Atmos or Intergas

[doitall]

One 22mm pipe cannot supply 3 x pumps.

The boiler pump (Shunt pump) serves the header only or should, the 2 heating pumps are supplied from the header, or should be

How did you adjust the Intergas pump.

 

[AlexCarp]

Why dont you chuck in some DRV and control stations and actually measure the flows, should be a laugh if not educational.

I have no need to measure the flows. I used thermometers. As long as the boiler had its minimum flow through the heat exchanger to cope with 40kW that is the only flow that really mattered as the boiler was fully protected.

The heating circuits were variable flow as they had TRVs and modulating pumps. The two heating circuits never interfered with each other.

This is not an fixed boiler output, constant flow heating circuits. Please understand the difference.

 

[AlexCarp]

One 22mm pipe cannot supply 3 x pumps.

The boiler pump (Shunt pump) serves the header only or should, the 2 heating pumps are supplied from the header, or should be

How did you adjust the Intergas pump.

Please read what I wrote before you type. The header is 28mm. One shunt pump serving the header and two smart pumps on two heating circuits. The shut pump is a Grundfos and has a three speeds like all others.

 

[doitall]

So there is flow through the header, how come it doesn't get hot

I think you should read what you type, not me.

How long have Intergas been using Grundfoss pumps.

 

[D_Hailsham]

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.

Your analogy of the car is not valid.

A boiler's output is limited by the capacity of the radiators to absorb the heat produced.

If you put 40kW into a system with only 10kW of rads the return temperature will rise so fast that the boiler will be unable to modulate down quickly enough. The boiler will then lockout until the temperature has dropped. The net result is that, instead of the house heating up quickly, it will heat up slowly and may never reach the required temperature.

There are many examples of this on this forum (mainly with combi boilers) and the solution has always been to reduce the heating output so it is comparable to the total capacity of the radiators.

If you apply full power to a stationary car you may initially get wheel spin, but that eventually turns into acceleration along the road.

 

[AlexCarp]

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.

Your analogy of the car is not valid.

A boiler's output is limited by the capacity of the radiators to absorb the heat produced.

On start up on cold the system will take all the boiler can throw at it until warm. In the analogy of the oversized car engine and the extra power used for acceleration. The spare power in the boiler is used for rapid warm up.

If you put 40kW into a system with only 10kW of rads the return temperature will rise so fast that the boiler will be unable to modulate down quickly enough.

They all modulate down quite quickly.

There are many examples of this on this forum (mainly with combi boilers) and the solution has always been to reduce the heating output so it is comparable to the total capacity of the radiators.

This problem was seen by the makers and they amended their control systems to suit. The Intergas modulates UP. It starts up on the lowest setting.

The boiler has been set to a lower rating. If I recall rightly the Intergas' CH rating can be turned down as a percentage of the maximum.

This does not lock out at all. It all works very well. Better than expected.

 

[AlexCarp]

So there is flow through the header, how come it doesn't get hot

The flow pipe from the boiler to the header gets hot, the part of the header to the two heating circuit' tees gets hot and the smart pumps pump all the heat out of the header into the heating circuits. The header is short circuited. When the smart pumps wind down the flow runs right through the header. I have explained this a few times to you.

I am pretty sure it is a Grundfos pump. I will check tomorrow. It is a three speed job for sure.

 

[Dan Robinson]

I am pretty sure it is a Grundfos pump. I will check tomorrow. It is three speed job for sure.

What were you saying about reading the manual?

A case of practicing what you preach me ol' muckka.

 

[AlexCarp]

I am pretty sure it is a Grundfos pump. I will check tomorrow. It is three speed job for sure.

What were you saying about reading the manual?

No. Read the label on the pump. duh! What the hell is an " ol' muckka"? No, don't reply. It is best you do not reply to anything.

 

[doitall]

So there is flow through the header, how come it doesn't get hot

The flow pipe from the boiler to the header gets hot, the part of the header to the two heating circuit' tees gets hot and the smart pumps pump all the heat out of the header into the heating circuits. The header is short circuited. When the smart pumps wind down the flow runs right through the header. I have explained this a few times to you.

I am pretty sure it is a Grundfos pump. I will check tomorrow. It is a three speed job for sure.

Repeat.

In that case explain how 3 pumps can be satisfied with 1 22mm pipe and the resistance from the boiler.

You can't have it both ways, and in every case the heating must be circulating through the header

 

[AlexCarp]

So there is flow through the header, how come it doesn't get hot

The flow pipe from the boiler to the header gets hot, the part of the header to the two heating circuit' tees gets hot and the smart pumps pump all the heat out of the header into the heating circuits. The header is short circuited. When the smart pumps wind down the flow runs right through the header. I have explained this a few times to you.

