Heating proposal P&ID. Please comment. GSHP, Stove, UFH.

[geoheated]

Hi All,

Would appreciate any feedback on my layout. It took some months for me to get this down on paper.
Its part of my renovation of the entire house.

I have no experience with stoves but have spoken to a few people and read alot about the requirements.

I have purchased a good used 6kW GSHP. Heat losses for the house are around 5kW peak.

I hope to extend the house in a few years, so ground loop and DHW tank are sized to allow for an 8kW GSHP and 2 bath's 1 Shower.

My only question at this stage is if the cylinder thermostats can be "smart" with 2 set points / channels. Or just use 2 stats per cylinder, as i need different set points, per that attached.

Hope it makes sense....

Thanks

 

[Roger928]

I'm looking up the esbe controller and will comment shortly.

 

[Roger928]

Is that a divertor valve on top of the heat pump?
And does the heat pump have its own circulator?

If the towel rails and spare stubs are making a demand for heat then surely the buffer will be starved? (At 80 litres its difficult to call it a buffer)
Which takes priority?
Also that circuit won't benefit from the stove input as far as I can see from your diagram.

On stoves the best set up is a HI-Lo stat configuration. That's a stat on the flow and a stat on the return. The return stat is triggered by a gravity loop. Which must never be blocked.
Whether that's through a cylinder coil, heat leak rad, by pass or other means, its very important.

When you fire up a stove the hot water cylinder should take priority.
That's easy when it gravitates. With your set up it requires more controls.
And good controls are expensive.

 

[geoheated]

Is that a divertor valve on top of the heat pump?
And does the heat pump have its own circulator?

If the towel rails and spare stubs are making a demand for heat then surely the buffer will be starved?
Which takes priority?

On stoves the best set up is a HI-Lo stat configuration. That's a stat on the flow and a stat on the return. The return stat is triggered by a gravity loop. Whether that's through a cylinder coil, heat leak rad, by pass or other means, its very important.

Thanks for the comments! I have spent far too long thinking about this to see fault in it now.

Yes that is a diverter valve on the outlet of the heat pump. It is controlled by the heat pump (not that that matters), the heat pump has 2 temperature settings and diverts the flow to hot water or heating when it changed it setting. 55 degC for DHW, 35 degC for heating.
Yes is has its own circulator pump.

The Towel rail i ran in parallel with the DHW coil. I chose this route so that the towel rail comes on when the hot water is being heated, including when the stove has heated the buffer and that water is being transferred via Pump P2 to heat the DHW cylinder. Maybe there is a better route. But i dont think it will starve the buffer, maybe the DHW coil?
I would throttle the towel rail with a lockshield to give back pressure / priority to the CHW coil.

 

[geoheated]

Is that a divertor valve on top of the heat pump?

On stoves the best set up is a HI-Lo stat configuration. That's a stat on the flow and a stat on the return. The return stat is triggered by a gravity loop. Which must never be blocked.
Whether that's through a cylinder coil, heat leak rad, by pass or other means, its very important.

I did go for 2 stats. Should i place the low stat (T1) on the return to the stove instead of the flow?

My logic is that Until the low stat T1 reached 40 degC, the pump to take the stove water away remains Off. Only gravity circulation will occur around the leak rad.

 

[Roger928]

Should i place the low stat (T1) on the return to the stove instead of the flow?

Yes, should be on the return. Then any low temps below 40c are checked.

 

[Roger928]

My logic is that Until the low stat T1 reached 40 degC, the pump to take the stove water away remains Off.

By that stage cold slugs of water would enter the boiler return reducing efficiency.

I've noticed the 4 way junction now that I hadn't seen before.

 

[geoheated]

Thanks Roger. I have moved the low temp stat.

 

[geoheated]

Revision attached. Also made the junctions clearer to see.

Not 100% happy with the towel rail take off point yet...