Glow-Worm 30Ci & bypass question

[Dazed]

Hi all, short time lurker, first time poster :P

First off, sister is having house done up by housing association - who have fitted central heating/radiators as so: 1 thermostat controlled radiator in bathroom, 1 TC rad in bedroom, 1 rectangular TC rad in living room and 1 small lockshield capped radiator in the hallway.

The problem is the hallway lockshield capped radiator - it heats up pretty hot and she has no way to disable it and doesn't want the dog to stick to it or something - in the meantime my dad has taken the cap off and 'isolated' it. [1]

My sister asked to have a TC rad to replace it, and today the foreman said it wasn't possible because it had to be done like that (for some un-described reason).

Now I read the manual of the 30ci recently, and remembered this gem from it : "If the central heating circuit is fitted with thermostatic radiator valves to all radiators then an additional bypass should be fitted not less than 1.5 meters from the appliance, see diagram 3.1."

I guess the non-TC rad was used so they didn't have to use a bypass?

So what I want to know is, /how hard is it to fit a bypass/what does it cost/how big is it/where does it go/how does it work/ as this would be helpful to negotiate with the foreman tomorrow (if he's there) to replace it with a TC radiator (this shouldn't be hard for them as they changed the radiator in the living room from a large TC rad to a long rectangular TC one for some reason during the day).

[1] = Which after reading the manual & googling sounds like a 'bad thing [tm]' if all the other radiators are shut off and the c.heating is on. ( )Glow worm's site is , I downloaded a manual for the 30ci last night but now the site seems to be down.

Also, as an aside - the manual programmer's clock doesn't keep time (e.g: set it to 8:30am and it'll be there still next week and keep the c.heating on!) - it just stays frozen but I can hear it ticking - HA said they will call out a co. to replace it - but I was just wondering what could be wrong with it?

[BillR]

Automatic bypass is easy to fit but costs a bit of money. Many boilers have them inbuilt. It may be of interest to note that building reg now say that all rads should have TRVs or a room stat so it sounds like they are in breach of these.

[Dazed]

Ah looking at the manual in the same section, it mentions just before my other quote that there is an automatic bypass built in - but that it needs an additional bypass if all radiators have TRVs ?

3.1 Bypass

? The boiler is fitted with an adjustable automatic bypass. Ensure that under no circumstances does the flow rate drop below the figure specified.

? If the central heating circuit is fitted with thermostatic radiator valves to all radiators then an additional bypass should be fitted not less than 1.5 metres from the appliance, see diagram 3.1.

Hmm, there is a 'temperature control' built into the boiler that allows a varied range of between winter and summer, is that classed as a room stat? Also does having only one floor apartment affect the regulations?

(Forgot to add that there is also a TRV rad in the kitchen, near where the boiler is located if that makes any difference).

[Erdefen]

Could it be that the thermostat sensor is located in the hallway? Erdefen

(Antispam, drop pants to EMail) All outgoing Emails checked for Virus with Norton.

[IMM]

This is the reason. It is called a control interlock. Which mean the boiler has to be switch off when the house is up to temp. the boiler can't cylce on itself if all the rad are closed down. This can be done with a thermostats on the wall of one of the rooms (hall). In your case thne rad is required so a heat sink.

[Dazed]

Well I can't see one there and it is a tiny hallway I guess. The boiler displays the temperature on its digital display when using the c.heating by using a thermistor on some pipe internal to the boiler, the TRVs on the radiators are made by Siemens if that is any help.

The glow worm site still seems to be down for me, so I have uploaded the acrobat/pdf manual to my webspace.

(30ci w/manual programmer)

[Ed Sirett]

AIUI you can either have all TRV and some sort of interlocked bypass to detect all TRV closed. or TRV on bedrooms and other cooler or less use rooms and an over-all Room Stat.

It is possible that the hall rad is permanently on to provide feed back to the Room Stat.

If the hall rad is too hot (when the time comes to use it) then see if the house can be heated at a lower boiler setting.

HTH

[John]

At this time of year he really should get it UNisolated PDQ before the boiler tries to dump heat through a closed (shut) circuit with potential for some instructive boiling within the heat exchanger tubes as the TRVs are closed off due to temperatures in their areas. I presume there is a room stat in the locality of the lockshielded radiator. Surely this is going to keep the heating off at present anyway or has she tried turning the heating off via the programmer?

Sounds very much like it!

Its relatively simple - Honeywell do an AVDO automatic bypass valve for about twenty quid. You need to insert it between flow and return pipes to achieve the appropriate distance from the boiler as per the instructions (although longer will not present a problem) The valve is claimed to be automatic insofar as it opens wider in response to an increase in pump pressure when other routes (ie radiator valves) close down. I don't think the claims really bear up when you consider the flow/pressure curve of a centrifugal pump but if it is passing a satisfactory minimum flow then that isn't going to matter. A similar effect can be achieved by using a simple lockshield valve albeit this is fixed at a certain opening just as the rad with the lockshields is. If the water was being circulated by a positive displacement type pump then there would be a definite pressure/flow effect (but there again a higher pressure would give a greater flw through a fixed orifice anyway so back to square one) :-(

ts probably got a stripped plastic gear and requires replacement rather than buggering about with it

[IMM]

The boiler is fitted with one.

[Dazed]

Have done this after reading an old Google posting, from reading the manual though it sounds like the boiler would disable itself in the event of overheating (but best not to try it, eh!)

There is no room stat in the house, but the boiler has a min - max kind of temperature setting and the boiler is about 3m from the ls'd radiator. Does that count as a room stat?

Yes the boiler has off/timer/on option switch as well as a programmer and it is all currently switched off. She just wanted to be able to control temps from all the TRVs when she turns the heating on at boiler/programmer, but not have hallway radiator on at the same time as the dog sits there sometimes.

Thanks for that, cleared up a few things for me.

Ah that'd make sense, still a bit strange on a brand new boiler. Glow- worm's own repair co. 'Heatshield' is being called out sometime (the foreman assures me..) to replace it as it is 'most likely faulty', lol.

Overall though in the end the foreman didn't turn up today and the apartment has been marked down as completed, so no chance of negotiations really - still I found the newsgroup postings interesting.

[John]

It would trip the overheat protection but in doing the boiler may sound as though it is trying to jump off its mountings as the water trapped within the tubes boils for a few seconds

No this is a water temperature control (stat if you like) for the boiler itself and has no feedback communication with the temperature of the house

instructions

The internal bypass of this model is simply an adjustable orifice which comes set at a typical position (if you are lucky) but Glow Worm seem to infer that this doesn't give a sufficient volume of water within the short route it provides to absorb a "volume" of heat if thr TRVs close, hence the distance from the boiler they quote which provides a buffer quantity for this heat

If you are not satisfied that the foreman is moving quickly enough try phoning Glow Worm/Hepworth Heating direct. (by the way it's "Heat-Call" IIRC)

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Regards, John