I am pretty sure it is a Grundfos pump. I will check tomorrow. It is a three speed job for sure.

Repeat.

In that case explain how 3 pumps can be satisfied with 1 22mm pipe and the resistance from the boiler.

It is clear you do not know how this is setup. Read what I wrote.

You can't have it both ways, and in every case the heating must be circulating through the header

The heating circuits are balanced and the smart pumps on the lowest. When startup from cold the heat from the boiler flow goes through the two heating circuits. The heating returns run back to the header and mainly run into the return. most flow is from the boiler into one end of the header, through the two smart pumps into the heating circuits and back into the end of the header and into the boiler forming that loop. The header is primarily by-passed.

What the 22mm return pipe cannot take back to the boiler will run up the header to the heating flows. As the system warms up and the smart pumps wind down the header may have flow in two directions but unlikely. As the smart pumps wind down, you will find the reverse will occur. The shunt pump will pump right through the header and the smart pumps take less out of the header taking the flows just in from the boiler. On the return as the smart pumps are wound down, the low flows returning from the heating circuits will mix with the flow from the shunt pump, lowing the temperature in the header and all will go to the boiler via the return 22mm primary - the 22mm pipe will take it.

The velocity slows up as water enters the 28mm pipe meaning mixing occurs. A similar thing as in a thermal store cylinder.

It is not complicated.

 

[D_Hailsham]

The heat carrying capacity of a pipe is limited by the maximum acceptable velocity for noise reasons. This is generally taken as 1.5 m/s.

You got the first part right. But 1.5 m/s is a maximum. Most systems are designed for less than that, say 1 m/s .

15mm = 18.1kW;
22mm = 40.2kW;
28mm = 67.5 kW.

I can guess where you lifted those figures from!

For a more normal max velocity of 1 m/s the capacities are:

15 mm: 12.07 kW
22 mm: 26.8 kW
28 mm: 45 kW

Now for the low-loss header. The ballpark to size the header is 3 times the area of the boiler's primaries pipe size into the header.

Don't you mean the secondaries?

Could you post a pic of you "low loss header"?

 

[AlexCarp]

The heat carrying capacity of a pipe is limited by the maximum acceptable velocity for noise reasons. This is generally taken as 1.5 m/s.

You got the first part right. But 1.5 m/s is a maximum. Most systems are designed for less than that, say 1 m/s .

15mm = 18.1kW;
22mm = 40.2kW;
28mm = 67.5 kW.

I can guess where you lifted those figures from!

For a more normal max velocity of 1 m/s the capacities are:

15 mm: 12.07 kW
22 mm: 26.8 kW
28 mm: 45 kW

13kw is somewhere between the 1 m/s and 1.5 m/s. Borderline but 15mm pipe can do it.

Now for the low-loss header. The ballpark to size the header is 3 times the area of the boiler's primaries pipe size into the header.

Don't you mean the secondaries?

No. Primaries. In a fixed output boiler and constant flows, the boiler will be sized for the whole heating load. The heating circuit pipes will be sized to suit. The primaries should deliver all the output from the boiler. In short, the primaries will be bigger than Heating circuit pipes. The primaries will match the heating circuits. Same in, same out. If the heating circuits are larger than the boiler's output the header should be upsized to a buffer tank, then boiler is too small and heat storage is needed.

 

[D_Hailsham]

Now for the low-loss header. The ballpark to size the header is 3 times the area of the boiler's primaries? (secondary) pipe size into the header.

Only just noticed that clanger! It should be three times the diameter, i.e nine times the area, so the velocity through the header is only one ninth of that through the secondaries.

The reason I queried 'primaries' is that it's the pressure drop between secondary connections which have to be minimised. The objective is to create a neutral point between the secondary connections.

 

[AlexCarp]

Now for the low-loss header. The ballpark to size the header is 3 times the area of the boiler's primaries? (secondary) pipe size into the header.

Only just noticed that clanger! It should be three times the diameter, i.e nine times the area, so the velocity through the header is only one ninth of that through the secondaries.

The reason I queried 'primaries' is that it's the pressure drop between secondary connections which have to be minimised.

No ballpark is using area. With 22mm primaries the header would be 66mm taking diameter.

I did consider doubling up the 28mm header, having two side by side and joined at the ends - I had enough 28mm and 22mm tees but needed 4 28mm elbows. Each 28mm pipe could have a heating zone on each. It would be interesting to see how it performed.

The objective is to create a neutral point between the secondary connections.

Exactly. The heating circuits and primary circuit must operate independently of each other with no influence to each other.