What water temperature would give you a "hot" shower?

Kashkai

I had a guy in yesterday to give me a quote for a new solar system and he said that even on cloudy days, my proposed system would give me a water temperature of about 35 - 40 degrees for our pumped showers. Would this be sufficient for a hot shower or would this still need a boost from the oil burner. He didn't seem to be too worried when I said that Legionella might be a problem at this temperature as he said that once I used all the water on a continuous basis, i.e. didn't let it stagnate, then I'd be ok. Thats not what I had been led to believe from my own investigations into this.

He was proposing to use flat panels supplied by Kingspan Thermomax as they are made in the north and are "superior" to the imported panels (his words not mine btw!). Has anyone else used these?

gizmo555

Prosperous Dave wrote: »

I had a guy in yesterday to give me a quote for a new solar system and he said that even on cloudy days, my proposed system would give me a water temperature of about 35 - 40 degrees for our pumped showers. Would this be sufficient for a hot shower or would this still need a boost from the oil burner.

40 degrees would be about right, but a lot depends on your personal preference - for example I find the setting my wife likes on our shower unbearably hot.

http://customer.honeywell.com/WaterControl/Cultures/en-US/Prevention/Burn+Chart/Default.htm

Check here for more info re Legionella:

http://customer.honeywell.com/WaterControl/Cultures/en-US/Prevention/Legionella+in+Your+Home/Default.htm

The short answer is that you would be taking a risk by not regularly raising the water temperature to 60 degrees. That said how big a risk is it in reality - when have you ever heard of anyone getting Legionella from their domestic hot water? There was the case a few years ago of an unfortunate man viewing a house for sale in South Dublin who got Legionella from a hot tub and subsequently died. Water in a hot tub would be stagnating though, if not regularly changed, unlike that in your hot water tank.

sinnerboy

Dave - safety 1st . Fit a stat on your cylinder and set it to 60 degrees - that way your boiler will kick in to raise it to - but not past this temp . In summer you could set the timer to do this for say 2 hours per day - should be ok

bonzos

just out of interest how long would it take your oil boiler the bring your water up from say 20deg to 60 deg ...using one zone only(HW)

sinnerboy

About - 20-30 mins typically

gman2k

sinnerboy wrote: »

In summer you could set the timer to do this for say 2 hours per day - should be ok

I'm under the impression that to remove the risk of Legionaires, you should set the stat to bring the water temp up once a week. I'm no expert:), I'll let Quentin G have the final say...

sinnerboy

"Arrangements should therefore be made to heat the whole water content of the storage water heater, including that at the base
to a temperature of 60°C for one hour each day".

http://www.ewgli.org/data/european_guidelines/eg_supplement1a.pdf

I would set timer for 2 hours just be safe

quentingargan

Prosperous Dave wrote: »

even on cloudy days, my proposed system would give me a water temperature of about 35 - 40 degrees for our pumped showers.

He didn't seem to be too worried when I said that Legionella might be a problem at this temperature as he said that once I used all the water on a continuous basis, i.e. didn't let it stagnate, then I'd be ok.

He was proposing to use flat panels supplied by Kingspan Thermomax as they are made in the north and are "superior" to the imported panels (his words not mine btw!). Has anyone else used these?

Others have already responded about the Legionnaires - yes, 60 degrees once a week is considered adequate to sterillise. I have to agree that very few installers are bothered by Legionnaires, and also, it hasn't actually arisen, but one case is one case too many. But if you are proposing a 300L cylinder and only have two occupants for example, your water use may be quite slow.

As for superior performance, ask for the EN12975 certs and assess for yourself whether they are superior. You can download our one here

I've come across Thermomax tubes but I don't know if they manufacture their own flatplates, or if they re-badge. In the UK I think they used to sell "Marvel" flatplates. If so, their collector is made in Denmark and their cert shows n0 (efficiency) at .772 (compared to .775) and their heat loss coefficient at 3.84 compared to 3.85. In other words, virtually the same. Marginally worse efficiency, marginally better heat loss, all within the margin of error.

But you would need to see a full EN12975 cert from the supplier, and that would give the details. I see on a site for the Irish distributor that Thermomax has a panel which their leaflet describes as being "designed specifically for North American climates".

sinnerboy

quentingargan wrote: »

Others have already responded about the Legionnaires - yes, 60 degrees once a week is considered adequate to sterillise.

I naturally disagree - based on the document I posted earlier .
I am not looking to provoke a further debate - the OP may take whatever action he wishes to himself now .

Kashkai

He proposed a 300l cylinder for our family, i.e. myself, wife, and 5 kids aged 9 down to newborn. I wondered if this would be a big enough system as my wife and eldest girl take long showers, i.e. the bathroom (using the electric Triton shower) is like a steamroom with water running down the walls. If they used the pumped showers, I'd need the oil burner running continously to keep water heated. Therefore with their preference for long showers, I'd think they'd get through 300l of solar heated water in no time and thus empty the tank. So would they be in danger of drawing the possibly infected water from the bottom of the tank?

sinnerboy

No - not with the constant flowing .

Longboard

• 70 to 80 °C (158 to 176 °F): Disinfection range
• At 66 °C (151 °F): Legionellae die within 2 minutes
• At 60 °C (140 °F): Legionellae die within 32 minutes
• At 55 °C (131 °F): Legionellae die within 5 to 6 hours
• Above 50 °C (122 °F): They can survive but do not multiply
• 35 to 46 °C (95 to 115 °F): Ideal growth range
• 20 to 50 °C (68 to 122 °F): Legionellae growth range
• Below 20 °C (68 °F): Legionellae can survive but are dormant

...sourced from wikipedia.

quentingargan

Prosperous Dave wrote: »

He proposed a 300l cylinder for our family, i.e. myself, wife, and 5 kids aged 9 down to newborn. I wondered if this would be a big enough system as my wife and eldest girl take long showers, i.e. the bathroom (using the electric Triton shower) is like a steamroom with water running down the walls. If they used the pumped showers, I'd need the oil burner running continously to keep water heated. Therefore with their preference for long showers, I'd think they'd get through 300l of solar heated water in no time and thus empty the tank. So would they be in danger of drawing the possibly infected water from the bottom of the tank?

Agree with sinnerboy on this - the tank would be getting swept clean more often, reducing Legionnaires risk, but you should still have a strategy for winter time when the cylinder would often stay at 35 to 40 at the bottom. As regards to doing this daily or weekly, weekly is standard in solar industry, but doctors differ...

If you don't have hard water, you can always use the 300L cylinder at temperatures up to 80 or 85 degrees so you are effectively storing more heat. The efficiency of flatplates falls off at those levels, but the essential component that generates heat is the area of your panel in sq m. Often the storage only has the effect of increasing the number of cloudy days that you can survive without using the boiler.

Kashkai

Many thanks for the replies guys. In our house, water in the cylinder would not get a chance to stagnate and we'd more than likely have either the oil burner or pellet stove going in the colder montsh of the year so that should take care of any nasty microbes.


I had a secondary reason for getting this work done now in that I have to get some plumbing work done on the cylinder/surrounding pipework and I thought I'd do this and the solar installation in the one go rather than go at the same job twice in a period of 6 months. However is it a daft idea to install a solar system now with winter rapidly approaching (I've started to think so) and thus its effectiveness on heating our dhw at this time of year would be minimal. My other concern is that installing a system now would not show up any deficiencies until the next time we get sun, i.e. April/May 2010 and therefore any warranty/guarantee might be gone.