Biomass domestic boiler issue

[Bloders]

that makes some more sense.
do you have details of the heat exhanger?

 

[rollestonpark]

So sounds like the kero boiler's heat does not go through the heat exchanger to get into the house heat network. It goes direct.
So probably the heat exchanger is too small, and/or there is insufficient flow of water through the heat exchanger on the house side (pump on slow setting or not big enough, on the house side)

We use a low loss header to exchange heat with the house, could try that... but this will mean the water in the biomass boiler and the house will become 1 and the same. (not an issue for us, but maybe for some)

 

[mountfarm]

that makes some more sense.
do you have details of the heat exhanger?

I’ll check tomorrow

 

[mountfarm]

So sounds like the kero boiler's heat does not go through the heat exchanger to get into the house heat network. It goes direct.
So probably the heat exchanger is too small, and/or there is insufficient flow of water through the heat exchanger on the house side (pump on slow setting or not big enough, on the house side)

We use a low loss header to exchange heat with the house, could try that... but this will mean the water in the biomass boiler and the house will become 1 and the same. (not an issue for us, but maybe for some)

Yes correct the kero is not connected to the biomass. It’s stand alone deliberately due to the ofgem.

There’s a main pump in the biomass room 100m away. Not sure on size but it’s physically big. Took 4 blokes to lift it into place as it’s fixed about 6ft up in the air. Then there’s a booster pump in the house to ensure flow is maintained. This is a much smaller pump though. Again not sure the size off the top of my head but I’ll check tomorrow.

 

[Frankzy]

if we put the motorised valve into manual then we get more heat in the house but then the return pipe is also red hot so we are sending heat back to the biomass boiler.

Seems pretty clear cut that the heat exchanger is not actually exchanging much heat..
We warm roughly 300m2 with 40 degree water and the hot side of the heat exchanger only needs to be around 60 to keep the house at 40.

 

[mountfarm]

The original exchanger which is currently removed is Nordic Ba 32-20. This was temporarily replaced with a used Bowman 3705 3 GM just to try it as it’s much bigger. I don’t know the size but they are used in the marine industry and commonly found in swimming pools. The plumber suggested we try it. https://www.bowman-tr.com/en/u-marine-heat-exchangers_20.html
The plumber (didn’t fit the biomass system) has suggested today we run both of the above in line as the next trial.

 

[mountfarm]

Seems pretty clear cut that the heat exchanger is not actually exchanging much heat..
We warm roughly 300m2 with 40 degree water and the hot side of the heat exchanger only needs to be around 60 to keep the house at 40.

The house is about 400sqm over 3 floors. It’s got double glazing which is new recently but it’s not properly insulated as there’s no cavity wall and the 3rd floor is bedrooms into the apex so no scope to run insulation as such.

 

[rogeriko]

You need a flat plate heat exchanger, not an exchanger with pipes inside. Flat plates work 5 times better than tubes for the same size. https://www.uk-exchangers.com/heat-exchange-products/brazed-plate-heat-exchangers/ Make sure you plumb it the right way around. One end is hot the other cool.

 

[rollestonpark]

You need a flat plate heat exchanger, not an exchanger with pipes inside. Flat plates work 5 times better than tubes for the same size. https://www.uk-exchangers.com/heat-exchange-products/brazed-plate-heat-exchangers/ Make sure you plumb it the right way around. One end is hot the other cool.

agreed you need 1 of these and the correct size for the heat output (or bigger) coupled with the correct pump size on the house side.

 

[mountfarm]

You need a flat plate heat exchanger, not an exchanger with pipes inside. Flat plates work 5 times better than tubes for the same size. https://www.uk-exchangers.com/heat-exchange-products/brazed-plate-heat-exchangers/ Make sure you plumb it the right way around. One end is hot the other cool.

The original looks just like that as mentioned above - see below. Google tells me it’s 125kw

http://www.lednet.info.pl/pdf/en/Ba-32-20.pdf

 

[rollestonpark]

That looks OK... is it blocked inside in anyway?
is the pump working and big enough on the house side?
is there any valves or mixers working incorrectly and thus not allowing water to go through it properly...

 

[wilber]

I know someone who's heat exchanger was flushed and they where shocked at the amount of sludge that had built up in. So maybe needs a clean?

 

[Wisconsonian]

If this system worked before, and doesn't work now, then it's not a problem with the wrong heat exchanger. The plumber who suggested switching the heat exchangers, and now suggests putting them inline, has an advantage of having seen the system in person, but has still given bad advice. Get a different plumber, or heating person. If you don't know what is going on, putting them both inline is likely to reduce the flow and reduce the heat transfer. Unfortunately this is not a question for an internet forum, it takes someone measuring temperatures and figuring the flow of the system.

 

[f0ster]

we find that heat exchangers require cleaned out from time to time, use hypoclorite but do not leave it in for more than a couple of hours, then pressure washer,