Bosch Worcestor

[Dave Plowman (News)]

My brother who lives in the NE of Scotland has finally cut his losses with his Potterton Envoy which has broken down more times than any other boiler I've heard of and had it replaced by Scottish Gas with their own brand made by Bosch Worcester. For the reasonable sum of 1200 quid.

This was only completed yesterday, and he phoned me last night for some advice before getting them back in.

Seems it's pumping over - and badly. Quite an achievement given the header tank is a whole floor above the highest rad - the attic floor of the very large house being unheated.

He'd rescued the installation instructions from the rubbish and couldn't find any instructions for setting the maximum (integral) pump speed. Or indeed anything about it being used on an open vented system.

The Potterton utilised the old pump and divertor valve from the original installation whereas now they've remove the old pump and are using the internal one.

He can't find a reference number that refers to any Bosch Worcester one so can't look it up for help on their site.

He was told it is actually a combi with the hot water side unused.

Given the last straw with the Potterton was the heat exchanger split while he was on holiday and badly flooded the utility room I'd have thought they'd have recommended changing to a sealed system anyway.

Any comments from the experts?

[TheScullster]

"Dave Plowman (News)" wrote

Without serious detail regarding pipe work layout, position of pump, valves, make up water etc it's difficult to comment. However, I have a Worcester Bosch 24Ri non-combi which works fine on a vented system. Fitting it did involve a lot of re-piping though, because the previous arrangement had a pumped return which none of the boiler manufacturers these days seem to agree with.

Phil

[John Stumbles]

The height of the header is irrelevant, it's the relative position where the feed and vent pipes connect to the main return (or possibly flow) pipework.

If the installers hadn't left the installation instructions with the boiler (and filled in the logbook) the installation hasn't been completed correctly. The instructions are considered a part of the installation.

He could compare with pictures of known W-Bs, or post us a picture we could have a go at.

Easy enough to see if it has 2nd brass connection from the left unconnected (preferably blanked off).

I don't think any of the current W-B greenstar (condensing) combis are specified for use on vented (header tank in attic) systems, in which case the system should have been converted to sealed. Sounds like a cowboy job that needs sorting, and that Scottish Gas make British Gas look good. If he hasn't yet paid for it I suggest he doesn't, and if he has I suggest he stops payment if possible.

[Dave Plowman (News)]

Don't you require enough head from the pump to overcome the friction of the system and if the header tank is only just above the highest rad there is more chance of pumping over? But it did work ok before with the Potterton - and as far as I've been told the only alteration was to the position of the pump.

Don't think that was done but I'll check. They left the owner's manual, though.

Heh heh. He doesn't have a computer. ;-)

This is what's worrying me. My quick glance at their site suggested they all have modulating pumps and I don't see how they could work on an open vented system - unless you could set a maximum speed. Scottish Gas employed a contractor to do the work.

[Dave Plowman (News)]

Having now had a chance to look at the W-B site I'd say you are right - all the suitable ones seem to have modulating pumps with integral expansion vessels. Of course one made for Scottish Gas may be different. The fitter has been back and agreed there is a problem but hasn't said how he'll fix it - except that 'we have the technology'. Doesn't give you much confidence, does it?

[TheScullster]

"Dave Plowman (News)" wrote

My original system had a pumped return and relied on the flow from the boiler to act as the (safety) vent as well. If he has moved the pump from the return side to the flow side, and the system was piped like mine, then he will have compromised the vent as well as introducing the pump over!

Phil

[Dave Plowman (News)]

Oh dear. Unfortunately it's a bit difficult to find out - my brother won't even remove the boiler case.

[John Stumbles]

Different badge on the front. I don't think W-B and SG are going to pay to develop and get approval for a different design just for their market.

I'd be inclined to get on to Scottish Gas and ask them to get an installer who knows how many beans makes five to sort it out. If they don't jump I'd give CORGI a ring and check on the credentials of the installers. If he has their registration number (e.g. on the benchmark log book) he could check that it matches the people who did the work. If he hasn't he could say that he wonders if they really were registered installers and could they (CORGI) investigate? (Unregistered installers are CORGI's bete noir at the moment.)

[Dave Plowman (News)]

Seems now they are going to convert it to sealed. Next week sometime. But it begs the question of just why they didn't do this in the first place. Not everyone is going to look in the roof space or even know that pumping over is wrong. Call me cynical but it's not something you do by mistake or omit through carelessness - he did put inhibitor in, and left the empty container by the tank.

[Bob Eager]

Well...he left an empty container by the tank, anyway...

[Doctor Drivel]

A trick by cowboy installers is to leave an empty container near the tank, when they haven't put any in at all. The rotting rads comes 5 years later.

[Bob Eager]

What I said.