restoring old boiler, suitable sealant for heat exchange ?

[markvan]

Hi everyone

Ive got an Ideal Concorde WCF, about 20 years old. Rather than go through the financial pain of ripping it out and getting someone to install a new boiler, I need to fix a leak on it....between the two halves of the heat exchanger.

The heat exchanger comes in two parts, and the gas flame goes up between the two parts. In the past there has been a weep on the outside edge where the two parts of the heat exchanger join, and Ive fixed that by cleaning off the loose crud and applying silicon. I now have a weep on the inside, unreachable. If the boiler is to go on being used Ive got to split the heat exchanger and reseal the halves together. That's an easy job, 4 bolts etc... no more difficult than say putting a new rocker box gasket on a car.

Problem: what sealant to use. Ideal's technical line is no help. Too old they say. Can't advise you. So I found fortafix http://www.fortafix.com/products.asp and the technical guy is on holiday ....

Some product choices are:
1. a silicone sealant will go up to 350 C see Fortafix High Temperature RTV Silicone http://www.fortafix.com/products/product-short.asp?ID=88 and
2. they have Fortafix High Temperature Sealant - T.C. Caulking Compound that goes to 1250 C at http://www.fortafix.com/products/product-full-a.asp?ID=84

Any recommendations? While the old sealant is some rock hard stuff, I wonder if I shouldn't be using something which has some flexibility.

Any advice appreciated., it would for example be good to know how hot boiler gas flames are, or maybe there is someone out there who knows a specialist product to recommend.

Thanks.... mark
[/b]

 

[ChrisR]

Standard questions Mark -
Are you corgi regd?
if not, Is it your own?
Do you have the right kit to test it ?

Are aware what it'll do to your/customer's house insurance if you make repairs the manufacturer has said you shouldn't?

 

[Terrywookfit]

You may find this post from an adjacent thread helpfull !!

Not only is Parkin delicious but it is useful as a non setting sealant for sealing sleeved gas pipe, for use as flashing round vertical flues and as sound deadening on reverberating boiler cases... When I'm down South I tend to stick to Guinness though I'm sure that there must be some decent pubs doing locally brewed ale..

 

[Agile]

***

What always amazes me is that this boiler is only about 60% efficient and a new condensing boiler could save humdreds of pounds a year in gas yet you dont want to change it !

Tony

Inappropriate advice has been deleted where there are ***s
See //www.diynot.com/forums/viewtopic.php?t=8090
Mod10

 

[markvan]

Standard questions Mark -
Are you corgi regd?
if not, Is it your own?
Do you have the right kit to test it ?

Are aware what it'll do to your/customer's house insurance if you make repairs the manufacturer has said you shouldn't?

Thanks Chris, its my own kit in my own place.

The advice from the manufacturer was not to not repair, rather it was that they no longer used that construction of a two part heat exchanger and therefore had no idea of what sealant to use between the halves.

Ok, Chris, here we are with what is basically a tank of water being heated by a flame, where the water is being pumped around the house. The tank is under no appreciable pressure. I am about to fix the tank, to stop it leaking, not to mess with the gas. What possible test could I apply that checks on the repair? The only one I can think of is to use my eyes... does the tank leak?

Ok it is plausible that I disturb some gas fitting.... its my risk. But thanks for your advice so far....

mark

 

[ChrisR]

SUrprised at you encouraging diy repairs like that Tony?

 

[markvan]

***

Thanks....

***y.

Hmm, the gas fittings are below the heat exchanger... unless you mean just the route that the gasses take to get to the flue. My impression is that the major job here is to seal the waterways, and if that is done the rest comes easily.

There is very old hard set paste like sealant between the halves.

What always amazes me is that this boiler is only about 60% efficient and a new condensing boiler could save humdreds of pounds a year in gas yet you dont want to change it !

Yes Tony, its sad but true. As I understand it the flue in use, while checked annually, is not one that gas fitters like to use anymore when fitting new kit (concrete block flue), so to change the boiler will take a bit of hassle due to relocation; new route for flue through wall, new piping inc lifiting floor.

A change in boiler will come, and indeed my savvy girlfriend told me the same yesterday, pay for itself in a few years etc...

Of course with plumbing of this age it is possible that any work will disturb old joints etc... so its all a tradeoff in time and money.

But thanks Tony! And for your advice re new boiler too.

regards
mark

 

[markvan]

SUrprised at you encouraging diy repairs like that Tony?

Fire away guys, its fine, I'm open to advice and realise that my past plumbing and gas work may have no bearing here.... the structural engineers maxim "just cause its stayed up for the last two hundred years doesn't mean it will stay up tomorrow", could of course apply here, "just because you've worked on this boiler before (thermostats, leaks) and installed gas fires doesn't mean that you won't be cinders tomorrow."

regards

 

[giblets]

There is very old hard set paste like sealant between the halves.

***

 

[markvan]

....****.

Tada! Now we're getting places, thanks Mr G.

Further refinement though would be appreciated: Normal rubber like comes out of a tree suitably processed??? I'm kind of wary about this, wandering down to my local plumbers merchants and saying do you have some rubber washers this size... I mean, I've seen old tyres burning, and the idea of putting rubber near a flame does worry me.

OK so we seal off all oxygen paths to the rubber, make sure the flame can not reach the rubber, take care there is no burnt gas escaping through the sides of the heat exchanger.

But I'm still concerned

 

[markvan]

But I could imagine schemes where the molding on the two halves was sufficient to keep the rubber out of flames way, say a protrusion on one side and a dent on the other, with the rubber seated in the dent.

I guess I will drain my system again and pull the heat exchanger apart, see what I can see and then report back here.

But oh no, unless more help is forthcoming on materials to reseal, its a new boiler and all that that entails. Its just that I was hoping to put this event off for a year, because with new boiler I can see what will ensue, new kitchen (yes I know one does not follow the other but its time for this to happen) and time is what I have the least of....

please continue this thread everyone...

 

[markvan]

Ive decided to give up and get a new boiler.The boiler connections would need recoinditionign no doubt by the time all thiws went on.
Thanks for the advice all.
mark

 

[doitall]

Ive decided to give up and get a new boiler.The boiler connections would need recoinditionign no doubt by the time all thiws went on.
Thanks for the advice all.
mark

Now that is a good idea, it's more then likey the section is split anyway.

For what its worth the section would probably been joined woth asbestos rope, or more recently an black boiler mastic (in strips)

 

[Agile]

I dont know who Mod 10 is as he does not identify himself!

In that case I will assume that he is not qualified to work on gas appliances.

In this case the heat exchanger is neither a gas carrying part nor a safety device and is therefore the least dangerous part for a DIYer to work on.

Please would MOD 10 identify himself and confirm that he is CORGI registered and explain his reasoning in considering my advice as inappropriate.

I will expect him to take the same action in future when anyone sugests that someone should replace a gas valve or any safety device. He must be consistant !

Please could you reply this evening or early tomorrow morning.

Tony

 

[Terrywookfit]

What supposedly innapropriate advice did you give?