Xerxes991 Posted October 9, 2022 Share Posted October 9, 2022 I have a 30 year old Glow-Worm Hideaway 70B balanced flue gas boiler, which I assume has pretty low efficiency compared with a modern boiler. It may also have a fairly limited residual life. My gravity system is a bit unusual as I have an old single storey house which is rather long, with a bathroom at each end. Because of that, it has a HW cylinder at each end of the house and the house has two CH zones. So I have a total of four circuits, each with a two port valve, for the two HW cylinders and the two CH zones. The two Room Stats are programmable WiFi, which I recently installed, and which work very well. The two HW circuits are still controlled by the original simple timers. My "simple" plan is just to replace the Glow-Worm with a new conventional condensing boiler in the same location. I don't really feel a need to remove the HW cylinders since I have a bath in one of the bathrooms and the pipe runs to it are quite long. So a Combi boiler doesn't feel right. Also, the HW cylinders are in airing cupboards, so the heat loss from them is not entirely wasted. But I feel I ought to consider other options...any thoughts from anyone? Many thanks. Link to comment Share on other sites More sharing options...
PeterW Posted October 9, 2022 Share Posted October 9, 2022 Not seen one of those for years !! Is it in a utility or the kitchen .? Only issue you may have is bricking up the old balanced flue and then finding a narrow boiler that will fit in the gap as they used to be about 18” wide from memory ..?? No issue (as long as the flue meets regs distances) doing a like for like and I would leave well alone, just get the system power flushed and then replace with something similar output (25kW) and hope it lasts the same..! Link to comment Share on other sites More sharing options...
Xerxes991 Posted October 10, 2022 Author Share Posted October 10, 2022 Many thanks for quick (and comforting) reply. The Glow-Worm is floor mounted in corner of utility room, under work surface, with cabinet above. I assume replacement boiler would be wall mounted, so cabinet would go, but I should be able to fit an under worktop cupboard to compensate. There is enough width, and it is adjacent to sink, so condensate piping should be fine. I'm hoping it will be a relatively minimalist job - but who am I kidding? 🙂 Anyone got suggestions for 25-30kW boiler? I see that the lowest rating Worcester Bosch Greenstar 8000 is 30kW. On a conventional system, does it matter too much if the boiler is a little overpowered? Link to comment Share on other sites More sharing options...
JohnMo Posted October 10, 2022 Share Posted October 10, 2022 Over powered boilers sound great, but you need to be careful of short cycling, which can use loads of extra gas. Not good. Other things to consider is you will be changing from a non condensing (I assume) boiler to a condensing one, which will benefit from lower flow temperatures (return temperature below circa 53 degC), the lower the return temp the better the efficiency. Link to comment Share on other sites More sharing options...
Xerxes991 Posted October 10, 2022 Author Share Posted October 10, 2022 JohnMo, thanks for that, but... Aaaagghh! Complications. My plumber has just got back to me to say that conventional boilers are getting difficult to get hold of. And so he proposes installing a Combi Boiler (35kW), BUT only using the indirect part of the boiler to feed the two CH zones (16 rads in total) and the two HW cylinders. Does that sound feasible? I suppose I could set it up as "Always On", and just use my controls and thermostats. At least it would give me a new pump. You could argue that it leaves me with some future flexibility if I wanted to re-configure the house. But on the other hand, is it giving me more complexity and more things to go wrong? I don't yet know what the cost implications are, but perhaps they are not significant. Link to comment Share on other sites More sharing options...
JohnMo Posted October 10, 2022 Share Posted October 10, 2022 Have a look at Screwfix (70+) and others, all seem to have heat only and system boilers suitable for vented or vented systems. Using a combi can work. Not sure of your current heating system setup, but most if not all combis, have a pressurised CH system. Link to comment Share on other sites More sharing options...
JohnMo Posted October 10, 2022 Share Posted October 10, 2022 Just looked at the spec of your old boiler and it has an output of 17.5 to 20.5kW. Make sure what ever you get can modulate down to below these figures, to flexibility in operation. There is also a similar thread a couple of month ago and that says the boiler they selected and had installed. Link to comment Share on other sites More sharing options...
PeterW Posted October 10, 2022 Share Posted October 10, 2022 23 minutes ago, Xerxes991 said: My plumber has just got back to me to say that conventional boilers are getting difficult to get hold of. Pardon ..?? No shortage at all.. sounds like he’s been to the bacon butty morning at the local merchant and they have an offer on Combi’s and he can get £100 Amazon voucher too … (yes, this happens…) Loads available online - Mr Central Heating is one of many suppliers with a lot of stock. Just checked local plumb centre and one or two WB are showing longer lead times but the rest are fine and next day delivery. Link to comment Share on other sites More sharing options...
Ferdinand Posted October 10, 2022 Share Posted October 10, 2022 When you think about your power flush, check the cost of replacing your rads and possibly your pipes as well. The last time I looked at one, the power flush would have been 70% of the cost of the entire replacement, so I just changed the whole shebang. Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now