Two Boilers

[BigBurner]

40 litre heatbank? What will that do exactly?

As guide, the two boilers will deliver approx 25 plus litres/min if a 100kW plate heat exchanger is fitted on them - converting them to a combi.

Install a 40 litres DHW only heat bank with a 100kW plate heat exchanger on it and he will get all the DHW he needs and never run out. The 40 litres acts as a buffer to fill a bath while the boiler catch up and pour heat into the small cylinder. The small cylinder save much space.

Also this guff about sequencing controllers is a nonsense. Just remind me how reliable controllers are and what happens when they fail. That's right, you are building in another single point of failure.

Sequencing controllers work superbly and only bringing on both boilers when need be, automatically. Have you come across controllers.

If you must have two diddy boilers, just link them together using the manufacturer recommended pipework. If you add fancy controllers, you may as well have had one boiler because you've just taken the resilience away.

A sequence controller is NOT a fancy controller - it may be top you. They are commonplace

Sequence controllers have their place in commercial installations where there is usually a dedicated maintenance person, in a domestic situation they are an unecessary contrivance.

Sequence controllers are automatic and need no man watching it all day. That is the idea. You should get to know more about them.

Using small integrated (CH & DHW) heat bank with both boilers connected directly - not via a header - will not require a sequence controller so much. The controler will then be a nice to unit.

A heat bank heated directly (no cylinder coil) will take all the heat a large boiler or two will throw at it. And it, or they, will not cycle. The heat bank is a natural buffer. Think of it as a pressure vessel on a pumped water system. The pressure vessel prevents pump cycling.

Re-heat is astounding. In summer just one boiler can be used. If heavy demands on showers then just switch on the second.

Lets say a house needs 40kW to heat it. And system with the rads heated directly from the boiler. Having a header and two boilers of 25 to 30kW fed into it and a sequence controller will reduce the boilers cycling. On start up a cold system will take all the two boilers will throw at it. As the house near temperature the boilers will modulate down. When both are injecting too much heat into the system the sequence controller will switch one out and the system will tick over on one boiler which will cycle occasionally when heat demand is below the minimum modulation limit, as in any other system.

You will find that, two 24ish kW boilers (or combis) will be cheaper to buy than one large boiler and backup too.

Having two boilers with weather compensation each, on a header, will work well and no sequencing controller needed either.

The Broag Avantaplus boilers (and Keston) have a control system with the cylinder stat wired directly to the boiler. When DHW is called it will override the weather compensation and reheat DHW ASAP. A 3-way diverter valve off he heater has to be used with DHW priority. Reheating a cylidner using a cheap dircet cylinder, a plate heatr exchnager and bronze pump will take both boilers output and reheat within a few mintes.

 

[BigBurner]

40 litre heatbank? What will that do exactly?

As guide, the two boilers will deliver approx 25 plus litres/min if a 100kW plate heat exchanger is fitted on them - converting them to a combi.

Install a 40 litres DHW only heat bank with a 100kW plate heat exchanger on it and he will get all the DHW he needs and never run out. The 40 litres acts as a buffer to fill a bath while the boiler catch up and pour heat into the small cylinder. The small cylinder save much space.

Also this guff about sequencing controllers is a nonsense. Just remind me how reliable controllers are and what happens when they fail. That's right, you are building in another single point of failure.

Sequencing controllers work superbly and only bringing on both boilers when need be, automatically. Have you come across controllers.

If you must have two diddy boilers, just link them together using the manufacturer recommended pipework. If you add fancy controllers, you may as well have had one boiler because you've just taken the resilience away.

A sequence controller is NOT a fancy controller - it may be to you. They are commonplace

Sequence controllers have their place in commercial installations where there is usually a dedicated maintenance person, in a domestic situation they are an unecessary contrivance.

Sequence controllers are automatic and need no man watching it all day. That is the idea. You should get to know more about them.

Using small integrated (CH & DHW) heat bank with both boilers connected directly - not via a header - will not require a sequence controller so much. The controler will then be a nice to unit.

A heat bank heated directly (no cylinder coil) will take all the heat a large boiler or two will throw at it. And it, or they, will not cycle. The heat bank is a natural buffer. Think of it as a pressure vessel on a pumped water system. The pressure vessel prevents pump cycling.

Re-heat is astounding. In summer just one boiler can be used. If heavy demands on showers then just switch on the second.

Lets say a house needs 40kW to heat it. And system with the rads heated directly from the boiler. Having a header and two boilers of 25 to 30kW fed into it and a sequence controller will reduce the boilers cycling. On start up a cold system will take all the two boilers will throw at it. As the house near temperature the boilers will modulate down. When both are injecting too much heat into the system the sequence controller will switch one out and the system will tick over on one boiler which will cycle occasionally when heat demand is below the minimum modulation limit, as in any other system.

You will find that, two 24ish kW boilers (or combis) will be cheaper to buy than one large boiler and gives backup too.

Having two boilers with weather compensation on each, on a header, will work well and no sequencing controller needed either.

The Broag Avantaplus boilers (and Keston) have a control system with the cylinder stat wired directly to the boiler. When DHW is called it will override the weather compensation and reheat DHW ASAP. A 3-way diverter valve off the header has to be used with DHW priority. Reheating a cylinder using a cheap direct cylinder, a plate heat exchanger and bronze pump will take both boilers output and reheat within a few minutes.

 

[Deleted member 105431]

So bigbullshit how many 3bed houses do you see with 2 combi's fitted.
(one on each floor)? How many 40 litre heat banks are fitted to two 30kw boilers domestically?

You are full of shyte just cutting and pasteing stuff from google. You have no practical experience or knowledge of the heating trade and claim to be an expert. I ask again for the umpteenth time what qualifications do you have? NONE!

 

[bengasman]

Is this Frank re-incarnated? It does seem like some of his statements don't quite add up.

 

[BigBurner]

Is this Frank re-incarnated? It does seem like some of his statements don't quite add up.

Is this Dangermouse called Frank? He little idea at all, and spams Vaillants. Should be banned.