best solution

[ambrosia]

vaillant 428 keeps locking out on f22 and f24 (dry fire)

its in a really tall house, 6 floors (no lift, lots of stairs)

boiler is in the basement with prv, 25ltr expansion vessel and filling loop.

Pump, zone valves and hot water storage is on the top floor between 15 and 20 meters above

boiler has been in 14 months and system was converted to pressurised system at that time

PRV unsurprisingly is already knackered

My dilema is whether to patch the system up with a new prv which i know wont last,
or think of some more permanent solutions, (which i'm hoping you guys are going to give me)

I thought of attaching prv to rad, on a midway floor, but dont like this idea as the prv wont be experiencing the same pressure as the boiler

 

[Ermintrude]

Relocate boiler? 27m is only 0.27 bar?

 

[doitmyself]

27m is only 0.27 bar?

I'm not sure what you are questioning. 27m is 2.65 bar.

 

[Ermintrude]

Oops . Yea sorry. The static head on prv is 2 bar max and expansion..... Fit a huge vessel set to 1.8? Then prv won't feel much above 2. Shouldn't chowder it. Might be knackered pressure sensor? Or grit blocking it? What's system water like? Also what size pump u got ?

 

[Ermintrude]

Some one bound to argue, but if it's at top it's got to suck up and push down at least a bottom it's got 2 bar pushing into it?

 

[happyflyer]

Ermi,

I thought sealed system PRV blow off at 3 bar which if I am right would put this system with the boiler in the basement right on the limit on a cold system,
2.7 bar static, blow off 3 Bar only 0.3 bar margin. Moving the boiler may well be one hell of a pain but an option, PEX might be the only way out, but it means more pumps.

Why do people fit systems like this and walk away.

Baldy Old Git.

 

[ambrosia]

Might be knackered pressure sensor

No pressure sensor on this boiler, just 2 ntc's

Relocate boiler

I was really hoping for an easier solution, besides the only place the customer will tolerate it is either where it is or in the loft conversion

Why do people fit systems like this and walk away

customer has lost faith and doesnt want them back



thanks guys, bit of a difficult one this one

I was thinking of putting the F and E back in

 

[happyflyer]

Not in the loft please, then PEX is the only safe and sound option, this happens in commercial a lot high rise buildings with boiler in basement, better on the roof in that case,

 

[Millsy 82]

If you put a plate heat exchanger in wouldn't you have the same problem on the pressure side unless you put a couple in and split the height of the house?

 

[EPH]

If you put a plate heat exchanger in wouldn't you have the same problem on the pressure side unless you put a couple in and split the height of the house?

The plate will take the additional pressure though quite easily and have the boiler sat at 1 bar on the other side.

Id agree, can't see a better alternative.

 

[happyflyer]

If you put a plate heat exchanger in wouldn't you have the same problem on the pressure side unless you put a couple in and split the height of the house?

That's just the point of a PEX you can have 20 bar on the system side and 1 to 3 bar on the boiler side, they are not just used to separate different liquids but pressure too!

 

[happyflyer]

You may need to run the primary side higher than normal to get the exchange to work, if you get a manufacture to look at your flow rates etc you could drop the primary temp.

 

[happyflyer]

There is another option depend on boiler size, a commercial boiler may not have the pressure restriction that a domestic one has. the OP needs to talk to someone who deals with this sort of thingy, what is the boiler size OP?

 

[ambrosia]

anyone have a link to the type of PEX i need

a commercial boiler may not have the pressure restriction that a domestic one has

athough it can work on a pressurised system the vaillant 428 is an open vented boiler, hence no pressure sensor

 

[happyflyer]

ambrose

i need he boiler size to point you

 

[happyflyer]

Brazed Plate Heat Exchangers – Stainless Steel Compact Brazed Design


There are two types welded, and sectional , the welded one you can't take apart, since the delta T will be small there should be no alarming
building up of crap on the secondary side ie the system side, the welded one will be much cheaper, if you fit a welded one just make sure it and be disconnected to flush it out if needed.

Now what's that boiler size????????

 

[stevetheplumber]

you can mount a header tank above the boiler if your using a pex

 

[ambrosia]

its 28kw,
i've never done an external PEX, when youre sizing it whats the margin for error

so you guys are saying follow flow and return to somewhere midway in the house put an expansion vessel, prv, pex and filling loop there.
leave another set of prv filling loop and expansion vessel with the boiler, and install a 2nd pump.
this way boiler only has to cope with half the amount of floors and the other side of the PEX will be okay doing rads on all 6 floors on one circuit

or do i need to move the zone valves so floors are on different circuits and not subject to 6 floors of pressure (there are only 2 zone valves presently, hot water and heating for all floors and yes its almost certainly over 150m2 and past doc L rules)

 

[happyflyer]

I will call a manufacture in the morning for you and give you an idea on price first and then see if moving the boiler might be the cheapest option, dread the roof space, mind you I won't be servicing it will I....


Baldy Old Git

 

[happyflyer]

Ambrose PM me!

 

[Millsy 82]

That's just the point of a PEX you can have 20 bar on the system side and 1 to 3 bar on the boiler side, they are not just used to separate different liquids but pressure too!

The problem I was thinking is unless you are going to have open vented on the opposite side to the boiler you will still have 2.7 bar and a pressurised system with a 3 bar prv on it and then same problem just moved from 1 place to another. Or can you fit a higher rated prv on the heating system side?

 

[happyflyer]

Millsy,

The primary side ie boiler side only needs 1 bar or thereabouts, the secondary side can be pressurised until the radiators burst, figuratively speaking, you wouldn't do that of course, you would fit a PRV that suits the system pressure , you could even take the vessel off and fit an header tank in the loft, then would you need to fit a PRV that's the question, you have no boiler with a flame in it on the system, that will having them dancing in the isles now!

Lots to think about, the problem will be the cost of the PEX 30Kws with the primary and secondary water almost the same temp, it will be a fair PEX, will need a fair bit of water going over the plates on both sides, a swimming pool PEX is rather small, the primary water is 80 Deg C and the secondary 28 Deg C, thus the small size.