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.
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:
- 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.
- 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.
- 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.
www.adey.com
