Loss of Pressure in Sealed CH System - Water only

[Jules]

Hello,

So now in the summer with just Water heating I have the problem that my new Valliant EcoMAX Pro Boiler keeps tripping out(Fault 26, possible Pump failure) I check the Sealed Expansion Pressure, and it measures around 0.5 Bar (From a normal 1bar). Its a new Boiler/ pump/ sealed system - less than 5 months old.

So I guess I have a leak somewhere. But nothing obvious.

But since it has occured since switching off the Central Heating, So I switch the CH Heating Demand On, the pressure recovers to 1Bar, and the system is OK. (But I have a hot house) I switch off the Central heating demand,just Water only, and the pressure drops within a few hours, and the boiler trips out.

I don't know how to recharge the system. Instructions says it should be done by installer, which will be frustrating/expensive if I have to do this every few days! - But I do seem to be able to recover pressure if I demand Central heating.

Any thoughts ?

I really wished I kept my old simple Gravity fed system. Lot less hassle.

Jules

[Ed Sirett]

Read the FAQ. What is that actual circuit pressure, when the boiler is idle? Have you tried topping up? The boiler is under warranty you can call for free help! I would expect that the expansion vessel should be around 0.8-1.0 bar but

0.5 is not very low? If no water came out of the 'tyre' valve I'd leave it well alone.

[Jules]

Ed,

I have called out the Vaillant Boiler engineer, but he just said there must be a leak in the system, and walks off. I think I will need an expert plumber to check out the system, and fit a proper re fill point, with instructions, because it is not at all clear, even with the FAQ.

I have read the FAQ, but the problem is that the filling point is not obvious. ( No Braided hose, no obvious two point valves, and despite it being a Vaillant EcoMax Pro, I cannot see any Water valves underneath the Boiler, as the FAQ would suggest. (Just the Gas Valve !) - hence my issue regarding how to Recharge/ top up the system.

I do have a open ended tap valve, above the three point valve, on the pump side, which I presume to be the top up point. But then how would I 'top up the system' - it is not connected to any supply ? The FAQ is not clear in this regard, So I guess I have a duff installation - necessitating an expert Plumber.

When idle the pressure is 0.5 Bar, but dropping, it is now 0.2 bar dropping to nothing.

Thanks

Jules

[Ian Stirling]

Have you read the manual? Some boilers AIUI have the top-up-point internally.

[Dave Plowman (News)]

Yes. Unless space is at a premium the old ways are often better.

[Tony Bryer]

For heating I've come round to thinking that sealed is better - no issues of air finding its way into the system, and if catastrophe strikes while you're away then there's only so much water to cause damage. If the OP's system is losing pressure in a matter of days he has a problem that needs resolving - it's true that if he had a gravity-fed system he'd have to do nothing but large quantities of fresh water would be being added to the system with a very likely chance of this causing corrosion and sludging.

[Dave Plowman (News)]

An open header type can have a stopcock in the feed if this *really* worries you. It should run for at least two years without needing topping up. Indeed, some installers never fitted a cold feed and ball valve.

Indeed.

[Ed Sirett]

The FAQ mentions that Vaillants have internal filling points. However in the turmoil of repricing after 1/4/5 they are now making (for the moment at least) boilers with shorter guarantees, no filling loops and some connection pipe work missing [1]. I believe the 'pro' versions are such and the 'plus' versions are as they used to be.

Given that the pressure has taken all the time since it was installed to get down to 0.5 bar I doubt you have a leak. The pressure recovers temporarily when you run the CH as the water expands. It sounds as if all that's needed is a one off top up.

Where was the top up loop on the old system or did use a header tank?

Look in the airing cupboard. Look under the kitchen sink. Account for the where all the heating pipework goes as far as possible and identify what is connected.

There must have been some way for the installer to commission the system. So there must be a filling loop somewhere. It is very unlikely that the installer use the connection inside the boiler.

Ask the original installer. Frankly he should have shown you where the filling point is. However many installers are reluctant to tell the customers about topping up because they then do so excessively and cause harm.

[1] You have to make you own 90degree bends (or use elbows) to go from the vertical into the boiler where previously these came with the unit.