Hi, my first post.... I have been reading.... and reading..... about thermal stores, heat banks and unvented cylinders.
I would like - good hot water flow, solar capability and eventually a wood burner at a later date. This kind of pushes the unvented idea to the sidelines - running the radiators off solar and free wood sounds too good to be true.
I already have - a sealed system condensing gas boiler, radiators and no loft (flat roof) for addition of feed and return tanks - so no DPS/Heatweb stores as they're open vented I think?
Insulation to majority of house is 2007-standard or better.
Have heat recovery system fitted, quite a few oversized rads, plus double glazing/fairly good airtightness.
We plan a shower with body jets (not fitted yet), already have another 'normal' shower, one bath and 4 bedrooms - so fairly standard requirements until the kids are big enough to sulk in the bathroom for hours at a time...
My plumber and I have decided a pressurised heat bank will work with the sealed system boiler and sealed system rads, allowing solar/wood burning input to space heating as well as water heating.
A large accumulator will be used to assist cold water supply to the heat bank, as it can vary through the day.
A plate heat exchanger is essential, in-cylinder coils don't appear to work as well at high flow rates/multiple drawoffs.
We are considering two cylinder stats in series, one near the top, one near the bottom of the store, to make the boiler burn longer and harder, initially from lower temperatures thus condensing for longer. I'm aware a 70 degC store will not allow the boiler to condense for 100% of the time, but a 60 degC store may not do the hot water well enough, so I'm prepared for that trade-off in gas efficiency in return for low cost heating via solar/wood burning.
The boiler needs to be directly linked to the store (no coil) to allow buffering and sub-dewpoint return temps for as long as possible.
The NuHeat EnergyMaster 300 litre solar appears right for what I want -
Clicky
It is designed specifically for underfloor heating, so the tappings for the space heating flow and return may be a bit low down on the cylinder for radiators, but we reckon we'll get away with it due to good house insulation levels and large rads, it has a plate heat X (albeit an internal one) which gives 40 l/min flowrate (way more than what is required) into the TMV, a solar coil and direct buffering for the boiler and rads, running at about 1.5 bar pressure as any sealed system does.
If the internal plate ever goes belly up, an external plate could be added easily (I am not in a hard water area) using the existing tappings.
A Magnaclean is part of the plan, on the radiator return into the store.
The woodburner is tricky, and will need it's own heat exchanger and pump inputting via the solar coil or boiler tappings, so the burner can stay vented and safe - I haven't discussed this point with the plumber yet.
Any thoughts from anyone? The store is coming in at around £1600 including the shunt pump, flow switch, TMV etc, so it's maybe double the kit cost of an unvented cylinder, install cost is the same, and I accept hot water *may* not be as good as an unvented, the setup may need tweaking and some tlc along the way, but for potential cheap energy input we think it's worth it?
Or am I certifiably insane for deviating from the unvented solar cylinder?
I would like - good hot water flow, solar capability and eventually a wood burner at a later date. This kind of pushes the unvented idea to the sidelines - running the radiators off solar and free wood sounds too good to be true.
I already have - a sealed system condensing gas boiler, radiators and no loft (flat roof) for addition of feed and return tanks - so no DPS/Heatweb stores as they're open vented I think?
Insulation to majority of house is 2007-standard or better.
Have heat recovery system fitted, quite a few oversized rads, plus double glazing/fairly good airtightness.
We plan a shower with body jets (not fitted yet), already have another 'normal' shower, one bath and 4 bedrooms - so fairly standard requirements until the kids are big enough to sulk in the bathroom for hours at a time...
My plumber and I have decided a pressurised heat bank will work with the sealed system boiler and sealed system rads, allowing solar/wood burning input to space heating as well as water heating.
A large accumulator will be used to assist cold water supply to the heat bank, as it can vary through the day.
A plate heat exchanger is essential, in-cylinder coils don't appear to work as well at high flow rates/multiple drawoffs.
We are considering two cylinder stats in series, one near the top, one near the bottom of the store, to make the boiler burn longer and harder, initially from lower temperatures thus condensing for longer. I'm aware a 70 degC store will not allow the boiler to condense for 100% of the time, but a 60 degC store may not do the hot water well enough, so I'm prepared for that trade-off in gas efficiency in return for low cost heating via solar/wood burning.
The boiler needs to be directly linked to the store (no coil) to allow buffering and sub-dewpoint return temps for as long as possible.
The NuHeat EnergyMaster 300 litre solar appears right for what I want -
Clicky
It is designed specifically for underfloor heating, so the tappings for the space heating flow and return may be a bit low down on the cylinder for radiators, but we reckon we'll get away with it due to good house insulation levels and large rads, it has a plate heat X (albeit an internal one) which gives 40 l/min flowrate (way more than what is required) into the TMV, a solar coil and direct buffering for the boiler and rads, running at about 1.5 bar pressure as any sealed system does.
If the internal plate ever goes belly up, an external plate could be added easily (I am not in a hard water area) using the existing tappings.
A Magnaclean is part of the plan, on the radiator return into the store.
The woodburner is tricky, and will need it's own heat exchanger and pump inputting via the solar coil or boiler tappings, so the burner can stay vented and safe - I haven't discussed this point with the plumber yet.
Any thoughts from anyone? The store is coming in at around £1600 including the shunt pump, flow switch, TMV etc, so it's maybe double the kit cost of an unvented cylinder, install cost is the same, and I accept hot water *may* not be as good as an unvented, the setup may need tweaking and some tlc along the way, but for potential cheap energy input we think it's worth it?
Or am I certifiably insane for deviating from the unvented solar cylinder?
