New Boiler Requirement

[fixitflav]

I found this information in another forum

Was there meant to be a link? I don't know what 'a more efficient “4-pipe” system' means.

I found this Weather_Compensation_Kit_User_Guide.pdf for Ideal boilers, shows how to wire to a Y-plan. I would get hold of the wiring diagram for the boiler you intend to use, it might not be just the same as Ideal.

 

[tech749]

Was there meant to be a link? I don't know what 'a more efficient “4-pipe” system' means.

I found this Weather_Compensation_Kit_User_Guide.pdf for Ideal boilers, shows how to wire to a Y-plan. I would get hold of the wiring diagram for the boiler you intend to use, it might be just the same as Ideal.

Here's some links to the item I was referring to:

https://viessmanndirect.co.uk/files/de36168a-6a60-42b9-b0e4-ada60112a767/WB1B%20Compact%20Outdoor%20Sensor%20Instructions%20-%20Mod.pdf

Vitodens 100 B1GA Heat Only Weather Compensating Kit - DHW

ZK07124 Vitodens 100 B1GA Heat Only Weather Compensating Kit - DHW

viessmanndirect.co.uk

 

[tech749]

I think 4 pipe is a Veissmann thing, to efficiently prioritise hot water when using WC, as far as I can gather from other forums.

 

[fixitflav]

Here's some links to the item I was referring to:

Edited earlier post - should have said "it might not be just the same as Ideal."!

Vitodens says "The outside sensor takes the place of a room thermostat" which is odd, I don't see how. Though earlier it says "A room thermostat may be connected in addition to the outdoor sensor", but it doesn't say how to connect it.
It says "In weather compensated mode, the boiler temperature is regulated subject to the outside temperature."
The profile is adjustable by the user, but it doesn't say where or how.

On Ideal, it's not too clear how the outside sensor connects to the system, it isn't shown on the wiring diagrams. Maybe it would come clear if you had the kit in front of you.

You haven't said yet where your 3-port valve is!

 

[tech749]

You haven't said yet where your 3-port valve is!

Sorry about that, in the airing cupboard, where all controls (Hive receiver, wiring block) are.

I think the temperature is adjusted on the boiler, then by regulating the flow and temperature according to the weather, to ensure the boiler is condensing most of the time. Not too sure how that works either, or how room stat works with WC. I'm guessing that optimum performance is achieved if the heating is on all the time, so the WC can keep a constant temperature inside the house, maybe the boiler is user adjusted and set, then the boiler keeps the correct temperature by regulating flow rate and heat accordingly. Not really sure.

 

[tech749]

Found this here just for info:

https://hhic.org.uk/uploads/5A5F2F2C7D545.pdf

Points to note Depending on appliance design, when weather compensation is fitted to a combi boiler the radiator temperature may not be able to be controlled with the boiler thermostat in the conventional fashion, as weather-compensation generally overrides this function. However, some manufacturers utilise the boiler thermostat to control the compensation “curve” or “slope”, and so allow greater flexibility of the flow temperature setting, based on the outside temperature. Further details will be contained in the appliance manufacturers’ instructions Some controls connected to “heat-only” appliances are able to differentiate a HW demand from a CH demand, ensuring that where HW storage is in place, this heats to a safe and acceptable temperature (typically 60C). Many weather compensators operate the boiler circulating pump continuously, so consideration of the householder and the proximity of radiators in bedrooms should be given. Some weather sensors still require a boiler programmer and room thermostat to be installed. The sensor will then adjust the boiler flow temperature based on outside temperatures only during a programmed period and the room thermostat will turn off the boiler and pump when it reached the correct internal air temperature.

 

[fixitflav]

Sorry about that, in the airing cupboard, where all controls (Hive receiver, wiring block) are.

OK, just curious about how it relates to your man saying the pipe needs to be rerouted.

I think the temperature is adjusted on the boiler, then by regulating the flow and temperature according to the weather, to ensure the boiler is condensing most of the time.

