Viessmann 100-W WB1B 26kw open vent `S`Plan Control Wiring

[picasso]

The instructions for the honeywell 3 ports are not very clear, they say up to 26kw but it has 28mm compression as an option, so I dont reckon the 26kw is through a 22mm valve, sure I have read somewhere that the max is 18kw on a 22mm but cant find it at the moment.

 

[mysteryman]

You are incorrect about 18kW being the maximum for Honeywell 3 port valves. The working ports inside the valves are the same size anyway.

It is clearly better for the pump overrun to put the residual heat into the cylinder. This cools the boiler and utilises the residual heat.

 

[Kellymont]

You are incorrect about 18kW being the maximum for Honeywell 3 port valves. The working ports inside the valves are the same size anyway.

It is clearly better for the pump overrun to put the residual heat into the cylinder. This cools the boiler and utilises the residual heat.

Hi thanks guys, this is a very good idea "mysteryman" it makes the best sense where to send the overrun letent heat.

However, my plumber has checked the system and he assures me that No hot water is going past the bypass valve if either of the motorised valves are open, so no hot water is short circuiting back to the boiler making in ramp down.

My real problem is that the boiler is just Not making enough heat, with the dial set to the spot just over the 4 mark is makes 52 degrees, it stays at that with flam on-off and holds that temerature constant, not enough i think? if i set the dial halfway between 5 and 6 it makes 59 degrees still not enough, i have to set it right off the dial to get anywhere near the temperature to warm the rads and get hot water, the system has 10 rads a towel rail and a hot water cylinder.

I have tested it in SERV mode and it really `kicks arse` 5 bars on dial 6 and 1 bar on dial 1 so i think all that is ok, we have just tonight fitted a new pump because he was told buy someone fitting these that flow is very inportant but it seems to have made no difference.

Any suggestions please chaps.

 

[simond]

It is designed to be able to be set off the dial, in other words, beyond 6.

The radiators in your house are probably a bit marginal and were sized for 81c flow. Most condensers are designed to work up to 75c. If memory serves me correctly, when the temp dial is all the clockwise you are still only pushing 75c on a 100 wbib.

You can turn it down a bit when the weather is milder.

 

[Kellymont]

It is designed to be able to be set off the dial, in other words, beyond 6.

The radiators in your house are probably a bit marginal and were sized for 81c flow. Most condensers are designed to work up to 75c. If memory serves me correctly, when the temp dial is all the clockwise you are still only pushing 75c on a 100 wbib.

You can turn it down a bit when the weather is milder.

Oh dear, well that explains just about everything, i was expecting a 26kw to do better as it is twice the size of the oil boiler it replaced, running it off the dial don`t seem right for a german bit of kit/quality that we are used to, the dial now is off the clock between 6 and Serv but you have to be carefull or it goes into serv and it is reading 68 degs and i expect it to rise a little more.

The rads are a bit old, convector type, but not ancient, so what you are saying is that most modern condensors only work up to 75 degs so you have to fit moden radiators to get the best out of the heat.
So how long should i expect it to heat the standard size hot water cylinder?
Can the boiler be tweeked up a bit,? cos i can`t understand where the 26kw is going!

Thanks any way for you help Simon.

 

[mysteryman]

Bear in mind what I wrote about excessive flowrate through these boilers - they have a return temp sensor, and if that gets into the 50s, the burner will modulate and the flow temp will be restricted.

REDUCE the flowrate, you get a greater temp rise across the boiler, and a higher flow temp at the same return temp. Why? To try to make the boiler condense as much as possible.