CH pump types in new boilers and other queries

[Jon]

Hi,

As part of a CH service earlier this year, I've fitted a few more TRV's on rads without them, leaving a couple with standard valves. The pump I have is now running too fast when most of the TRV's are closed, so I am going to replace it with a Grundfos Alpha+ pump.

From reading bits and bobs on here, I decided to have a look at a couple of condensing boilers specs just to get some knowledge for when my Glowworm Micron bites the dust. From my limited research, I see that new boilers come with pumps and three port valves in them (don't want a combi as we like the redundancy of a storage tank) already.

1) Are the pumps they put in new boilers these days comparable to the self modulating Alpha (plus as they're now called) pumps or smart pumps? Or are they just the standard three speed setting pumps of old?

2) Do boilers not come as my micron is any more? I.E. Just a boiler without the fancy pump and valve in it? Or will I have to have new pipework routed in the house to provide a separate feed for the HW an CH circuits instead of one feed and one return to the boiler?

3) When I move to a condensing boiler, will I have to move to a sealed CH system too?

Thanks,

Jon

[John Rumm]

Many are just set speed devices. Some may have proportional speed control... someone more model experience may be able to give actual examples.

Yes, this is a "heating only" boiler. What you have been looking at are "system boilers" (i.e. they include the pump and valves etc).

pipework routed in the house to provide a separate feed for the HW an

You can still get heating only boilers if you want.

Generally yes. There are a few modern boilers around that will work with a vented system, but staying with vented operation[1] will limit your boiler choice somewhat.

[1] There is no real advantage in staying with vented operation unless there is a particular aspect of your system that requires it.

[Dave Plowman (News)]

The one in my Viessmann Vitodens 200 is a modulating type.

Mine is known as a 'system' boiler. It contains all the bits and pieces needed including electronics. So perhaps easier for a new install - but maybe not so as a replacement. However, there are instructions for using an external pump and divertor valve if you wish to. Which is how my setup was originally - the pump and valve were situated next to the storage cylinder on the opposite side of the room from the boiler. After much thought I decided to modify the pipework to use the boiler as supplied.

Another thread says you can get either. Mine says only sealed. Which doesn't involve much in the way of pipework to change to - assuming you have a convenient source of mains water.

[Jon]

Hi John,

Thanks for your reply. Looks like I'll be looking at a heat only boiler then. It will allow me to buy non-boiler-specific replacement 3- port valve or pump (in case of failure) and change myself with relative ease rather than boiler specific parts which I would guess are more expensive and more likely to become obsolete in the future. It'll also save the un-necessary addition of pipework to feed hot water to cylinder.

I have no issues with going to a sealed system.

Thanks for your help,

Jon