How does this look as a plan?

[Pip895]

I want to upgrade my current 15 year old two gas boiler system to a heat pump.  I have been trying to decide weather to go all the way and apply for the BUS grant or to simplify things and concentrate on the under floor heating and heating our swimming pool water which both require lower temperatures and are ideally suited to an ASHP.  My previous discussion on the subject is here:- 

Having now had another couple of installers in (both of whom seemed to know what they were talking about- not just sales men) I really have to make a decision on which way to jump. 

 

The first installer quoted for a full BUS compliant system a 12kW Vaillant doing DHW and house heating - it also involved putting in radiators into our swimming pool room which is currently heated by a blown air system.  This solution would hopefully be  BUS compliant and should end up with a cost of around 10k to us. One boiler would be retained but would only be heating the pool water. 

 

The second installer came down on the other side of the argument and thought all the BUS grant and more, would be used up by replacing the tank and re running its pipework to little advantage (we have solar thermal providing much of our DHW) and he suggested a 16KW Midea unit - approximate cost to us similar, although I am yet to get a formal quote.  This installer is also quite flexible and happy to install any system we want within reason.

 

I like the Vaillant unit but am not keen on the amount of disruption or on radiator(s) in the pool room so we are currently looking at the option without the BUS grant or involving changing the DHW tank.  Because we aren't using the BUS grant we have the option to create a true bivalent system, whereby the gas boiler can take over when conditions dictate eg. when temperatures are sub zero and during the day when we have run out of battery power to run the heat pump.   I have come across  the NRG Awareness manifold that looks like it could greatly simplify the installation - has anyone got experience of these?    Does this look like a reasonable plan?  

[sharpener]

On 14/12/2023 at 12:34, Pip895 said:

 I have come across  the NRG Awareness manifold that looks like it could greatly simplify the installation

 

Still looks mighty complicated. Can you post a link to this magic manifold so we can see what it is supposed to do?

 

Also you have got two check valves in series in the return from Manifolds 2 - 4.

[JohnMo]

Looks ok, I also looked at the NRG manifold, look interesting.

 

Check that antifreeze valves are the best solution.

 

 

[Beelbeebub]

That NRG manifold looks alot like the manifold Grant are putting forward for their hybrid box.

[SimC]

My concern would be how to modulate/balance the water flow rates through the currently active heat source with that through the total of 5 pumps serving the loads.

There would appear to be a total of 7 pumps required in the system, assuming 1 in the outside ASHP and 1 in the system boiler.

 

Too low a flow rate through the heat source, and the manifold ends up containing predominantly cool return water from the loads so not meeting the load heating requirements.

 

Too high a flow rate through the heat source, and the manifold ends up containing predominantly hotter water from the heat source resulting in a high return temperature to the heat source with its knock on effect on the COP/efficiency.

[Beelbeebub]

On 14/12/2023 at 12:34, Pip895 said:

I want to upgrade my current 15 year old two gas boiler system to a heat pump.  I have been trying to decide weather to go all the way and apply for the BUS grant or to simplify things and concentrate on the under floor heating and heating our swimming pool water which both require lower temperatures and are ideally suited to an ASHP.  My previous discussion on the subject is here:- 

Having now had another couple of installers in (both of whom seemed to know what they were talking about- not just sales men) I really have to make a decision on which way to jump. 

 

The first installer quoted for a full BUS compliant system a 12kW Vaillant doing DHW and house heating - it also involved putting in radiators into our swimming pool room which is currently heated by a blown air system.  This solution would hopefully be  BUS compliant and should end up with a cost of around 10k to us. One boiler would be retained but would only be heating the pool water. 

 

The second installer came down on the other side of the argument and thought all the BUS grant and more, would be used up by replacing the tank and re running its pipework to little advantage (we have solar thermal providing much of our DHW) and he suggested a 16KW Midea unit - approximate cost to us similar, although I am yet to get a formal quote.  This installer is also quite flexible and happy to install any system we want within reason.

 

I like the Vaillant unit but am not keen on the amount of disruption or on radiator(s) in the pool room so we are currently looking at the option without the BUS grant or involving changing the DHW tank.  Because we aren't using the BUS grant we have the option to create a true bivalent system, whereby the gas boiler can take over when conditions dictate eg. when temperatures are sub zero and during the day when we have run out of battery power to run the heat pump.   I have come across  the NRG Awareness manifold that looks like it could greatly simplify the installation - has anyone got experience of these?    Does this look like a reasonable plan?  

How are your two boilers set up at the moment? Are they linked in parallel or do they serve different functions? Do you ever end up running both at the same time? 

 

If most of your DHW is already sorted with solar, then can you use the existing tank but with the Vailant running in max temp mode which should replicate a gas boiler (albeit at poor efficiency - but who cares if it's just occasional use). Then run the rest of the systems direct off the Vailant

 

TBH that scheme looks really complicated and usually the more complex the system the harder it seems to be to get it running sweetly, especially with complex hydraulic schemes.

[JohnMo]

The more I look at it, I would split into two systems. Gas boiler as a backup to the solar for heating domestic hot water and heat star unit. Leave the ASHP to do the pool and UFH all year round. Go directly from ASHP to pool HE, and use close coupled tees from the supply line to the UFH pumps and mixers - the flow would come off this line and the return would also go the same line. No need for the NRG unit.

 

Follow the layout as attached

 

CCT WORCESTER BOSCH.pdf

[Beelbeebub]

On 14/12/2023 at 12:34, Pip895 said:

 

I like the Vaillant unit but am not keen on the amount of disruption or on radiator(s) in the pool room so we are currently looking at the option.....

Is there a reason the blown air unit in the pool room cannot be used by the HP or replaced with a hydronic fan coil unit that can interface with the HP?

 

The Americans have blown air units as they often have warm air heating.

Edited December 18, 2023 by Beelbeebub

[JohnMo]

Simplified sketch, also just noticed you can remove the pump prior to CCT (close coupled tees) if your heat pump has its own circulation pump and is a suitable size.