New Boiler - Recomendations

[Fredxx]

You really do have a chip on your shoulder. Lost an argument recently?

I have never lived in a terraced house, nor a gas holder.

[The Natural Philosopher]

Well you would say that wouldn't you?

You dont like losing arguments, do you?

[Jim]

A war of turds, lovely!

[tabbypurr]

Surely if it won't run at its manufacturer described power it's either faulty or not as described.

There are external factors that can cause boilers to do such things of course, but since your primary cct is running at such a low temp, poor flow does not appear to be the cause.

NT

[tabbypurr]

There are worse problems with Which reports, but is there a better survey out there?

[tabbypurr]

In some installs boilers simply won't work passably on default settings.

NT

[John Rumm]

Too much bypass flow would do it - the boiler would modulate right down to try and not exceed the set point flow temperature.

[John Rumm]

Pump?

[Fredxx]

External to the boiler.

[The Marquis Saint Evremonde]

It ran at the output level set by the manual dial (which I assume was a potentiometer connected to a thermometer or thermistor).

I don't want it to do that.

I don't see what any of that has to do with it. If I set the flow temperature setpoint to be 65degC, then that's what I want the boiler to heat it to, as quickly as possible. What's the point of having a flow temp control if the boiler then says to itself, Oh surely he doesn't really mean that, I'll do what I prefer to do and he can lump it?

I will grant you this: when the flow temp has reached a few degrees short of its setpoint, *then* the boiler can reasonably look at the return temperature and modulate itself down a bit to prevent overshoot. But meantime its business is to do what the room thermostat is telling it to do - warm the place up as fast as it can.

Instead, it sits there with the burner modulated right down to the lowest level, pumping out tepid water at 35-40degC. No wonder the return temp is close to the actual flow temp; at those working temperatures it's hardly going to lose much heat to the house is it?

And cannot the Vaillant be configured to do this? If not, why not? As it is, it's not much use to people like me, whose houses get cold and who need them heated up quickly in the early morning.

[Dave Plowman (News)]

Which make of system boiler doesn't include a pump?

Would seem silly to me, since the idea of a system boiler is pretty well everything in the one unit?

[Tim+]

That was my understanding. Pump, boiler and expansion vessel all in one box.

Tim

[mm0fmf]

And 3 way valve option as well.

[rmlaws54]

My advice is: buy something very common and easy to get serviced. We previously had an ATAG boiler, very fancy, stainless steel heatex, elaborate software, big modulation range, very expensive. We could never get it to behave as we wanted because it was so clever. Plus expensive parts. Service people typically had no experience of it.

Eventually we replaced it because it was so hard to find anyone to service it!

[Fredxx]

Ok I confess to meaning a heat only boiler such as:

These don't have a pump, or any of the other over priced paraphernalia that can go wrong.

[charles]

I had my system pump replaces after 29 years. They don't go wrong that frequently.

[Fredxx]

I've had a pump fail, and a neighbour has gone through 2 3-port diverter valves. It's pot luck. If it's outside of a boiler then it can def be a DIY job.

[tabbypurr]

IIRC the water was returning to the boiler way below temp. I know the Vaillant 4 series can be set to limit P_out to any velue in its range, I presume the 6 series can too.

NT

[tabbypurr]

Vaillant 4 series have a compulsory timeout after every burn during which it refuses to fire up. Replace an old boiler that ran flat out & cycled a lot and those timeouts can cause an issue.

NT

[John Rumm]

So its not a system boiler. (which should have all the components to make a fully operational sealed system including pump, expansion vessel, over temp / pressure release valve etc).