Honeywell 2 port zone valve question

[Mister Banks]

I had the same with mine a few years ago. It turned out to be the auto bypass valve opening. Adjusting it cured the problem.

The problem i have at the moment is that the ABV is set to 2 (0.2bar) and the knocking is still there. How low should I go, according to the ABV instructions most systems should be set between 2 and 3.

 

[Mottie]

The problem i have at the moment is that the ABV is set to 2 (0.2bar) and the knocking is still there. How low should I go, according to the ABV instructions most systems should be set between 2 and 3.

I took no notice of numbers, I set mine up by running the system at max with the valve closed and then slowly opening the valve until I could feel it passing. I then just tightened it up a bit and that was it. What speed is your pump on? I run mine on number 1 speed.

 

[Mister Banks]

I took no notice of numbers, I set mine up by running the system at max with the valve closed and then slowly opening the valve until I could feel it passing. I then just tightened it up a bit and that was it. What speed is your pump on? I run mine on number 1 speed.

I have turned the ABV all the way to 0 and it still doesn't allow any water to pass. The pump is integral to the boiler.

 

[Johntheo5]

I have set up a few but I set the ABV to just start passing at the lowest demand because this is where the system head loss is least and the remaining pump head is greatest, as zone valves open then the system loss increases so less remaining pump head....ABV closes., this even works with pumps in constant pressure mode where most system boilers now run and at a pump head of 6 to7M. The (DU144) ones that I set worked well at ~ a 4.5/4.8M index setting.

The DU145 has very strange characteristics. You set the index higher than the available pump head, for example, just below, you set the index to 4.2M with a pump head of 4.0M to get a flowrate of 300LPH, 5LPM. On the DU144 you set it to 0.35 (3.5M), (makes sense) with a pump head of 4M to give that 300LPH, 5LPM.
Also the maximum flowrate of the DU145 is 3000LPH, 50LPM, the DU144 is 1500LPH, 25LPH.
The only difference is that the DU145 is a angled ABV, the DU144 is straight.

 

[Johntheo5]

I have turned the ABV all the way to 0 and it still doesn't allow any water to pass. The pump is integral to the boiler.

Your ABV is knackered IMO, you will probably have to renew it as its probably now set to 5/5.5M or even 6.0M, does it still bypass when you shut everythng off?.

 

[Mister Banks]

Your ABV is knackered IMO, you will probably have to renew it as its probably now set to 5/5.5M or even 6.0M, does it still bypass when you shut everythng off?.

The ABV operates correctly when both the zone valves are closed i.e. the valve opens and allows water to circulate back to the boiler. Its just that turning the ABV to its lowest setting doesn't allow water to pass when either zone valve is open and setting the ABV over 3 (0.3 bar) causes the boiler to become noisy when both zone valves close.

 

[Mister Banks]

I think I have found the problem....... when the CH 2 port zone valve closes it occasionally causes the clunk in a central heating pipe, my thoughts are that I need to slow down the speed of the valve closing or maybe the valve is faulty.

 

[Johntheo5]

Both my 13 year old Honeywell close in less than 3 seconds.

 

[Mister Banks]

Both my 13 year old Honeywell close in less than 3 seconds.

My zone valves are Honeywell as well, they close within 3 seconds too. There must be an answer to my issue without me having to pull up all my floors looking for a loose pipe that occasionally makes a clunk.

 

[dilalio]

What size expansion vessel?

 

[Harry Bloomfield]

The flow and return are both correct. The issue is the number of times the Drayton system starts and stops the pump. Last night I jammed open the CH zone valve and didn’t hear a single thud . I will jam the valve open again tonight.

Starting from a cold system, it is easy to tell by feeling the temperature of pipes, which is flow and return around all parts of the system.

 

[Mister Banks]

What size expansion vessel?

I don’t know the size, it’s what came in the boiler, a Greenstar 24i

 

[dilalio]

I don’t know the size, it’s what came in the boiler, a Greenstar 24i

Well, you mention 4.5m of 32 and then 28. How many rads? Potentially sounds like fairly large system volume. Built in EVs are designed to cope with a certain volume, maybe you have more than that... It's quite often the case!

 

[Mister Banks]

Well, you mention 4.5m of 32 and then 28. How many rads? Potentially sounds like fairly large system volume. Built in EVs are designed to cope with a certain volume, maybe you have more than that... It's quite often the case!

It’s not that large. I have 11 radiators and 2 towel rails in a 186m2 4 bed detached house. The heating pipework is 28mm out of the boiler which goes to 32mm before it disappears into the ceiling, it then exits into the airing cupboard on the first floor but is back to 28mm reducing to 22mm in the airing cupboard. All radiators have 15mm connections.
It’s a pressurised system, 1bar cold and 2.5bar when hot.