Air source heat pumps

[Penninetrader]

I have never heard of any case in a domestic situation

Where water is stored, prior to heating, is a potential for bacteria and contaminants. A quick look in some of the cold water tanks in attics might horrifying you. I myself have been making progressive changes to a 30 year old system. New boilers, addition of some wet underfloor, unvented on the heating side. The next stage will be a decent amount of work and that is an anvented water storage cylinder, this will provide mains pressure and none of the water will ever be exposed to air prior to heating, much like a combie system. That should be a big plus both for health and a decent shower pressure.

 

[Gilberdyke John]

Yes you should probably factor-in one's expected longevity.

External insulation was the way to go for us as the oldest part of the house is wood frame with single brick replacing the original wattle and dub. Extensions built either side in the 20th century left two gable ended walls with very poor insulation. Luckily it is not listed.

Old houses never cease to find ways of emptying ones wallet.
2 years ago we had to replace the septic tank ( a tree had grown through it) with a full sewage treatment plant. We failed the ground percolation test so we now have a pumped effluent system now and a constantly running electrically powered air pump.
Overall costs work out around £3 per poop for the next 20 years LOL

You ASKED/TOLD someone about the job??? Fortunately I'm on mains sewers but I think I'd have hired a digger and fixed the problem when I was fit and mobile.

 

[Newbeeneil]

I have never heard of any case in a domestic situation

When I owned a company installing these systems they had to raise the temperature above 60 once a week. I believe the specifications say once a day now but as long as water doesn’t remain in pipes, taps and shower heads for any extended time it should be safe.
I do the legionella control for my parish council and we are only required to heat it once a week, ensure that incoming water to the building is within acceptable temperatures and empty “dead ends” weekly.

 

[enrico]

Where water is stored, prior to heating, is a potential for bacteria and contaminants. A quick look in some of the cold water tanks in attics might horrifying you. I myself have been making progressive changes to a 30 year old system. New boilers, addition of some wet underfloor, unvented on the heating side. The next stage will be a decent amount of work and that is an anvented water storage cylinder, this will provide mains pressure and none of the water will ever be exposed to air prior to heating, much like a combie system. That should be a big plus both for health and a decent shower pressure.

An ashp uses water like a combi, unvented straight from the mains... My point exactly

 

[enrico]

When I owned a company installing these systems they had to raise the temperature above 60 once a week. I believe the specifications say once a day now but as long as water doesn’t remain in pipes, taps and shower heads for any extended time it should be safe.
I do the legionella control for my parish council and we are only required to heat it once a week, ensure that incoming water to the building is within acceptable temperatures and empty “dead ends” weekly.

In domestic situations it is still once a week but .......

 

[Jules59]

You ASKED/TOLD someone about the job??? Fortunately I'm on mains sewers but I think I'd have hired a digger and fixed the problem when I was fit and mobile.

Unfortunately the septic tank was beyond repair - one side wall had given way.

Also these days a prospective buyer wont be able to obtain a mortgage on a house with non-mains sewage unless it has been certificated - which no old septic tank will have been .

 

[Penninetrader]

An ashp uses water like a combi, unvented straight from the mains... My point exactly

Not really, it can never achieve the temperatures of a gas or solid fuel boiler

 

[enrico]

Not really, it can never achieve the temperatures of a gas or solid fuel boiler

Which is far too hot for a domestic system anyway. I run my hot water at 50⁰. I heat the tank once a day for an hour, that gives me ample water for two showers and all the daily usage. Why do I need it any hotter?

 

[simonwig]

Not really, it can never achieve the temperatures of a gas or solid fuel boiler

Most modern heat pumps can heat water up to 75 C, they run a separate hot water cycle so no immersion is needed, and often can run legionella cycles at higher than you set the normal hot water temperature to if you're worried about that.
Not quite as efficient as cooler running for heating, but still more efficient than an immersion.
Simon.

 

[Gilberdyke John]

An ashp uses water like a combi, unvented straight from the mains... My point exactly

Noooo. A combi (with one or two rare exceptions) heats the water as it passes through in a similar mode to an electric shower. ASHPs work with a cylinder (usually unvented but not necessarily so) so the ASHP heats the water stored cylinder for use later. Being unvented the water is at mains pressure but it's been kept stored while warm awaiting use, hence the risk of legionella.

 

[JamezF]

Noooo. A combi (with one or two rare exceptions) heats the water as it passes through in a similar mode to an electric shower. ASHPs work with a cylinder (usually unvented but not necessarily so) so the ASHP heats the water stored cylinder for use later. Being unvented the water is at mains pressure but it's been kept stored while warm awaiting use, hence the risk of legionella.

I thought that ASHP heated a permanent store of water (like a heat bank) and that mains water was heated from that via a heat exchanger on demand. How disappointing.

James

 

[enrico]

Noooo. A combi (with one or two rare exceptions) heats the water as it passes through in a similar mode to an electric shower. ASHPs work with a cylinder (usually unvented but not necessarily so) so the ASHP heats the water stored cylinder for use later. Being unvented the water is at mains pressure but it's been kept stored while warm awaiting use, hence the risk of legionella.

Ah! I see what you mean. Fair comment but it is always under pressure with never any air in the tank. It is forced out of the tank by the mains pressure. No different to the water remaining warm in your pipes after you have turned the tap off, maybe

 

[Sutty]

Ah! I see what you mean. Fair comment but it is always under pressure with never any air in the tank. It is forced out of the tank by the mains pressure. No different to the water remaining warm in your pipes after you have turned the tap off, maybe

My mains pressure hot tank (heated by an immersion) has a pressure (expansion) vessel that is pumped up with air, so there may be  some exposure to air.

 

[Penninetrader]

My mains pressure hot tank (heated by an immersion) has a pressure (expansion) vessel that is pumped up with air, so there may be  some exposure to air.

Should be nitrogen not air