Design and cost of hot water heating system

[volcane]

My back of the envelope PV was very similar but a bit worse as I added in a replacement inverter and a diversion unit. I also spoke to 3 salesmen who never even attempted to sell, they are all looking South now.

I had  a 5.5k budget for PV and am considering directing that to a larger Sunamp stack.

[Guest Alphonsox]

2 minutes ago, volcane said:

My back of the envelope PV was very similar but a bit worse as I added in a replacement inverter and a diversion unit. I also spoke to 3 salesmen who never even attempted to sell, they are all looking South now.

 

That's pretty much what I had heard on the local grape vine - No RHI means no installs, so all the installers are heading south where there is still some money to be made.

[volcane]

Decision reached.

 

Heat and hot water via a Daikin HT split ASHP feeding a Sunamp 26kWh 6x2 Stack.

 

My issues with the above system are

• the lack of any back up hot water if the ASHP stops working and
• the lack of any future PV integration (if PV panels are grant aided or become cost effective)
• there also seems to be a problem with circulating the UFH water when we won't be using the Stack to provide space heating.

All solutions suggestions welcome

 

 

[Jeremy Harris]

Fit a Willis immersion in a branch off the ASHP flow to the Sunamp Stack.  That gives you a 3Kw electrical input for little additional cost, that could be hooked up to a future PV installation if you wished. 

 

Not sure how the primary pump is arranged, if it's within the Daikin then you may need to add a second pump that's only inline with the Willis branch, fit the Willis in a branch from the flow pipe, with an NRV in the main leg between the branch with the Willis and pump in.  That gives you redundancy if the ASHP fails and the ability to use excess PV.

[volcane]

3 hours ago, JSHarris said:

Fit a Willis immersion in a branch off the ASHP flow to the Sunamp Stack.  That gives you a 3Kw electrical input for little additional cost, that could be hooked up to a future PV installation if you wished. 

 

Not sure how the primary pump is arranged, if it's within the Daikin then you may need to add a second pump that's only inline with the Willis branch, fit the Willis in a branch from the flow pipe, with an NRV in the main leg between the branch with the Willis and pump in.  That gives you redundancy if the ASHP fails and the ability to use excess PV.

 

@JSHarrisThanks for that, I'm also not sure where the primary pump is but Sunamp have said to be that I couldn't use a secondary control just to use that to circulate the UFH, Perhaps could combine a Willis unit and a pump that I could use for non heating UFH circulation. I'll get back to Sunamp and see if we can work out a solution.

 

I forgot my further query,!

 

• Being able to use the ASHP for cooling, the weather has been so good here for days on end I'm now concerned (more than before) about overheating. A system where any excess heat in the house could be harvested and stored in the Stack would potentially be useful.

[Jeremy Harris]

This is how I think you could add a supplementary 3kW electric heater:

 

 

The non-return valve is there to allow the Willis and pump to work when the ASHP is off, and assumes that when off there is an open path through the ASHP secondary (there should be).  In the electric boost mode, if the ASHP is running and the Willis is running all that will happen is that the flow temperature to the Stack will be hotter.  If the ASHP is not running, and the Willis is running, it will be the only source of heat to the Stack. 

 

Not sure about being able to take heat from the house and store it in the Stack, to do that would need another heat pump to take heat from the house somehow and transfer it to the Stack.  Not too easy to do, I suspect.  Getting the Daikin to cool should be possible, as it will be capable of doing it, it's really a question of whether or not Daikin have built in the controls to allow this to work.  I found that I had to reverse engineer the control system of our Carrier ASHP, as although it is designed to work in cooling, as well as heating, mode, there was very little information on how to get cooling mode to work.  Cooling the UFH to a modest level is very effective, but care needs to be taken as to how cool the flow can get, in order to prevent condensation.  I've found how to programme ours to give a minimum flow temperature of 12 deg C in cooling mode, and in practice that means the floor surface never drops below 18 deg C, which means there's a very low probability of condensation (the RH would need to be around 65% or more, which isn't very likely in UK hot weather).

[le-cerveau]

I have the hydraulic diagram of the stack and you can't draw heat out of the stack for UFH:

 

 

I am looking at this to see how I can re-configure my SunAmp specification.