Water flow for combi

drummer_666

thank you,

i'll get the materials and get my dad and bro to build the platform when they are up in a week

ListysDad

keithgillyon wrote: »

...the pressure in your taps shower etc in a conventional system ie cylinder & roof tanks is all about head of water this means the distance from the bottom of your roof tank to the outlet on the top of your cylinder

Ermm. Sorry to disagree here Keith but my understanding isn't as yours.

Measured head is the distance from the bottom of the cold water storage to where ever the outlet happens to be. It's that because it includes the losses associated with the specific pipe run. If it was as you've said, then the pressure at the HW tap in the kitchen on the ground floor would be exactly the same as the pressure from the bath HW tap in the bathroom on the first floor. The kitchen is always better - UNLESS of course the pipework is so hiss poor the additional resistance balances out the additional head - seen that a few times but it's rare.

By raising the cold water storage tank as high as poss in the loft, and that means the outlet to the hot water cylinder MUST be above the outlet of the hot water cylinder, he will have better flow. It is always possible to get a horizontal hot water cylinder if height is an issue. I've fitted plenty. To improve flow, use the biggest pipe possible in copper and pull all bends before reducing down where required.

With regard to frost, Ideally you fit the HW cylinder directly under the CW storage tank. What you then do is construct a 'tunnnel' of the likes of kingspan (taped together and 75mm is fine) all around it so what heat escapes the cylinder heats the underside of the CW tank. You can then insulate the rest of the loft as per normal. Remember, DO NOT use the grey foam (climaflex and the like) to insulate pipework. It CAN NOT protect against frost. You must use a nitrile based product AND GLUE EVERY JOINT if you want to do it properly. More on that if you need it.

David

Mr_Ted

LMAO Your actually both wrong!!!

Head of water is actually measured from the water level IN THE CWS TANK to the particular outlet!

1 Atmosphere = I Bar = 14.7 PSI = 33.455 256 555 feet head of water

So you would have to raise the tank to 33.455 256 555 feet above any outlet to achieve 1Bar pressure at that point!

As for putting in the biggest size pipe lol maybe 50mm would do the trick lol what a ridiculous statement!

Most domestic properties suffice with a 15mm coldwater supply and a maximum for the bath of 22mm pipe!

I would definately NOT go with either a Combi or raising the tanks as the performance of a Combi would be compromise under the circumstances, and the additional cost of raising the tanks would be extortionate!

A pressureised unvented Cylinder, as per here http://www.gledhill.net/page/138/Stainless-Lite-Slimline.htm , or other makes are available, given the circumstances would give the best performance!

It can be fitted in a loft space, and wouldnt need the excessive carpentry indicated, and would not have a problem with frost as they are insulated, only the pipework work need protection!

Jeez people stick to what you know as salemen, and no you would never get a beer off me with your expert opinions lol

drummer_666

Mr_Ted wrote: »

LMAO Your actually both wrong!!!
I would definately NOT go with either a Combi or raising the tanks as the performance of a Combi would be compromise under the circumstances, and the additional cost of raising the tanks would be extortionate!

It can be fitted in a loft space, and wouldnt need the excessive carpentry indicated, and would not have a problem with frost as they are insulated, only the pipework work need protection!

Well the tank and cylinder need to be moved anyway, so isn't it better to move at least the tank to the loft?

You say it wouldn't need the excessive carpentry indicated - what would it need then? How would I know if the roof will hold the weight?

Why do you recommend an unvented cylinder over a vented one?

southcoastrgi

Mr_Ted wrote: »

LMAO Your actually both wrong!!!

Head of water is actually measured from the water level IN THE CWS TANK to the particular outlet!

1 Atmosphere = I Bar = 14.7 PSI = 33.455 256 555 feet head of water

So you would have to raise the tank to 33.455 256 555 feet above any outlet to achieve 1Bar pressure at that point!

As for putting in the biggest size pipe lol maybe 50mm would do the trick lol what a ridiculous statement!

Most domestic properties suffice with a 15mm coldwater supply and a maximum for the bath of 22mm pipe!

I would definately NOT go with either a Combi or raising the tanks as the performance of a Combi would be compromise under the circumstances, and the additional cost of raising the tanks would be extortionate!

A pressureised unvented Cylinder, as per here http://www.gledhill.net/page/138/Stainless-Lite-Slimline.htm , or other makes are available, given the circumstances would give the best performance!

It can be fitted in a loft space, and wouldnt need the excessive carpentry indicated, and would not have a problem with frost as they are insulated, only the pipework work need protection!

Jeez people stick to what you know as salemen, and no you would never get a beer off me with your expert opinions lol

OMG & you tell us we don't know what we are talking about, i have been a plumbing & heating engineer for 30 yrs i'm not a salesman.

i def would not go with an un-vented cylinder if they are installed correctly with the req pressure & flow rate you can get 35 ltrs/min how good do you think the performance will be with the OP only having 9 ltrs/min, a average un-vented cylinder holds 210 ltrs of water & you are trying to tell the OP that he doesn't need any additional carpentery to stop that weight falling through the ceiling.

Maybe you should stick to what you know because you obv don't know anything about this subject.

P.S. it's a cold water storage cistern not tank.

Mr_Ted

Yes, moving the CWS tank and cylinder into the loft will give you an extra head of water, but what you will also have is the combined weight to have to contend with, which will need the distribution of the weight load in the loft which is all combined into a small footprint area as the cylinder and tank need to be upright!

