Octopus Heat Pumps

Martyn1981

1961Nick said:

Martyn1981 said:

orbit500 said:

If they have achieved an SCOP of 3 with the capability to flow at over 70C when required, then that's a significant achievement imo.

I will believe that when I see it. I’m sure many here already know this but there is a limit to heat pump efficiency given by:
COP=T1/deltaT where T1=flow temp in kelvin and deltaT=flow-outdoor temp.
so at 70c and 0c outdoor (which is when you’d want 70c flow):
CoP=343/(70-0) = 4.9
in real life more likely 2, I’d say.

This is all very interesting to me, as I have microbore, so not 100% sure that a 'normal' HP would manage for the coldest one or two weeks per year.

But, my reading of Nick's comment was an overall SCOP of 3, rather than a COP of 3 at 70C.

Not being pedantic, but the "70C when required", fits with my concerns and wants. If it's not needed for any significant length of time in the heating season, perhaps 2/26 weeks, then even allowing for the extra weighting of that period (more hours per day, and colder outside temps), then a lower, but acceptable SCOP may be achievable?

However, totally agree/appreciate that expecting or hoping for a SCOP of 3, if run at 70C all year, isn't achievable.

Another factor to take account of Mart, is what type of microbore plumbing you have. Those with a central manifold & long microbore pipe runs are the ones that will struggle with the higher flow rates required by a heat pump. If your heating circuit is mainly 28mm/22mm/15mm with the microbore tee'd off for each rad then it won't make much difference from being piped entirely in 15mm - the number of bends in microbore is a key restriction.

Many thanks, I didn't know that. I was partially involved with the GCH install, as I took up floorboards ahead of the work, and also crawled around under the downstairs floors (about 500mm gap) to install insulation.

Yes, the main runs are 28mm and 22mm, with microbore feeding off to each rad. Some runs will be long, perhaps 2m due to the need to get around corners, and through the gaps in the two brickwalls to get to the rads. Those wall act to support and separate the underfloor areas into thirds.

I'm pretty sure a normal ASHP would work for us, but all depends on the concerns of those assessing the situation.

mickyduck55

If anyone has had one fitted did they remove the cold water tank from the loft?

Netexporter

mickyduck55 said:

If anyone has had one fitted did they remove the cold water tank from the loft?

I'm going to leave the cold water tank in my loft, when I get a heat pump installed. I shall have the toilets connected to it and pump up rainwater for flushing. That'll greatly reduce my water bill as the sewage bill is calculated on a proportion of the mains water going in to the house.

shinytop

Netexporter said:

mickyduck55 said:

If anyone has had one fitted did they remove the cold water tank from the loft?

I'm going to leave the cold water tank in my loft, when I get a heat pump installed. I shall have the toilets connected to it and pump up rainwater for flushing. That'll greatly reduce my water bill as the sewage bill is calculated on a proportion of the mains water going in to the house.

I like it! My unused tank is still in the loft. Hmmm...

mickyduck55

Netexporter said:

mickyduck55 said:

If anyone has had one fitted did they remove the cold water tank from the loft?

I'm going to leave the cold water tank in my loft, when I get a heat pump installed. I shall have the toilets connected to it and pump up rainwater for flushing. That'll greatly reduce my water bill as the sewage bill is calculated on a proportion of the mains water going in to the house.

Not a bad idea I would have to run a new feed to the toilet (s) but I already have a 1000l BIC full of rainwater and a submersible pump

EricMears

mickyduck55 said:

Netexporter said:

mickyduck55 said:

If anyone has had one fitted did they remove the cold water tank from the loft?

I'm going to leave the cold water tank in my loft, when I get a heat pump installed. I shall have the toilets connected to it and pump up rainwater for flushing. That'll greatly reduce my water bill as the sewage bill is calculated on a proportion of the mains water going in to the house.

Not a bad idea I would have to run a new feed to the toilet (s) but I already have a 1000l BIC full of rainwater and a submersible pump

Until mid 20th century,  filling WC cisterns from a cold water tank in loft was the norm.  Connecting them to mains instead was a very short-sighted cash saving idea.  Should water mains fail,  you really don't want to have to carry up two buckets of pond water every time you need to flush.   Also,  it's a profligate waste of resources to use drinking standard water for WC  flushing.

