Which Vaillant/Glowworm?

[livingstoned]

We've decided to get a combi in place of the old stored-water system.
I'm interested in longevity and maintainability though I'm not looking for the 43 years the old boiler and pump lasted.
(one thermostat, one FFD, one Ignition module went. I have spares of all of them, but now's its time)
A GSR friend is qualified to get the 10 year guarantee on Vaillant or Glow worm boilers.

The gas (5m 28mm Tracpipe) and water supplies (24l/min) are good so I'd like a boiler with a high water output capability.
Heating demand will be no more than 18kW.
Simple rear flue, out of the back or on top.

I see there's a big difference between the prices of things like Ariston Clas and Vaillants, I'm willing to be convinced if it's worth it.
A Vaillant Ecotec Plus would fit, or the smaller Ecotec Pure. (Kits) I assume the larger would be easier to work on??
Is one better - eg free of splitting plastic manifolds?
I'd go for about a 35-38kW HW model. (Currently have a 4 bar Monsoon, though won't miss the max throughput from that).

Or there are the Glow worm's which I understand are from the "same Company". (??)
Are they as good?

I would go for any options for efficiency which make sense. Historically I'm not sure they all did.
I haven't checked things like turn-down ratio.
I wouldn't need phone control or its like, previously had a prog thermostat and trv3's, replacing those with similar.

I wonder if installers would express a preference based on what they've seen?

 

[Mottie]

A Vaillant Ecotec Plus would fit, or the smaller Ecotec Pure.

I have an EcoTEC plus 418 heat only. I also had the choice of the cheaper EcoTEC pure 418 heat only at the time but someone on here told me the pure was a rebadged Glow worm. I think Vaillant make Glow worm boilers but I might be wrong about that. I’m sure I’ll be corrected if I am!

 

[CountryFan]

Vaillant and glowworm are part of the same group. Parts are similar and I believe some Vaillants are identical to glow worm.

 

[spile]

I had a bad experience with my 8 year old Ecotec but the later models appear to be more reliable.

 

[muggles]

Are you thinking of switching to a combi boiler? You'd be better off with a system boiler and unvented cylinder there really. The ecoTEC Plus is an excellent boiler, especially when paired with sensoCOMFORT controls

 

[livingstoned]

Thank you Andrew.
I know what you mean about an unvented, but a combi will do for us two, and we'd get the cupboard back!
I see Sensocomfort uses
outside compensation - outside sensor, hmm, I remember when they arrived. I was never convinced about that.
Load comp, sure that makes a lot more sense to me
3+ zones.

To date, we leave all the doors open and rely on TRVs to turn the upstairs rads down. There are no zone controls at the moment though there's a gate valve I could put some modulating valve in place of. Is that what's intended??

How about the boilers - is the more compact one, or the Glowworm "made cheaper" in your estimation?

I'd appreciate any insights you have there.

 

[muggles]

Weather compensation makes a lot of sense. Heat loss - the amount of heat energy your home needs - is a direct function of the difference between desired indoor temperature and actual outside air temperature. A home that needs 10kW when it's -3°C outside will only need 5kW when it's 9°C outside. Weather compensation adjusts boiler power and flow temperature to match the requirements.

If you prefer load compensation though, sensoHOME does that.

You've said 3+ zones but also said 1 zone...

I can't help much with a direct product comparison just now as their websites are down but I'll check back in later on that. Given your home's size and potential hot water requirements though, I'd suggest the ecoTEC Plus 840

 

[livingstoned]

I said 3 zone (+) just because that's a highlit feature of the SensoHome system when you look it up. I don't think I need multi zones. I don't have any info on how much having cooler unused rooms, saves.
Yes the boilers part of the website was down when I looked!

The outside-sensor-only was widely hailed by boiler makers wanting to make claims to help them sell, and was fed to installers, who usually wouldn't have had the education in the area.

It has always annoyed engineers. It's a bit like trying to tell the wife she isn't cold because the weather forecast said so.

If you have an outside sensor, it's a feed-forward, open-loop input.
Load comp is a feed BACK closed loop input; it knows about the heat loss from the rads, though not directly the room temperatures.
The wall "stat", depending on type, is a direct input from where you need it.

If you do a three-term PID exercise on a system with the target of getting Critical Response, or Critical Damping - which means getting to your target (temperature) ASAP with minimum or controlled overshoot, and you have a system with a lot of
1) time delay and
2) (thermal) inertia
the outside sensor approach won't be very powerful in the equation for getting the instantaneous boiler output right.
In other words it can only give you a terrible response

It comes out of the math. PID is Proportional , Integral, Derivative.
P is using the difference between the current Room Temp and what you want
D is about how fast the RT has changed, and needs to change
I is the integral over some long period of time. It's one the outside sensor is supposed to be useful for.

If P and D are sorted, I tends towards redundancy. In other words, not helping.
If you set up tests on such a control system, you can get your computer to work out the weights given to each input, if you programmed it right .
You see the constant applied to the feedforward open loop input's data reduce to near nothing. It was standard uni stuff in my day. It applies to things like car suspensions, too, any response system. When you add time delays, stores of energy, and safeguards (if it's something like pulling control rods in and out in a nuclear reactor), it's really nothing.

I once had a go at a Keston techie. They had a crude "WC" system; the techie didn't have a clue about Control Systems.
Viessmann were better, earlyish, but they put nonsense in their literature. I lost track after that.

Sorry for the lecture!

I shall call Vaillant/Glow worm again, but they won't tell me much about how easy they are to access for maintenance, without slicing your fingers off..

 

[muggles]

Well sensoCOMFORT has adjustable room influence in the settings so it's the best of both worlds.

The GW Compact is max 28kW as far as I can see, with a horribly high minimum modulation of 6.9kW and an aluminium heat exchanger. Their flagship Ultimate 3 35kW is also aluminium and again minimum modulation of 7kW. They're equivalent to the Valiant ECO FIT Pure range.

Vaillant's ecoTEC Plus 836 is stainless steel with a minimum of 3.7kW so much better modulation which should give much better real world efficiency, and the 840 goes down to 4.5kW.

 

[livingstoned]

Thanks Andrew. I called V, and got the Spanish(?) guy I think I remember from decades ago.
Both share the same control options. I wasn't keen on the mandatory flush out of the Al heat exchangers at 5 years.
836 or 840,. looks about right.

Only reservation, is that it's an old system. The water came out clean from the boiler though some pipes were choked with magnetite because of a configuration error a long time ago. Replacing those. There will be a mag filter. Would a cast AL boiler have bigger flow-ways? I haven't found flow resistance figures yet. I don't understand all the numbers. Remaining pump head available 0.25 bar , it says. What's that?

I HAVE found that the 40kW is 386 deep , not 352, so it won't fit the cupboard.
36kW will do.