Optimising hot water schedule

[johnny]

I have a large, old gaff with long pipe runs. The kitchen tap needed running for ever to get hot water so I installed and undersink water heater that does the job perfectly. I think it's the 15 litre capacity version and provides all the kitchen sink water I ever need, and should it run out, it takes only a few mins to reheat. It was about £100.

thats an excellent solution. We have the same problem with along run from our boiler on the first floor to our kitchen sink. Extremely wasteful waiting for all that pipework to heat up and inconvenient when all you need is a bowlful of hot water for washing up. I am going to fit an undersink water heater shortly too.

 

[johnny]

Back in 2005 I was the Surveyor responsible for maintaining the Legionella register for one of the Somerset Councils for a year or so. This was for all public buildings owned and used by the Public. Naturally we had to have a constant ongoing program of surveys , risk assessments, remedial works and treatment and I was required to attend several courses on the subject.

It was an onerous task, not least because legally as the person responsible for the legionella Register I would have been personally liable for any deaths or short comings in the register ,...not the Council ! The register was inspected regularly and I remember that there had been numerous well publicised Deaths from Legionaires Disease around the Country .

There are a lot of simplistic uninformed and misleading opinions about the risks and mitigation of of Legionella on the internet but the Government guidelines are a useful source of information Managing legionella in hot and cold water systems

 

[Suffolk Brian]

Pardon me for showing my ignorance, but can someone explains what a “smart” pump is, and how it would be controlled? Does it rely on some form of instruction from the boiler, or is it a freestanding unit that could be retrofitted to an existing system?

 

[Chris70]

...and while we're on Boiler recommendations (we are, aren't we?) avoid Keston. What do I know?

 

[Phil Pascoe]

I spent a couple of months in a small hospital in 2014. Everyone knew that to get a decent shower you had to unscrew the legionella filters fitted to the shower heads. They were fitted and forgotten until water could no longer find its way through them.

 

[Glitch]

My boiler regulates itself to achieve a Delta T of 20C across the boiler heat exchanger, DHW cylinder temperature is on its own stat. On heating duty I have zero room room thermostats and control is effected using weather compensation and during commissioning the slope and origin of the control curve was set up to match the heat loss of the house. It is an iterative process (at different ambients) and no heating engineer working for a customer would spend the time required to optimise it as I have. But once set up that’s it and it will use the minimum of energy to keep the house at ‘set point’ monitoring outside ambient to ensure minimum burn (boiler modulates down to 1.9KW) ensuring maximum condensing at the hex.

It is a Viessman 200W fitted with priority DHW on a 4 pipe system. I also fitted IMI constant flow valves on all radiators (these are set to match flow rate to emitter capacity ) so no need for guesstimate balancing on low authority lockshield valves (which are honestly not really up to that task). Standard (non smart) TRVs fitted on every emitter (radiator).

I also range rated my boiler to 6KW to match the heat loss of my house (did my own heat loss calcs).

In my opinion the Viessman 200 has the best boiler controls and modulation in the current market.

That sounds impressive. Was it an upgrade, or a complete new system. New build house?

Did you design this yourself?

 

[Glitch]

Pardon me for showing my ignorance, but can someone explains what a “smart” pump is, and how it would be controlled? Does it rely on some form of instruction from the boiler, or is it a freestanding unit that could be retrofitted to an existing system?

I think I assumed there might be some truly integrated pumps and called them Smart.

The one @Spectric mentioned is this one.

https://www.wolseley.co.uk/product/grundfos-alpha1-15-50-60-130-circulating-pump/
It automatically adjusts the pressure. The brochure says:

'Contrary to an uncontrolled pump, the proportional pressure-controlled ALPHA1 pump reduces the differential pressure in case of falling heating demand'

 

[leisurefix]

I also fitted IMI constant flow valves on all radiators (these are set to match flow rate to emitter capacity ) so no need for guesstimate balancing on low authority lockshield valves (which are honestly not really up to that task). Standard (non smart) TRVs fitted on every emitter (radiator).

Really interested in these, or similar. Am just researching replacing Combi boiler with a condensing boiler, and any other appropriate upgrades.
There are some really useful posts in this thread, I had not realised the differences with condensing boilers & importance of temperature drops across radiators & return temperature for example. Are flow valves worth the expense? Or will a well balanced (14 radiators all turned on to fairly low output with TRVs) system achieve similar results, with a bit of ongoing maintenance?
IMI Hydronic products don't seem easily available in UK, so are there alternate products, or a recommended UK stockists that elude Google.
Thanks

 

[Glitch]

Really interested in these, or similar. Am just researching replacing Combi boiler with a condensing boiler, and any other appropriate upgrades.
There are some really useful posts in this thread, I had not realised the differences with condensing boilers & importance of temperature drops across radiators & return temperature for example. Are flow valves worth the expense? Or will a well balanced (14 radiators all turned on to fairly low output with TRVs) system achieve similar results, with a bit of ongoing maintenance?
IMI Hydronic products don't seem easily available in UK, so are there alternate products, or a recommended UK stockists that elude Google.
Thanks

https://www.mpmoran.co.uk/imi-hydro...iO8-7nf0wo95tf7rGFqNvje0d_-a5cmUaArZSEALw_wcB

 

[Fergie 307]

I have a large, old gaff with long pipe runs. The kitchen tap needed running for ever to get hot water so I installed and undersink water heater that does the job perfectly. I think it's the 15 litre capacity version and provides all the kitchen sink water I ever need, and should it run out, it takes only a few mins to reheat. It was about £100.

