New boiler & contols - how ensure efficient operation?

[p7777m]

I'm having a new boiler installed to replace my exceedingly reliable (and still working) 25-yr old Potterton Netaheat 16/22.
I've been offered this:
Glow Worm Ultracom 18HXI or Vaillant Ecotec Plus 418 (+£360)
Grundfos 15-60 high head pump
S plan, autobypass valve
Magnaclean
Power flush
Honeywell cylinder stat, (single) room stat, programmer.
Fully vented.
(HW cylinder is indirect, fully vented)
How do I ensure that my boiler runs as efficiently as possible & spends as much of its time as possible in condensing mode...
(a) - at install time, by influencing the choice of components and how/where theyr'e installed - ?
(b) - and after install, when the system is in use?
I believe I should be asking for a Grundfos Alpha instead, in order to give the boiler a better chance of minimising non-condensing operation. Is that right?
Have the releability issues of earlier Alphas really been addressed?
Any thoughts or recommendations on this setup and how it could be improved?
Is there anything else I should consider?
I've been told the Glow Worm Ultracom 18HXI is pretty much identical to the Vaillant except for the case. Is this correct? What does "pretty much" mean - are there any internal differences you're aware of?

 

[bert large]

They are the same boiler. Originally a Glow worm boiler I think but also sold as a Vaillant. No mention of two port valves there.

 

[Plumbstar Tom]

speak to your installer and he will show you how to use your conrols

Also discuss which programmer suits you as a householder

 

[p7777m]

Thanks for your replies.
Bert: They differ in casing at the very least. I wonder if they were tempted to make other changes too. How sure are you that they are the same internals... identical heat exchanger etc etc?
I didn't mention 2-port valves because I thought S-plan implied that where heating water + radiators. Proposal is two 2-port valves - one for each of those circuits.
Tom: I was looking for extra input on configuration and choice of controls and other components. For example, weather compensation, optimising roomstat, chrono-proportional roomstat (maybe those last two are the same thing - are they?)

 

[SimonG]

As Plumbstar Tom has said, you need to have more of an in depth conversation with your installer, each install is different and budget will play a big part. There are a lot of fancy gadgets out there costing big money for little return. I always find simple is best, hope you get sorted.

 

[bert large]

Pretty sure they are exactly the same inside. Heat ex, fan, condensate trap etc. The PCB is possibly different as the Vaillant model seems to have more adjustable settings. I could be wrong about that though.

I only mentioned 2 port valves as you had specified good quality gear for the rest of it but omitted to mention the valves, depending on the make these can vary greatly in quality & longevity.

As far as controls go, I'm with Simon G on that, simple is best.

 

[Gray0689]

If you want better control go for 3 Chanel time clock ( 3 zone valves)
Upstairs and downstairs heating and hot water only and yes go for A rated pump modulating

 

[p7777m]

... and yes go for A rated pump modulating

I've seen suggestions that there may be problems using a variable speed pump and auto-bypass - any views on this?

Also, how does a modern low-water-content condensing boiler cope with a power cut? It's not possible for the pump to run on in order to dissapate heat - so should I expect likely need for heat exchanger replacement every time there's a power cut when the boiler is at full tilt?

 

[Halesowen1]

You aint gonna be changing heat exchanger every time the power goes, it aint good for it but not gonna wreck it EVERY time, I worked on a contract for 2 years where we fitted grundfoss modulating pumps and everyone had a auto by-pass fitted too, never had a problem.

 

[Halesowen1]

Pretty sure the gas valve in the Vaillant is much better, it modulates better so will be saving you on your fuel bill too.

 

[Halesowen1]

An extra £360 for the Vaillant, they are only about £100 extra to buy.

 

[p7777m]

I worked on a contract for 2 years where we fitted grundfoss modulating pumps and everyone had a auto by-pass fitted too, never had a problem.

What adjustments/choices are there with an auot-bypass valve - is it just choosing the pressure at which it opens?
If so, how do you do this with a modulating pump - do yuou simply choose a pressure just (barely) above the maximum published pressure that the pump claims to deliver?

 

[dontknowitall]

I don't know the official answer but I recently had a whole load of air in our heating system.

I felt the temperature of the pipes and listened to the effects of having the by-pass fully open. Then I closed it and the pump speed increased quite dramatically. Opened again to hear the tone (I'm musical) of the pump when the by-pass was fully open. Then closed it again until the tone started changing and the pump just started to increase it's speed again.

Whether this is correct or not I have no idea but I do know that water is passing through the by-pass and all the relevant pipes are giving the same temperature. And, more importantly, since doing this there has been no noticeable extra air in the system as all the radiators are quiet and there are no bubbling noises in the flow and return pipes!

 

[p7777m]

...I do know that water is passing through the by-pass and all the relevant pipes are giving the same temperature

You mean all pipes, including both sides of the auto-bypass, are the same temperature, and you therefore reckon that the autobypass is (at least part)open all the time?
If so surely that's not right (the situation, not your deduction)? - since it means your pump is needing to work harder than it would if it was just driving your zone(s).

 

[dontknowitall]

The by-pass has to be open. The point of it is to allow a circulation of water with the boiler in case all the trvs close (and another safety piece in case of blockage or zone valve closing unexpectedly).