When we built our house,  we arranged to collect rainwater from roof in tanks in basement then pump it to a header tank in loft for WC flushing.  In our case that only saves a third of the cost of mains water as we have a septic tank but for those with mains sewage it also saves a third of the (usually bigger) sewage disposal charges.

shinytop

EricMears said:

mickyduck55 said:

Netexporter said:

mickyduck55 said:

If anyone has had one fitted did they remove the cold water tank from the loft?

I'm going to leave the cold water tank in my loft, when I get a heat pump installed. I shall have the toilets connected to it and pump up rainwater for flushing. That'll greatly reduce my water bill as the sewage bill is calculated on a proportion of the mains water going in to the house.

Not a bad idea I would have to run a new feed to the toilet (s) but I already have a 1000l BIC full of rainwater and a submersible pump

Until mid 20th century,  filling WC cisterns from a cold water tank in loft was the norm.  Connecting them to mains instead was a very short-sighted cash saving idea.  Should water mains fail,  you really don't want to have to carry up two buckets of pond water every time you need to flush.   Also,  it's a profligate waste of resources to use drinking standard water for WC  flushing.

When we built our house,  we arranged to collect rainwater from roof in tanks in basement then pump it to a header tank in loft for WC flushing.  In our case that only saves a third of the cost of mains water as we have a septic tank but for those with mains sewage it also saves a third of the (usually bigger) sewage disposal charges.

But where did the water come from?

Reed_Richards

I presume @shinytop means where did that water in the loft tank come from until mid 20th century.  Surely it still came from the mains?  It was just in those days the plumbing was not considered up to having water throughout the house at mains pressure so water from the rising main went straight to a header tank in the loft.  

mickyduck55

EricMears said:

mickyduck55 said:

Netexporter said:

mickyduck55 said:

If anyone has had one fitted did they remove the cold water tank from the loft?

I'm going to leave the cold water tank in my loft, when I get a heat pump installed. I shall have the toilets connected to it and pump up rainwater for flushing. That'll greatly reduce my water bill as the sewage bill is calculated on a proportion of the mains water going in to the house.

Not a bad idea I would have to run a new feed to the toilet (s) but I already have a 1000l BIC full of rainwater and a submersible pump

Until mid 20th century,  filling WC cisterns from a cold water tank in loft was the norm.  Connecting them to mains instead was a very short-sighted cash saving idea.  Should water mains fail,  you really don't want to have to carry up two buckets of pond water every time you need to flush.   Also,  it's a profligate waste of resources to use drinking standard water for WC  flushing.

When we built our house,  we arranged to collect rainwater from roof in tanks in basement then pump it to a header tank in loft for WC flushing.  In our case that only saves a third of the cost of mains water as we have a septic tank but for those with mains sewage it also saves a third of the (usually bigger) sewage disposal charges.

The only minor flaw I think I see in your description is that my loft tank as I suspect others does still fill with drinking standard water ?

EricMears

mickyduck55 said:

EricMears said:

mickyduck55 said:

Netexporter said:

mickyduck55 said:

If anyone has had one fitted did they remove the cold water tank from the loft?

I'm going to leave the cold water tank in my loft, when I get a heat pump installed. I shall have the toilets connected to it and pump up rainwater for flushing. That'll greatly reduce my water bill as the sewage bill is calculated on a proportion of the mains water going in to the house.

Not a bad idea I would have to run a new feed to the toilet (s) but I already have a 1000l BIC full of rainwater and a submersible pump

Until mid 20th century,  filling WC cisterns from a cold water tank in loft was the norm.  Connecting them to mains instead was a very short-sighted cash saving idea.  Should water mains fail,  you really don't want to have to carry up two buckets of pond water every time you need to flush.   Also,  it's a profligate waste of resources to use drinking standard water for WC  flushing.

When we built our house,  we arranged to collect rainwater from roof in tanks in basement then pump it to a header tank in loft for WC flushing.  In our case that only saves a third of the cost of mains water as we have a septic tank but for those with mains sewage it also saves a third of the (usually bigger) sewage disposal charges.

The only minor flaw I think I see in your description is that my loft tank as I suspect others does still fill with drinking standard water ?

There's no flaw in my description.

If you haven't arranged to collect rainwater then your only option is to flush your WC with potable water.  A loft tank wouldn't therefore save you any money although it would still be some insurance against being unable to flush your WC if there was a fault in the supply system.  For most areas that's probably fairly rare though nowhere can actually be guaranteed never to experience loss of mains.