Use a similar setup for hot water at a sink in the workshop. Very easy installation and works a treat.

 

[NormanB]

That sounds impressive. Was it an upgrade, or a complete new system. New build house?

Did you design this yourself?

Replacement system. I specified the ‘design’ and equipment selection. I also upscaled four existing radiators so the system as a whole would be more effective with the lower temperature circulating temps.

I did room by room heat loss calculations which informed me which emitters needed upscaling and the summation of all room heat losses gave me the total heat loss for the house which enabled me to select the correct size boiler. I was then able to tell the heating engineer what capacity to range rate the boiler to.

The heating engineer was a pleasure to work with.

 

[NormanB]

Really interested in these, or similar. Am just researching replacing Combi boiler with a condensing boiler, and any other appropriate upgrades.
There are some really useful posts in this thread, I had not realised the differences with condensing boilers & importance of temperature drops across radiators & return temperature for example. Are flow valves worth the expense? Or will a well balanced (14 radiators all turned on to fairly low output with TRVs) system achieve similar results, with a bit of ongoing maintenance?
IMI Hydronic products don't seem easily available in UK, so are there alternate products, or a recommended UK stockists that elude Google.
Thanks

The fundamental problem with trying to balance a system using conventional lock shield valves is you are setting up for one condition only and as TRVs operate a new set of variables kick in. I had no problem sourcing IMI valves - on holiday at the moment - but will try and remember to post a link to a supplier. There is also an IMI app for setting up calculations which may give supplier contact details.

Here is one example: Eclipse TRV + Thermostatic head DX – Hydronics Direct

But shop around.

 

[NormanB]

Pardon me for showing my ignorance, but can someone explains what a “smart” pump is, and how it would be controlled? Does it rely on some form of instruction from the boiler, or is it a freestanding unit that could be retrofitted to an existing system?

The smartest of smart pumps are burner linked pumps so the more gas being burned the greater the pump output and vice versa. Normally achieved by controlling Delta T across the heat exchanger.

 

[NormanB]

Much has been written in this thread with respect of stored hot warter temperature and potential legionella risks. Overall the absolute risk is small in most domestic properties but there are factors that require consideratio.

i commend this video to those interested in this subject and in fact this chaps You Tube channel to further your understanding of heating systems in general be they gas boilers or heat pumps.



BTW. I have a 210 litre cylinder, thermostat set at 45c and the boiler is programmed for a ‘hygiene cycle‘ of 60c once per week.

 

[Phil Pascoe]

A little larger than my tank, but not much. Mine is electric only, and inaccessible - it's in the roof. I wonder how long it take for the upper of the two elements to heat the the whole tank to 60°? This could be turned on once a week. The hygiene cycle is once a week? The water in my (mains pressure) tank probably turns over every two or at most three days, so I wonder how much danger there actually is there.

 

[furnace]

thats an excellent solution. We have the same problem with along run from our boiler on the first floor to our kitchen sink. Extremely wasteful waiting for all that pipework to heat up and inconvenient when all you need is a bowlful of hot water for washing up. I am going to fit an undersink water heater shortly too.

A note of caution. If the model you choose requires a sacrificial anode, stick the date of the required change in your diary and write it on the unit as a reminder. Depending on the hardness of your water, it's just a matter of time before it will corrode and leak if the anode is not changed. DAMHIK.
I believe versions are available with stainless steel tanks that don't require anodes.

 

[Adam W.]

We have a system boiler with a 30 litre tank and I stuck a circulator pump on the DHW, so we get hot water at the tap straight away, even though its 15m from the water tank.

 

[furnace]

We have a system boiler with a 30 litre tank and I stuck a circulator pump on the DHW, so we get hot water at the tap straight away, even though its 15m from the water tank.

Do you find it cools the tank unduly? I tried that on my bathroom, and even with insulation around the pipes (running through the loft) it sucked too much heat from the cylinder causing the water to be lukewarm. I took it out, and have now got used to waiting 2 mins before getting in the shower...

 

[Adam W.]

No, the water is just fine and it seems to have increased the amount of hot water for showers.

It's nice knowing that we're not wasting 7.5 litres of hot water every time we run the kitchen or bathroom taps, I think it has saved us an enormous amount of gas and water over the year. I think it works well, as we only have a 30 litre tank, so it's not mixing the layers of hot and cold water in the tank.

I'm looking at putting in a solar hot water system with panels, using a 1000 litre tank as the storage battery for the panels, instead of trying to power the electricity supply to the house.

 

[furnace]

No, the water is just fine and it seems to have increased the amount of hot water for showers.

It's nice knowing that we're not wasting 7.5 litres of hot water every time we run the kitchen or bathroom taps, I think it has saved us an enormous amount of gas and water over the year. I think it works well, as we only have a 30 litre tank, so it's not mixing the layers of hot and cold water in the tank.

I'm looking at putting in a solar hot water system with panels, using a 1000 litre tank as the storage battery for the panels, instead of trying to power the electricity supply to the house.

Solar thermal panels to the tank, or solar PV powering an immersion in the tank?