How to set a honeywell auto bypass valve?

[bengasman]

You don't need to know the resistance of the system, just the minimum flow rate through the boiler and the pump curve, which is in their published literature.

Are you trying to demonstrate the extent of your lack of knowledge? If so, you are doing a pretty good job.
The flowrate is ALWAYS the result of:

Flowrate= pressure divided by resistance.
Resistance unknown= flowrate unknown.

It can NOT be calculated for a live system.

 

[picasso]

an ABV can be set up to do either system bypass or boiler bypass, it also functions as both at the same time, it looks like d hailsham is setting up a system bypass and gasafengineer is doing a boiler bypass.

 

[D_Hailsham]

You don't need to know the resistance of the system, just the minimum flow rate through the boiler and the pump curve, which is in their published literature.

Are you trying to demonstrate the extent of your lack of knowledge? If so, you are doing a pretty good job.
The flowrate is ALWAYS the result of:

Flowrate= pressure divided by resistance.
Resistance unknown= flowrate unknown.

It can NOT be calculated for a live system.

It's obvious that you think you know it all, which is why you haven't bothered to read Honeywell DU144 Instructions, so I'll quote the relevant section:

Setting Procedure
1) Commission and balance the Heating System – take note of the selected pump speed.
2) Using the Boiler manufacturer’s instructions, find the minimum flow requirement for the Boiler.
3) Using the Pump manufacturer‘s Pump curves determine the available Pump head when operating at the required minimum flow and the selected Pump speed.
4) Using the DU144 Setting chart, the calculated Pump Head and the minimum Boiler Flow to find the optimum setting for the DU144

The actual flow rate is not important; it's the minimum flow rate stated by the manufacturer which is the relevant factor. All you need is the boiler minimum flow rate (from the MI), the pump curve and the ABV curves to set an ABV.

However Honeywell do add:

Should persistent water velocity noise occur in the Heating System, gradually turn the DU144 to a lower setting until the noise is eliminated.

So the setting given by their procedure could be considered a starting point.

 

[gasafengineer]

Domestic heating systems only require auto bypass valve to be set so as noise velocity is @ a minimum , in all cases this will be sufficiently set for correct volume of water through boiler for heat dissipation/nuisance lockout..............using this approach on some commercial type systems can cause PRV seatings to lift. ..........not rocket science.

 

[D_Hailsham]

an ABV can be set up to do either system bypass or boiler bypass, it also functions as both at the same time, it looks like d hailsham is setting up a system bypass and gasafengineer is doing a boiler bypass.

Not according to Honeywell's Instructions, which are concerned with maintaining a minimum flow through the boiler, i.e. a boiler bypass.

How do you define a "system bypass"?

 

[picasso]

Yes, or slightly lower. The test is that the valve is not open when all rads are working with any TRVs fully open. The crude way of setting an ABV is as follows:

1. With boiler/system cool, set valve to max.
2. Switch heating system/boiler/pump on.
3. Reduce setting until valve is just open (by-pass/valve starts to get hot).
4. Turn adjuster back (anti-clockwise) one revolution (ie. valve closes).
5. Valve will automatically open when system flow reduces.

this is setting of a system bypass.

 

[gasafengineer]

Drayton TR4 instuctions advise to balance system , NEVER have i had to balance a system when using these valves , the orifice through these valves are soooo small you would be lucky to maintain correct deltaT with any emmiter exceeding 10,000 btu (2.9kw) , hands on experience counts for a lot more in most cases , some may go by the book & balance the sytem using a thermometer , the trained hand is a better instrument in most cases.

Sometimes i don't care much for instructions , could of been written by a spotty face just come out of college or worse still a CCC/keyboard jockey.

 

[D_Hailsham]

this is setting of a system bypass.

How do you define "system bypass"?

 

[picasso]

an automatic valve that opens as the pressure differential rises, (as I am sure you know) motorised valves or trv,s closing could make the pump deadhead and the system noisy.

 

[bengasman]

So the setting given by their procedure could be considered a starting point.

It could be considered anything.
I wonder what you are like when you are sitting in the backseat of your grandson's car.

 

[D_Hailsham]

I wonder what you are like when you are sitting in the backseat of your grandson's car.

Haven't had that pleasure yet as he is only nine years old!

 

[D_Hailsham]

an automatic valve that opens as the pressure differential rises, (as I am sure you know) motorised valves or trv,s closing could make the pump deadhead and the system noisy.

So what's the difference between that and a boiler bypass. They both have to open when the differential pressure rises and, as far as I can make out, the pressure at which they open is the same in both cases.