Atmos or Intergas

[doitall]

If that were the case SH2 one would only need 1 pump not 3.

 

[SimonH2]

Whether the burner is running @ low modulation or high modulation then design criteria has to be catered for the latter and not the former.

And what's it been ranged down to ? If it's been left at full output then (unless it's a very unusual installation) whoever is responsible for the design is not competent - I know it will rankle with some of you to hear suggestions that there are professionals who aren't competent at their job, but then the truth sometimes isn't palatable.

Using the correct size header won't exactly break the bank as opposed to fabricating using a smaller diameter , or are you suggest a low loss header is not necessary on this particular boiler?

I didn't suggest using a larger one wouldn't be preferable, but I question whether "low loss" is strictly necessary. Ultimately, the design criteria is to ensure adequate flow through the boiler under all conditions, and unless there's something very unusual then it's hard to see how a short length of 28mm and a couple of short lengths of 22 are going to produce less flow than a whole system with various points where the flow is throttled down.

Having the primary loop throttled with too small a pipe will create some pressure drop, which will in turn promote a small flow through the secondary loops, but that's unlikely to be a big issue here (it'll just mean the upstairs rads won't be completely off when the system is running for downstairs only. There'll also be a little bit extra noise (I doubt it'll be noticeable) - and it'll be insignificant compared to what most systems produce when they are pumping hard through an ABV and all the TRVs are "hissing".
On that last point, if you insist on ranging the boiler to a full 40kW when less than 10kW is needed, then it's going to be a very noisy and wasteful system indeed.

 

[SimonH2]

If that were the case SH2 one would only need 1 pump not 3.

If you are going to make statements like that, please specify what "that" is referring to - otherwise it makes no sense !

 

[Steelmasons]

Sorry to say it but you fail miserably regarding g correct system design , then again what can one expect from one who is not experienced.

 

[AlexCarp]

Shall I work it out for him?

Flow rate for a 40 kW boiler with a 20C differential is 40/(4.18x20) = 0.478 litre/sec or 478 cc/sec.

Inside diameter of 28 mm pipe = 26 mm or 2.6 cm. So area of pipe = (2.6/2)² x π =5.31 cm².

Velocity = 478/5.31 = 90cm/sec = 0.9 m/s.

Now repeat with more sensible values. As usual, 40kW is the high power needed to make a combi vaguely usable and it pretty irrelevant to heating requirements - the heating load for most properties is much much less than that, if it isn't then it's unlikely to be a property where a combi is sensible ! So say 10kW tops (note he said he has the primary pump on it's lowest setting), and probably much less than that most of the time.

Whatever you may say about terminology and whether this is a "low loss header" or not - it's a system that works and it's a system I'd consider (where I couldn't fit in a thermal store, or at least a buffer tank).

How wrong can one be..

Whether the burner is running @ low modulation or high modulation then design criteria has to be catered for the latter and not the former.

May I bring you to the attention an electrical ring main. It is designed for average use. If a 3 kilowatt heater is plugged into each outlet the mcb would trip. If these "plumbers" designed an electrical circuit they would design it to take a 3 kilowatt heater from each socket - total overkill. A modulating boiler is like having a auto variable mcb.

If a boiler modulates, as long as it has the minimum flow through the heat exchanger the maker states, then an "oversized" boiler will modulate down pretty quickly to an applicable rate after giving a rapid heat up from cold. It is like having a large engine in a car. Most of the time only fraction of the power is used - it takes only 20hp to propel a large car at 70mph along an Mway, yet the engine may be rated 100hp. The power available can be used for acceleration, like the rapid heatup in a large boiler. If anyone took notice of the drivel spouted by the "plumbers" here no one would fit a combi as the heating side is way oversized for 90% plus of properties.

As your signature suggests you are an enthusiast and not a professional.

But he has common engineering sense, which most here are bereft of.

Using the correct size header won't exactly break the bank as opposed to fabricating using a smaller diameter, or are you suggest a low loss header is not necessary on this particular boiler?

The header I used was determined by experimentation. My intention was to use a 35mm header, maybe be with a pipe stat in the header to prevent any cycling. The pipe stat was unneeded as the boiler controls modulated down the burner rate and then switched out the burner for long periods. The weather compensator lowered the flow temperature the vast majority of run time. But I found a 28mm header worked very well. I gave the results of my findings. I never made them up. I advise all to adopt this route. I did write I advised a 35mm header to anyone who does go this route just to be sure.

