Pressurised boiler system, need some advice

stonevibe

We are currently getting quotes for a pressurised boiler system. When we moved house, we noticed the water pressure in the shower was rubbish, and we might extend the house in the next few years.

Does anyone here know much about them? 

I had a couple of engineers round for quotes, and I am just waiting for them to get back to us with prices. British Gas is coming out to quote today as well.

Are there any that are better? Things to watch out for? 

Any advice would be helpful, as the last boiler we purchased was a combi at the old house, and this new house is looking too large for one of those.

Dominic

Step 1.......check your standing incoming water pressure ....if it isn't good then the Pressurised system cannot perform to it's potential without addition of an Accumulator which is bulky and expensive .
I assume any decent engineer tested this as part of the preliminary diligence.
Get a good SYSTEM BOILER like Vaillant /Worcestor Bosch ....you don't need to pay the huge price of a Sadia Heatrae Megaflow cylinder .....only paying for name......Triton or Ariston is equally good at much lower cost ......it's only a steel drum.
 Get a large cylinder.....if you have great water pressure the enhanced flow rate will drain it quickly ...no point having a great shower if it doesn't last long.
-As regards cylinders try and use a pre-plumbed cylinder.......it will save labour install costs and looks a lot neater.
Ask your engineer to calc the flow rate anticipated in terms of litres per min (this will sort men from the boys )
Whilst installing have a secondary return loop installed with a brass impellor pump ....if it's a large house this will save you waiting for taps to run hot rather than wait a minute or 2  for the hot to come through .
MOST IMPORTANT RULE ; Forget you ever heard of British Gas ......joke prices,joke labour quality,joke customer care
oh , and also very important.........forget you ever heard of British Gas !

SteveRobinson

We have a Grundfos shower pump installed to provide pressure for the shower. It switches on and off automatically as you turn the tap.

elstoof

Do you mean an unvented system, ie mains pressurised hot water as opposed to gravity fed?

Is your cold water pressure currently good? Your hot water will only be as powerful as your cold mains supply is in an unvented system. If that’s weak you’ll need a pump really. An existing vented, gravity fed system can be converted, how simple that is depends on the layout it’s currently in - could be a couple of days, could be a week of rearranging. You need space to fit expansion vessels if you keep the same boiler, and the pressurised hot tank would generally just replace the existing one. You will be able to get rid of the cold water F&E tank for radiators, but you’ll need external access for pressure relief valves etc which can be a headache depending on the property 

stonevibe

Some good advice here, thank you all

stonevibe

Dominic said:

Step 1.......check your standing incoming water pressure ....if it isn't good then the Pressurised system cannot perform to it's potential without addition of an Accumulator which is bulky and expensive .
I assume any decent engineer tested this as part of the preliminary diligence.
Get a good SYSTEM BOILER like Vaillant /Worcestor Bosch ....you don't need to pay the huge price of a Sadia Heatrae Megaflow cylinder .....only paying for name......Triton or Ariston is equally good at much lower cost ......it's only a steel drum.
 Get a large cylinder.....if you have great water pressure the enhanced flow rate will drain it quickly ...no point having a great shower if it doesn't last long.
-As regards cylinders try and use a pre-plumbed cylinder.......it will save labour install costs and looks a lot neater.
Ask your engineer to calc the flow rate anticipated in terms of litres per min (this will sort men from the boys )
Whilst installing have a secondary return loop installed with a brass impellor pump ....if it's a large house this will save you waiting for taps to run hot rather than wait a minute or 2  for the hot to come through .
MOST IMPORTANT RULE ; Forget you ever heard of British Gas ......joke prices,joke labour quality,joke customer care
oh , and also very important.........forget you ever heard of British Gas !

Oddly enough the British Gas guy is here now and the only one so far  that has mentioned water pressure/flow rate  and is currently testing it. 

elstoof

Brace yourself for a 5 figure quote

blobb

What's the beef with BG? Just had them quote for a new combi at my place, it's a tank system that's about 40 years old and needs ripping out. It's top end of combi size so they need to bring a new gas line in and deal with all the complications of however the old system worked. Quote was on the high side but not as high as I thought it might be, considering there is some work to get under flooorboards and manage the chaotic pipe runs. We had another firm come in and they didn't have a clue.  

stonevibe

elstoof said:

Brace yourself for a 5 figure quote

Yeah, I’m guessing this won’t be cheap

elstoof

BG aren’t cheap, I’ve used them once and they did a good enough job though. I guess they can be hit and miss due to their size.

