Ahhh is there an M&E plumbing contractor in North East that can help me

[king of pipes]

Darren jackson is in leeds based another possibility ?

 

[Chalked]

Hi mate
Sorry I didn't ring you back. I didn't save your number, so could you ring again?.
Pm sent too.

 

[Chriswareham]

loveing your calculations will relook when sober

 

[n141311]

hey guys,

Just a quick update. So I've got an M&E engineer involved and he's come up with the same conclusions as some of the posts here. Kudos to @ShaunCorbs -

- M&E challenged boiler size if I'm to reheat the 2 x 300l cylinders at 25 litres per minute in tandem. Says it needs to be bigger than 50kW - probably closer to 80kW. Thoughts?

- he also reckons that I'm going to struggle to get 11.5 litre per min pressure to the showers thanks to the plumber cocking up pipework with 15mm. His suggestion is to use a series of 3 Rennai gas-powered condensing heat generators that operate similar to boilers for endless hot water which gets around cylinder capacity / reheat. No idea if this solves the pressure problem though. I am keen to retain unvented system because a) it delivers high pressure hot water b) is super energy efficient which means low running costs c) highly reliable . the rennai website link is here: Rinnai :: Products

- third issue he sees is that the 15mm pipework will prevent sufficient hot water temperature reaching the showers so said we might need to compensate and increase temperature to shower supply but that this might take away from radiators. I don't quite understand this but will explore when I chat with him again.

What are you thoughts on this? My view is that if possible I'd like to retain unvented cylinder system, up-size boiler if needed but not sure if there's any equipment we can add to design to compensate for pressure loss to showers thanks to 15mm pipework

 

[ShaunCorbs]

would think if you wanted the re heat times as you stated with heating on the same time 100 kw is what you want, if your happy with a slightly longer re heat time (approx 20 mins more 80kw sounds about right)

rinnais are very good and can handle the load but its more cost (alot more) esp if you have already bought the cylinders but agree with his pressure/flow thoughts as hes on site

dont agree it will limit hot water temp, under sizing will only limit flow rate and esp if you havent got a secondary return it will add to the water draw off before it hot

you have two options (one you might not like)

one try and get as close as you can and re pipe in correct size (and hope its enough)

two re pipe the lot and either put the costs onto the inexperienced plumber for any damage to the walls / finish

best option is normally the worst sorry to say

sorry i couldn't be of more assistance

 

[n141311]

would think if you wanted the re heat times as you stated with heating on the same time 100 kw is what you want, if your happy with a slightly longer re heat time (approx 20 mins more 80kw sounds about right)

rinnais are very good and can handle the load but its more cost (alot more) esp if you have already bought the cylinders but agree with his pressure/flow thoughts as hes on site

dont agree it will limit hot water temp, under sizing will only limit flow rate and esp if you havent got a secondary return it will add to the water draw off before it hot

you have two options (one you might not like)

one try and get as close as you can and re pipe in correct size (and hope its enough)

two re pipe the lot and either put the costs onto the inexperienced plumber for any damage to the walls / finish

best option is normally the worst sorry to say

sorry i couldn't be of more assistance

Hi Shaun,

Cylinders and boilers haven't been purchased yet.

What are the pros / cons of the Remmai solution vs unvented cylinders in your opinion? I'm concerned about the 3 things: instant hot water, delivered high pressure, in a cost efficient manner so I don't get killed by running costs

Appreciate your experience mate.

 

[ShaunCorbs]

Right ok (thought they had been )

Both if installed correctly will give instant hot water

Your water main governs both so no difference there

You need a high pressure water source either mains fed or tank and booster set (I would recommend the second if you have the space)

Usage should be about the same

One downside to the Rinnai's is more to go wrong than an unvented cylinder

Other than that there about the same

 

[n141311]

Right ok (thought they had been )

Both if installed correctly will give instant hot water

Your water main governs both so no difference there

You need a high pressure water source either mains fed or tank and booster set (I would recommend the second if you have the space)

Usage should be about the same

One downside to the Rinnai's is more to go wrong than an unvented cylinder

Other than that there about the same

Gotcha. Ok so my thinking is if I have a breakdown, I really don't want to stuck trying to find a plumber that can sort it. appreciate your other points - didn't realise it was virtually identical in all other aspects.

Got another thought: if we upgrade where we can & pray...there is still the rest of the house yet to be piped up. If we do that properly, will those other rooms at least get high pressure water without any issues? Or are we now f* through the whole house because part of the piping is in wrong size?

