Plate heat exchanger

[Bennett]

Hello everyone,

I have been reading posts on this forum for some time and find all your insight very interesting.
I was hoping some of you could help me with answering a few questions regarding using a plate heat exchanger.
Firstly, has anyone installed one of these:
Brazed plate heat exchanger for domestic hot water at high pressure.

I was hoping I could install one to supply a shower and bath with instant hot water. Much like a combi-boiler except the heat exchanger will be in the airing cupboard.
The system is a Y-plan with hot feed going to a vented cylinder. I would then have the hot feed to the plate heat exchanger come from the cylinder return. The thinking is that the water in the cylinder will help keep the feed to the heat exchanger hot when onll small demand for hot water is required.
Would this work? and is it allowed?
A alternative is to fit a flow switch on the cold main so when demad is required the boiler will fire up. Have another 3-port valve that goes to the cylinder flow a to the plate heat exchanger. But the seems much more complicated although the HW will not have to be switched on all day.

i want to avoid using a pump and the cost of a unvented cylinder can be costly?

Your thoughts are appreciated.

 

[mountainman]

I've seen things like these fitted in large properties with high hot water demand.
I doubt this piece of kit and the associated equipment would make it cost effective for a domestic installation.
Go for a pump, so much simpler and cheaper.

 

[Mike Jackson]

Pointless in my opinion unless it is fed with a boiler with a huge output. If you've got sufficient mains pressure get an unvented fitted.

 

[ecowarm]

With Mike need a huge output boiler or a thermal store

 

[Bennett]

Ok, thanks. Unvented I think then. How do combi-boilers cope with there heat exchanger? Is it because they are close to the heat source that the HW demand is met?

 

[Roger Welton]

The picture won't load for me but I have seen plate heat exchangers in a couple of old folks homes before, with the hw being continualy circulated round the main and reheated, seemed to work well, though they were on the end of some fairly hefty boilers!

 

[M.Joshi]

Picture doesn't load for me either! Must be a problem with the website.

 

[Bennett]

Well thanks again. I like the unvented system. Quiet with no pump and extra loft space. Cheers. Drinks all round.

 

[mountainman]

Website ok on my phone.
160kw heat transfer is a tad over the top for a domestic property IMO

 

[jtsplumbing]

160kw a bit undersized for your place mountainman 1 how do you keet th RR warm at night ?? :66:

 

[BLOD]

fitted a few heat exchangers with pumps & flowswitches in flats, that worked well.
DPS do it as a ready made piece of kit called highflow

 

[Bennett]

This is what I have been told from the manufacturer:

We supply an assembly which comprises:

Heat exchanger and housing

TMV mixing valve for hot water
Flow switch
Obviously the brass fittings and pipework

The TMV is already piped on to the heat exchanger and there are simply pipe tails for you to connect to. You get a wall strap so the assembly can be put on a wall if you need to.

When the customer turns on a tap, the flow switch senses the movement of water and sends the switched live to the boiler.

Simple as that!!

I know my description was different but I am in doubt of the hot water available and do not want to remove a cylinder that is working well but not to customer spec.

 

[Bennett]

I don't unerstand how a combi-boiler is different apart from the heat exchanger being located within the boiler?

 

[ecowarm]

One thing to think about, at the moment you have a store of hot water, if the power goes off you still have a certain amout of hot water.

Change and no power = no hot water

 

[ecowarm]

I don't unerstand how a combi-boiler is different apart from the heat exchanger being located within the boiler?

Where will you mount the H/E next to the boiler? on large commercial systems the heating is running 24/7 so the heat ex has instant hot water, If you are to mount away from the boiler, you turn on the tap, the boiler fires it heats up the water in the pipework between boiler and H/E to maybe 80c and then you will get H/W could be quite a delay and waste of water

 

[Bennett]

I agree. atleast with unvented I have a imersion heater plus on disscussion with the client a option for solar heating.

 

[Bennett]

ahhh thanks ecowarm. That is perhaps the reason why then, although sometime combi-boilers have long runs to their HW point, but then I guess that is bad system planing and a cylinder with bronze pump on secondry circuit should be used. I am trying to think slightly out the box but I think if it was a proven idea then it would be far more common rather than as stated in large industrial models.

 

[Mike Jackson]

You also need to look at the size of combi boilers to get a good flow rate. The smallest one is 24Kw but that gives a Paltry 9 l/min at 35 degree temp rise.