I’ve had truly awful work done by a big company, Aspect. We hired them to do exactly what the OP wants, convert to unvented so we could lose the noisy pump and F&E tanks. The guy literally built a bomb in our house - installed a sealed system with no expansion vessels or pressure relief valves. It looked like a dogs dinner as well, the most shocking workmanship I’ve ever seen, I can dig some pictures out. Had to get it all redone before it blew a hole in my roof

strtdv

If it's literally just to fix a shower with poor pressure it's vastly cheaper to just fit a pump to a gravity fed system.

A pressurised system requires: 
-Good mains pressure (and either an accumulator or new water main if it's not)
-A new system boiler
-A pressurised stainless steel water cylinder. It doesn't need to be a megaflo though i think they have the highest efficiency. Ours is a Gledhill, I think heat loss is about 70watts on a 300 litre cylinder which isn't bad at all.
-You may need to replace some of your shower outlets 
-your plumbing for radiators will need to be pressure tested and may need to be replaced

We did it when we did a major house renovation and we were putting in underfloor heating etc, but it's an expensive job 

elstoof

You don’t need a new system boiler, an existing conventional boiler will be fine. You will need external expansion vessels though

exocet

As Dominic says, check incoming mains pressure...even how fast you can fill a bucket using a kitchen tap can be useful. If you get 30 litres per minute, you're fine. I only get 22 - 25 but still run a pressurised tank - running 2 showers simultaneously is compromised a bit with lower flow rates.

Best tanks on market are by OSO, most thermally efficient and they do models that support Heat Pump operation so that you could use that option should you need to in future OSO tanks are rated for 25 years use). These models have a much larger heating coil so you'd get quicker reheat times. If space allows, get a larger tank - min 250 ltrs capacity, again, may prove future proof for a Heat Pump centric future.

If you go "system boiler" that'll mean that the heating circuits are also pressurised. I run a standard "open vent" boiler because I didn't trust the legacy pipework in my house....much of which is buried in concrete in my place. You can have "low pressure" heating with high pressure stored hot water tank.

I've always found Vaillant to be very good. If you go down that path the Vaillant tanks integrate very nicely (you can use the thermocouple temp sensor which gives the boiler accurate information as to current tank temperature...instead of the more common U.K heating control approach from the 1950's that uses a simple on / off thermostat. 


 

stonevibe

Thank you all for your help. I appreciate that you took the time to answer, as will save me money and time.

crosstownvamp

As others say just fit a decent shower pump, Stuart Turner are good. In my last place the boiler and cylinder were in the first floor bathroom. The house water was gravity feed from cistern in the loft so not great pressure.

We had one pump under the bath to feed the shower - hot feed via a Surrey flange on the cylinder - I did it all myself.

Then when we had a loft done, a second shower pump for pumping up a floor to the shower and basin.  That was a different type that can pump 'up'.

Great pressure on both.

Dominic

^ What you used was a Negative Head Pump........not needed anymore ;Stuart Turner Monsoon make a Universal pump now which is cheaper than a full size negative head and easier to install.
@stonevibe needs to know that you cannot use any kind of pump on a combi system

crosstownvamp

Dominic said:

^ What you used was a Negative Head Pump........not needed anymore ;Stuart Turner Monsoon make a Universal pump now which is cheaper than a full size negative head and easier to install.
@stonevibe needs to know that you cannot use any kind of pump on a combi system

Yeah I remembered 'negative head' after typing this. Good to know there's a universal option now.

But I had no idea combis can't take pumps. Figures I guess.

Dominic

I thought I should mention that as some people are saying " Easy,get a pump "
They can now be fed by a mains boost pump now in new water regs but a pump on the other side of the boiler would simply suck the water through faster than it could heat it .