Big pressure difference between running and not running CH

[Albumen]

Boiler is an Ecotec Plus 831.
House is a smallish 4 bed 1920s semi. 10 rads (counting the 3 small ones round a bay as 1). No huge radiators. Pipework mainly 22mm and 15mm copper. Some plastic.

Fair bit of boiler work done recently:

1. New heat exchanger.
2. New pump.
3. Some internal pipes he said (flexible pipe?)
4. He repressurised the Pressure Vessel.

Before this I used to keep an eye on the system pressure. If the display was showing 65deg (flow temp) but the pump and flame weren't on, then the pressure would always increase by 0.2bar when they did come on.

Now I'm getting a difference from 'off' to 'on' of about 1.1 bar.

Just now I turned it off. Let it cool down to about 40deg. Pressure went to 1.0 bar. Turned it back on waited for it to get to 75 deg. Pressure was 2.1

Is that sort of difference OK? The digital and analogue sensors agree with each other.

One thing I've noticed is that the return temp isn't cold enough. If the flow is 75deg, the return is 68 deg. So it looks like I've got some work to do balancing the radiators to slow the flow down.

Thanks.

 

[triplexxx]

Boiler seems ok,what`s with the obsession? Read a mag or grow huge tomatoes or summat.

 

[Albumen]

Last night it went down to 0.7 bar when the system was off. Then up to 2.1 bar today when it was on and up to temperature.

So I called Vaillant's technical helpline. He said there's something wrong. The rise in pressure should be more like 0.4 or 0.5 bar.

He suspects the PV is faulty so there's an engineer coming out next Friday.

But thanks for your advice. I'll bear it in mind.

 

[triplexxx]

I stand corrected, sounds like faulty expansion vessel,have a look, big red thingy,you can press it where the little valve is,if water comes out it`s faulty.May need recharging,you can do it yourself if you want.post back for` How to` or search expansion vessel.

 

[Agile]

TrippleXXX needs to find out about all the FAQ on this site which cover common repetitive tasks!

 

[triplexxx]

Thanks Agile, How can he do a search if he does not know the possible fault? Just advised him to do a search where fault may lie. It`s Triplexxx by the way.

 

[Albumen]

Thanks for your advice TrippleXXX.

I have seen the inside of my boiler, and know what the PV looks like thank you. It's not red. Infact a Vaillant engineer repressurised it a few days ago at the same time as he changed the heat exchanger and pump.

I've done a fair bit of work on my own Central Heating system. Often after advice from the kind people on this forum. New radiators, draining, refilling, adding inhibitor, fitting magnetic trap etc.

I've taken the front cover of my boiler off (which I believe I'm not really supposed to do). But that is the limit of what I'm prepared to do. There's no way I'm going to start tinkering with something that's got explosive gas and very hot water under pressure in it. Especially if messing it up means I've got no heating or hot water.

I like to know what's what in the boiler, and I do monitor how it's working. That way at least I might have a clue what's wrong. And also have a better chance of assessing the competence, or otherwise, of any engineers.

 

[triplexxx]

Fair enough Mikey,

know what the PV looks like thank you.

Fix it then.

It's not red.

Is it silver/grey? Don`t be so snotty mate, if you want advice fine,don`t ask, then tell a qualified Gas fitter `what you know` You don`t know anything.

 

[andytw]

Expansion vessel may just need a new valve (Halfords). They get corroded and leak the air out. Replacement and re-pressurising should be easy.
If you are on a contract then you may not be inclined to bother.

andytw

 

[Albumen]

Thanks Andytw.

We are in a service contract. In fact Vaillant service are sending somebody as a recall on the previous HE and pump job. So depending on the assessment of the engineer we may or may not get a new PV.

I suppose if a valve cures it then problem solved. Though a new PV would be nice, one more part replaced.

This boiler is rapidly becoming like your grandfather's axe. You know, all original apart from the head and the shaft.

So far we've had a new HE and pump. Diverter valve is 2 years old, I think. New flexlible pipe. Graphite seal. Seals for secondary HE. New pipes up to HE. Various new seals.

The insulation on the inside of the case is a bit tatty though. But apart from that we're up on the deal. Still that's the nature of insurance, I suppose.