hard sell for combi

[rhinosaw]

Hi Dan
Would that include an expansion vessel somewhere in the system?

 

[dilalio]

Hi Dan
Would that include an expansion vessel somewhere in the system?

Eco RF includes an EV as part of the standoff jig kit or one can be supplied separately as a robokit... This is similar across a few boiler brands.

 

[Dan Robinson]

Hi Dan
Would that include an expansion vessel somewhere in the system?

Yep, but they come in a range of shapes. I don't like using the back packs. They can go more or less anywhere. Have a coupe in the kickspace of a kitchen unit, another mounted to the wall above the kitchen units.

 

[hard-work]

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.

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.

Unless you think the rads will pop, so have the pressure lower.

 

[Dan Robinson]

Unless you think the rads will pop, so have the pressure lower.

If there is a risk yes. The filling loop is still disconnected as usual.

 

[hard-work]

Ideal recommend an air separator with low heads. Works every time on any boiler.

 

[Dan Robinson]

Great.

 

[rhinosaw]

what does an air separator do?

 

[Dan Robinson]

It's a glorified air vent. I can see a point in situations of extreme low head, but in my opinion, it's just one more point of failure that can be mitigated by other means.

 

[John D v2.0]

I'm no expert, but extreme low head presumably means that the pump isis 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?

 

[fixitflav]

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?

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.
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.

 

[John D v2.0]

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.
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.

Yep that was exactly what i was trying to say, just my terminology was on the blink! Cheers

 

[Hot&Cold]

. 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 they have a valid point,they have seen your property and discussed "your needs & demands"

 

[rhinosaw]

Fair point Old & cold but I did say to the quoters that there is no excessive demand for hot water and only 7 rads so can't see how a combi would benefit me particularly as I like the backup of a hot water cylinder.

 

[fixitflav]

Ideal recommend an air separator with low heads. Works every time on any boiler.

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.