Mega Flo vs Thermal store

[Onetap]

Two 300 litre cylinders are OTT, IMHO, as is giving up that area of a house for plant.

A 300 litre MF will only do 2 X 15 minute showers before it starts to run cool.

Thats the stored hot water; it will do more because the coil will start to heat the water once a few litres have been drawn off and it will reheat more water in 15 minutes.

Another option might be an unvented cylinder with two additional tappings. These are connected to a plate heat exchanger, as in this;

http://www.heatweb.com/techtips/hx/ta.html

Ignore what they say about legionella. Note that they sell components to make a conventional boiler act as a combi, but without the maintenance problems of having the combi components shoe-horned into restricted boiler casing.

The DHW is usually heated by the unvented cylinder. At times of high demand, all the output of the boiler goes to the PHX (space heating goes off) and the water is reheated as fast as the boiler allows. The PHX will scale up in London (unless you have a softener); while it is off-line being descaled, you still have DHW from the OSO/Megaflo.

The PHX has a large heat-exchange surface area, so it re-heats the water much faster than the coil in the cylinder.

It is similar to what Jonas (Drivel) has suggested above ( how embarrassing is that?) but you are not solely reliant on one PHX. Similar systems are being installed in hotels and offices (usually with 2 or more PHXs and no coil in the storage cylinder) replacing large storage water heaters.

 

[SimonH2]

And on that subject, I was browsing on the internet and I came across this ...

http://wiki.diyfaq.org.uk/index.php?title=Drain_Heat_Exchanger[/QUOTE]
The problem with that (it was rowed about) is that it has a huge fouling factor due to the accumulation of hair (long, short and curly) soap scum, limescale and other hideous things that go down the drain. It would need regular cleaning and the heat excahnger proposed was plastic!

Yeah, I wasn't too impressed with some of it. The idea itself is sound, but it's a very low grade heat source so quite low temperature differentials. I'd not want to put the grey water down anything but a plain pipe - and then the challenge is getting the water to run down the walls rather than dropping down the middle.

 

[indus]

Thanks guys.

My issue with the Mikrofill is that wouldn't it be another system (like my TS) that 99% of plumbers/heating techs wouldn't understand and so lands me in the brown stuff when there is a fault?

Anyway given that the thread has gone for so long and things may have become confused shall we start with a blank page? If you were to design my system from the ground up rather than fix what I have what would you do?

I'll provide information and please tell me what else you need to know.

1) Approx 3200 sq ft

2) Five showers and one or two baths

3) Approx 23 rads

4) Please assume that I have enough pressure/flow to run any system and I can change my gas supply to do the same.

Thanks

 

[Dan Robinson]

We have fitted several of those DPS (now Specflue) units and their performance is excellent. The idea is to have a large output system boiler to drive the plate as hard as possible.

Mikrofill only do huge units mind you.

Here are the last two DPS ones we fitted. Rather embarrassingly, the first one was one of the last ones DPS made before going under, and there were several components incorrectly fitted. Made for a rather noisy reheat

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• Dan Robinson
• 17 Oct 2011
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• Dan Robinson
• 17 Oct 2011
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[Dan Robinson]

Indus. The second photo there is a VERY similar base requirement to yours - albeit peak demand was far higher than normal loads - which is another advantage of the system - you are heating a fraction of the water.

 

[JonasX]

Thanks guys.

My issue with the Mikrofill is that wouldn't it be another system (like my TS) that 99% of plumbers/heating techs wouldn't understand and so lands me in the brown stuff when there is a fault?

The 300 litre Mikrofill delivers 539 litres in 10 ins. They will have dealers to do any servicing.

The best is a combi. the cold inlet is taken from the bottom of a direct cylinder. The DHW outlet is taken to the top. A cylinder stat switches a bronze pump on the cold inlet to the combi. Very simple and cheap and ultra efficient. The combi needs to accept hot water on the cold inlet. All legal.

 

[Biggles..]

With those sort of DHW figures I'm really surprised that people aren't advising things like rinnai water heaters,or even a lochinvar/Andrews/AO smith.
These are going to give far superior DHW than any plate/thermal store.

 

[Onetap]

Yeah, I wasn't too impressed with some of it. The idea itself is sound, but it's a very low grade heat source so quite low temperature differentials. I'd not want to put the grey water down anything but a plain pipe - and then the challenge is getting the water to run down the walls rather than dropping down the middle.

Discussed here, at length;

https://groups.google.com/group/uk....st&q=nt+draIN+heat+exchanger#6d95802e8142cf01

Some bloke wibbling about legionella and Dr. Drivel drivelling.

I need to get out more.

 

[JonasX]

DPS (now owned by Specflue) used a 250 litre cylinder and plate heat exchanger to heat it and a 24 kilowatt boiler. To supply a house with multi-bathrooms and 6 bedrooms.

http://www.heatweb.com/products/cases/CaseStudy1790.html

600 litres? get rid of him. Does he still think England have just won the world cup?

 

[JonasX]

With those sort of DHW figures I'm really surprised that people aren't advising things like rinnai water heaters,or even a lochinvar/Andrews/AO smith.
These are going to give far superior DHW than any plate/thermal store.

They will not. Just uprate the cylinder and plate size and DHW delivery is improved to whatever you like.

 

[Biggles..]

Anyone specified a heat web/DPS unit lately,I did the other week it was nearly £6k,would have cost no more than £2.5k previously,spec flue have put prices up beyond belief.
The units aren't that good to justify those prices,which is a shame as I've fitted loads.

View media item 19282
That does 6 bathrooms with 2 baths and 5 mira discovery showers quite easily.
Only reason I went for it was for solid fuel input otherwise 2X HD70i would have given the same if not better flow/temperature range,and based on today's DPS prices would have been 2-3K cheaper.

 

[Dan Robinson]

The TS/TB have gone silly prices... The Amazons aren't too bad IIRC.

 

[JonasX]

Anyone specified a heat web/DPS unit lately,I did the other week it was nearly £6k,would have cost no more than £2.5k previously,spec flue have put prices up beyond belief.
The units aren't that good to justify those prices,which is a shame as I've fitted loads.

View media item 19282
That does 6 bathrooms with 2 baths and 5 mira discovery showers quite easily.
Only reason I went for it was for solid fuel input otherwise 2X HD70i would have given the same if not better flow/temperature range,and based on today's DPS prices would have been 2-3K cheaper.

What size is the cylinder doing 6 bathrooms?

 

[Norcon]

That does 6 bathrooms with 2 baths and 5 mira discovery showers quite easily.

Is it plate dhw delivery?
Edit. Think I see it on the left hand side. Nice job.

 

[Biggles..]

Yes it's plate heat,but like I said chosen because of the 40Kw solid fuel burner.