Non return on a sealed system - dangerous location?

[Boris1585]

Hi, had a new sealed/unvented hot water tank installed. Hot water was back flowing up cold inlet and out pressure valve.

Plumber rechecked and adjusted position of expansion unit in the multi non return/pressure regulator valve and changed pressure - no issues there. However they have however then put a non return valve in the cold inlet pipe between the expansion vessel and hot tank. Doesn’t this stop the expansion vessel working?

Now when boiler comes on, water comes out the high temp and pressure valve on hot tank. Isn’t this becoming a bit dangerous, am I right to get them back asap?

On a side note, is it acceptable to have a slow leak on central heating plumbing. Water droplet hanging of joint, but not actively pouring out. Again needs fixing?

 

[oldbutnotdead]

Yeah, situation 1 sounds not good. You should only be getting water out of the pressure relief valve in a fault condition (temperature or pressure outside safe limits). On a new install that's not acceptable- get them back in on an emergency basis. Aside from anything else, those temp/pressure relief valves aren't designed for frequent operation. While they are on site, check their credentials- there is a specific qualification (G3) required for working on unvented cylinders, if they have that qualification they'll be somewhere between not stressed and proud to show you their card. Any erring and umming and 'the boss has the ticket' tell them to GTFO and don't pay.
No, a professionally installed heating system should not leak. That's one of the things you pay professionals for- again if its part of the system they've been working on get them back in- that one would be a 'next time you're passing' call rather than full flap mode.

 

[Madrab]

Were the guys working on this qualified? Please confirm with them that they are qualified and have them show their ticket to you, check the dates etc. If they can't or wont then boot them off the job and don't pay. Please don't use the HW cylinder until this is sorted out.

There should be no valves between the take off for the Expansion vessel (EV) and the unvented cylinder, especially a check valve. Can you post a couple of pics of the over all install with the focus on the EV take off, combination valve, and T&PRV/PRV connections.

There is only one place on the combination valve where EV connection can be taken from. The other is the balanced cold supply and that's after the internal check valve.

The leak is another matter and low on the priority right now TBH, but no there shouldn't be an leak left on a system.

 

[Boris1585]

I'll grab some photo's and put them up. I've flicked off the boiler to be safe until sorted. Thanks for confirming what I though would be the case, but good to know I'm not being a dick of a client.

The firm has good accreditations, and prev had good experiences, but the latest install has been endless issues. I don't know the qualifications of the individual who fitted it, but will be looking into it. Boss is due to come out tomorrow so lets see what comes from that!!!

Depressingly invoice has been paid, as system 'worked' and intial snags were sorted, then more issues arose after, then really paniced me when the non return valve put on.

 

[oldbutnotdead]

Can be a problem when a company (one man and his apprentice) grows. His work ethic may be excellent, but if/when he starts employing others and sending them out on their own it can go wrong. See what happens when the boss turns up....
Best builder I ever used was one man and his boy. He had an excellent reputation, lead time of 6 to 8 months for anything and refused to expand 'I don't want to be an employer, I'm a builder and that's what I do'. He's retired now but I'm still using his plasterer cos he's a magician.

 

[Johntheo5]

A combination valve set has a NRV between the mains supply PRV and a 6bar expansion valve nearer the cylinder so if the E.vessel has failed then that 6 bar safety valve should lift before the cylinder TPRV, temperature(95C) and Pressure (7bar) safety (PRV) valve.