Vaillant Ecotec pro 28 Help with use / diagnosis please.

[Unklian]

Hi all.
Thanks for the previous help, I'm back here with my boiler's first problem.
(Vaillant Ecotec pro 28 ) 2.5 years old.
Sorry if this is long-winded, I'm trying to give you as much information as possible.

Yesterday morning, no hot water. I checked the boiler to find 0.3Bar pressure.
I topped it up for the first time in 6 months. (1Bar) made water, heated the house.
This morning, no pressure again.

I suspected the expansion vessel. The pressure being released by the PRV due to expansion. There was no water in it. I isolated the boiler,
de-pressurised the boiler. re-inflated the expansion vessel to 0.75Bar.
Opened the isolating valves to the heating flow & return.
Re-pressurised the system to 1Bar.

Currently I have closed the isolating valves again with the idea that......
If the boiler pressure drops again, it is something "boiler side" rather than a leak in the house pipework. I don't want to be lifting floors & carpets to find it is a boiler problem. The house thermostat is turned to 5 degrees so there will be no call for heat.

Do you have any suggestions that could help me to diagnose where the loss of pressure could be?
Yesterday, after the first pressure dump, I had a look under the PRV and couldn't find any evidence of it having blown. It is difficult as it is half-way up the house side.

Another question......Wife is going barmy of course. With the heating valves closed, can the boiler be used for making hot water? Will this cause any problems? Might it help in the diagnosis?

Just trying to get as much info. as possible. I will NOT be doing any work myself, my usual bloke is away for Easter and when he comes back, I want to save him as much time as possible.

Thanks.

Ian.

 

[sooey]

From what I can make out you've repressurised the vessel and the system but have isolated the boiler before seeing if that had cured the problem. Is that right, why?
Open the valves and use it as normal and see how it goes.

 

[Unklian]

I did that,......
"I topped it up for the first time in 6 months. (1Bar) made water, heated the house. This morning, no pressure again. "
It didn't cure whatever the problem is, the pressure went again.
Ian.

 

[sooey]

Sorry, missed that bit. In that case open the valves and run the heating and keep an eye on the pressure, if it goes high before dumping out of the prv you've still got a vessel problem. Either not pumped up correctly or blocked tube leading to the vessel. Also keep an eye on the discharge pipe outside to see if it drips. Difficult if it's raining round your way.

 

[Unklian]

Cats & Dogs at the moment.

With the heating valves closed, can the boiler be used for making hot water? Will this cause any problems? Might it help in the diagnosis?

Ian.

 

[sooey]

Yes you can still use it for hot water. It won't help diagnose an expansion problem.

 

[Unklian]

Update.

Pressure with boiler isolated from heating pipework has remained rock steady at 1Bar for several hours.

I powered off the boiler (so it didn't light) and ran the bathroom hot tap slowly for about a minute.

Powered boiler back on......Pressure is now steady at 1.7Bar.

Is this now pointing to the DHW heat exchanger passing?

What is your opinion on starting the boiler (still with the heating circuit isolated)
and see if making some hot water causes over-pressurisation or PRV valve blowing.

Ian.

 

[ServiceNumpty]

If your plate heat exchanger was passing you wold have a constant 3 bar pressure showing on your gauge and the PRV constantly passing.

 

[Unklian]

Yesterday evening......
Didn't use any hot water.
Powered boiler up. Thermostat calls for heat.
From 1.8Bar,
28 degrees, 2.1Bar.
gradual rise. 5 minutes later, boiler throttles up.
Runs flat-out until temperature is 60 degrees (where I'd set it) at 2.3 bar.
Boiler maintains this then gradually throttles back until it is running at minimum.
60 degrees, 2.1Bar.
Later......Heating satisfied. Boiler over-runs for 5 mins.
cools to 52 degrees, 1.7Bar.

Lovely......powered off, went to bed.

This morning......
Powered boiler up. Thermostat calls for heat.
From 1.7Bar,
28 degrees, 2.1Bar.
gradual rise. 5 minutes later, boiler throttles up.
Runs flat-out until temperature is 60 degrees (where I'd set it) at 2.3 bar.
Boiler maintains this then gradually throttles back until it is running at minimum.
60 degrees, 2.1Bar.
Later......Heating satisfied. Boiler over-runs for 5 mins.
Cools......cools......
49degrees, 0.9Bar.
47 degrees, 0.8Bar......Hmmmm looks like I have a leak?
One minute later......47 degrees, 1.7Bar......Where did that come from?
30 minutes later......45 degrees, 1.9Bar.

The filling loop is not passing as I disconnected it.

How does the pressure suddenly rise 1Bar when the boiler is not heating?

 

[sooey]

The pressure sensors on these aren't very good, possibly a problem with that.

 

[Unklian]

Long story short......
I'd written a very long post with unusual temperature / pressure readings.
I lost the post somehow.
The jist was......
In the middle of a long constant heating session, the pressure went from a constant 2.2Bar down to1.4Bar then went back up again after about 2 minutes.
I can't think of any other explanation than your suggestion of
a faulty pressure sensor.
No leaks, no venting, just very odd pressures.

I'll get back after I've seen my Gas Man after his holiday and see if a
new sensor is in order.

Cheers for the suggestion.

Ian.

 

[dreadnoughtheating]

It goes without saying that to access the expansion vessel, you have to remove the front cover, which Is Gas Installer territory afraid to say.... (it is a 'room-sealed' appliance, and the front panel is part of that seal)

Forum rules then kick-in, which means no more free info from the Registered Gas Installers here, as your and your households Gas Safety could be compromised.

DH

 

[Agile]

Exactly!

It must have been stated here so many times that a DIYer must not open the front panel on a Vaillant Ecotec style boiler.

How many rads have you got?

Tony

 

[Unklian]

Sorry all if I have overstepped the mark.

6 radiators, Tony.
6 small, (about 600 x 600mm) 1 large 2400 x 500 K2.

Yesterday, watched the temperature & pressure all day while the boiler did its thing.

Most of the time, it was very predictable, slight pressure rise as temperature went up.
Constant pressure as boiler maintained max set temp.
Then......Sudden drop to 0.9Bar for a minute, then back up.
Happened a couple of times.
Did it later to 0.6Bar, and the pressure didn't rise. Boiler shut down.

Wife opened hot tap while I was looking at the boiler.
I asked her to turn the tap off as the boiler was acting up.
she turned the tap off (quarter-turn type) quickly and the pressure gauge
popped back up to 1.5Bar.

Perhaps the water hammer has given the sensor a nudge.

I'll contact my Gas Man when he returns on Tuesday with all this info.

Any comments / suggestions?

I won't be doing this myself,

Again......sorry if I delved too far into the boiler.

Ian.