golightlygl]

We have recently had fitted a Quinta Pro 45 with a Megaflo 300l in a completely new installation (i.e. all new pipework etc.). This is feeding a house of 3000 sq ft with four occupants. Unfortunately, though, our installers have gone AWOL and we are unsure how the system should work. In particular we have a number of specific queries/problems that we hope you can assist us with:

Every now and then we experience a catastrophic loss of pressure in the system. The boiler display will show 1.1B for a few weeks then drop to 1.0 or 0.9 over a couple of days and then suddenly drop to 0.5 or 0.4B complete with the "top up" warning. Can you explain to me how this can be? Where can the water from this sealed system go to? There are no obvious leaks.
I manually top up the pressure to 1.1B. No matter how long I have the tap on, it seems that the pressure will not go above 1.1B However, several hours later the boiler will show a pressure of 1.6B. How can that be?

At the same time, our gas bills are astronomic. We appear to be using 290KwH per day. Albeit it was a cold winter, the house is pretty well insulated (having been extended it was inspect for building regs etc. and many new double glazed windows installed). Heating was on 12 hours per day heating across three zones to between 19.5 and 20.5 degrees C. About 700 sq ft was heated via hot water fed UFH under a concrete floor with a system that had no set back but heated to 20 degrees C. Any ideas what could be going wrong and do you think it could be related to the above issue?

 

[HERTS P&D]

our installers have gone AWOL and we are unsure how the system should work.

Didn't they show you how it all works?

Don't they have a land line number you could call?

Was it a 'cash' job?

Andy

 

[golightlygl]

Thanks for the speedy reply, but the answers are No, No and No respectively.

It was a very reputable firm through a very reputable (but appalling) well know builders. Unfortunately, both builder and mechanical services company are more used to large commercial installations and both have taken a bath (no pun inmtended) on the project, as have we.

Whilst we are embroiled in the legal processes of getting them to finish, they will not return to site yet we still have £600 per month gas bills and system that doesn't seem to work. Which is why I'm taking a crash course in unvented heating systems so I can better understand what the problems are.

So what I'm really looking for is answers to my heating questions rather than the "engineers have gone awol" bit.

 

[Dan Robinson]

Pictures please.


Of the controls, boiler, tank, expansion vessels, safety discharge pipes etc,.

 

[newbuildinstaller]

hate to say it but safest way could be to get another plumber in, if you are going the legal route you could always pass the new plumbers bill on.

UV systems can be dangerous and installers must be trained to G3. You are more than welcome to try and get some help but I would consider my idea.

Your system loss of pressure could be a leak somewhere on your heating system or maybe undersized expansion vessel or a dripping PRV

Shames as it sounds like you have spent decent money on a decent system (many people wont) and you have been let down, hope you get it sorted

 

[golightlygl]

@Dan_Robinson: pictures attached; please let me know if there's more specific things you need.

@newgasinstaller: The installers were a professional G3 qualified company and Remaha themselves commissioned the boiler. But that doesn't necessarily means that all is correctly done! I have put some absorbent material in the tundis to see if anything is leaking there overnight. The expansion vessel is pretty large (see pictures) but I'm not sure how I test if it is healthy or not.

Expansions vessel

• golightlygl
• 5 May 2013
• 1

Note that the automatic filling loop is close as we don't want it working until we can...

System pressure according to boiler

• golightlygl
• 5 May 2013
• 1

System pressure according to valve

• golightlygl
• 5 May 2013
• 1

Hot water circulation pump

• golightlygl
• 5 May 2013
• 1

temp and pressure valve

• golightlygl
• 5 May 2013
• 1

Untitled

• golightlygl
• 5 May 2013
• 1

Whole system

• golightlygl
• 5 May 2013
• 1

automatic filling loop

• golightlygl
• 5 May 2013
• 1

 

[Dan Robinson]

Is it an 18 or 25 litre expansion vessel? It is going to be too small IMHO.



I would be thinking of adding another as well as double checking the charges - which is explained in the FAQ section.

 

[golightlygl]

Dan,

This is a Megaflo: I understood the expansion capability was built in to the tank with an air gap? I had assumed the expansion vessel was for the secondary circulation. If I understand correctly, this circuit is to allow the hot water to be circulated around the system so that there is not a long wait for hot water at the taps. The expansion vessel is 18l. There is no pressure gauge on the expansion vessel. Given that, could this still be a factor?

I will see if I can check the charges on the main Megaflo air gap.

 

[simond]

Dan is probably right on the money. For a larger system especially with UFH, which has a lot of water in it, the vessel looks on the small side.

The expansion vessel is red therefore is central heating, nothing to do with the Megaflo - which as you say is a bubbletop (leaks only start on these after around 24 months once the bubble gets diminished)!

Gas consumption is unlikely to be a faulty boiler, as it cannot easily destroy energy without somewhere for the heat to go.

For gas consumption blame the weather and the way you set the the room thermostats. An Evohome or Hometronic set up would help you control heat use by splitting into 8 or 16 zones respectively.

Have to say it doesn't look very 'commercial' to me.

 

[golightlygl]

OK, I have double checked and tried to label everything. You're right (of course). The expansion vessel is on the primary return. So it looks like this could be the culprit for the pressure changes which makes sense if it goes from 1.1 to 1.6 and then back down again (currently static at 1.0). What size expansion vessel would you recommend? There is a PRV and gauge on the same circuit which shows the same pressure as the boiler is showing (currently 1.0). Should there be an additional gauge on the vessel itself monitoring what's going on inside?

As a secondary question, I'm confused by what is happening around the primary flow to the Megaflo. as you can see here

Untitled

• golightlygl
• 6 May 2013
• 1

there are two connections to the primary flow: one before the two port motorised valve and one after. I believe the one after is something to do with the heated towel rails (which should come off the primary) as this was one of the few pipes labelled as "HTR Return". Is this just an error in labelling, i.e. it should be HTR flow. But why is it located before the 2-port? And why can I not see a corresponding HTR return?


Really sorry for all the newbie questions: I'm not stupid but I am new to this and am trying hard to understand what's going on with a lot of reading round the subject. Any help you chaps can give is greatly appreciated.

 

[golightlygl]

@Simon

What do you mean it doesn't look very commercial. Is this because the installers put in a Quinta pro 45? If so, I have no idea why they chose that heater. Another one of the mysteries of this installation?

 

[golightlygl]

When the boiler is at rest it is showing pressure of 1.0. When it is firing it is showing 1.5b. Does that point even more to the expansion vessel?

 

[simond]

If the exp vessel is running between 1.0 cold and 1.6 when the boiler and all rads/UFH circuits are up to temperature - this isn't the cause of your pressure loss.

I meant that it looked like a typical domestic install. Don't read anything negative in there.

 

[golightlygl]

It's the boiler pressure that goes from 1.0 to 1.5. The expansion vessel itself doesn't have a gauge, but the PRV in line with it goes from 1.1 to 1.2 when boiler is firing.

 

[simond]

The pressure on the boiler should be the same as the expansion vessel, so you are not likely to have a fault with this as explained earlier.

Sounds like a leak to me. Shouldn't be getting this on a wholly new system, of course. While you are in dispute with the installers this is not good.

I'm surprised you cant get any more than 1.1bar into the boiler - if the water pressure is that poor in the loft I can only assume the Megaflo is a minorflo.

We looked at fitting a Quinta earlier in the year, i recall the warranty lasted a whole 12 months and that excluded wearing parts such as burner electrodes.... Went elsewhere.