 

[ShaunCorbs]

The only part that will be effected is the bits he's done / you can't get at

If the other parts / the rest is done right / to what somone works out they should be fine

(Hope that makes sense)

 

[n141311]

The only part that will be effected is the bits he's done / you can't get at

If the other parts / the rest is done right / to what somone works out they should be fine

(Hope that makes sense)

Thanks mate. That message made my night. Have been crapping myself thinking the whole house might be compromised. Thankfully the guy only did 4 rooms.

 

[ShaunCorbs]

We're all here if you have any other questions / want to pass somthing by us

 

[n141311]

Hi all

Hi mate
Sorry I didn't ring you back. I didn't save your number, so could you ring again?.
Pm sent too.

Hi mate, no worries - I replied to your PM? Did you get it? Can you also let me know the following (forgive me for asking but I've been burned by one plumber so figure I should ask Qs up front):

- what's your trading name
- are you gas safe registered for unvented system installs (I think this part F cert or something)
- do you have a commercial ticket / able to install boilers at 65kw - 100kw (I don't want to go anywhere near 100kw due to monthly heating bills)
- are you insured for your work
- are you VAT registered (impacts whether I get hit with an extra 20%. ouch)

Feel free to PM me on the above and let me know if you got my mobile number from the message I sent you. I'll text you if not.

 

[n141311]

Hi all,

So did some additional thinking based on messages from yesterday. Wanted to share and get thoughts based on people's input so far.

- Achieving that 25 litre per minute reheat capacity on two cylinders (12.5 litre per min * 2 cylinder) will require an upgrade of boiler from current proposed 50kw to 100kw
- But this would effectively double my monthly gas heating bill assuming I'm using boiler for same amount of time but its consuming 100kwh instead of 50kwh :O

Therefore, I did some thinking around how to lower flow rate demand through the pipes and from cylinders:

MID CASE DEMAND (MOST REALISTIC)

• 7 bathrooms (not 8) to be used during peak times for av. 10mins
• each shower will have flow rate of 9.5 litres per min instead of 11.5
• Litres per min used: 66.5 (9.5 x 7 showers) (total demand over 10mins = 665 litres)
• At 600 litres cylinder capacity, house will run out of hot water in 9 minutes
• However if boiler is able to re-heat two cylinders at 12.5 litres a minute (6.25 l x 2 cylinders), in that 9mins, an additional 113 litres of hot water would be available due to reheat capacity (9 mins * 12.5 litres per min reheat)
• This gives a total capacity of 713 litres of hot water (600 litre core capacity + 113 litres reheated over 9mins)
• NOTE 1: the 600 litres in 9 minutes indicates a flow rate of 66.5 litres per minute from the cylinder - Would this also require installation of a pump to support that kind of flow rate out?
• NOTE 2: At 66.5 litres per minute from cylinder + 12.5 litres per minute recharge capacity = 79 litres per minute flowing through the pipework
• NOTE 3: The above takes no account of radiators, toilets being flushed or sink basins being used. Should I factor more for this?
• NOTE 4: Assumes the 8th bedroom which is a staff room will not use the shower during peak periods

I'm taking a guess here but based on lower re-heat capacity of 12.5 litres per minute (6.25 litres per min x 2 cylinders) - what boiler size would I need? Could I get away with 65kw?

RUNNING COSTS

• KwH boiler: 65
• Hrs used per day in winter: 6hrs
• Total KwH per day: 390 (65 x 6 hrs)
• Total KwH per month: 11,830
• GBP per KwH: 0.06
• GBP gas bill per month: 710

• Winter demand assumption is that heating will run for 3hrs in the morning and 3hrs in the evening. Is this realistic based on modern u-value homes?
• Finally, not sure if all of the above is based on faulty logic because of the way the unvented cylinders would work, ie. boiler usage will actually be a lot less than 6hrs as cylinders will keep water hot minimising need for boiler to be hammered during heating periods? Let me know your thoughts.

Thanks to everyone who has helped out on this thread so far. I can't explain how much it has helped me get through this nightmare. I'm posting updates so a) others can learn and hopefully benefit from it b) to see this thing through to the end with hopefully a happy ending

 

[n141311]

I think you should seek advice from a company, or consultant, who does a lot of this type of work. It definitely looks 'commercial' not 'domestic' to me and needs to be 'designed' not lashed up using rules of thumb.

