Secondary Heat Exchanger on Halstead Ace High

[pinheadplanet]

I had the plumber who serviced my boiler recently come back to finish some work and asked him why the hot water was now running hot cold hot cold, he said it would be the secondary heat exchanger, showed me where it is and more or less how to take it off for a clean, and then left.

question?:

1) I just read whilst searching the forum that cleaning out the S.H.E is part of the service on another boiler (i think it was a Gloworm), would that also be the case for my boiler as well?

2) I s this something I can do myself, how long would it take you as a plumber and is there anything specific I should be aware of?

Cheers

 

[Agile]

Cleaning the plate is a fault and not part of a routine service.

Many DIYers will replace it as thets easier.

As a professional I would use chemicals to clean it and dont really like to do that at a clients premises as its quite messy.

A DIYer can do a half hearted clean by just shaking some dirt out but thats not very effective although it will often stop the hot/cold cycling.

Tony

 

[pinheadplanet]

But to take off the unit I need to drain down the system right?

and isolate the supply, flow and return? Is that right?

 

[Agile]

Yes!

 

[pinheadplanet]

Having read other posts on this I'm going to try to flush the system through first.

To do this I guess i need to open all the radiator valves fully, connect a drain hose to the drain valve on the rad, open the drain and open the mains feed valve at the same time, is this right?

What pressure could I go up to? i think it says that the boiler is good to 10bar but the pressure gauge goes to 4 bar and I don't want to over pressure the joints in the pipework.

Ta

 

[MANDATE]

Firstly, you can't exceed the mains pressure.
Secondly If you take the pressure in excess of 3.5 bar you would blow the pressure relief valve and highly likely have another problem cause they don't always seal again properly.
Whether or not you can achieve a pressure when the drain valves are open is all down the resistance created. With no resistance you can't.
If a pressure is created under these conditions, what reason would there be to exceed normal working pressure of 1 to 2 bar.

 

[pinheadplanet]

I tried it and the pressure went up to 3 bar even with the drain valve open. I turned the heating on and then turned on the hot tap in the kitchen just to vary the pressure through the system to try to dislodge any crud that might be in the DHW heat exchanger.

It didn't work!

Going to have to look at taking off the exchanger and stick it in solution to clean it. Then of course it might not even be that.

Or I might just get someone else in to sort it. that way he could tell me if there's any reason why all three of my newly installed rads don't get evenly hot all over and get hotter on the top more than the bottom.

 

[MANDATE]

As your radiators are new I can't see sludge causing the top to be hotter than the bottom.

You know my radiators are hot, top and bottom just after the hot water has been pumped through, but after the stat has switched the pump off and the radiators cool off the top is always hotter than the bottom.
I believe this is due to (a) the cooler air being nearer floor level, (b) the fact hot water rises and (c) perhaps the curtains restrict the cooling at the top. So maybe yours is the same.

 

[pinheadplanet]

No, afraid not.

My rads are much much cooler along the bottom when the heating and the pump is on.

 

[Agile]

Badly installed new systems can get sludged up very badly within a short time.

However, you need to measure the flow and return pemperatures on each rad.

It just may be inadequate flow !

Tony

 

[pinheadplanet]

Yeah I'm gonna have buy a digi thermometer and check the flow and return temps. to balance the system.

Got the boiler apart at the moment and the DHW heat exchanger is getting a clean out with some DS3 as we speak.

 

[pinheadplanet]

Having got the heat exchanger off it seems that the front holes for the heating system are the ones that are gunked up, but the rear holes for the DHW look pretty clear to me.

Not being entirely sure what a heat exchanger does I couldn't say if this is what is to be expected.

When i put the solution of DS 3 into the HE it doesn't self level. If i put it in the holes of the Heating system it seems to stay there and if i put it in the holes for DHW it seems to stay on that side.

However, when i tip the HE up at one one the liquid does flow slowly from one side to the other. DOES this mean that it is all clogged up inside? Should the liquid flow freely from side to side?

How long should I leave the ds3 inside? I can't see if it is turning green as it says on the tub...

 

[Paul Barker]

It is the balckened primary side you have to clean. The solution should not transfer to the clean water side. Put the ds3 into the black side until it is full then poor boiling water into the clean hot water side. Leave it for the time allowed.

 

[pinheadplanet]

Sorry paul I got your post too late, anyway here's an update.

I just had a HOT shower!!!

I cleaned both sides of the SHE with the ds3 for a few hours, stuck it all back together and hey presto.

I'm not gonna hold my breath as I see many other posts talk of problems returning and replies saying that people need to powerflush etc to get their system clean.

I'm gonna wait a few days to see if the hot water maintains, then I'm gonna drain a little water out and chuck in the X100

Thanks to everyone for you help. Every bit of encouragement is well appreciated.

 

[Agile]

DS3 is for lime scale compounds!

You need citric acid ( or DS 40 ) for metal oxides which are the black deposits you have mentioned.

You have to rock the HE from side to side AND end to end to distribute the chemical to the deposits.

Tony