Had a couple of plumbers around to give me a quote for a megaflo. One plumber mentioned that I would need an F&E tank for the heating particularly as one of my options is to retain the old boiler but the other plumber said nothing about it and it does not appear on his quote.
Does a megaflo need an F & E tank fitted for the heating in all cases or only if an old boiler is being retained. If not where does the expansion go?
It's got nothing to do with the megaflo per se. That will let you loose the Cold Water Storage tank, if you wish.
The F+E tank is to do with the boiler.
If the existing boiler has an open vented primary, it will already have a F+E tank. It will be a smaller tank, usually located close to the larger Cold Water Storage tank. If you retain the boiler, you retain the F+E tank.
If you replace the boiler with a sealed system, then the F+E tank becomes redundant, and can be removed also.
Thanks Ron. My existing tank is a Flowmax thermal store with the header tank built into it so when the existing tank goes so does the header tank.
Are all boilers capable of being part of a sealed system? My existing boiler is a Potterton flamingo which is 18 years old. By being part of a sealed system does than mean the CH pipes and radiators are under pressure because the expansion has no where to go?
It's scaled up, others in our road have had leaks from the seams so it is time for a change. A direct replacement for my flomax makes a megaflo seem like a bargain.
Anyway back to my question anyone. Also is it a bad idea to seal an 18 year old boiler that was once part of an open vented system. Looking at the boiler manual it would appear that it can be part of a fully pumped sealed system.
On Thu, 17 Apr 2008 19:23:44 +0100 someone who may be "PC Plod" wrote this:-
Hard water area presumably. An "unvented" cylinder will also scale up. With a heat bank the only thing to scale up is the heat exchanger, which can be cleaned or replaced while leaving the majority of the system in place.
That is not a function of any particular general design of heat exchanger. All designs can leak at the seams.
No, not all boilers can be used in a pressurised system. I don't know about yours.
Your description of a pressurised system is pretty much correct. The primary loop is filled with mains-pressure cold untill it reaches around
1 - 1.5bar. When it heats up, the thermal expansion will raise this to a couple of bar.
There will be an expansion vessel on the circuit somewhere, either in the boiler or mounted externally ( sometimes both ). Otherwise, the water which has a very low compressibility would raise in pressure so much that it would crack open the relief valve, and you'd loose the loop pressure, and the boiler would then shut down for lack of pressure.
If your existing setup has a F+E tank, then the plumber needs to consider this issue. Assuming the boiler cannot be used in a sealed system, then some F+E will need to be provided.
The scenario which could cause the guy to say this is if the existing arrangements use a Harcopak "Just add water" (sic). In which case the existing CH circuit has a small F*E tank built into the top of the Harcopak unit, so will need to be added if the harcopak is being traded for a Megaflo.
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