Hello - I recently got a new Worcester Greenstar 30i 30kW Combi Boiler 7733600005 installed in my property. Previously I had a 37KW combi boiler but that was 10 years old. But my plumber said that 30KW combi boiler should be more than enoguh. The day this was installed, I also had my water supply pipe changed from 15mm to 25mm PE to increase the water flow. Since the day these two things were done, my hot water cycles continuously between extremely hot and freezing cold in all the tap mixers. I am not sure what's gone wrong as the plumber who fixed it confirms that this has nothing to do with the boiler. Any pointes / advise based on your experience will help.
New boiler setup - hot and cold water cycles repeatedly
- Thread starter JT_Singh
- Start date
Sponsored Links
At what rate does the cold water flow?
At what rate does the hot water flow?
Answers in litres/pints per minute please (not very/fairly/quite good)
At a similar rate to the cold?
Was the new cold mains thoroughly flushed before the stop-cock was fitted?
At what rate does the hot water flow?
Answers in litres/pints per minute please (not very/fairly/quite good)
At a similar rate to the cold?
Was the new cold mains thoroughly flushed before the stop-cock was fitted?
So you've increased your water flow rate and reduced the power of your boiler? These two things are never going to be a happy marriage. I'd suggest that your boiler possibly has an airlock. Try running the heating for a while. I'm afraid you're going to be disappointed if you think that your shiny new water main is going to be of any use to you though, unless you like to use a lot of cold or tepid water
All - thanks for the all the help and guidance to date. I have a few additional things if you can kindly help me out with. Apologies for a long message.
Previously I had the WB 37CDi which was working fine in terms of hot water and heating in the house. The only issue was the water pressure was low i.e. if I have the washing machine or the dishwasher ON, taking shower was painful as the pressure used to drop drastically and the water used to turn cold. So I could not have two showers or my washing machine/dishwasher running at the same time.
I am currently getting an extension done and therefore changed the previous 15mm lead supply pipe with a 25mm PE pipe with an intention to increase the water supply as a whole in the house. The pipe from the water mains to this new supply pipe is yet to be changed by the Water Company - hopefully in a couple of weeks.
Simultaneously, the builder and his plumber recommended me to change the boiler to a new one. I asked them to confirm what KW boiler I should go for as I am now getting the underfloor heating done in the newly extended area. The plumber said a 30KW will be more than enough for the existing and the extended area. I categorically asked him that if that's correct as I currently have a 37KW and I was I expecting that I might need a higher output boiler. He said KW isn't the issue, it's the water pressure. If the water pressure increases all be okay with 30KW. I believe he's has messed up on this bit as I have read yours/others comments on my post. Now I have spend 1500 on the boiler plus spare parts and 1800 on the fitting of it! Given that the work is currently ongoing and I have spent 3300 on this altogether, I can't really fire him unless I intend to write off this 3300! He said he'll come and check the boiler and identify the problem and fix it - and if the problem is because of his doing, he'll suck up the additional cost. As you'll appreciate my trust and confidence in him is running quite low, and I am not sure how honest he will be in telling me what was the problem he fixed, if at all he does.
My dilemma is that I don't want him to reduce the main water flow which have just got increased in order to fix the current cycling of hot water. Then I am back to square one with a low pressure still in my house even after spending more than a thousand in getting the supply pipe changed.
Given that my knowledge is limited in this area, can you help me understand the below:
- My assumption is that only a part of the incoming water supply pipe is connected as an inlet to the boiler. For e.g. water supply for washing machine/dishwasher or an american fridge won't go through boiler and will by pass it. Is this assumption correct?
- If this assumption is correct, is it possible to lower the flow of the water in the inlet pipe to the boiler - to the limit it can handle (11l/min) so that I don't get the hot water cycling continuously? Will that work? And if it does, then at least I can have hot water continuously in a shower and run the washing machine/dishwasher in parallel if need be. However I think I won't be able to run two showers together at the same time without the pressure dropping. And I sincerely hope come winters, my heating can cope
- If nothing of the above works, and if I want to keep the increased water flow supply in the house, then I think the only option I have is to buy another new boiler with higher KW? I bought the 30i from City Plumbing and as expected they refused to exchange or offer any refund. So are there any places/forums I can sell this 2 week old boiler at a reasonable cost to cut my losses?
This is quite stressful! But I appreciate all your guidance.
Thank you!
Previously I had the WB 37CDi which was working fine in terms of hot water and heating in the house. The only issue was the water pressure was low i.e. if I have the washing machine or the dishwasher ON, taking shower was painful as the pressure used to drop drastically and the water used to turn cold. So I could not have two showers or my washing machine/dishwasher running at the same time.
I am currently getting an extension done and therefore changed the previous 15mm lead supply pipe with a 25mm PE pipe with an intention to increase the water supply as a whole in the house. The pipe from the water mains to this new supply pipe is yet to be changed by the Water Company - hopefully in a couple of weeks.
