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Discuss Vaillant 624 System Anti-Cycling / Power question in the Plumbing Jobs | The Job-board area at PlumbersForums.net

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rmistry22

Hi all,

Please be gentle, my first post.

OK. I had a vaillant 624 System boiler fitted by a Gafe Safe engineer, who wanted me to fit a Worcestor Bosch combi, because he has NO knowledge of the Vaillant.

I did lots of research and the current 5 year warranty made my decission for me. However I have a few small queries.

The problem I am experiencing is the water in the hot water cyclinder, driving a shower force shower coil in the cyclinder becomes cold after one shower and due to the anti-cycling the boiler does not fire up quickly enough to heat the water for person 2. The water is set to run for 2 hours, the tank reaches temperature in 15 - 20 mins! then boiler starts pump overrun and then anti-cycling mode.

I've deliberatly over sized the boiler planning to extend / convert garage in the near future, calculations show I needed 14.2KW (cuurent radiators + Water), or 17.7Kw depending on method used.

So currently set d0 to 18KW, reducing boiler output.

1) Will changing the anti-cycling from 20 minutes to 10 or less cause damage to the boiler / heat exchanger? can set from 2mins to 60mins
2) what is the best temperature / setting for the cyclinder stat - currently set at 70C
3) what should the water temperature on the boiler be set to? - currently set at 60C

I've also tweaked d1 to 7 mins, so the pump overrun is longer.

Any help advise appreciated.
Thanks in advance.

System Boiler 624
Showerforce Cyclinder (approx 5 years old, was running in combination mode, now only used as hot water cyclinder)
Danfoss 3 Port Valve
Danfoss Room Stat
Danfoss Cyclinder Stat
Danfoss Timer
---- All Danfoss stuff is new, bought as a control pack------
 
Not familiar with your boiler or cylinder but do know a bit about stuff... If your cyl stat is set to 70 and the circulating water to it is set to 60 it will never reach temperature so I'm wondering how it manages to heat it to temp in 15-20 mins? I'd imagine by the time the water gets to the cylinder it'll be even cooler than the 60 the boiler is set to ....

If I'm interperating what you've wrote correctly I'd suggest you set your boiler temp higher.... However there are plenty installers here who may be more familliar with the bits and bobs you're taking about :)
 
That's a logical answer, but the thermostat on the cyclinder does get to 70c, taking away demand for heat when set at 60c on boiler? I think there's a deeper setting in the boiler that pushes the water out at 75c.

I'm beginning to think its the anti-cycling that's my main problem.

The water heats up.... Used to drive shower force coil, water in cyclinder cools, demand from cyclinder stat, boiler says NO, I'm in anti cycling mode, then after 20 mins fires up to reheat cyclinder to 70c, by which time 2nd person has had a cold shower!

Any more thoughts anyone?
 
im suprised a full cylinder doesnt do 2 showers but not come across shower force coil is this a mains fed coil working like a heat store?
 
rmistry - if you can manually set the anti cycle as low as 2 mins according to manufacturers instructions, I'm assuming that's where you're posting the info from. I'd reduce the anti cycle to its minimum. Manufacturers say you can and it sounds like you need rapid recovery for the cylinder in question...
 
im suprised a full cylinder doesnt do 2 showers but not come across shower force coil is this a mains fed coil working like a heat store?

That was my thoughts too Steve, a thermal store cylinder ... Google doesn't help on a search though!
 
Thanks for the input, the cyclinder remains warm and still is ok for domestic water supply directly from the tank, so another person could still run a bath. The water I think is just not hot enough to supply to the shower.

Two settings I'm considering changing,

1. The anti-cycling time down to 10 mins
2. d20 max hot water temperature currently 65c to 70c maximum allowed

Any further thoughts?

Thanks in advance for any help.
 
Thanks for the input, the cyclinder remains warm and still is ok for domestic water supply directly from the tank, so another person could still run a bath. The water I think is just not hot enough to supply to the shower.

Two settings I'm considering changing,

1. The anti-cycling time down to 10 mins
2. d20 max hot water temperature currently 65c to 70c maximum allowed

Any further thoughts?

Thanks in advance for any help.






can you increase the HW storage, system boilers are ideal when linked to large unvented cylinders,small cylinders wont get a condenser working to its best(high return temp)
 
Didn't really want to change the cyclinder, we particularly wanted to retain the shower force shower coil aspect as previously used with the glow worm economy F 40 000 btu it worked quite well.
The only problem with that system was it was getting old and taking too long to heat up the water and central heatin, I think after 21 years constant use it had done its duty.

If we had to replace the cyclinder, any suggestions?

Thanks again to everyone so far for the help & advise.

RM
 
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