Buffer Tanks - 2 or 4 port connections

[missplumb]

This is why we don't use the 2 port method. Always have heat and boiler only fires on demand from the buffer

 

[Ermintrude]

2 port is a buffer 4 port accumulator which incorporates buffer. I've just fell off a ****ing wall in the dark. Should bay more attention to where I'm walking the dog at 23.17

 

[Nostrum]

As Worcester said you could use the hot water module on the buffer and pipe the boiler direct to the buffer and come out the other side to your heating. You then add the middle sensor to help monitor the buffer charging status. Difference between the two schematics you've shown is the ETA shows a shunt circuit with mixer valve, the Froling does not.
We have always used the 4 port buffer system, we set top of buffer to 80 min with 5 deg hysteresis and bottom off at 70 deg. We find that the systems are never short of heat as the buffer is always already 70% charged and boiler only fires using buffer sensors only.

That's how I would have done so prior to this conversation, but if you are being recommended to pipe it in another way to increase efficiency then you've got to look at why?

For me, efficiency is top of the list, after all, that's what it is being sold on. For you perhaps being non domestic, efficiency is lower on the list because of the non domestic RHI returns.

The domestic RHI covers the majority of the upfront cost but for it to really stack up financially, it needs to be as efficient as possible for the long term.

 

[missplumb]

For non domestic rhi, it's more about making the boilers last the 20 years, when we commission and put the fga on, we still have them running at 92-94% efficient, it's what the rest of the system does with that heat.
Ermi, a 2port would be used as an accumulator and the 4 port would be the buffer as it is inline

 

[Nostrum]

Just spoken to the technical team at ZCF. Very interesting and the boilers controller is smarter than I first thought.

The controller can load the buffer and export at the same time. On the P1 and P4 the modulating pump is purely for buffer loading. The boiler uses the internal water ways as Worcester talked about to divert flue gases through various sections of the boiler to achieve the required return temperature, eliminating the need to a return riser. If the buffer temperature drops, the buffer pump will run and the boiler will charge the buffer to the desired set point and provide output for export until it cannot modulate low enough to continue running. When this happens the boiler will switch off, buffer pump goes off and export will come from buffer only by reversing the flow on that section of pipe. So interestingly, the boiler and buffer don't appear to be able to output simultaneously.

The mixing valve ensures water is only circulated through the export with a minimum temperature as well as a set flow temp. The ESBE controller can also be directly controlled through the boiler controller for weather compensation for blended heating flow but maintain the higher set point for the buffer.

 

[missplumb]

Interesting, mind you ive not looked at the Froling pellet boilers as all we do are chip.

 

[Nostrum]

Same setup for chip

 

[Nostrum]

Even upside down as well!

 

[missplumb]

Yes but that has a mixing valve which allows the boiler to fire and run whilst drawing from the buffer

 

[Worcester]

Yep, we're back to the capabilities of the controllers and boilers. With the changes to the RHI, we're finding that the clients are also looking at the most efficient way to control the heating, and using the built in controllers in both ETA and Froling you'll benefit from weather compensated flows to the heating circuits and hence higher efficiencies from the boilers.

If you're not using the built in controllers, then the next most efficient is to use the 4 port buffer.

Next thing is self learning optimised start - we have that built in to our heating circuit controllers that we use with underfloor heating and heat pumps - typically the Heatmiser controls, they offer both comfort levels (i.e different temperatures at different times of day) as well as optimised start. At the moment I'm not aware that either ETA or froling offer optimised start - YET

 

[Nostrum]

Windhager controls have optimum start but they're in my opinion not very user friendly!

 

[missplumb]

We don't use the built in controllers as most of our systems are district heating pumped from a remote plant room to PEX so temperature control becomes a bit more awkward

 

[Worcester]

Are you mixing the flow as it leaves the buffer to keep the temperature down in the heat distribution mains? I am aware of a few doing that so as to allegedly prolong the life of the heat main.

 

[missplumb]

No, it generally leaves the plantroom at about 80 and according to the rehau rep, the pipe can easily cope with them temps fire the duration. I don't see the point in heating the buffers up and then cooling it before it leaves

 

[Worcester]

The reason for different temperatures is to operate all parts of the system at their most efficient temperatures.

Biomass boilers work well with high output temperatures, and controlled return temps. (say 80/60)

Most heating systems for houses in a retrofit environment should have been designed for condensing boilers, so would be expecting 65 flow /55 return.

You lose more heat through a district main pumping at 80° than at 70° because of the temperature gradient.

Do you therefore mix down at point of use? If not then you'll presumably that means greater cycling of the end user heating system, are the end user control systems updated? - Are the end user heating systems rebalanced and flow / return temperatures of the radiators optimised as part of the installations?

There are loads of extra efficiencies to be had that way. So far all our clients are using significanlty less than predicted when they have comprhensive heating management systems in place.

