Navien Combi Boilers

[Deleted member 221031]

57kw running of 15mm. That’s a quality install.

Navien’s Claim of being able to run off 15mm is only the same as other manufacturers who produce the gas tail in 15mm. They aren’t saying 15mm will be enough. You need minimum WP.

All modern boilers are Negative pressure. Just because the fan pulls it doesn’t mean you can get away with a smaller pipe.

 

[hard-work]

The greater the negative pressure the fan creates, the greater the pressure differential. The greater the differential, the faster the gas will move. This means a smaller bore pipe need only be used for a part of the run. That is what Navien are doing. Some HVAC equipment also does something similar.

 

[Deleted member 221031]

The greater the negative pressure the fan creates, the greater the pressure differential. The greater the differential, the faster the gas will move. This means a smaller bore pipe need only be used for a part of the run. That is what Navien are doing. Some HVAC equipment also does something similar.

And only Navien boilers work like that ?

Sounds a lot like a zero pressure governor to me

https://www.diynot.com/diy/threads/modern-boilers-different-type-of-gas-valve.216616/

 

[hard-work]

Some commercial equipment use negative pressure gas valves, like Trane. You can have pressure on the inlet of a negative pressure gas valve, when the pressure on the outlet port is above zero it will shut off the gas. When the outlet pressure drops below zero it opens. It is a valve. A governor will not shut off the gas. So the combustion fan stops then valve shuts off the gas. The negative pressure gas valve is a shut off valve and enables gas pipes to be downsized.

The fan can turn with the negative pressure gas valve not opening until a pre-set deferential occurs. This will purge the burner and flueways.

 

[Deleted member 221031]

Some commercial equipment use negative pressure gas valves, like Trane. You can have pressure on the inlet of a negative pressure gas valve, when the pressure on the outlet port is above zero it will shut off the gas. When the outlet pressure drops below zero it opens. It is a valve. A governor will not shut off the gas. So the combustion fan stops then valve shuts off the gas. The negative pressure gas valve is a shut off valve and enables gas pipes to be downsized.

The fan can turn with the negative pressure gas valve not opening until a pre-set deferential occurs. This will purge the burner and flueways.

I’m really hungover so I can’t quite understand the difference between that and a negative pressure fan set up an most modern boilers.

Negative pressure is created by the fan. It sucks gas at the desired rate, set by demand/fan speed.

In my opinion Navien’s gas valve works the same as a zero pressure one.

There’s no difference.

 

[hard-work]

There are similarities. The Navien valve, with its combustion fan, is obviously creating a greater pressure differential that will allow gas to move down a pipe faster.

Look at the two opening vids. They ripped out an existing storage based installation, cutting back the existing pipes and then connected onto them. The gas pipe would have been undersized for a 200,000 BTU/hr boiler, as it was a burner-under-tank typical American setup. The valve got them out of jail, as they did not need to run a whole new run of larger bore pipe.

 

[Deleted member 221031]

Do you have a WP stated by Navien ?

Negative pressure is just another way of saying “zero pressure governor”

Their fan works the same as all modern boilers. Sucks gas, mixes and blows it into the burner. Which looks quite like an Ideal one.

 

[Deleted member 221031]

I can’t put a pic up, but the gas valve looks just like any other gas valve.

 

[hard-work]

Gas is not sucked, otherwise it can create a negative pressure in the gas mains. it is allowed to flow at a faster rate at the burner.

 

[Deleted member 221031]

Gas is not sucked, otherwise it can create a negative pressure in the gas mains. it is allowed to flow at a faster rate at the burner.

 

[Deleted member 221031]

Page 10 of Navien UK manual states the gas pipe is 22mm.

 

[hard-work]

You have only half a clue at best.
Navien do not promote the negative pressure gas valve in the UK - yet.

 

[Deleted member 221031]

You have only half a clue at best.
Navien do not promote the negative pressure gas valve in the UK - yet.

Their negative pressure gas valve is the same as on all premix boilers. The negative pressure comes from the fan sucking gas and air. Then it mixes it and blows it into the burner for combustion.

If you understood the concept of Negative pressure it would be a lot cleare to you.

Navien’s gas valve is nothing new. Been around for 10 years.

 

[Dan Robinson]

BS says no such thing

So what does it say eh?

Navien do not promote the negative pressure gas valve in the UK - yet

 

[Deleted member 221031]

Navien do not promote the negative pressure gas valve in the UK - yet

So where have you got all the information on this new, fantastic Gas Valve ? That sounds like all other modern gas valves. You cant explain it, so you don’t understand it.

It’s jusy a normal gas valve. They have called it something different to impress