Is a pool heat exchanger suitable for a communal heating system?

[ShaunCorbs]

It is listed on their website under "Commercial and Industrial:

Commercial | ADEY

ADEY Solutions delivers central heating system protection and maintenance for plumbers using MagnaClean magnetic filter technology removes black iron oxide from new and existing domestic and commercial central heating systems

www.adey.com

Sorry I mean the filter part it’s in the manual but you would of thought it’s a selling point

 

[LordWest]

You are right. It is not obvious they have filters, though the pdf does make it clear:

https://www.adey.com/storage/app/media/Commercial/MagnaClean%20CMX%20-%20Product%20Specification%20-%20March%202020%20-%20v.1.0.pdf

 

[Timmy D]

Speak to UK Exchanges Ltd, they can make plates for any output/connections you need. They have a large selection off the shelf.

If you call them, they will also spec the required plate for your supply/demand.

I’ve used them a few times. Reasonably priced, great service.

I know you said the design is for another post, but I’d seriously be considering 2 boilers and a low loss header instead of 1 boiler.

Like this. Multiple boilers/LLH/plates for heating/hot water.

 

[John.g]

Regarding PHE, because you need both the HW flow & return temps to be the same as the boiler flow&return then you need a very high output HX, around 550kw IMO with 3M2 hearing surface, a Nordic BA 60/50 might be suitable and give 100kw output. The BA -27-30, 175kw, 0.96M2 will only give ~ 33kw if my basic calcs are anyway correct.
If you email Nordic and state your requirements, ie boiler output, boiler flowrate&flow & return temps and heating flowrate& flow&return temps then they will suggest the exact fit for your system.

 

[LordWest]

Thanks Tim and John,

I am aware of UK Exchanges Ltd, which they seem to have a good reputation. They are certainly on my list.

Nordic has an interesting blog on their website about sizing.

How to choose a heat exchanger to connect a gas boiler?

Many Customers ask us how to size the right heat exchanger to connect a gas boiler with installation. We got a simple converter of heat exchange area of the exchanger to a nominal power of a boiler in kW. Feel free to check and use it!

nordictec-store.com

According to Nordic, for every 10kW of boiler output you need a heat exchanger surface of 0.3m2. Thus, a 100kW boiler would need a heat exchanger with a surface of at least 3m2, and they have advised me on what heat exchanger to get, preferably a brazed one.

The issue I am faced with is as follows. Our heating system has been badly maintained and I want to avoid the heat exchanger getting clogged. We recently placed a commercial 2’’ Magnaclean filter, but I am concerned that this will not be enough. I am faced with 3 options:

1. Install a brazed heat exchanger, which in principle is ideal and the most efficient. However, they usually come with waterways of 1.8-2.2 mm depth and can be clogged, despite having a magnetic filter. Magnaclean’s CMX commercial MIDI and MAXI filters can work as inline filters and if suitable then I could possibly use them with a brazed HE. The CMX come with 50 micron replaceable filters, which will certainly limit any clogging. But I am not sure if this will impact the flow into the return of the heat exchanger.
2. Install a shell-and-tubes heat exchanger (sold for pools by Nordic), which will not be as efficient as a brazed HE but will not clog easily. Our installer prefers this method for our circumstances.
3. Install a gasketed HE, which can be cleaned easily. Danfoss Sondex makes a gasketed HE that has 4.3mm depth in the waterways and thus would clog less and it is cleanable. However, they are also more expensive, and in theory they can leak.

Thus, this is the dillema I have.

Tim is correct that two boilers would be preferable to one, and the instalation he has done as shown in his photos are admirable. The reason we are likely to use one boiler is because the heating boiler is installed in the basement and ideally we would use existing flue. We would place a liner in the flue and the distance from the boiler to the top of the chimney stack is about 23 meters and they are a few 45 degree angles on the way up. A 100kW GB162 V.2 boiler allows us to have a flue up to a theoretical 50m high. Once you incorporate the turns, then this become less. If we use two 50kw GB162s then the theoretical distance becomes shorter and we may even have to use a slightly wider diameter liner. Thus, using one boiler enables to use a smaller diameter liner to ensure it passes through the flue and also we will not be close to the limit once we incorporate 45 degree turns. Note that this is not for a concentric flue, but just for the output. The air input will be from ventilation in the basement.

We have a separate WB 35kW CDI boiler for the hot water. The flue is in the front basement lightwell, but it would be a challenge to also have the heating boiler flue(s) in the basement lightwell, and in case I am told we are not supposed to. This is a conversion of two terraced houses in a conservation area and the building is grade ii listed.

 

[John.g]

A shell&tube heat exchanger might require multiply times the heating surface of a PHE but (thermal) efficiency doesn't come into it except the exchangers have no external lagging/insulation.

 

[siricosm]

Not sure I should comment, because I am just a DIY guy, but wouldn't a small buffer tank, or large vertical LLH work? The return from the rads would come in at the bottom, and the return to the boiler could come off half way up. If the water is not moving too fast, then most of the sludge should settle to the bottom. It would not give complete isolation, but combined with a decent filter on the boiler return, maybe that would be enough?

 

[John.g]

The LLH looked like a good suggestion but looking at the "HeatGeeks" presentation shows plenty of mixing if the conditions are right so defeats the "physical" separation requirement?.

Low Loss Headers: The Complete Guide For Efficient Design

The complete guide to Low Loss Headers. What are low loss headers and why would you need one? All you need to know directly from the experts.

www.heatgeek.com

 

[siricosm]

Hi John, That is why I was thinking a small buffer tank might work better, as the water would move more slowly, and give more chance for anything large to settle out. Plus you would not want the two returns across from each other like in the picture in your link, but rather staggered something like this:

I suppose a stainless tank around 90+ litres could be had for a few hundred pounds. Of course it would take up space, and you would have to up-size the expansion vessel accordingly (OP is going to seal this system, correct?). Another challenge might be to find a small tank with large enough connections, although some places will make whatever tank you want. In this case a tall thin tank would work best, basically just a larger volume vertical LLH.

 

[John.g]

There's that advantage all right, but the whole system has to be looked at, think its a vented single pipe system, whatever system is decided on and even with it cleaned out and depending on a successful result it may be deemed best to install a LLH or that buffer tank of a PHE or a shell&tube Hx, depending on installation space available.