 

[missplumb]

Where necessary our temps are reduced at point of use but the reason for the higher temps is that the systems we retrofit into are old stone stately houses with over 100 rooms, old column rads, no temperature control and they are tight with they're money. They are not interested in altering the internal plumbing because "it worked before on the oil boilers" and because we are financing the systems anyway they don't want anything disturbed because other than a cheaper fuel bill, they don't get anything out of it.

 

[Nostrum]

Unfortunately there are buildings out there now that have never been heated before as its not required, with a biomass boiler installed burning wood for the fun of it. Like wise although a renewable technology is being used, energy efficiency goes out the window as it has an opposite effect on the repayments. It all makes a mockery out of the whole scheme really.

We went to see a district system in North Devon, no lagging on any of the pipe work, all the pumps and HIUs purposely fitted in outside 'sheds' with no insulation etc

In some respects I'm glad the tariffs have dropped. I'm in it for the long haul and just hope the domestic tariff dropping is enough for the gold rush installers to move on, leaving the rest of the money to fund the customers who make the most of it.

Oddly we are getting more enquiries now for biomass then were we 2 months ago. Fortunately the customers aren't solely interested in it for any return. I just hope it continues like that!

 

[Worcester]

Yep, it's one of those anomalies, if you're metered, you'll consume as much as possible. Even in the domestic market, when we install systems to maximise efficiency, if they aren't using up to the EPC figure, then open the windows and wind the heat up else you'll never get the maximum back, and when the payments are greater than the cost of fuel that's what the clients (some of them not all) will do.

 

[missplumb]

I agree, but there is a big difference in thinking between the domestic customers with sub 50kw boilers and the larger commercial customers we have. Wealth breeds wealth, that's all they think about - how much they can get for least outlay. Domestic customers i guess would be much more receptive to having the most efficient controls and systems fitted as the benefit to them is cheaper bills.
We've been to see installations on farms where they have installed copper pipes in the concrete yard to warm the tractor tyres! !!!! And warm air blowers fitted externally .

 

[Nostrum]

Yep, it's the way of the world. People will find a way to make money out of anything. They should have sewn up the loop holes long ago, somehow. with the amount of money they are giving away they should be doing more inspection to check eligibility. Perhaps they will, I hope they do.

 

[Worcester]

Just for info read here, the press rumors are circulating like wildfire that there will be an announcement at 7am tomorrow morning...
Here we go again- Feed in tariff cuts to come in weeks | Electricians Forums

Got my DECC twitter feed on ...

 

[Nostrum]

The rumours have been kicking around for solar and on shore for a while, hopefully not a repeat of 2011, do you still do much on the solar side?

RHI is guaranteed until 2016 I believe? Although judging by that meeting, there doesn't seem to be much in the way of security for it beyond then.

The difference with solar/wind and renewable heat is that solar is an emerging market still and a lot of money has gone into the R&D of the technology, which has led to a sharp fall in manufacturing costs. Much of the renewable heat market already existed, we've just been late adopters to it all.

As a small company we're very competitive and can often spec a much better system for less than our competitors. Theres not much room for movement, the capital cost won't come down like it has with wind and solar, maybe it could for non Domestic, the latest cuts will soon see. In fact the RHI may have inflated the installation costs at the beginning?

 

[Sparkgap]

We put in a couple of pellet boilers to feed a couple of primary schools about 9 years ago. Absolute disaster! Ripped out one after a couple of years and put oil back, other went about three years later, a year after the manufacturers replaced the boiler with another! :banghead:
One site didn't have a buffer tank to start with, soon had the biomass boiler bods changing their minds and saying it needed one putting in as boiler needs to develop a temperature difference from top to bottom to provide a load. Did that but school eventually got sick and tired of the boiler and wanted it out.
Also did a survey at a new PFI school in Bedford four years ago: both Hovel pellet boilers had broke within 6 months to a year of opening, school didn't bother fixing them and happy to run on backup gas boilers as problems with dust from pellet store was causing problems.

 

[missplumb]

we have taken out quite afew biomass boilers from schools, but when you looked at the system, they were never designed correctly and tbh, the boilers were s~*t, but 10 years ago we didnt know any different. we have replaced some of these boilers with new ones, altered the systems and controls, and had them accredited to Rhi which makes a huge difference to them - and now they are much happier using them.
i just think there wasnt enough technical knowledge in the uk about biomass back then!

 

[Sparkgap]

we have taken out quite afew biomass boilers from schools, but when you looked at the system, they were never designed correctly and tbh, the boilers were s~*t, but 10 years ago we didnt know any different. we have replaced some of these boilers with new ones, altered the systems and controls, and had them accredited to Rhi which makes a huge difference to them - and now they are much happier using them.
i just think there wasnt enough technical knowledge in the uk about biomass back then!

The other issue is staff not wanting to get dirty clearing the ash. One site the caretaker said it wasn't in his job description to clean out the boiler!