Viessmann four pipe system, What do people think

[steosman]

Hi, just joined this forum but have been looking at posts for a while. I run a domestic/commercial heating and plumbing company in Ireland and started using Viessmann vitodens 100-w boilers in Domestic side a year ago. Before these boilers arrived on the market here i installed the old reliable two zone s plan central heating system with either Glowworm or Bosch. When i've installed the Viessmann and upgraded the pipework i used there four pipe system as i think weather comp is going to be the next big thing and i want the boilers to be in full condensing mode most of the time, 50 degrees flow and 30 degrees return.
Has anyone been installing the four pipe system and what do you think about the cylinder getting priority over space heating. I'm getting a few customers that can't understand why the two can't be on at same time. I only realized this was the case after my first four pipe install and found it strange. Any thoughts anyone. Cheers

 

[yorkieplumber]

As far as i am aware, cylinder as always had priority over heating circuit.

 

[yorkieplumber]

Hi, just joined this forum but have been looking at posts for a while. I run a domestic/commercial heating and plumbing company in Ireland and started using Viessmann vitodens 100-w boilers in Domestic side a year ago. Before these boilers arrived on the market here i installed the old reliable two zone s plan central heating system with either Glowworm or Bosch. When i've installed the Viessmann and upgraded the pipework i used there four pipe system as i think weather comp is going to be the next big thing and i want the boilers to be in full condensing mode most of the time, 50 degrees flow and 30 degrees return.
Has anyone been installing the four pipe system and what do you think about the cylinder getting priority over space heating. I'm getting a few customers that can't understand why the two can't be on at same time. I only realized this was the case after my first four pipe install and found it strange. Any thoughts anyone. Cheers

Have had issuses with this particular system, had to call viesmann out as we could never satisfy hot water demand so valve never clicked onto heating side, they turned stat down and off they went, customer then phoned me saying there is a chance of catching legionaire, it took a lot of sorting, so i stick to who i have always used valliant, never ever had any problems with them.

 

[steosman]

Thanks for replies, How does the vallaint go to full condense mode and does it not require independent pipe run to cylinder. I'm regretting installing the four pipe system now but i want to have a system whereby once the cylinder is up to 60 degrees the boiler can reduce flow and return temps to full condense. I am sizing radiators to operate at low temp, 45 degrees. The bosch boilers need the same four pipe system as the viessmann does to use there weather comp. i don't think Vallaint are available in Ireland which is a shame because they appear to be very good boilers and customer service seems good also.

 

[Blackcatgas]

Awesome when used with a new cylinder, with a 20kw coil and proper lagging, as they can reheat in 20 mins with the 4 pipe system. You can still run them as a y or s plan but have to use the grey wiring centre that comes with the boiler, they wont work properly without the box.

 

[steosman]

Thanks Blackcatgas, That's a good tip about the cylinder. The system i'm installing now is two space heating zones and cylinder. Using a three zone sauter time clock, two motorized valves will do the zones and wiring the cylinder stat that came with the heating control pack to the boiler via the Viessmann demand box. I was thinking of changing the cylinder stat to a temperature probe, I think this is what viessmann prefer. The house i'm having problems with has an old hot water cylinder and it's not even lagged. He's a family friend and wanted the four pipe system once i told him about the benefits of weather comp. Don't know if i'm totally sold on the idea but it's the only way the Viessmann weather comp will work. I cant understand why both heating and hot water can't be on at same time but i suppose it's just the way they want it. I was finding it hard enough to convince customers about upsizing there rads and running them at lower temperatures, most people want their rads to be as hot as the surface of the sun. I'm going to contact Vallaint and see if they require a four pipe system for weather comp

 

[tackleburger]

Any system with weather compensation has to prioritise hot water. If you think about it there isn't really any other option as if the outside temperature is say 12 deg you are only going to get say 40 - 50 on the boiler flow, not high enough to heat the cylinder quickly as required. I have used the Viessman system a few times and always program the water to heat up before the heating is due to rise to avoid this outcome.The main problem with these systems is it is a mind set change the heating has to be on all the time or you are then adversely adjusting the heat curve to compensate for misuse and hot water issues. I set the system up and convince the client to use it as designed. I usually go with the Vaillant system with the VR65 wiring centre. These systems keep the water at about 50deg and have an inbuilt anti legionella function that brings the cylinder upto temperature once a week.

I'd say the issue you have is your clients are not leaving the heating on and trusting the controls then they are finding themselves cold in the morning as the system has prioritised hot water. Trouble is people think they are wasting gas.

 

[tackleburger]

Vaillant also have a mixer module the vr61 which will allow you a three zone system with weather comp top notch it is. Just fitted one for a chap. Upstairs rads, downstairs underfloor heating and the cylinder with probe works a treat Although we haven't yet connected the underfloor as we are waiting on others.

With this system you also need a vr81 i think it is, as a roomstat for the other heating zone.

 

[steosman]

Thanks tackleburger, unfortunately i can't get vallaint in Ireland which is a shame. I'm just going to make it clear to customers that it's a new way of thinking and it will save them gas!. Just finished my parents house and going to set the system up so they won't have an issue with it, hot water comes on at 5 in the morning and heating will be on most of day to keep house 20 degrees. I am also going to run system like most houses , then with it on most of day and then finally with weather compensation and compare gas usage. Cheers for all replies