HOW TO CLEAN A HEAT EXCHANGER

D

DAJ

Hi, I am in the middle of installing a new bathroom and kitchen. I have also just finished a complete loft conversion. I had a new boiler (Jaguar Combi) fitted by a plumber around 3 years ago when I first decided to convert the loft. I ensured that the new boiler could handle the additional 4 rads in the loft. I asked the plumber to fit iso valves for both hot and cold water to for the new bathroom and iso valves for the heating in the loft. I have now sucessfully installed the pipework and rads in the loft conversion. I've used all soldered joints and had no leaks when commisioned (very proud of myself). The rads have been working fine since (about 2 years) and still are. I have recently drained the system several times to remove old plumbing and install new rads elsewhere(again with no leaks). I started to have problems with the hot water running hot and cold and obviously the boiler igniting and stopping etc. I assumed it was the heat exchanger. I called the plumber and told him what was happening. He wasn't happy that I'd done so much work myself but agreed, it was the exchanger. He wanted to replace it but I asked him to remove it and clean it, which he did. He said it was my fault as draining the system caused the blockage in the exchanger which I felt was fair comment. The hot water has been fine for several months but the problem is back. I have several questions, 1) can I remove the exchanger myself and clean it 2) can I prevent this problem from reoccuring by flushing somehow 3) do I need a new exchanger. THANKS for reading this and I hope you are able to help. Regards Den.[/i]
 
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If your (secondary) heat exchanger (the one producing hot water) blocked once, was unblocked and is now blocked again, the question has to be what's blocking it?

Did your plumber who did the work first time say what he found in it? If he found installation debris (especially lumps of solder!) he SHOULD have made some attempt to flush the system to get out any more bits lurking in there. If it was black oxide flakes formed because you refilled the system without any corrosion inhibitor - that's a different problem.
 
D

DAJ

Thanks for your reply. The plumber didn't say what was found upon cleaning the exchanger, just that it was my fault. From this comment, I can only assume it was debris as you've indicated in your reply. He didn't flush the system, he simply replaced the exchanger. To be fair to him, he only charged £60 and he was working for around 2 hours. Can you tell me the cures for each problem, black oxide flakes and debris. Also, how would I get an anti-corrosion chemical in the system. Regards, Den.
 
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If you do a search on flushing you should find stacks of advice and info.
Yours rads now hold the grot, it's rust in them which is blocking your boiler. Sometimes draining a system can bring it down to where the boiler is.

Chems of various types come in syringes you can inject via the filling loop.
 
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hi,
£60 labour plus the head exchanger?
if it included the head exchanger that sounds to cheat to be true. If it was the plate to plate head exchanger it could have been cleaned which would save a lot of money
 
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maka2k2 said:
hi,
£60 labour plus the head exchanger?
if it included the head exchanger that sounds to cheat to be true. If it was the plate to plate head exchanger it could have been cleaned which would save a lot of money

Personally I never clean them, it is totally impossible to know how well you have done them.
 
D

DAJ

When I said he replaced the exchanger, I meant he CLEANED it then replaced. My fault, I didn't make myself clear, sorry guys.
 
T

thetortoise

Excuse my ignorance and I aplogise if I'm totally wrong here but surely if the secondary heat exchanger is blocked then flushing the system (being the central heating) wouldnt help because that heat exchanger is only for the hot water?

Its just I have the same problem at home at the moment, although I havent had any work done, but I am getting intermittent hot and cold water from my hot taps?

I have a Vaillant ecotec boiler, I've checked the fault codes and there dont seem to be any so I'm not sure whats wrong? I was told that it might be the secondary heat exchanger?

Can anyone help?

Cheers
 
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Excuse my ignorance and I aplogise if I'm totally wrong here but surely if the secondary heat exchanger is blocked then flushing the system (being the central heating) wouldnt help because that heat exchanger is only for the hot water?

you are totally wrong ;)
 
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maka2k2 said:
hi,
£60 labour plus the head exchanger?
if it included the head exchanger that sounds to cheat to be true. If it was the plate to plate head exchanger it could have been cleaned which would save a lot of money

Personally I never clean them, it is totally impossible to know how well you have done them.

I find cleaning them does help. I've used Oust desclaer to clean a couple, a few sachets in a tub of boiling water, leave the exchanger in their for 20 mins, then use a soft bottle cleaning brush to get right in there and give it a good scrub to remove the scale and debri.

Then wash it out, put it back together and bobs your uncle!
 
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Excuse my ignorance and I aplogise if I'm totally wrong here but surely if the secondary heat exchanger is blocked then flushing the system (being the central heating) wouldnt help because that heat exchanger is only for the hot water?

Its just I have the same problem at home at the moment, although I havent had any work done, but I am getting intermittent hot and cold water from my hot taps?

I have a Vaillant ecotec boiler, I've checked the fault codes and there dont seem to be any so I'm not sure whats wrong? I was told that it might be the secondary heat exchanger?

Can anyone help?

Cheers

I have the same problem with intermittent hot water coming from another Vaillant 937 ecotec boiler. Its 3 years old... something dodgy going on with this boiler? Anyone else know of that problem affecting new vaillant boilers?
 
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Got same problem except my boiler is from Oct 2006 install, Vaillant ecomax 828/2 e. Recently replaced a radiator in the bathroom then done a chemical flush left in for 2 weeks as advised on the tube, after completely flushing then refilling with inhibitor have had hot tap going hot and cold.

Got to laugh at the reply above telling the poster he's totally wrong then not explaining how a secondary heat exchanger works. Helpful.

A British Gas engineer has said yeah probably heat exchanger but he doesn't have a sonic cleaner with him, will have to get his mate out to help (mates rates).
 
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Secondary heat exchangers can be cleaned but never as good as just putting a new one in. On the Jaguar make sure you have a pack of o rings as they do not seal up well after being disturbed. As for the vaillant if its the 937 are you getting f81/f91 fault. Vaillant have recently updated the software on the store pcb. Also on the 937 you can get problems with the shift load pump which is a b**ch to change. On the other vaillant if the secondary heat exchanger is blocked the temp on the display will usually go up to 84- 85 degrees then cut out usually if the dhw is set on maximum it should only be going up to around 70 degrees
 
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On the other vaillant if the secondary heat exchanger is blocked the temp on the display will usually go up to 84- 85 degrees then cut out usually if the dhw is set on maximum it should only be going up to around 70 degrees

yes that describes it exactly, though in the manual it says to only it set it at 12 o'clock if you live in a hard water area. New secondary heat exchanger is £100+ though.
 
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The best solution for blocked plate heat exchangers is powerflushing the system, provided the boiler can withstand fx2.
Changing the hex, or only cleaning it, is fairly pointless as the reason it got blocked is crap in the system. If you don't clean the system, you have a high probability of reoccurance.
Powerflushing will clean the system and the hex.
 

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