Buffer Tanks - 2 or 4 port connections

[Worcester]

View from across the pond....
https://blog.heatspring.com/2-pipe-versus-4-pipe-buffer-tank-configurations/

Interesting post, a bit lightweight though considering his 'qualifications' and disappointingly from such an expert nothing new there that hasn't already been covered in this thread.

The BIG thing that he misses though is how Log gasification boilers work, and the REQUIREMENT to be able to use all the heat from the fuel load at the maximum efficiency.

Their are also the significant benefits of being able to apply weather compensation to the flow to the rads and still maintain the boiler at its maximum efficiency.

 

[Worcester]

Remember that the heat loss from the pipework will most likely be going into the fabric of the building, so be careful not to count it twice - it's common practice to include the pipe losses as part of the emmitter output in large systems.

Even so it sounds significantly undersized and a recipe for disaster.

With a stack that high, won't the bigger problem be too much draught?

IF you take it on, first part of the contract should include a design revue...

 

[Nostrum]

Cooling of the flue gases with such a large external run would be my concern, condensation etc. Although being an induced draft I'm not entirely sure if I'm honest.

The sizing tends to suggest that the biomass is to cover a base load ( buffers to smooth out and absorb heat main losses) with the gas boilers ready to fire for peak demands, hot water etc. I'd be interested to see the design calculations.

Where did you get the heat load figures from? 8kw for a flat seems high. 37kw to hot water would give a flow rate of approx 13-14ltrs/min. Even running a bath would would only require a demand at that rate of approx 5 mins.

 

[missplumb]

They were in the spec that Wilmot Dixon sent us as part of the tender docs. We gave them 3 options, we put in a ridiculously high price to cover all the penalty fines we would get for not providing enough heat via biomass, or we knock the energy centre down, and build a new one with a suitably sized boiler that will cover all heat load all at our cost and we collect rhi, or we speak to Leeds council and have the terms amended to a deliverable outcome. I think option1 is the only thing they will want to do.

 

[Sparkgap]

Cooling of the flue gases with such a large external run would be my concern, condensation etc. Although being an induced draft I'm not entirely sure if I'm honest.

The sizing tends to suggest that the biomass is to cover a base load ( buffers to smooth out and absorb heat main losses) with the gas boilers ready to fire for peak demands, hot water etc. I'd be interested to see the design calculations.

Where did you get the heat load figures from? 8kw for a flat seems high. 37kw to hot water would give a flow rate of approx 13-14ltrs/min. Even running a bath would would only require a demand at that rate of approx 5 mins.

Looks like an existing block, so probably insulation not all that great. Also what size of flats there are. Just looking at heat demands and HIUs for some new 1-2 bed flats at the moment, which are working out at between 3-5.5kW each for heating.
Hot water loading for HIUs is about 35-40kW depending on make then you take into account the coincidence factor (I'm using DS439) so for 249 flats it comes out as about 0.08.

I agree with Worcester about having weather compensation for the rads and if this was individual condensing combi boilers to each flat it would enable the boiler to work at maximum efficiency. However in this case any compensation would have to be done after the HIU on an individual flat basis, probably not feasible, as you'd still have to keep the mains at full temperature 24/7. Best for the biomass to tick over keeping the buffer/mains satisfied and the backup gas to kick in when needed.

 

[Worcester]

Option 3 is the best 'win/win' solution, however that requires them to admit that the existing installation isn't up to the job, which they are unlikely to do.

The Council won't have its own heating experts and will have appointed a consultant to advise them, it would take a heck of a lot to admit that the consultant was wrong.

Knowing the way councils work, they are likely to choose option 1 and then when (if) you win it, prepare option 2, the problem you'll have is that they'll then want to go to tender for option 2... Councils!!

 

[Sparkgap]

The Council won't have its own heating experts and will have appointed a consultant to advise them, it would take a heck of a lot to admit that the consultant was wrong.

Having worked for three councils, two contractors and done consultancy work as well it now seems that many councils have got rid of the people who actually know how things work and just hive off stuff to some favourite consultancy! The consultants in their turn don't seem to bother designing the jobs and just churn out a load of standard spec clauses and expect the contractor to design and price the job in only a few weeks :83:
My latest job at a school was tendered out by some :asshole: who threw several pages together, missing a load of stuff, didn't bother to do a proper survey of the site to actually find out what needed doing..... you get the picture! And this on a job which needs to be done ASAP and is probably in the region of £300k. Must have money to burn!!!
As I said to the estimating guys, make sure you clearly state the exclusions in our price coz I can see somebody coming a cropper.

 

[Norcs]

There's always option 4.
Knock that great ugly monstrocity off a building down.
Which floor is del boy on?

 

[Norcs]

All councils have money to burn. That's why you pay extortionate council tax.

A worker at my local council office blew the lid on the amount of tar that they dump.

An official on a large salary goes out with some yellow paint and marks the pot holes that he has decided should be filled.
For some reason the tar gang are not allowed to just fill every hole they come across.

The tar gang goes out and fills the holes he has marked and at the end of the day several tons of expensive tar is dumped which was paid for by tax payers.

 

[missplumb]

The original tender design was done by consultants in London and a spec produced for pricing. Wilmot Dixon won the contract on that spec. When the contract was signed, the consultants pulled the design and said WD had to use their own design to which they just rebadged the original with out checking to see if it will do the job, so the responsibility lies with them. Hence the QS sat with his head in his hands when we said it won't work. No one had told him why, the just refused to price the job.

 

[Sparkgap]

The original tender design was done by consultants in London and a spec produced for pricing. Wilmot Dixon won the contract on that spec. When the contract was signed, the consultants pulled the design and said WD had to use their own design to which they just rebadged the original with out checking to see if it will do the job, so the responsibility lies with them. Hence the QS sat with his head in his hands when we said it won't work. No one had told him why, the just refused to price the job.

So, if the job was tendered on a design, the design was pulled and they had to do it themselves (which presumably wasn't included in the original spec)..... let's see, redesign from the original, V.Os/AIs, I'm sure somebody looking at it on the contractual side could make a very good case for ££££££ of extras! :grin:

 

[missplumb]

Possibly, but I think now the system has been commissioned, the council will not accept any AI's or variation orders for major system and plant alterations. WD will lose out big time.

 

[missplumb]

had an email today from Wilmot Dixons QS basically saying to give them a list of what our demands are to take the installation on and give them a price for it. They are getting desperate as the council want to take ownership of the system to claim RHI but WD cant fulfil their contract without having an O&M agreement in place. could be ££££££'s for us and a good 1st step for our new business venture.

 

[Sparkgap]

Basically, a complete redesign incorporating the existing plant plus whatever extra is needed to get it working correctly. At least an additional boiler, pump sizes?, incoming gas large enough? etc. etc.
Merry Xmas!! :clap:

 

[missplumb]

exactly, we need to redo all the calculations to check everything will work, the hydraulics are ok. dont think we'll put another boiler in but will get the council to accept that a 200kw boiler is not gonna cover 70% of a 1.4mw of peak demand. although the biomass will be running flat out and they will get the full rhi, they have to realise its a token boiler and a tick in the renewables box but thats about it and the gas boilers will be doing most of the work.