ABV settings

[Steve200]

Hi, I'll be fitting a Honeywell DU144 ABV to replace a corroded gate valve. Honeywell's instructions require the pump head and flow rate to calculate the ABV setting. I've found the pump head (2.0m) in the technical data of my Greenstar 24i sealed system but the flow rate is not listed. Is this because the pump runs at variable speeds according to the demand?
Should I simply set the ABV by adjusting it to just open during the 3 minutes after the boiler has shut off when the pump is in overrun?
Thanks

 

[Johntheo5]

That's probably your best bet but ABVs are really made to be set in conjunction with a pump with the traditional 3 speed settings (constant curve) where the pump head rises as the flowrate decreases, your boiler circ pump runs in constant pressure mode so quite difficult IMO to set up, I would try and locate the ABV as far away from the boiler/pump as possible as the flow/return piping losses should mean that the pressure at the ABV will be slightly lower at normal circulation rates and will rise a little with the reduced flowrate required on pump overrun which should make setting the ABV easier?. I would also install a new gate valve with the ABV which may make it easier to get the ABV setting right.

Honeywell DU144

 

[Steve200]

Thanks for your reply Johntheo. You've suggested fitting a gate valve and an ABV. I'm not sure how the gate valve will help with the setting of the ABV. Could you help me out please? Thanks

 

[Johntheo5]

I think the theory is that by throttling the gate valve and letting/setting the ABV doing the rest, I'm a bit skeptical myself but ìf all else fails you can always set the ABV to be fully open and control the bypass as you always did, with the gate valve.

 

[Steve200]

Got it! Many thanks

 

[Mottie]

This was how I set mine. I read it somewhere, possibly on this site. Anyway, it’s worked fine ever since.

Im not a professional but the way I set mine was to wait until my system had cooled right down and turn off all my TRV's but leave the rads without TRV's on - in my case just the lounge and bathroom. I then fully closed off my bypass valve, turned my room stat up high and put the heating on. When closed, the bypass should remain cold. Let the rads get up to temperature and then start opening the bypass valve a bit at a time while feeling the temperature of the bypass. At one point the bypass will start to get hot when the valve starts to open. Close it off a quarter of a turn and that should be it. In future, the bypass should remain cold or slightly warm but when you turn the thermostat down or switch the heating off and the boiler is on the overrun, the bypass should get hot almost instantly. I do reset my bypass in summer when the heating is not used, just the hot water, when I change the pump speed.

 

[Steve200]

Thanks Mottie - really useful practical advice. Cheers