Hi Dan
Would that include an expansion vessel somewhere in the system?
Hi Dan
Would that include an expansion vessel somewhere in the system?
So you are making a sealed system from a vented. Fine. Then why not fill it to 1 bar as per normal? Guys put pressure reducing valves on old systems because there is an undetectable weep so stops constant callbacks when the customer sees the pressure guage drop.On extreme low head situations, we seal the system, put a pressure reducing valve on the filling loop and leave at about 0.75 bar. If a system can't take that then you have major problems.
Unless you think the rads will pop, so have the pressure lower.
No, I don't think so. The pump head can be higher than the static from the header tank. As an example, if the header tank static is 2m, and the pump head is 5m, the head just after the pump is 7m. Head is then lost going through the rads and boiler, back to 2m again at feed inlet.I'm no expert, but extreme low head presumably means that the pump is creating more head than the static head of the system?
Would you have to be sure to pump as close as possible away from the feed and expansion connection in order to avoid the risk of drawing in air due to having part of the system below atmospheric pressure?
Yep that was exactly what i was trying to say, just my terminology was on the blink! CheersNo, I don't think so. The pump head can be higher than the static from the header tank. As an example, if the header tank static is 2m, and the pump head is 5m, the head just after the pump is 7m. Head is then lost going through the rads and boiler, back to 2m again at feed inlet.
The feed should be close to the pump suction. The head at pump suction is slightly lower than the static, due to headloss in the pipe between the two. Making that pipe longer makes it worse, though it would need to be a long run to cause a negative pressure situation.
. I have had quite a few heating companies round to give quotes but in most cases they try to persuade me to go down the combi route
Maybe I'm missing something here. I assume an air separator is a canister with water in and out, and a gas vent at the top. I can see that could be better at venting gas than a simple tee on the pipe, but after commissioning there shouldn't be a significant quantity of gas. But I can't see why it would be better in a low head situation.Ideal recommend an air separator with low heads. Works every time on any boiler.
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