low loss header / open vented

[Fishpond]

Has anyone installed a LLH on an open vented system? If so, have there been any issues or anything to look out for?

 

[hammers4spanner]

you can but have never done nor come across it myself always been sealed.

 

[hammers4spanner]

Would imagine the feed would be sizeable thinking about it

 

[hammers4spanner]

tank size and height more than likely as well , you got one to install??

 

[stevetheplumber]

most comercial stuff is open vent and often have lowloss headers what boilers are you using?

 

[hammers4spanner]

most comercial stuff is open vent and often have lowloss headers what boilers are you using?

Not the ones i have seen been on/off commercial for years and all sealed systems that i come across with llh's unless i managed to miss large tank somewhere !!!

 

[Fishpond]

I've only installed LLHs on sealed systems to date.

I am quoting for a job where I'll be putting in 2 boilers (probably Viessmann) to provide 65-70kw total. It's an old system, old pipe work, old rads etc so would be too risky to convert to sealed...

 

[hammers4spanner]

Sounds like nice job , thought about contacting boiler manufacturer for a schematic ?

 

[chris watkins]

I've only installed LLHs on sealed systems to date.

I am quoting for a job where I'll be putting in 2 boilers (probably Viessmann) to provide 65-70kw total. It's an old system, old pipe work, old rads etc so would be too risky to convert to sealed...

Boilers may need to be sealed but you could do a hybrid using a large plate heat exchangers so new boilers on sealed side & separate from the dirty old open vented side. I have not done one myself but understand it is being used as easer to clean / replace exchanger than risk a new set of boiler heat ex's.

 

[hammers4spanner]

How does that work chris? Like the idea of that but always thought that the circuit draws from header or am i in thick mode and not thinking ??

 

[Fishpond]

How does that work chris? Like the idea of that but always thought that the circuit draws from header or am i in thick mode and not thinking ??

Boiler to header is the primary circuit and then on the other side of the header the secondary circuit is to the plate HEX back-to-back with the CH circuit. This provides total separation and removes the need for sealing the CH, whilst the boiler/header circuit is sealed. I haven't done this yet, but have heard it talked about...

Do you know if there is some other type of HEX that can be used (other than a plate HEX) with bigger waterways that are less likely to clog up with gunk on the CH side?

 

[chris watkins]

Depends how big you want to go, I am sure someone on here recommended these people a while ago
UK Exchangers Ltd - Heat Exchanger Specialists
as far as blocking you would still need to install filters / dirt separators to try to protect the ex.

 

[doitmyself]

Boilers may need to be sealed but you could do a hybrid using a large plate heat exchangers so new boilers on sealed side & separate from the dirty old open vented side.

If you did that, would you still need a low loss header? I wouldn't have thought so.

 

[chris watkins]

Boilers may need to be sealed but you could do a hybrid using a large plate heat exchangers so new boilers on sealed side & separate from the dirty old open vented side.
If you did that, would you still need a low loss header? I wouldn't have thought so.

It would depend on what circuits there are on the system but the plate would be high resistance, so I would have thought it may be better to have a pump to deal with just this & then a header to distribute out to each circuit in the normal way.
The LLH will also act as a dirt separator (if installed vertically) being a low velocity area, that along with a strainer / magna clean type filter might help to keep the heat EX clear?