New Central heating but problems, Please help

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Dale Sanders

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Hi.

hopefully someone can help me here.

I have a recently had a new gas central heating system consisting of 7 rads and a Worchester 36cdi compact located in the lofty controlled by the wave thermostat.

I used to have electric storage rads and the electric controlled heating with were on tanks.
after install i have a drop in hot water pressure. if the cold is on then the hot drops and even running the bath takes forever.

any ideas?
i want to make sure i have all my facts straight before speaking to the plumber who installed as he did come arounf measureing pressure and said it was about average on the set up up i requested.
the main in pressure was 3 bar and the flow was 14l/m with the hot being 10l/m.
thanks for your help in advance
 
You need to call back the installer to check water flow your about 3Ltr per min short on hot water delivery,
 
He checked flow when I was present.
Everything is open.
I have 15mm that enter house that run in the loft but then goes to 22mm. Would it help to increase to 22mm from 15mm pipe.
The flow seems fairly quick on top taps on sinks but very poor on bath.
 
All your outlets are 15mm to the hots but on your bath i presume its still old 22mm probably delievers the same litres per minute just seems slower.
 
The flow on your boiler will be preset. Im not 100% familiar with your boiler but id say 12litres per minute. Thus cant be adjusted.
As for the 22mm to the bath. Ideally it should be 15mm from a combi...you may find you have to draw off alot more water before it becomes hot.
 
Tbh it's sounds like there's not much wrong. Your water main is giving 14lpm. Your getting a little less once the flow has been restricted by your pipe work and boiler. If you open the cold then it is sharing the 14lpm with your boiler, probably have less restriction than your boiler it gets more of the share.
 
So if I am getting 14lpm and it enters the boiler at 14lpm why isn't it coming out at 14 or even 13lpm.
Sure it shouldn't drop 4lpm.
 
1. Your boiler will provide 13 lpm at a 40 degree temperature rise, plus or minus 15%. If you're unlucky, and its minus 15%, the maximum hot flow rate will be about 11 lpm. Also, the Compact ERP version has a flow restrictor to limit the flow necessary to ensure that 40 degree, which may also reduce the flow rate.

2. The hot (and cold) flow rate at the bath outlet will be lower than an open pipe immediately after the boiler, as it has to navigate the pipework and fittings / bends. Friction in the system will reduce the rate of flow.

3. With a tank system, the hot and cold flow rates are largely independent as both come from large stores of water, usually (in the case of a bath) via 22mm pipes. With a combi, the cold comes off the mains via 15mm pipe, and the hot also comes off the mains via the boiler, again with (usually) 15mm pipe.

4. It would help to know what the cold mains flow rate is at the point of entry to your property. This would give you the maximum possible flow rate for both hot and cold. Measuring separately at the bath taps doesn't give you a full picture.
 
Thanks for this.

I have measured all taps and the all cold measured around 14-15 Lpm and all hot is around 9-10lpm. The mains in is on 15mm until it gets to the loft transferring to 22mm it then runs the length of the loft to other side to where the boiler is situated.
Should I be lose 4-5lpm on flow just going via the boiler?
 
Dale Sanders said:
Thanks for this.

I have measured all taps and the all cold measured around 14-15 Lpm and all hot is around 9-10lpm. The mains in is on 15mm until it gets to the loft transferring to 22mm it then runs the length of the loft to other side to where the boiler is situated.
Should I be lose 4-5lpm on flow just going via the boiler?
Click to expand...
Check the instruction manual for the boiler. It will tell you roughly what flow rates to expect at what temps. But as stated above this is a rough guide only and may not be spot on.
 
Under sized pipes if it's run from the mains to the boiler in 15mm also all hot in 15mm
 
What will be most effective to Do?
My options are:
Change 15mm main in to 22mm
240litre Accumulator on hot
Pump on the hot line
 
change the 15mm to 22mm

accumulator wont work nor a pump
 
I am being advised by the guy who installed the system an accumulator will give me the max pressure the boiler can cope as effectively it's a storage of water so I can fill 2 baths at max flow.
 
Dale Sanders said:
I am being advised by the guy who installed the system an accumulator will give me the max pressure the boiler can cope as effectively it's a storage of water so I can fill 2 baths at max flow.
Click to expand...

Combi boilers will never fill two baths they struggle with one
 
Dale Sanders said:
I am being advised by the guy who installed the system an accumulator will give me the max pressure the boiler can cope as effectively it's a storage of water so I can fill 2 baths at max flow.
Click to expand...
In my opinion a combi will never run a bath and a shower at full rate together let alone 2 baths.
 
Think someone's been sold a dream :)
 
Dale Sanders said:
Yes I am aware of that but currently it's doing 10lpm so any more will be an advantage
Click to expand...

I would do 22mm to the boiler that should sort it unless your mains flow is 10lpm

Any ISO valves on the hot pipework that arnt full bore get them changed as well
 
yea
 
Dale Sanders said:
Why don't you think an accumulator will benefit my system? Why won't it work
Click to expand...

because you will have 10lpm coming out, they dont increase the flow
 
Chap I work with always increases mains to combis in 22mm all the way. He doesn't win jobs on price, but gets a lot from recommendations.
At home I only have 15mm but family have learned not to turn tap on when anyone the shower. Even thought of putting a solenoid valve on mains but managed so far. also we turn dishwasher and washing machine off. You learn to live with it. Worse at 7-8 in the morning when incoming pressure low. Might put in mains boost pump.
 
I am struggling to understand.
I have spent 5 grand on a new combi boiler to control heating and water from electric storage rads and electric thermostat controlling the water in a cylinder. The hot flow was as good as the cold.
I am prepared to spend more money to get the flow up but what is a guaranteed fix to improve flow on hot?
 
Upgrade pipe as stated before and as shauncorbs has said change ISO valves to full bore.
 
Are you wanting to run more than one outlet at the same time tho ?
 
I have just been up in loft and was under impression by my plumber that he changed to 22mm up in loft but it runs 15mm from mains in all the way to the boiler.
 
Dale Sanders said:
Yes I would like too run 2 outlets at the same time
Click to expand...

Dale Sanders said:
I have just been up in loft and was under impression by my plumber that he changed to 22mm up in loft but it runs 15mm from mains in all the way to the boiler.
Click to expand...

There's your problem you won't get 14+ lpm out of 15mm with elbows etc

Sorry to say you will struggle to have two outlets open at the same time With a combi

Best option would be heat only boiler and unvented cylinder if your flow and pressure are ok
 
Dale Sanders said:
Am I getting a new bathroom and want a powerful shower. Can I put a boost for water pressure on the shower?
Click to expand...

Nope as your on a combi

You need to think about if your going to need two outlets open at the same time e.g. Kitchen tap and shower etc if you are, you have the wrong system
 
Dale Sanders said:
What system do I need and what can I do too change
Click to expand...

Three options but both require a new boiler

One heat only boiler with a unvented cylinder
Two heat only boiler and gravity cylinder with a pump
Three storage combi (Viessmann 222) depending on your mains flow maybe an accumulator if less than 20lpm
 
Also with it being in the loft you will instantly be on a downer as the pressure has to travel up three floors before reaching the boiler. Upgrade the pipes to the boiler. You should get more flow as long as you have the pressure in the mains

Edit. Got to be a cheaper option to start with
 
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