That's right, it's automatic, higher boiler temp when lower outside temp. The profile should be adjustable by the user. If there is plenty of rad area, can use a lower boiler temp for a given outside temp, giving better economy.

Not too sure how that works either, or how room stat works with WC. I'm guessing that optimum performance is achieved if the heating is on all the time, so the WC can keep a constant temperature inside the house, maybe the boiler is user adjusted and set, then the boiler keeps the correct temperature by regulating flow rate and heat accordingly. Not really sure.

With WC you can still control the CH with the roomstat. When it's satisfied boiler and pump stop, as normal. Probably best to leave the HW on 24/7 on the timer, as due to the PDHW (needed for WC) if it's been off for a while there's a delay before the cylinder stat is satisfied, with no CH. That's how W-plan, which incorporates PDHW works. It's what I have. IMO there's very little point in having HW on timer (with Y or S-plan), as HW is going to be needed at some time every day. Heat loss from a modern cylinder is low and any saving from it being cold(er) part of the day negligible.

 

[tech749]

Thanks for the reply.
Hmm.....not sure I understand about not timing the hot water, I only have it on now for an hour in the morning, and half hour mid afternoon. That is more than adequate for our needs, or am I missing your point somehow, our cylinder is the old copper type with a new jacket and stat on it, which I fitted recently, sorry if I seem a bit dim on that point

 

[fixitflav]

I only have it on now for an hour in the morning, and half hour mid afternoon. That is more than adequate for our needs, or am I missing your point somehow, our cylinder is the old copper type with a new jacket and stat on it

I doubt it saves you much money, but a cylinder with strap-on jacket won't be as good as a pre-insulated, so could be worth it. But don't forget heat lost from the cylinder ends up in the house, which alters the balance a little.
Thinking about it again, with your proposed scheme you can have CH on at the timer when HW is off (which isn't possible with W-plan) so having to wait for the cylinder stat to be satisfied before getting CH is less of a problem.

 

[tech749]

I doubt it saves you much money, but a cylinder with strap-on jacket won't be as good as a pre-insulated, so could be worth it. But don't forget heat lost from the cylinder ends up in the house, which alters the balance a little.
Thinking about it again, with your proposed scheme you can have CH on at the timer when HW is off (which isn't possible with W-plan) so having to wait for the cylinder stat to be satisfied before getting CH is less of a problem.

On your last paragraph, I was thinking the same, I can time the HW to come on before CH, we don't normally have the, CH on all the time anyway, but reading about WC, it seems it works more efficiently if you do. Can always experiment with it anyway. One thing I am very clear on now is I definitely don't want the extra piping.....too much hassle at my age ! . I think heat only is a viable alternative for me.

 

[fixitflav]

On your last paragraph, I was thinking the same, I can time the HW to come on before CH, we don't normally have the, CH on all the time anyway, but reading about WC, it seems it works more efficiently if you do. Can always experiment with it anyway. One thing I am very clear on now is I definitely don't want the extra piping.....too much hassle at my age ! . I think heat only is a viable alternative for me.

Looking at this again, CH on at the timer when HW is off, is possible on the Vitodens external time control, but as it says, needs a programmer with isolated contacts (aka volt-free contacts). None of the programmers I've looked at have that feature, they all have the common contacts at mains voltage, and not accessible. I emailed Viessmann to ask if they know a supplier that does, I'll post if they come back.

Judging by the wording, their internal time control doesn't support it either.

 

[DP]

None of the programmers I've looked at have that feature

Danfoss 975

 

[fixitflav]

Danfoss 975

Thanks, I hadn't found that one
Though it says on the site "Unfortunately this product is showing as no longer available with the manufacturer; please contact us if you have any queries"

 

[ianmcd]

A nest thermostat will do what you want

 

[tech749]

Did a bit of digging, as I understand it, you can control the boiler via Veissman app, so no need for an external controller. App details say you can control all functions, HW and CH timing remotely using wireless technology.
I have a Hive system now, but not sure if that can be integrated into Veissmann system. Probably not I'm guessing.