Simultaneously, the builder and his plumber recommended me to change the boiler to a new one. I asked them to confirm what KW boiler I should go for as I am now getting the underfloor heating done in the newly extended area. The plumber said a 30KW will be more than enough for the existing and the extended area. I categorically asked him that if that's correct as I currently have a 37KW and I was I expecting that I might need a higher output boiler. He said KW isn't the issue, it's the water pressure. If the water pressure increases all be okay with 30KW. I believe he's has messed up on this bit as I have read yours/others comments on my post. Now I have spend 1500 on the boiler plus spare parts and 1800 on the fitting of it! Given that the work is currently ongoing and I have spent 3300 on this altogether, I can't really fire him unless I intend to write off this 3300! He said he'll come and check the boiler and identify the problem and fix it - and if the problem is because of his doing, he'll suck up the additional cost. As you'll appreciate my trust and confidence in him is running quite low, and I am not sure how honest he will be in telling me what was the problem he fixed, if at all he does.
My dilemma is that I don't want him to reduce the main water flow which have just got increased in order to fix the current cycling of hot water. Then I am back to square one with a low pressure still in my house even after spending more than a thousand in getting the supply pipe changed.
Given that my knowledge is limited in this area, can you help me understand the below:
- My assumption is that only a part of the incoming water supply pipe is connected as an inlet to the boiler. For e.g. water supply for washing machine/dishwasher or an american fridge won't go through boiler and will by pass it. Is this assumption correct?
- If this assumption is correct, is it possible to lower the flow of the water in the inlet pipe to the boiler - to the limit it can handle (11l/min) so that I don't get the hot water cycling continuously? Will that work? And if it does, then at least I can have hot water continuously in a shower and run the washing machine/dishwasher in parallel if need be. However I think I won't be able to run two showers together at the same time without the pressure dropping. And I sincerely hope come winters, my heating can cope
- If nothing of the above works, and if I want to keep the increased water flow supply in the house, then I think the only option I have is to buy another new boiler with higher KW? I bought the 30i from City Plumbing and as expected they refused to exchange or offer any refund. So are there any places/forums I can sell this 2 week old boiler at a reasonable cost to cut my losses?
This is quite stressful! But I appreciate all your guidance.
Thank you!
Sponsored Links
The cycling can be caused by shower non return valves sticking open and lets the cold mix with the hot supply, can you isolate your showers an kitchen mixer tap (if you have one) it could be that the higher pressure has made an existing problem worse.
30kW will be more than enough to run your heating unless you live in a mansion, but if you're expecting it to be able to heat enough water to run two showers at the same time you're going to be very very disappointed. Unfortunately, as you've supplied the boiler yourself, your installer has no responsibility for it not meeting the performance you're hoping for, beyond correcting any installation faults that might exist. It looks like a decent installation from the photos provided though.
If you do want to run two showers at the same time, you either need to add a hot water cylinder or change to a more powerful combi boiler. You could probably sell the one you have on eBay.
This will run two showers at the same time... https://www.cityplumbing.co.uk/Worc...=6b88cc3707f498aeb0b73389dac79dd4&fo_s=gplauk
If you do want to run two showers at the same time, you either need to add a hot water cylinder or change to a more powerful combi boiler. You could probably sell the one you have on eBay.
This will run two showers at the same time... https://www.cityplumbing.co.uk/Worc...=6b88cc3707f498aeb0b73389dac79dd4&fo_s=gplauk
Funny you say that because why do companies (such as WorcestorBosch) and my plumber asked for how many bathrooms in the house when all the resulting suggestion can only run a single shower at a time. Anyway - I'm glad at least this is clear that I can't run two hot showers at the same time, but can this 30KW susport 1 hot shower, washing machine/dishwasher at the same time? How about underfloor heating (59m2 area), and 7 radiators? Can it do this? Or should I just replace this with my old working 37KW.
If yes, then its fine. My only regret is buying this new boiler when my 37CDi could have done this anyway after the water pressure was increased!
Last edited by a moderator:
With a 50 kW boiler ? you could run a district heating system and heat a few of your neighbour's houses.
What are you on about mate? I am not talking about 50KW - that was suggested by muggles if I want to run two hot showers at the same time. I don't have this one and I don't plan to buy one either.
I am talking about the new 30KW WB boiler - the pics are from that in the previous post.
your washing machine and dishwasher almost certainly heat the water electrically, which takes around ten minutes each for a hot wash at about 3kW, at the beginning of the cycle (and, for a dishwasher, again for a hot rinse and possibly a drying cycle, depending on your program). They use very little hot water. Some can run on a HW supply but there is little cost saving on electricity.
Underfloor heating and radiators demand depend on the heat loss of your house. You can calculate it but, when it's freezing outside, it would probably need less that 15kW. I once had a house with a 30kW heat demand, but it was unusually big and, being old, had uninsulated solid walls. my current house has a 12kW calculated heating demand. It's OK to have radiators adding up to more, because they can heat the house faster can cold, and can also keep the house comfortable without the rads needing to be scorchingly hot.
p.s.
I am not a plumber, but if you have excessive water flow through the combi boiler, I don't see any need to reduce the cold water flow that feeds, for example, your washer and dishwasher or your garden tap, so they need not be affected.
I am not a plumber, but if you have excessive water flow through the combi boiler, I don't see any need to reduce the cold water flow that feeds, for example, your washer and dishwasher or your garden tap, so they need not be affected.
My comment referred to Muggle's suggestion of a 50 kW boiler
I'm talking about hot water production Bernie boy, do try to keep up, or better still butt out
Could you shut the water stopcock down partially to check if water supply rate is causing the problem?
DIYnot Local
Staff member
If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.
Select the supplier or trade you require, enter your location to begin your search.
Are you a trade or supplier? You can create your listing free at DIYnot Local
Sponsored Links
