I was just about to start a thread asking for advice as I've been getting conflicting advice. Hopefully this is not seen as unreasonable hijacking however I'll happily move it to a new thread.
As OP I have a rental flat with 3 1980's NSH's, 3.6KW and 2.4KW in lounge and 2.4KW in bedroom. A previous tenant used to hang wet washing over them to dry, all 3 had gone rusty and the internal overheat thermostat had tripped.
nov 2017 to april 2018 the property was empty for full refurb; kitchen, bathroom, total decoration, CU & accessories, carpets, the lot and my decorator took the NSH covers away to clean up and respray.
3 years on the tenant reported 2 of the NSH have failed and all 3 are rusty.
Agent sent in a local heating company to repair, they quoted £1200 to replace all 3 with Qrads and reconfigure CU to do away with E7. I haven't seen quote but agents says it includes an energy assessment, including immersion heater, showing no increase in running costs bearing in mind the inflated E7 day rate.
I've checked and find 3 failed elements and one internal overheat tripped, those 2 are working with one element each.
Contacting a refinisher he has come up with a figure of £200-£300 each to strip and refinish with a 2 part polymer heat resistant finish, another has quoted £800 to strip and powder coat, both seem very conversant with the product, knew exaclty which panels were being discussed etc. Working parts are available for these units but not external covers.
It doesn't make sense to me to spend £1K on 35 year old heaters.
I've checked with my EPC inspector, currently on 68D She indicates replacing with Qrads and removing E7 will place flat around 36F to 40E, instead suggests replacing lounge;
3.6KW dual feed with HHR NSH, one 2.4KW with Qrad will move it to 71C or
3.6KW dual feed with HHR NSH, both 2.4KW to HHR NSH will move it to at least 78C or possibly 81B depending on models used.
I've been sent a list of 'qualifying' HHR NSR's, am I right to think they only go up to 1.5KW?
I have no experience of running NSH's and I can't see how immersion heater can be cost effective unless very carefully manually controlled by tenant.
So my question is which of the 2 professionals is wrong?