The assumptions you put in about what performance is needed at periods of maximum demand are going to make a big difference to the cost and performance of the system. E.g. where did you get the '20 mins' average figure from? The average (domestic) shower apparently lasts 8 minutes:

People's showering habits revealed in survey - BBC News

and that average includes teenagers!

I imagine that, if one knows where to look, there are data available for shower usage patterns in hotels.

Hi @Chuck - forgot to stay thanks. You're spot on with that point about ave shower times. I ended up revising down from the crazy 20mins (based on how long my wife takes!) to a more realistic average of 10mins

 

[Chuck]

Hi @Chuck - forgot to stay thanks. You're spot on with that point about ave shower times. I ended up revising down from the crazy 20mins (based on how long my wife takes!) to a more realistic average of 10mins

You're welcome.

I've only skim-read the rest of the thread as you seem to on the right track and it's looking like site-specific details. I will point out one incorrect assumption you seem to be making in your revised estimates, which is that a 100kW boiler will cost twice as much to run as a 50kW one. This is not going to be the case because if you want to heat a certain number of litres of water, e.g. 8 showers worth, the gas required will be the same in each case. The 100kW boiler will just be able to deliver it in half the time.

 

[ShaunCorbs]

Hi all,

So did some additional thinking based on messages from yesterday. Wanted to share and get thoughts based on people's input so far.

- Achieving that 25 litre per minute reheat capacity on two cylinders (12.5 litre per min * 2 cylinder) will require an upgrade of boiler from current proposed 50kw to 100kw
- But this would effectively double my monthly gas heating bill assuming I'm using boiler for same amount of time but its consuming 100kwh instead of 50kwh :O

Therefore, I did some thinking around how to lower flow rate demand through the pipes and from cylinders:

MID CASE DEMAND (MOST REALISTIC)

• 7 bathrooms (not 8) to be used during peak times for av. 10mins
• each shower will have flow rate of 9.5 litres per min instead of 11.5
• Litres per min used: 66.5 (9.5 x 7 showers) (total demand over 10mins = 665 litres)
• At 600 litres cylinder capacity, house will run out of hot water in 9 minutes
• However if boiler is able to re-heat two cylinders at 12.5 litres a minute (6.25 l x 2 cylinders), in that 9mins, an additional 113 litres of hot water would be available due to reheat capacity (9 mins * 12.5 litres per min reheat)
• This gives a total capacity of 713 litres of hot water (600 litre core capacity + 113 litres reheated over 9mins)
• NOTE 1: the 600 litres in 9 minutes indicates a flow rate of 66.5 litres per minute from the cylinder - Would this also require installation of a pump to support that kind of flow rate out?
• NOTE 2: At 66.5 litres per minute from cylinder + 12.5 litres per minute recharge capacity = 79 litres per minute flowing through the pipework
• NOTE 3: The above takes no account of radiators, toilets being flushed or sink basins being used. Should I factor more for this?
• NOTE 4: Assumes the 8th bedroom which is a staff room will not use the shower during peak periods

I'm taking a guess here but based on lower re-heat capacity of 12.5 litres per minute (6.25 litres per min x 2 cylinders) - what boiler size would I need? Could I get away with 65kw?

post 2 should help you out with most of that

 

[n141311]

Caught up with @Chalked who gave the great idea about having a few smaller boilers in tandem. Plus M&E feedback that I need to have bigger cylinder capacity at c 840 litre minimum.

Now looking at having:

1x Bosch Greenstore TC300 indirect unvented cylinder
1x Megaflo 570 litre indirect unvented cylinder.
2 x 27.5 kW boilers in tandem

Can anyone recommend a good boiler? I was looking at Vaillant ecoTEC Pro 28 but really haven't the foggiest what is best. Looking for something durable that won't break down and will last.

 

[ShaunCorbs]

For the price I would go with 3 300L ones

As you will be looking at aprox 2.5-3k for a commercial megaflow

And what kw earring are you looking at total 65kw ?

 

[Chalked]

Looking at this tomorrow, so will need to size it up first, before any real recommendation.
Like Shaun mentions, commercial cylinders are more expensive than multiple domestic ones.
I like to fit vaillants, so would normally reccomend them. Others are available, but I get a good service from the manufacturer.
See you tomorrow.

 

[n141311]

Hi All,


@Chalked came over today and was super helpful. Came up with a design along the lines of have a couple of boilers in tandem and arranging the pipework in 36mm branching off in the remaining part of the house, leaving open the option to add a water storage tank in the future. The property has two mains water supplies – one is apparently 4.0 Bar (measured by original plumber) but the one we measured only came out at 2.5 bar.


