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Dales-Electronic
Dales-Electronic, Home Appliance Technician
Category: Appliance
Satisfied Customers: 1466
Experience:  I am a Home Appliance / Refrigeration Technician of 25yrs+ with my own business and for multi-brand national companies.
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We have recently done legionella risk assessments on 3 Vaillent

Resolved Question:

We have recently done legionella risk assessments on 3 Vaillent combi boilers, the requirment being that with water temp set at min of 60 degrees the outlet/tap furtherest from the boiler must ahcieve a temperature of at least 50 degrees, the water temperature in each case only achieved 46 - 47 degrees even after the water temp for taps on the boiler was set to max
Submitted: 2 years ago.
Category: Appliance
Expert:  Dales-Electronic replied 2 years ago.
Dales-Electronic :

Hello My name is Ian ~ I am not on the site constantly so please be patient whilst waiting for responses to you queries

Customer:

please could we have the answer to the question

Dales-Electronic :

Could you just confirm for me where you got this figure of 50 degrees, all the information I have is that the danger area is between 20-45C. Whilst I agreed that the 60C is the normal set temperature for the Vaillent together with standard immersion heaters, as you will be aware one would be scalded if you got under a shower at 60C and the HSE suggests turning down the temperatures to below 60C. With regard to the problem, if there is a requirement to have outlet temperature at 50C then the only cause you have is to either lag the pipes to maintain temperature or move the boiler closer to the outlet ~ Ian

Customer:

This was the information given on legionella risk assessment course

Customer:

WE were advised that "It is important to identify whether:
• water is stored or re-circulated as part of the system (particular areas of risk include water tanks, dead legs, shower heads and/or long runs of pipe work containing warm water)
• the water temperature in some or all parts of the system is between 20 – 45°C (hot water should be stored in any tanks at 60°C)"

Customer:

advice to residents was:

Customer:

The advice supplied to be given to residents was "The boiler or hot water tank are not working properly, particularly if the water is not coming out of the taps at a sufficiently high temperature. It should come out at a temperature of 50°C after it has run for a minute at the latest."

Customer:

As they are combi boilers there is no tank to lag

Customer:

Shall I continue to wait for a reply?

Dales-Electronic :

OK well the Vaillent doesn't use stored or recirculated systems it is direct supply and it would seem that if you want to follow this 50 degrees you will need to as stated insulate the pipework or move the boiler. However, I attach the HSE booklet covering Legionella ~ http://www.hse.gov.uk/pubns/priced/hsg274part2.pdf see page 4 item 11. I was not talking about lagging the tank but lagging the pipes between the boiler and outlet to maintain the temp.

Customer:

It is not a question of wanting to follow this 50 degree, it is a regulation. Thank you for the attachment

Dales-Electronic :

Page 21 item 3 seems to support my point of either moving the boiler or lagging the pipes. I would therefore be grateful if you would explain why you have given a poor rating? The information supplied is correct and in line with the HSE guidelines.

Customer:

I got the message that you had "stepped out of the chat", before I had finished and before you had given this final piece of information, and I took that to mean you had finished.

Dales-Electronic :

OK sorry it does that sometimes, it just means that I was looking at a document on the server that we use. I think in Your particular case You are going to be up against it, if you can lag the pipes between the boiler this may help but otherwise the only other option rather than moving the boiler is to have some form of instantaneous water (readily available using electric) nearer the taps. Just as an afterthought what size are the pipes 15 or 22mm?

Customer:

We are not plumbers, and the regulations do not require the risk assessments to be done by plumbers . I think we need to take this up with the HSE or whoever have brought in these assessments for residential properties.

Customer:

I do not know what size the pipes are as I did not do the assessment but what is the significance of the size of the pipes? The solutions you have suggested whilst they might be quite correct are impractial for a rented residential property.

Dales-Electronic :

OK the reason I asked is that I get asked all the time about shower temperatures being too low when they are some distance from the boiler. This is usually caused by plumbers using 22mm pipework which has a larger surface area (ie more area of metal to lose more heat) when they should have used 15mm.

Customer:

What is the significance of the size of the pipes? I did not do the assessment so I do not know what size the pipes are but I can find out.

Dales-Electronic :

Reducing the size of pipes quite often solves the problem ~ an aside thought that was all ~ Ian

Customer:

OK, that's helpful - might have to get the landlord to have a word with their plumber.

Dales-Electronic :

If you reduce the size of the pipes as mentioned the ability to lose heat through there surface area is equally reduced, the downsize is there is a slight (hardly noticeable) reduction in flow but as you're only filling up a sink or bath hardly significant as you are using a combi boiler.

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