 

[Steelmasons]

'Just to be sure' , you sound like you have every confidence within yourself.

 

[Dan Robinson]

Yes but what your (Mr Crap) fragile little mind can't seem to understand is that if the minimum rate of the burner is more than the maximum requirement of the property then the system is fooked from day one.

How many days a year does a property need its rated heat input?



I have data logs showing my poor boiler - which I persuaded to modulate down to 4kW or so going on and off like a tarts draws.

Now that is a 3rd of the requirement of my house.

With an outside temperature in the low teens, occasionally single figures.

So with a (potential) 20 minute anticycling time, things are not going to be very comfortable are they?

What about hot water recovery if the place has an old cylinder?

 

[AlexCarp]

'Just to be sure' , you sound like you have every confidence within yourself.

I do because I did it and tested it. You never, I did.

 

[Dan Robinson]

I think Steel has done his fair share of LLHs over the years dude.




BTW - realised my error on the big pumps... I was looking at the ecoTEC 80 (and larger) books.

Silly error grants you.


However, the fundamental principle remains the same.

You're an idiot.

 

[AlexCarp]

Yes but what your (Mr Crap) fragile little mind can't seem to understand is that if the minimum rate of the burner is more than the maximum requirement of the property then the system is fooked from day one.

What this "plumber" does not understand is that by the time a boiler starts to cycle the property is up to temperature and the controls switch the lot off until it cools off. It does not run away with itself and cycle like crazy. Boilers also have integrated anti-cycle control. That is how heating controls work.

I have data logs showing my poor boiler - which I persuaded to modulate down to 4kW or so going on and off like a tarts draws.

This sounds like it is designed and/or not fitted properly. I gave the results of mine. and no such thing occurred.

What about hot water recovery if the place has an old cylinder?

I used high output DHW combi. You could take a fixed rate pump off the header to heat a cylinder.

 

[AlexCarp]

You're an idiot.

A wonderful technical response. That is all you ever have responded like. I pity the people who allow you to walk into their homes.

 

[Dan Robinson]

I'm not a plumber numbnuts Steel wouuld have your guts for garters implying as such.


Do you think a property heats up linearly?

Do you think that every room (with TRVs especially) will self regulate to ensure that the absorption of the boiler is precisely its minimum output and the system controls switch off at the perfect moment to stop a stupidly oversized boiler from cycling?

You're mental.

Fact is - I have a heatloss of 12kW at -3. I have a boiler that can go from 4 to about 22kW (in hot water mode boost).

Do you think my house still needs those 12kW when it is +9 degrees outside?

No .

You ******.

Do you think my little bathroom will stay on full tilt all the while my 60 metre square living room is warming up?

No.

The fricking controls at room level will start to close off one by one reducing the load of on the boiler so it will start to shut off.

FFS - do you really struggle to understand that basic principle?

 

[Dan Robinson]

You're an idiot.

A wonderful technical response. That is all you ever have responded like. I pity the people who allow you to walk into their homes.

Like I said - until you answer questions directly, I might as well. It is therapeutic.


How many days a year do you reckon a house needs its rated heat input?

 

[AlexCarp]

I'm not a plumber numbnuts

You are a poor heating man then.

Do you think a property heats up linearly?

Do you think that every room (with TRVs especially) will self regulate to ensure that the absorption of the boiler is precisely its minimum output

No. That is what the low-loss header puts right. Each heating zone can have very different heating demand and flows, yet they do not affect the flow through the boiler or the other heating zone.

A heating man would know that.

You ******.

A wonderful technical response.

I forgot to mention. The bathroom towel rail is off the flow and return from the boiler to the header, so it is always on no matter what heating zone is on or off. One of these electric immersion heaters that are fitted in the towel rail for summer when the heating is off, to keep towels warm - none was fitted. Instead a push timer button that brings in the boiler to heat the towel rail for only 5 minutes was fitted. That is enough for the boiler to heat the towel rail in summer and the residual heat in the towel rail keeps the towels warm. So when you want a shower or bath you hit the button and if a combi it will heat the rail while you get undressed and brush your teeth warming up the towels. If having a bath the boiler heats the rail up while in the bath. After bathing when the towels are wet, just put them on the rail and hit the button, again heat helps dry the towels.

Simple and easy and cheap.

See if one of these "plumbers" would ever have thought of that.

 

[AlexCarp]

Like I said - until you answer questions directly,

I gave my findings. It was clear enough.