Plan is to use the 2.5 Bar supply for toilets (already plumbed in that way by original plumber) and the other mains bar for everything else. If it turns out that demand is high and we suffer from poor pressure due to mains water, I’d then look to add a duty point tank in the future with piping already in place for a pump capable of 120 litres per minute flow rate. But I’m hoping all is good without having to go down that route


Here’s what I’m looking to go with in interim, let me know thoughts:


Proposed Equipment


· Go with unvented indirect cylinder approach and Grohe showers at 9.5litres per min

· 1 x RM Stelflow 400 Litre Indirect Unvented Stainless Steel Cylinder £885 inc VAT

· 1 x RM Stelflow 300 Litre Indirect Unvented Stainless Steel Cylinder £616 inc VAT

· 1 x Esi Dual Cylinder Thermostat to prevent legionalla – is this still needed for the RM cylinders?

· 2 x Worcester Greenstar 32CDI Compact Combi ERP Boiler £1206 inc VAT

· 2 x Worcester FW100 weather compensator £187 inc VAT

· 1 x WORCESTER WAVE SMART HEATING CONTROL £211 inc VAT

· Total equipment: £4,498 inc VAT


Few questions:


1. The cylinder pricing seems too good to be true – what am I missing here? I want to avoid buying duff equipment

2. Are the selected boilers any good in terms of running efficiency and reliability / durability? Radiators will require about 38kW. Chaulked recommended getting a total of about 60kW so I figure two 38s should be more than enough.

3. The weather compensator seems a bit crap. Is it worth the outlay in people’s opinion?

4. @Chalked - where plumbing should take 35mm from plant room for other side of house, should he branch off into 28 and then into 15 when he gets to shower / rads?


Links:


· RM Stelflow 400 Litre Indirect Unvented Stainless Steel Cylinder

· RM Stelflow 300 Litre Indirect Unvented Stainless Steel Cylinder

· Worcester Greenstar 32CDI Compact Combi ERP Boiler

· Wave smart heating control - 7716192072

· Worcester Greenstar FW100 Weather Compensator

 

[ShaunCorbs]

1, down to personal opinion and what your budget is my preference is gledhill

StainlessLite Plus Indirect - Gledhill

2, very good (my brand of choice) but thats a combi you have linked / talked about, you want a heat only boiler/regular

something like this

Worcester Greenstar 40CDI Classic Regular ErP Boiler

Vitodens 200-W wall mounted gas condensing boiler - Viessmann UK

ecoTEC plus - Vaillant

3, wouldnt go with weather comp, just invest in a decent simple control system (chalked im sure will agree with this)

 

[Chalked]

Hi
Your missing quite a lot
My spec was
2 rm 300 cylinders or preferably ACV same size.
2 vaillant system boilers giving a total of 60kw
Low loss header.
Suitable sized main heating pump
Mixing valve to give hot water priority
Vaillant sequence controller
Duty point pump set to give 120 lpm

This will need 42 mm primaries and connecting pipework
Motorised valves to all circuits

Think you may find your closer to £10,000 for materials
Regards
Paul

 

[n141311]

Hi
Your missing quite a lot
My spec was
2 rm 300 cylinders or preferably ACV same size.
2 vaillant system boilers giving a total of 60kw
Low loss header.
Suitable sized main heating pump
Mixing valve to give hot water priority
Vaillant sequence controller
Duty point pump set to give 120 lpm

This will need 42 mm primaries and connecting pipework
Motorised valves to all circuits

Think you may find your closer to £10,000 for materials
Regards
Paul

Hey thanks! What size should the main heating pump be in your opinion & any recommendations for a brand I should go for?

Finally, if 42mm primaries go in, what would you recommend secondaries at - 22 or 15mm?

 

[king of pipes]

Chalk is on the right track N14 dump the worcester wave and you will need a bespoke control panel built to control your system time, tempreture control and weather comp will be built in this with a programable room thermostat in each room this may help you the last two projects i did we used Ideal Evomax worked very well . wishing you all the best kop

 

[ShaunCorbs]

Chalk is on the right track N14 dump the worcester wave and you will need a bespoke control panel built to control your system time, tempreture control and weather comp will be built in this with a programable room thermostat in each room this may help you the last two projects i did we used Ideal Evomax worked very well . wishing you all the best kop

Wouldn't go ideal