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

[LordWest]

Hello all and Merry Christmas,

We are in the process of planning the replacement of our 50-year old heating boiler serving a residential block of 12 flats with a total of 60 radiators. It is a vented single-pipe heating system, which has not been properly maintained, and we only recently installed a commercial magnetic filter to filter out as much sludge as we can prior to the replacement. We will be installing a 100kw boiler. I know that we could also install two 50kw boilers, but this is a matter for a different post. A heat exchanger will protect the new boiler from the old vented system. Our installer suggested that we use the following pool heat exchanger, because it has 2 inch connections matching our 2 inch pipes and also has larger waterways so that it does not get clogged.

POOL HEAT EXCHANGER NORDIC B300 88KW (300KBTU/H)
Pool Heat Exchanger NORDIC B300 88kW (300kBTU/h) - https://nordictec-store.com/b-line-pool-heat-exchangers/171-pool-heat-exchanger-nordic-b300-88kw-300kbtuh.html

How suitable is this pool heat exchanger for our purposes? I am concerned that it may not be as efficient as a normal heat exchanger. Also, the suggested heat exchanger is 88kw, yet the new boiler will be 100kW.

I can order a normal heat exchanger with 2 inch connectors and to address the clogging issue I could use a CMX inline filter like this one here from Addey: MagnaClean CMX® | ADEY - https://www.adey.com/product/magnaclean-cmx The medium and large models can also be used inline.

I would appreciate your feedback.

Below is information for the pool heat exchanger:

POOL HEAT EXCHANGER NORDIC B300 88KW (300KBTU/H): €319.99 VAT included
Pool&Spa Heat Exchanger B300
Nordic Tec B-Serie
Nominal Capacity: 88kW
based on 60 °C difference between heating and heated medium (water to water),
with counter-courent work

Material: Stainless steel 316L
Heat Exchange surface: 0.64 m²
Connections: 2x 2" & 2x 1 1/2"
Important Note: If one of media is glicol, the capacity will be only 85-90% of nominal one
Pool&Spa Heat Exchanger B300

Nordic Tec B-Serie
Technical Details:
Nominal value 88kW (power/capacity) is based on 60 °C difference
between heating water and pool water (calculations are different for other media).
If there is other temperature difference, the capacity is following:
60 °C = 100%
50 °C = 85%
40 °C = 70%
30 °C = 55%
The nominal flowrates values are also required to achieve the declared capacity.

Nominal flowrates: 42/325 l/min (one of opportunities)

Pool Heat Exchanger NORDIC Tec B300 88kW ( 300 kBTU/h )

Swimming pool heat exchanger B300 90 kW- full catalogue of pool heat exchangers by Nordic Tec with quick delivery in every European country.

nordictec-store.com

 

[ShaunCorbs]

No as normally pool hex are slow flow rates and also low surface area

Better Plate Heat Exchanger NORDIC Ba-27-30 1 1/4" 175kW - https://nordictec-store.com/ba-27-serie-0027mplate-54-thread-/84-347-plate-heat-exchanger-nordic-ba-27-30-1-14-175kw.html#/52-en_accessories-exchanger_only_without_accesories

 

[Gasmk1]

Use a plate heat exchanger so you basicaly have two systems

 

[LordWest]

Is there a plate heat exchager with 2 inch connectors (to match our existing pipe) and with wide enough waterways so that they do not get clogged?

 

[ShaunCorbs]

Plates don’t like dirty system so you might need a cleanable one with individual plates this won’t be cheap

 

[LordWest]

What do you think of the Addey CMX as an inline filter prior on vented system's return to the plate heat exchanger?

 

[ShaunCorbs]

Good for metal particles but not good for everything else

 

[LordWest]

The CMX uses 5, 10, 20, or 50 micron filters to capture non-metalic particles:

Plumbing Supplies | Plumbing Materials | Plumbing Superstore®

Plumbing Superstore is one of the UK's leading online plumbing suppliers, offering John Guest Speedfit, Armacell, Pegler Yorkshire and more.

www.jtmplumbing.co.uk

 

[ShaunCorbs]

That’s perfect strange adey don’t spec it on there website

 

[LordWest]

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

 

[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.