Viessmann diverter valve triggers 30 psi PRV

[xuevin]

The System in question is a vitodens 100 with combi plus.

I currently have an issue where water is released from the 30 psi pressure relief valve when the boiler is servicing heat through the house and then calls for domestic hot water.

I believe it is an issue of the diverter valve, as it only occurs when switching from space heating to domestic hot water. When the system is fixed on servicing domestic hot water, there is no issue when calling for water.


Does anyone have any ideas what it might be?

 

[Gasguru]

When the heating is on the system pressure will rise as the water expands in volume...when using just the hot water there is no significant rise. Get the expansion vessel checked...it's probably low on air pressure or flat.

 

[xuevin]

I spoke with a plumber and viessmann specialist and they said that installation of the boiler is incorrect.

The pressure expansion tank is currently located immediately downstream of the the system water supply of the combi unit. (Hot side) They said that when the three way valve activates, the expansion tank is isolated from the boiler, which results in excess internal pressure.

The correct placement (also indicated in the manual) should be on the system water return side (Cold side). In retrospect, this makes sense as the pressure is generated in the boiler, and the shorter distance to the expansion tank (not through the 3 way valve) should provide relief.

I am having someone come in to do the re-piping. I will provide further updates to see if this fixes the problem.

 

[Agile]

You seem to be totally unaware, or just don't understand, the difference between hot water and system water in the boiler.

You also seem to be been given incorrect advice by someone. Or you have not conveyed what they told you correctly.

Tony

 

[xuevin]

To clarify, when I say hot water, I mean the system water. I have edited my texts to reflect this.

 

[xuevin]

The problem has been resolved. The plumber moved the expansion tank to the system return side and the PRV no longer triggers on DHW usage.

 

[Steelmasons]

The problem has been resolved. The plumber moved the expansion tank to the system return side and the PRV no longer triggers on DHW usage.

.....
Get a life FFS and stop with the trolling.
So you're saying when the heating is on the PRV discharges due to the EV being down stream of the diverter valve causing high 'internal' pressure to boiler???....this would suggest that the diverter valve is closed to heating side along with the heating return also closed....

 

[xuevin]

Well - whatever the problem is - it is now resolved. I have pictures if anyone wants to challenge this. I come here for advice and get accused of trolling. This forum is ridiculous.

 

[xuevin]

Pictures of the before and after.

http://imgur.com/a/2rnK6

 

[xuevin]

this would suggest that the diverter valve is closed to heating side along with the heating return also closed...

Considering the house is a 3 story building, having the pressure travel through the pipes through the supply return might have caused this isolation.

 

[Steelmasons]

Well what can I say.....a chimp would made a better job of that pipework ..absolute disgrace.
Industry has gone to the dogs FFS..

 

[Gasguru]

That's just a typical rough American install...for some weird reason Unistrut and trunking hasn't made it across the water.

Scary flue off the tumble...nicely wedged with a bit of foam.

Looks like that vessel's not supported on a bracket, is the air valve accessible?

 

[oilboffin]

This forum is not rediculous it's supported by lots of guys who give their time freely and I can feel their frustration from time to time when faced with ****potical prats like you who come on and feel your allowed to abuse them at your lesure.Bob