Combi or unvented direct cylinder?

[RickyLee53]

This cylinder is tripple coil, not sure on the brand, but might be the way to go.

http://www.discountedheating.co.uk/...wave_Plus_Triple_Coil_Indirect_Cylinders.html

 

[Agile]

The unit will exceed the performance of a 300 litre unvented tank
with only 170 litres of storage and therefore has a smaller foot print.
You would install the ultrapower where the cylinder would have gone.
It will be smaller foot print. The ultrapower can supply up to 36litres a minute of hot water.

Can you justify that technically?

Taking into account the 300 li cylinder being reheated during the draw off ?

 

[ALEC1]

a recirculation loop just runs from cylinder to hot taps and back to the cylinder..it is usually timed and must be well insulated...it reduces water and gas wastage as the hot arriives at the tap much quicker...


bathing temperature is about 38c-42c. you mix in the bath so your hot water requirement is much less...

 

[RickyLee53]

The unit will exceed the performance of a 300 litre unvented tank
with only 170 litres of storage and therefore has a smaller foot print.
You would install the ultrapower where the cylinder would have gone.
It will be smaller foot print. The ultrapower can supply up to 36litres a minute of hot water.

Can you justify that technically?

Taking into account the 300 li cylinder being reheated during the draw off ?

I also thought this, He could be correct, if the flow rate was 20lpm or similar, and the boiler is "clever" enough to figure it can use 12lpm from the combi and 8lpm from the tank. I doubt this is the case though.

I'm still not sure how much usable hot water I will get from the 300l tank though.

300l at 60*, 30l per minute for 5 minutes is 150l used. By this point the temp would be 40 degrees plus maybe a couple from 5 minutes of heating. Maybe I've missed something?

 

[RickyLee53]

That is something worth looking into I guess.
To me though it looks like it could cost more. Yes the hot water arrives quicker. But you also have a much larger surface area for heat loss, an extra pump which could fail, and uses power etc etc. It would be nice, but i'm keeping the pipe runs very small, apart from a couple which cannot be helped.

Very true on the bathing temp, however the water temp lets say is 60, so you'd need roughly 1/3 cold water. Realistically probably more like 25% given heat loss through pipes/bath etc. Also the 260litres quoted isn't to fill the bath completely.

a recirculation loop just runs from cylinder to hot taps and back to the cylinder..it is usually timed and must be well insulated...it reduces water and gas wastage as the hot arriives at the tap much quicker...


bathing temperature is about 38c-42c. you mix in the bath so your hot water requirement is much less...

 

[ALEC1]

I also thought this, He could be correct, if the flow rate was 20lpm or similar, and the boiler is "clever" enough to figure it can use 12lpm from the combi and 8lpm from the tank. I doubt this is the case though.

Thats exactly how they work...

yes recirc loops can be wasteful...

 

[RickyLee53]

I also thought this, He could be correct, if the flow rate was 20lpm or similar, and the boiler is "clever" enough to figure it can use 12lpm from the combi and 8lpm from the tank. I doubt this is the case though.

Thats exactly how they work...

yes recirc loops can be wasteful...

Interesting. So with my 30lpm flow i'd be using 18lpm from the tank, so I would get a true 10 minutes out of this boiler. About the same as I will from the 300l cylinder.

Could I do it so I had a cylinder and combi on the same circuit? Would this work? Its pretty unorthodox i'd imagine, and it would depend on the balance of pressure between the 2 I guess.

Today i've cut out 100 meters of old copper. 30 meters of which was 15mm to the shower! No wonder the shower was pitiful before! (electric)

I've just found another issue. I knew the "loft space" wasn't high, The roof's a low pitch, and the upstairs rooms have very high ceilings, (2.9meters) but the roof cuts into the rooms, so they are lower at the edges. the result is a loft that is 1.6 meters at the highest point. Realistically the tallest cylinder can be around 1.4 meters which rules out anything over 200 litres it seems.

However, I'm thinking the best way is to run 2 smaller cylinders. (unless you can get some horizontal ones?)

I could be miles off here but...

If I run 2 cylinders the advantages are, twice the coils.
Better distribution of weight (the house was built in the late 1800's) and until recent improvements wasn't the most structurally sound.

The other thing is put the cylinder into a room, or go for the Glow Worm.

Disadvantages. Cost to run and install.
My main concern is the balance. If the first cylinder has a slightly higher flow. All the water will be used, so the water would drop in temperature while the other cylinder still has hot water it would only be flowing slowly.

Can you get a controller, so when the water temperature at the output drops it reduces the flow or turns off the cylinder?

Thanks for putting up with the long/thinking out loud posts.

 

[ALEC1]

you will need a cylinder sensor which monitors the hotwater temperature as opposed to a thermostat which just tells turns the boiler on and off.

But with his level of technology you can't have two cylinders easily..


Dont forget that the system will be pressure regulated by a pressure reducing valve...and also taps will be flow regulated...look at them too...

 

[RickyLee53]

I've found a suitable Horizontal cylinder, buts it's over 2k. I could easily get 2 smaller cylinders for less than that, with about £500 left over for the controller. If there is such a thing.

I'm not sure what you mean with the pressure reducing valve? My incoming mains is only 3.6 bar. Do you mean a pressure reducing valve for the cylinder? I've seen most have around 3 bar input.

I've been looking for "high flow" tap's and shower's. At the moment I have can run the bath tap's and sink tap's and still not get 30lpm.

I thought about having a the bath fill through a custom jet from the Jacuzzi system, I could bore it out to 20mm or so at work, then once the water is a couple of inches deep it'd be silent to fill. I'd have to use a shower mixer on the wall or something but it'd be a much neater solution than regular tap's. The bath is completely sunk into the floor.

Like this

you will need a cylinder sensor which monitors the hotwater temperature as opposed to a thermostat which just tells turns the boiler on and off.

But with his level of technology you can't have two cylinders easily..


Dont forget that the system will be pressure regulated by a pressure reducing valve...and also taps will be flow regulated...look at them too...