The use of an unvented cylinder, by virtue of the fact that it is a sealed unit not dependent on gravity to fill means you will have lost the weight factor of a CWS tank, the unvented cylinder will give you virtually the same pressure as the incoming cold water supply, which a gravity system WONT, and not only that as an unvented cylinder is a sealed unit it could be fitted horizontally thereby distributing the weight load over a bigger area which would need less extensive timbering, a solid base would probably be sufficient, but that is obviously dependent on the construction of your property!

If you have any queries, rather than listening to multiple and possibly misleading option on here, try giving Gledhill a ring, they are a Family business with a very good reputation and if you tell them your position I am sure they will give you good advise.
I am also sure it will not be just a sales patter for the sake of selling you something as they only sell through distributors, and they may well have a more suitable alternative to any suggestion on here.
I have dealt with them in a commercial setting and they are not a firm that spouts BS, they give considered technical solutions to fit the needs and requirements!

Give them a try, you may well also get to speak to a Family member as they have genuine family business values, and before anyone has a sarcastic pop, NO I DONT HAVE ANY CONECTION IN ANY WAY TO THIS SUPPLIER!

southcoastrgi

An unvented cylinder is not designed to be laid flat that's why it has a base, you would need to get one properly designed for the job, a unvented cylinder is connected to the incoming supply via a pressure reducing valve & strainer & this in it's self will reduce the available flow available due to resistance if nothing else, by also raising it into the roof you will be reducing the pressure & flow due to the height from the incoming mains so it just won't work as designed, if the OP doesn't have enough pressure & flow to make a combi work (bearing in mind that if he followed your advice the whole house would be on 2 bar & 9 ltrs/min) then how the hell do you think an unvented cylinder will work properly.

OP I have giving you my advice as to the best you will get in your situation, I'm not doing the job but if you go unvented/combi or put the cylinder in the roof you won't be happy with the performance & will have spent alot of money for nothing. IMO.

ListysDad

Mr Ed

When you posted your rude response, my immediate reaction was to let you have both barrels. I resisted. I have no doubt you are well meaning but your posts are actually quite offensive. You know nothing about the people you so rudely criticise and leap to (incorrect) conclusions about. As that is a fact might I suggest that you try harder to get yours right. With that in mind let me take apart your response to me line by line and teach you how to do your job as, based on your response, you plainly need it.

1 -

Mr_Ted wrote: »

LMAO Your actually both wrong!!!

Please do everyone a favour. When you respond to a post give both the original poster and the contributors the respect they deserve by reading through the whole thread. To be honest you'll save yourself a lot of time, as you won't be commenting on stuff already covered, and you won't waste ours either.

2 -

Head of water is actually measured from the water level IN THE CWS TANK to the particular outlet!

That, dear boy, I have already said. No doubt you'll now trawl my words and discover that I've said from the bottom of the storage tank. That was done for a reason. Depending on usage, the tank level will alter continually. Therefore the only 'consistent' datum is the tank bottom.

3 -

1 Atmosphere = I Bar = 14.7 PSI = 33.455 256 555 feet head of water

So you would have to raise the tank to 33.455 256 555 feet above any outlet to achieve 1Bar pressure at that point!

Well done! And your point is?

4 -

As for putting in the biggest size pipe lol maybe 50mm would do the trick lol what a ridiculous statement!

Most domestic properties suffice with a 15mm coldwater supply and a maximum for the bath of 22mm pipe!

Oh dear. Back to point 1. Just for you, what I said was take the largest pipe size FROM (that means going away) the cold water storage tank. That way, Google it if you wish, flow resistance will be lower giving a better flow rate. QED.

5 -

I would definately NOT go with either a Combi

We agree! :T

6 -

or raising the tanks as the performance of a Combi would be compromise under the circumstances, and the additional cost of raising the tanks would be extortionate!

Forgive me. Try as I might, I fail to understand is how you can understand how the performance of a combination boiler might be compromised yet cannot turn the coin over and see how raising tanks can deliver better flow! I can only assume that you are talking about raising tanks to your Googled 33m! The cost of raising tanks is minimal compared to other options when we are talking budget solutions as we are here.

7 -

A pressureised unvented Cylinder, as per here http://www.gledhill.net/page/138/Stainless-Lite-Slimline.htm , or other makes are available, given the circumstances would give the best performance!

Oh dear oh dear. Look again dear boy and read the minimum flow and pressure requirements. The OP has nothing like it and its cost, in a budget situation, is unviable.

8 -

It can be fitted in a loft space, and wouldnt need the excessive carpentry indicated, and would not have a problem with frost as they are insulated, only the pipework work need protection!

Once again point 1.

9 -

Jeez people stick to what you know as salemen, and no you would never get a beer off me with your expert opinions lol

Mr Ed. Please try harder. No matter how many 'lol's you pepper your responses with, they do not excuse rudeness or ignorance. Hence forth I withdraw my offer of a beer, no matter how much you try and stalk me...

Good luck OP.

ListysDad

Keith.

I say, "don't teach him!" and give him the benefit of 'your' knowledge. He's a waste of space.

D

gas4you

Mr_Ted wrote: »

try giving Gledhill a ring, they are a Family business with a very good reputation

This statement alone proves you know nothing about the plumbing industry.

Gledhill and good reputation can never be put in the same sentence:rotfl: