bolier

[james2006]

Hi - I am replacing my hot water system. Initially I thought a combi, and 4 plumbers agreed with me (currently on vented system). However a mate of mine reckon me water pressure and demands do not suit a combi.

I have 3-4 bar of pressure and 13l/min flow rates from mains. 4 bed house, 2 x bathrooms, utility room, clockroom, kichen sink,dishwasher and washing machine.

Any thoughts? I am now thinking go unvented?

Read more: //www.diynot.com/forums/viewtopic.php?p=2027124#2027124#ixzz1PubjqkxP

 

[Agile]

You seem to have had nupty plumbers who did not measure the dynamic flow rate and explain to you what that means. Madness if they fit combi boilers without knowing if they are going to work properly. But its your money they are spending and their pockets being filled!

For an unvented to work properly you need a dynamic flow rate of 22 li/min @ 1.0 Bar minimum and better at 1.5 Bar.

Tony

 

[mickyg]

neither a combi or unvented will be any good. your options are improving your mains flow rate, various ways, mostly costly, or fitting a vented system.

 

[james2006]

So with the unvented system how bad will the perfromance be on my current pressure and flow rates?

Also to measure the flow rate, one of the plumbers used a 'cup' and he told me I had in excess of 20l/min flow rates. However, I measured the rate again by turning on 2 taps at once. I then measured the flow rate of one and added it to the flow rate of the other - this is how I determined 13l/min. Did I stuff this up?

Cheers

 

[mickyg]

it will be terrible with 13l/min. where did he measure 20l/min from and what do you get from the same place? There was nothing wrong with your measurement but it doesnt all add up.

 

[Agile]

Nothing wrong with the measurement except that its an open pipe figure whereas whats needed is the dynamic flow rate!

The dynamic figure could be half or less of the open pipe!

Tony

 

[bengasman]

Hi - I am replacing my hot water system. Initially I thought a combi, and 4 plumbers agreed with me (currently on vented system). However a mate of mine reckon me water pressure and demands do not suit a combi.

Any thoughts? I am now thinking go unvented?

4 professionals are now considered untrustworthy because your amateur mate questions their judgement. I am glad you are not my customer.

 

[james2006]

We got the measurement from the same place - first tap connected to the mains.

Really confused! But out of interest only one pumber out of 4 tested the pressure and this plumber only tested flow rate becasu I asked. He could have pu;lled the wool over my eyes on the test eg I assume you need to adjust the size of the whole in the opening on the flow rate cup to work out the equalibrium point and therefore the flow rate?

 

[simond]

Any heating technician with a brain would measure the flowrate before advising on the suitability of a combi or an unvented.

Since the 4 you have had round failed to do this, I have to assume you got them from ebay or typed 'cheap boiler installer' in Google?

Seriously, you must be looking in the wrong place. As an installer, there's no way I'm going to wing it without taking simple measurements because if I get it wrong, bad news rides a fast horse.

It is a common misconception amongst customers that all Gas Safe Registered technicians are the same standard. Of course they aren't, any more than a random sample of 4 staff in an office environment can be expected to be the same quality. Choose carefully.

 

[Jordon]

Note as bengasman said, four guys walk in you the op suggested a combi boiler, did you ever ask for there opinion first? By the sounds of it your a tightwad that wastes people's time I mean jesus four engineers?? Four quotes! I wouldn't bother testing nout for free if I walked in you asked for a combi I would cost for one end of people like you don't usually listen anyway shoulder hawks spring to mind, had to quote for these type before and suggest what your friend has, then you get all interested so do a quote to find out you went for a combi anyway, or get a million other blokes in to quote on my recommendation. Most guys now a days just do as told think that hour or so you have wasted with each of these guys time cost them so its in out and quote, so don't come on here all high and mighty that your pal is a hero and all us lot are useless jump in the shoes of the trades men you have had in.